January hits new record low in the Arctic

January Arctic sea ice extent was the lowest in the satellite record, attended by unusually high air temperatures over the Arctic Ocean and a strong negative phase of the Arctic Oscillation (AO) for the first three weeks of the month. Meanwhile in the Antarctic, this year’s extent was lower than average for January, in contrast to the record high extents in January 2015.

Overview of conditions

sea ice extent map

Figure 1. Arctic sea ice extent for January 2016 was 13.53 million square kilometers (5.2 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Arctic sea ice extent during January averaged 13.53 million square kilometers (5.2 million square miles), which is 1.04 million square kilometers (402,000 square miles) below the 1981 to 2010 average. This was the lowest January extent in the satellite record, 90,000 square kilometers (35,000 square miles) below the previous record January low that occurred in 2011. This was largely driven by unusually low ice coverage in the Barents Sea, Kara Sea, and the East Greenland Sea on the Atlantic side, and below average conditions in the Bering Sea and Sea of Okhotsk. Ice conditions were near average in Baffin Bay, the Labrador Sea and Hudson Bay. There was also less ice than usual in the Gulf of St. Lawrence, an important habitat for harp seals.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of February 3, 2016

Figure 2a. The graph above shows Arctic sea ice extent as of February 3, 2016, along with daily ice extent data for four previous years. 2015 to 2016 is shown in blue, 2014 to 2015 in green, 2013 to 2014 in orange, 2012 to 2011 in brown, and 2011 to 2012 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Figure 2b. These graphs show average sea level pressure and air temperature anomalies at 925 millibars (about 3,000 feet above sea level) for January 2016. normal.||Credit: National Snow and Ice Data Center, courtesy NOAA Earth System Research Laboratory Physical Sciences Division| High-resolution image

Figure 2b. These graphs show average sea level pressure and air temperature anomalies at 925 millibars (about 3,000 feet above sea level) for January 2016.

Credit: National Snow and Ice Data Center, courtesy NOAA Earth System Research Laboratory Physical Sciences Division
High-resolution image

January 2016 was a remarkably warm month. Air temperatures at the 925 hPa level were more than 6 degrees Celsius (13 degrees Fahrenheit) above average across most of the Arctic Ocean. These unusually high air temperatures are likely related to the behavior of the AO. While the AO was in a positive phase for most of the autumn and early winter, it turned strongly negative beginning in January. By mid-January, the index reached nearly -5 sigma or five standard deviations below average. The AO then shifted back to positive during the last week of January. (See the graph at the NOAA Climate Prediction Web site.)

The sea level pressure pattern during January, which featured higher than average pressure over northern central Siberia into the Barents and Kara sea regions, and lower than average pressure in the northern North Pacific and northern North Atlantic regions, is fairly typical of the negative phase of the AO. Much of the focus by climate scientists this winter has been on the strong El Niño. However, in the Arctic, the AO is a bigger player and its influence often spills out into the mid-latitudes during winter by allowing cold air outbreaks. How the AO and El Niño may be linked remains an active area of research.

January 2016 compared to previous years

extent trend graph

Figure 3. Monthly January ice extent for 1979 to 2016 shows a decline of 3.2% per decade.

Credit: National Snow and Ice Data Center
High-resolution image

The monthly average January 2016 sea ice extent was the lowest in the satellite record, 110,000 square kilometers (42,500 square miles) less than the previous record low in 2011. The next lowest extent was in 2006. Interestingly, while 2006 and 2011 did not reach record summer lows, they both preceded years that did, though this may well be simply coincidence.

The trend for January is now -3.2% per decade. January 2016 continues a streak that began in 2005 where every January monthly extent has been less than 14.25 million square kilometers (5.50 million square miles). In contrast, before 2005 (1979 through 2004), every January extent was above 14.25 million square kilometers.

Predicting decadal trends in Arctic winter sea ice cover

sea ice change graphic

Figure 4. The map shows areas of the Arctic where sea ice models predicted ice gain and loss for 2007 to 2017

Credit: S. Yeager et al.
High-resolution image

Observations show an increase in the rate of winter sea ice loss in the North Atlantic sector of the Arctic up until the late 1990s followed by a slowdown in more recent years. The observed trend over the period 2005 to 2015 is actually positive (a tendency for more ice). In a paper recently published in Geophysical Research Letters, scientists at the National Center for Atmospheric Research (NCAR) show that the Community Earth System Model (CESM) was able to predict this period of winter ice growth in the North Atlantic. The study further suggests that in the near future, sea ice extent in this part of the Arctic is likely to remain steady or even increase (Figure 4). The ability to predict the winter sea ice extent in this region is related to the ability of the model to capture the observed variability in the Atlantic Meridional Overturning Circulation (MOC), an ocean circulation pattern that brings warm surface waters from the tropics towards the Arctic. When the MOC is strong, more warm water is brought towards the North Atlantic sector of the Arctic, helping to reduce the winter ice cover. When it is weak, less warm water enters the region and the ice extends further south. However, while there is an indication that the MOC may be weakening, this winter so far has seen considerably less ice than average in the North Atlantic sector.

References

Yeager, S. G., A. R. Karspeck, and G. Danabasoglu. 2015. Predicted slowdown in the rate of Atlantic sea ice loss. Geophysical Research Letters, 42, 10,704–10,713, doi:10.1002/2015GL065364.

A variable rate of ice growth

The rate of ice growth for the first half of November 2015 was quite rapid, but the pace of ice growth slowed during the second half of the month, only to increase again at the end of the month. Throughout the month, sea ice extent remained within two standard deviations of the 1981 to 2010 average.

Overview of conditions

sea ice extent map

Figure 1. Arctic sea ice extent for November 2015 was 10.06 million square kilometers (3.88 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Arctic sea ice extent for November 2015 averaged 10.06 million square kilometers (3.88 million square miles), the sixth lowest November in the satellite record. This is 910,000 square kilometers (351,000 square miles) below the 1981 to 2010 average extent, and 230,000 square kilometers (89,000 square miles) above the record low monthly average for November that occurred in 2006. At the end of the month, extent was well below average in both the Barents Sea and the Bering Strait regions. Extent was above average in eastern Hudson Bay, but below average in the western part of the bay.

Conditions in context

sea ice extent graph

Figure 2a. The graph above shows Arctic sea ice extent as of November 30, 2015, along with daily ice extent data for four previous years. 2015 is shown in blue, 2014 in green, 2013 in orange, 2012 in brown, and 2011 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Air temperatures at the 925 millibar level were above average over nearly all of the Arctic Ocean; the area north of the Barents Sea, between Svalbard and the Taymyr Peninsula, was unusually warm (6 to 8 degrees Celsius, or 11 to 14 degrees Fahrenheit above average). Elsewhere, temperatures at the 925 millibar level were 1 to 4 degrees Celsius (2 to 7 degrees Fahrenheit) above average. NSIDC uses the 925 millibar temperature (about 3,000 feet above the surface) instead of the surface temperature because the 925 millibar temperature provides a better measure of overall warmth of the lower part of the atmosphere. From autumn through spring, the temperature at the surface can be greatly affected by the presence or absence of ice, while during summer, the surface temperature over ice will stay very close to the melting point.

air temperature and pressure anomaly plots

Figure 2b. The plot at left shows Arctic air temperature anomaly (difference from the 1981 to 2010 average) for November 2015 in degrees Celsius, at the 925 millibar level. Reds and yellows indicate higher than average temperatures for this month. The plot at right shows Arctic sea level pressure anomaly (difference from the 1981 to 2010 average) in millibars for November 2015. Sea level pressures were higher than average (red colors) over northern Eurasia, and lower than average (purples) over the Arctic Ocean and northern North Atlantic. This led to strong winds from the south and east over the region north of the Barents Seas, contributing to high temperatures in the area (observed at the 925 millibar level).

Credit: NSIDC courtesy NOAA/ESRL Physical Sciences Division
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The unusual warmth at the 925 millibar level north of the Barents Sea is related to an atmospheric circulation pattern featuring unusually high sea level pressure centered over northern Eurasia and unusually low pressure centered over the Arctic Ocean and northern North Atlantic. The strong pressure gradient (difference in pressure) between the areas of high and low pressure led to strong (and apparently warm) winds from the south. Open water in this area also extends unusually far to the north; while this likely contributed to above average temperatures even as high as the 925 millibar level, the wind pattern itself likely also helped to keep the ice from advancing south.

November 2015 compared to previous years

sea ice trend graph

Figure 3. Monthly November ice extent for 1979 to 2015 shows a decline of 4.7% per decade.

Credit: National Snow and Ice Data Center
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Arctic sea ice extent averaged for November 2015 was the sixth lowest in the satellite data record. Through 2015, the linear rate of decline for November extent is 4.7% per decade.

The average rate of ice growth for November 2015 was 29,800 square kilometers per day (11,500 square miles per day). However, this value averages out the rather rapid growth rate during the first half of the month with a much slower rate during the second part of the month and rapid growth near its end.

Loitering of the retreating sea ice edge in the Arctic seas

ice edge map

Figure 4. This image shows the daily average ice edge (thin black contours) for every day from March 13 to September 23, 2012. Constant ice edge retreat would produce equidistant contours through the retreat season. Instead, the contours point to areas of rapid retreat (where the contours are far apart, e.g., the central Amerasian Basin) and other areas where the ice edge retreat has stalled, or “loitered” (where the contours are over-plotting on top of themselves, producing darker areas, e.g., the Beaufort Sea). Some areas are prone to loitering in most years (north Baffin Bay; the east Beaufort, north Chukchi, Laptev, and Barents seas) and others are unlikely to see loitering behavior (west Beaufort, east Siberian seas).

Credit: M. Steele and W. Ermold, University of Washington
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A recent paper by colleagues M. Steele and W. Ermold of the University of Washington, in press with Journal of Geophysical Research Oceans, provides insight into pauses that are often observed in summer sea ice retreat. On some days, the ice in a region is observed to retreat at a rapid pace, while on others it hardly moves at all. Steele and Ermold term this stationary behavior “ice edge loitering.” They find that loitering occurs through interaction between surface winds and warm sea surface temperatures in areas from which the ice has already retreated. When ice retreat in a particular region happens early enough in the melt season, the water warms above the freezing point from being in contact with warmer and and from sunshine. If winds later in the season push the ice floes into the warmed ocean area, the ice floes will melt until that surface layer reaches the freezing point. Thus while individual ice floes are moving, the ice edge as a whole appears to remain fairly stationary. The time scale of loitering (typically, 4 to 7 days) is naturally tied to the typical time scale of passing weather systems.

Steele and Ermold argue that loitering likely has important effects on both physical and biological conditions at the ice edge during the summer. Consider an ice edge that retreats at a constant rate through the spring and summer. In this case, air/ice/ocean conditions remain fairly constant along the ice edge, simply translating northward with the ice edge through the summer. By comparison, loitering induces persistent melting and thus changes in sea ice morphology, enhances ocean stratification, reduces upwelling of nutrients, and leads to changes in the atmospheric boundary layer. If the wind then shifts and allows rapid northward ice retreat, what happens to the area of loitering that has been left behind? And what are the conditions within the rapidly retreating ice edge? These are questions for future studies.

Comparisons between observed and modeled September sea ice extent

model comparison graph

Figure 4. This figure shows projected and hindcasted September sea ice extent (colors and shading) for climate models participating in the Intergovernmental Panel on Climate Change 5th Assessment, along with observations (black line). The projections are for four scenarios of greenhouse gas concentrations for the future (starting in 2006), termed Representative Concentration Pathways (RCPs) that relate to the radiative forcing at the top of the atmosphere that could occur at the year 2100. The shading indicates the one standard deviation range in the hindcasts and projections.

Credit: J. Stroeve and A. Barrett, National Snow and Ice Data Center
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A paper accepted for publication by NSIDC scientist Stroeve and colleagues includes model hindcasts and projections of September sea ice extent and comparisons with observed extent. The hindcasts and projections are from the global climate models that participated in the Intergovernmental Panel on Climate Change 5th Assessment, and the observations include data that extend the record back to 1953.

The extent projections are shown for four different scenarios of future greenhouse gas growth (starting in 2005), termed Representative Concentration Pathways (RCPs). The RCPS relate to the radiative forcing at the top of the atmosphere that could occur at the year 2100. RCP 8.5 assumes a vigorous increase in greenhouse gas concentrations, while RCP 2.6 assumes a modest initial growth, followed by a reduction in concentrations. The shaded areas indicate the one standard deviation range of the sea ice extents projected by each model and the hindcasts.

The figure indicates that at least for the next few decades, which greenhouse gas scenario that becomes our reality is not especially important (there is much overlap between the projections). Instead, the simulated sea ice evolution is more strongly determined by both the natural variability in Arctic climate and by ongoing forcing from the current greenhouse gas content of the atmosphere. Only in the middle and later part of the 21st century do the differences in the greenhouse gas concentration from the different scenarios become important, and even then, there is a large range in projections from the different models for the same RCP. If our future climate and greenhouse forcing follows RCP 2.6, September ice extent may begin to stabilize by around the middle of the century. Figures like this are useful to policy makers negotiating climate treaties at the Paris 2015 U.N. Climate Change Conference.

References

Steele, M. and W. Ermold. 2015. Loitering of the retreating sea ice edge in the Arctic Seas. J. Geophys. Res. Oceans, in press. doi:10.1002/2015JC011182.

Stroeve, J. and D. Notz. 2015. Insights on past and future sea-ice evolution from combining observations and models. Global and Planetary Change, in press. doi:10.1016/j.gloplacha.2015.10.011.

Antarctic sea ice at its 2015 maximum

Antarctic sea ice appears to have reached its annual maximum extent on October 6. The maximum occurred relatively late compared to past years. In contrast to the past three years, the 2015 maximum did not set a new record high for the period of satellite observations, but was nevertheless slightly above the 1981 to 2010 average.

Overview of conditions

sea ice extent image

Figure 1. Antarctic sea ice extent for October 6, 2015 was 18.83 million square kilometers (7.24 million square miles). The orange line shows the 1981 to 2010 median extent for that day. The black cross indicates the geographic South Pole. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Antarctic sea ice extent reached its likely maximum for the year, at 18.83 million square kilometers (7.24 million square miles) on October 6, 2015. This year’s maximum was the sixteenth highest in the 35-year record. It was 120,000 square kilometers (46,000 square miles) above the average maximum daily extent computed over the 1981 to 2010 period of 18.71 million square kilometers (7.19 million square miles), and 1.33 million square kilometers (514,000 square miles) below the record maximum set in 2014. The date of the maximum was quite late in comparison to the 35-year satellite record. Only one year, 2002, has had a later maximum (October 12).

At the date of the 2015 maximum, Antarctic sea ice extent was greater than average in the Antarctic Peninsula region, the Weddell Sea, and the Wilkes Land coast area; and below average in the Ross Sea and Indian Ocean sectors.

Conditions in context

extent time series

Figure 2. The graph above shows Antarctic sea ice extent as of October 13, 2015, along with daily ice extent data for four previous years. 2015 is shown in blue, 2014 in green, 2014 in orange, 2012 in brown, and 2011 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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temperature and pressure plots

Figure 3. Panel (a) shows sea level air pressure anomaly for the Southern Ocean region, August 1 to September 30, 2015. Panel (b) shows air temperature anomaly for the Southern Ocean region, August 1 to September 30, at the 925 millibar level (approximately 1,600 feet altitude).

Credit: NOAA ESRL Physical Sciences Division
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concentration anomaly images

Figure 4. The images compare Antarctic sea ice concentration for Septembers during two strong El Niño events (2015, left; 1997, right) to 1981 to 2010 averages. Colors show percent difference from average sea ice concentration surrounding Antarctica. Oranges and reds indicate concentrations higher than average; greens and blues indicate concentrations lower than average.

Credit: National Snow and Ice Data Center
High-resolution image

As recently as July 12, Antarctic sea ice extent was at a record daily high extent for the satellite period of observations. For much of early 2015, Antarctic sea ice extent was either slightly above or slightly below the levels seen on the same date in 2014, the record high year. However, beginning in mid-July, the growth rate for Antarctic sea ice slowed significantly, causing the 2015 maximum extent to be only the sixteenth highest in the record.

It is likely that this slowing of late-winter ice growth is related in part to the build-up of the El Niño conditions. El Niño occurs when a large area of the surface waters in the tropical eastern Pacific Ocean warms, and it has widespread effects on weather patterns. In the Southern Ocean, El Niño conditions are typically associated with a weakening of the Amundsen Sea Low, a persistent region of low air pressure in the southernmost Pacific sector of the Antarctic coast (Raphael et al., 2015). Air pressure in the Amundsen Sea region for the months of August and September was higher than average, indicating a weakening of the low-pressure tendency in the region. Higher-than-average air pressure was also observed in the Indian Ocean sector. These regions saw reduced sea ice growth and even local sea ice retreat as the austral winter progressed, and areas of higher-than-average temperatures near the ice edge.

Patterns of sea ice concentration around Antarctica (the deviation from average ice concentration) for El Niño years show a similar pattern, with more ice near the Peninsula.

References

Raphael, M. N., G. J. Marshall, J. Turner, R. Fogt, D. Schneider, D. A. Dixon, J. S. Hosking, J. M. Jones, and W. R. Hobbs. 2015. The Amundsen Sea Low: Variability, change and impact on Antarctic climate. Bulletin of the American Meteorological Society 2015, doi:10.1175/BAMS-D-14-00018.1.

2015 melt season in review

The Arctic melt season has ended and sea ice extent is now increasing after reaching the fourth lowest minimum on record, on September 11. Sea ice extent in Antarctica has not yet reached its seasonal maximum.

Overview of conditions

sea ice extent image

Figure 1. Arctic sea ice extent for September 2015 was 4.63 million square kilometers (1.79 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Following the seasonal daily minimum of 4.41 million square kilometers (1.70 million square miles) that was set on September 11, which was the fourth lowest in the satellite record, Arctic sea ice has started its cycle of growth. Arctic sea ice extent averaged for the month of September 2015 was 4.63 million square kilometers (1.79 million square miles), also the fourth lowest in the satellite record. This is 1.87 million square kilometers (722,000 square miles) below the 1981 to 2010 average extent, and 1.01 million square kilometers (390,000 square miles) above the record low monthly average for September that occurred in 2012. As of this writing, Antarctica’s winter maximum has not yet occurred, but is anticipated within several days.

Conditions in context

sea ice extent graph

Figure 2. The graph above shows Arctic sea ice extent as of October 5, 2015, along with daily ice extent data for four previous years. 2015 is shown in blue, 2014 in green, 2013 in orange, 2012 in brown, and 2011 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Note: This graph was updated to show the most recent years, in order to be consistent with our monthly posts. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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For two weeks following the minimum extent on September 11, air temperatures at the 925 hPa level (about 3,000 feet above the surface) were 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) lower than average in the Chukchi and Beaufort seas, helping foster ice growth in those regions. Elsewhere over the Arctic Ocean, there has been fairly little ice growth, in part due to near average to slightly above average air temperatures. Both the Northern Sea Route and Roald Amundsen’s route through the Northwest Passage appeared to remain free of ice at the end of the month. The deeper northern route through Parry Channel, which consists of M’Clure Strait, Barrow Strait, and Lancaster Sound, never completely cleared of ice.

September 2015 compared to previous years

extent trend graph

Figure 3. Monthly September ice extent for 1979 to 2015 shows a decline of 13.4% per decade relative to the 1981 to 2010 average.

Credit: National Snow and Ice Data Center
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Through 2015, the linear rate of decline for September Arctic ice extent over the satellite record is 13.4% per decade. The nine lowest September ice extents over the satellite record have all occurred in the last nine years.

Conditions leading to this year’s minimum

ice fraction and age maps

Figure 4a. The map at left shows multiyear ice fraction in mid-April derived from ASCAT, and the corresponding map at right shows ice age. ASCAT image courtesy of R. Kwok, NASA Jet Propulsion Laboratory. Ice age image derived from data provided by M. Tschudi, University of Colorado Boulder.

Credit: National Snow and Ice Data Center
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air temperature graphs

Figure 4b. The graphs show Arctic ocean air temperatures for May, June, July, and August at the 925 hPa level, ranked according to year from lowest (in blue colors) to highest (in red colors). Ranking of 2015 is given in yellow.

Credit: D. Slater, National Snow and Ice Data Center
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sst maps

Figure 4c. The maps show Arctic sea surface temperature (SST) and anomaly in degrees Celsius, for September 2015. The image at left shows average temperature, with reds indicating higher temperatures and blues indicating lower temperatures. The map at right shows temperature anomaly, compared to the 1982 to 2006 average. Reds and oranges indicate higher than average temperatures, and blues lower than average. The grey line indicates the sea ice edge. SSTs are from from the NCDC OIv2 “Reynolds” data set, a blend of satellite (AVHRR) and in situ data designed to provide a “bulk” or “mixed layer” temperature. Ice edge is from NSIDC near real time passive microwave data.

Credit: M. Steele, Polar Science Center/University of Washington
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The summer melt season began earlier than average. The maximum winter extent, reached on February 25, 2015, was also the lowest recorded over the period of satellite observations. However, a relatively large amount of multiyear ice was transported into the southern Beaufort and Chukchi seas during the winter, as documented by images of multiyear ice fraction derived from the Advanced Scatterometer (ASCAT) instrument on the METOP-A satellite (Figure 4a). The corresponding ice age image shows that the multiyear ice largely consisted of floes that had survived several melt seasons, indicating that it was fairly thick. Thick ice is more difficult to melt out during summer than thinner ice; if not for this thicker ice, the September minimum extent would likely have been lower.

Melt onset began earlier than average in the Beaufort Sea, especially along the coast of Canada, leading to early development of open water in this area. Melt also began earlier than is usual in the Kara Sea, fostering early retreat of sea ice in the region. However, air temperatures at the 925 hPa level during May and June for the Arctic ocean region were not particularly high, ranking as the 26th and 13th warmest since 1979 (Figure 4b). As a result, although the winter maximum extent was the lowest in the satellite record, ice extent at the end of June was only the third lowest.

The pace of seasonal ice loss picked up rapidly in July, with Arctic ocean region temperatures at the 925 hPa level reaching the second highest during the satellite record (with 2007 ranked as the highest). Daily ice loss rates averaged 101,800 square kilometers (39,300 square miles) per day, the fourth largest rate of ice loss recorded for the month. Nevertheless, sea ice was slow to melt out of Baffin Bay and Hudson Bay, resulting in a July average extent for 2015 that was the eighth lowest on record. By the end of July however, the fast pace of ice loss during the month resulted in 2015 extent falling within 550,000 square kilometers (212,000 square miles) of the level recorded in 2012, and tracking below the levels recorded for 2013 and 2014. By the middle of August, the difference in extent between 2012 and 2015 had dropped to less than 500,000 square kilometers (193,000 square miles), hinting at the possibility that this year would rank among the lowest minimum extents recorded. However, temperatures for August were not particularly warm, and extent ended up fourth lowest.

Higher than average Arctic sea surface temperatures dominated the Arctic Ocean in September 2015 (Figure 4c), though not as high as seen in 2007 or 2012. Early melt onset as well as strong spring winds in the eastern Beaufort Sea led to early ice retreat in this area (Steele et al., 2015). These winds were particularly strong in April 2015, but then they abated, so that while the resulting summer sea surface temperatures were higher than surrounding waters, they were only around 2 to 3 degrees Celsius (4 to 5 degrees Fahrenheit) higher than average near the coast. The Kara Sea was also unusually warm this year, while sea surface temperatures were generally lower than average in the Nordic seas.

What happened to the old ice in the Beaufort and Chukchi Seas?

Figure 5a. The map shows Arctic sea ice age, in years, for the week of September 7 to 13, 2015. ||Credit: M. Tschudi, University of Colorado Boulder| High-resolution image

Figure 5a. The map shows Arctic sea ice age, in years, for the week of September 7 to 13, 2015.

Credit: M. Tschudi, University of Colorado Boulder
High-resolution image

ice survival graph

Figure 5b. The plot shows survival rates of first-year, second-year, and older ice, in percentage of area that survived.

Credit: National Snow and Ice Data Center
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Maps of ice age at the beginning of the melt season and at the time of the September minimum extent (Figure 5a) reveal that most of the old ice transported into the southern Beaufort and Chukchi seas melted out this summer. This resulted in a 31% depletion of the multiyear ice cover this summer for the Arctic as a whole, compared to only 12% in 2013 and 38% in 2012. There was also more first-year ice lost this summer than during the last two summers. Sixty-two percent of the winter first-year ice was lost. Overall, this was the third largest amount of first-year ice lost in a melt season, behind 2012 (73%) and 2007 (67%).

References

Steele, M., S. Dickinson, J. Zhang, and R. Lindsay. 2015. Seasonal ice loss in the Beaufort Sea: Toward synchrony and prediction, J. Geophys. Res., 120, doi:10.1002/2014JC010247.

Erratum

A reader alerted us that Figure 5a was mislabeled. Instead of Mid-March 2015, it should have been labeled September 2015. On October 8, 2015, we corrected the label and its caption.

Steady decline, seasonal minimum approaching

August saw a remarkably steady decline in Arctic sea ice extent, at a rate slightly faster than the long-term average. Forecasts show that this year’s minimum sea ice extent, which typically occurs in mid to late September, is likely to be the third or fourth lowest in the satellite record. All four of the lowest extents have occurred since 2007. In mid-August, Antarctic sea ice extent began to trend below the 1981 to 2010 average for the first time since November 2011.

Overview of conditions

sea ice extent map

Figure 1. Arctic sea ice extent for August 2015 was 5.61 million square kilometers (2.16 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Average sea ice extent for August 2015 was 5.61 million square kilometers (2.16 million square miles), the fourth lowest August extent in the satellite record. This is 1.61 million square kilometers (621,000 square miles) below the 1981 to 2010 average for the month, and 900,000 square kilometers (350,000 square miles) above the record low for August, set in 2012.

The rapid pace of daily ice loss seen in late July 2015 slowed somewhat in August. The pace increased slightly toward the end of the month, so that by August 31 Arctic sea ice extent was only slightly greater than on the same date in 2007 and 2011. The ice is currently tracking lower than two standard deviations below the 1981 to 2010 long-term average.

Sea ice extent remains below average in nearly every sector except for Baffin Bay and Hudson Bay, where some ice persists in sheltered coastal areas. A striking feature of the late 2015 melt season are the extensive regions of low-concentration ice (less than 70% ice cover) in the Beaufort Sea. A few patches of multi-year sea ice surrounded by open water remain in the central Beaufort Sea.

Conditions in context

sea ice extent graph

Figure 2. The graph above shows Arctic sea ice extent as of August 31, 2015, along with daily ice extent data for four previous years. 2015 is shown in blue, 2014 in green, 2013 in orange, 2012 in brown, and 2011 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Ice loss rates were quite steady through most of the month of August. Sea ice loss for August averaged 75,100 square kilometers per day (29,000 square miles), compared to the long-term 1981 to 2010 average value of 57,300 square kilometers per day (22,100 square miles per day), and a rate of 89,500 square kilometers per day for 2012 (34,500 square miles per day).

Cool conditions prevailed in the East Siberian, Chukchi, and western Beaufort seas, where air temperatures at the 925 millibar level were 1.5 to 2.5 degrees Celsius (3 to 5 degrees Fahrenheit) below average. However, a broad region of higher-than-average temperatures extended from Norway to the North Pole, 1.5 to 2.5 degrees Celsius (3 to 5 degrees Fahrenheit) above average. Sea level pressures were up to 10 millibars above average over the central Arctic Ocean, paired with slightly below average values in north-central Siberia, similar to the dipole-like pattern seen for July. The Arctic Oscillation was in its negative phase for most of the month, again similar to July.

August 2015 compared to previous years

trend graph

Figure 3. Monthly August ice extent for 1979 to 2015 shows a decline of 10.3% per decade.

Credit: National Snow and Ice Data Center
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Arctic sea ice extent averaged for August 2015 was the fourth lowest in the satellite data record. Through 2015, the linear rate of decline for August extent is 10.3% per decade.

 

Forecasting the minimum

||Credit: RESEARCHER'S NAME/ORGANIZATION *or * National Snow and Ice Data Center|  High-resolution image

Figure 4. The graph shows ice extent forecasts, based on ice extent as observed on August 31, 2015 and past years’ observed rates for selected years.

Credit: W. Meier, NASA Goddard Cryospheric Sciences Lab
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One way of estimating the upcoming seasonal minimum in ice extent is to extrapolate from the current extent, using previous years’ rates of daily sea ice loss. Assuming that past years’ daily rates of change indicate the range of ice loss that can be expected this year, this method gives an envelope of possible minimum extents for the September seasonal minimum. However, it is possible to have unprecedented loss rates, either slow or fast.

Starting with the ice extent observed on August 31 and then applying 2006 loss rates, the slowest rate in recent years, results in the highest extrapolated minimum for 2015 of 4.50 million square kilometers (1.74 million square miles), and a September monthly average extent of 4.59 million square kilometers (1.77 million square miles). The lowest daily minimum comes from using the 2010 pace, yielding an estimated 4.12 million square kilometers (1.67 million square miles) for the daily minimum, and a September monthly average extent of 4.33 million square kilometers (1.67 million square miles).

Using an average rate of ice loss from the most recent ten years gives a one-day minimum extent of 4.38 ± 0.11 million square kilometers (1.79 million square miles), and a September monthly average of 4.49 ± 0.09. As of August 31, the 5-day running daily average extent is 4.72 million square kilometers. If no further retreat occurred, 2015 would already be the sixth lowest daily ice extent in the satellite record.

The forecast places the upcoming daily sea ice minimum between third and fourth lowest, with fourth more likely. There is still a possibility that 2015 extent will be lower than 4.3 million square kilometers, the third lowest sea ice extent, surpassing the 2011 sea ice extent minimum, and a small chance of surpassing 2007, resulting in the second-lowest daily minimum. This assumes that we continue to have sea ice loss rates at least as fast as those of 2010. This was indeed the case for the final ten days of August 2015.

Northwest Passage icy; Northern Sea Route remains open

Figure 5. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque et condimentum nunc. Maecenas tempor cursus fermentum. Donec nulla quam, commodo eu urna nec, aliquet accumsan lorem. Mauris justo orci, sollicitudin quis diam vel, vehicula mollis diam. Donec sollicitudin nisi vel blandit gravida..||Credit: RESEARCHER'S NAME/ORGANIZATION *or * National Snow and Ice Data Center|  High-resolution image

Figure 5. Click on the image to view an animation of sea ice concentration north of Canada for August 23 to September 1, 2015.

Credit: Canadian Ice Service Daily and Regional Ice Charts
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The southerly route through the Northwest Passage is open. The passage was discovered during 1903 to 1906 by Roald Amundsen, who made the first transit of the passage from Baffin Bay to the Beaufort Sea. This route passes south of Prince of Wales Island and Victoria Island before entering the Beaufort Sea south of Banks Island. Data from the AMSR-2 satellite, which uses passive microwave emission, suggests that this path is ice-free. The higher-resolution Multisensor Analyzed Sea Ice Extent (MASIE) product, based on several data sources and human interpretation, shows only a few areas of low-concentration ice. The broader and deeper passage through the Canadian Arctic Archipelago, between Lancaster Sound, Parry Channel, and McClure Strait, is still obstructed by ice, but at the end of August ice blocked only a short portion near Victoria Island. Before drawing conclusions about navigability, however, it is important to check with the operational services such as the National Ice Center (NIC) or the Canadian Ice Service (CIS). The Northern Sea Route, north of the European Russian and Siberian coasts, has remained largely clear of ice for the entire month.

Warm surface water near Alaska and the Kara Sea

Figure 6. The map shows average ocean sea surface temperature (SST) and sea ice concentration for August 30, 2015. SST is measured by satellites using thermal emission sensors (a global product, adjusted by comparison with ship and buoy data). Sea ice concentration is derived from NSIDC’s sea ice concentration near-real-time product. Also shown are drifting buoy temperatures at 2.5 meters depth in the ocean (about 8 feet deep: colored circles); gray circles indicates that temperature data from the buoys is not available.

Credit: M. Steele, Polar Science Center/University of Washington
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Strong winds from the east in spring of this year opened the ice pack in the eastern Beaufort Sea quite early, allowing early warming of the ocean surface. However, the winds shifted in later spring, forcing the warmed water layer against the North American mainland rather than dispersing it further into the Arctic Ocean. Sea surface temperatures (SSTs) were high as of late August 2015 in the Beaufort, Chukchi, and Laptev Seas, as well as in Baffin Bay and the Kara and northern Barents seas.

The remaining area of low concentration ice in the Beaufort Sea has large pockets of warming open water. This area is likely to melt out by the September ice minimum; however, maximum SSTs in this region will probably not be especially high (currently about 2.5 degrees Celsius, or 5 degrees Fahrenheit above the freezing point of seawater) owing to how late we are in the melt season.

NASA airborne mission flies over sea ice in 2015 to support ICESat-2

images from air campaign

Figure 7. The map at left shows flight tracks flown by NASA to evaluate laser reflection characteristics over sea ice and land ice. The image at top right shows sea ice with melt ponds in the Lincoln Sea. The photo at bottom right shows the view from the aircraft window of moderately loose pack in the area.

Credit: K. Brunt/NASA
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In support of the upcoming Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) mission, NASA recently deployed two instrumented aircraft to Thule Air Force Base, Greenland (near Qaanaaq) to collect data for the development of software to process the satellite data. Instrumentation for the three-week campaign (July 28 to August 19) included a laser altimeter called SIMPL and an imaging spectrometer called AVIRIS-NG. ICESat-2 is a satellite-borne laser altimetry mission that uses a new approach to space-borne determination of surface elevation, based on a high measurement rate (10,000 times per second), multiple ground tracks of laser data, and closely spaced orbital tracks to provide more detailed mapping. Specific science goals of the airborne campaign include assessing how melting ice surfaces and snow-grain-size variability affect the surface return of green-wavelength light (the color of the ICESat-2 lasers).

Over sea ice, the aircraft data provide important information on sea ice freeboard (height of flotation) and snow cover on sea ice. Both are important parameters for correcting satellite measurements of sea ice thickness. Of the more than thirty-five science flight hours of data collected based out of Thule, four flights targeted sea ice in the vicinity of Nares Strait, where loose pack ice, covered in surface melt ponds, was found. These data will be available on the NASA ICESat-2 Web site later in the year.

 

 

Open and shut

Arctic sea ice extent is well below average for this time of year, although ice has persisted in Baffin Bay and Hudson Bay. The Northern Sea Route appears to be mostly open, except for a narrow section along the Taymyr Peninsula. The Northwest Passage is still clogged with ice. Antarctic sea ice extent remains high, but the growth rate has slowed and extent is now closer to its long-term average for this time of year.

Overview of conditions

extent map

Figure 1. Arctic sea ice extent for July 2015 was 8.77 million square kilometers (3.38 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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July 2015 average ice extent was 8.77 million square kilometers (3.38 million square miles), the 8th lowest July extent in the satellite record. This is 920,000 square kilometers (355,000 square miles) below the 1981 to 2010 average for the month.

While Arctic sea ice retreated at near average rates during the month of June, the pace of ice loss quickened in July such that the extent at the end of the month was within 550,000 square kilometers (212,000 square miles) of the extent recorded on the same date in 2012, and is now tracking below 2013 and 2014. Ice extent was at below average levels within the Kara, Barents, Chukchi, East Siberian, and Laptev seas, while extent was near average in the Beaufort Sea and the East Greenland Sea. Sea ice extent remained more extensive than average within Baffin Bay and Hudson Bay. While the ice extent remained overall higher than in 2012, this is largely a result of the higher extent within Baffin and Hudson bays. Despite average sea ice extent within the Beaufort Sea, higher resolution passive microwave satellite imagery from AMSR-2 and visible-band imagery from MODIS (Figure 6) reveals that the ice has become rather diffuse (low ice concentrations) with many large broken ice floes surrounded by open water.

Conditions in context

extent graph

Figure 2. The graph above shows Arctic sea ice extent as of August 2, 2015, along with daily ice extent data for four previous years. 2015 is shown in blue, 2014 in green, 2013 in orange, 2012 in brown, and 2011 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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Although the pace of ice loss is almost always faster in July than in June, the July rate of loss for 2015 has been pronounced. The rate of ice loss for July 2015 averaged 101,800 square kilometers (39,300 square miles) per day, compared to 97,400 square kilometers (37,600 square miles) in 2012 and 86,900 square kilometers (33,500 square miles) per day in the long-term 1981 to 2010 average. This rapid loss is in part a result of fairly high air temperatures over most of the Arctic Ocean. Temperatures at the 925 hPa level (3,000 feet above sea level) reached nearly 6 degrees Celsius (11 degrees Fahrenheit) above average directly north of Greenland, and up to 5 degrees Celsius (9 degrees Fahrenheit) above average in the East Siberian Sea. In contrast, temperatures were up to 5 degrees Celsius (9 degrees Fahrenheit) cooler than average in the Barents Sea. Sea level pressure was above average over most of the Arctic Ocean, most pronounced near the pole, and over the Greenland Ice Sheet. This was paired with below average pressures over Siberia. Overall, this pattern is very similar to what has come to be known as the Dipole Anomaly.

July 2015 compared to previous years

trend graph

Figure 3. July ice extent for 1979 to 2015 shows a decline of 7.2% per decade relative to the 1981 to 2010 average.

Credit: National Snow and Ice Data Center
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Arctic sea ice extent averaged for July 2015 was the 8th lowest in the satellite data record. Through 2015, the linear rate of decline for July extent is 7.2% per decade.

Seasonal ice hanging on in Baffin and Hudson bays

Figure 4. The graphs show daily sea ice extent from July 1, 2015 to August 3, 2015 (solid green line) compared to previous years, for the Baffin and Hudson bays. Data are from the Multisensor Analyzed Sea Ice Extent (MASIE) product.

Credit: National Snow and Ice Data Center/National Ice Center
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This summer, the ice has been slow to retreat in the Baffin and Hudson bays, as highlighted by the Multisensor Analyzed Sea Ice (MASIE) product. Throughout July, ice in the bays remained more extensive than in recent summers, adding an extra 500,000 square kilometers (193,000 square miles) of ice to the Arctic total. These areas, normally navigable at this time of year, are reported to be clogged with ice. The heavy ice conditions made fuel resupply difficult for some coastal communities in Nunavut and Nunavik. A supply ship was delayed three weeks attempting to reach Nunavik, and Arctic research projects have been delayed as well. More extensive ice than usual in the eastern part of Hudson Bay also resulted in delays of resupply for communities in Northern Quebec. Polar bears, which are usually farther out on the ice edge at this time of year, were observed in Iqaluit.

Melt started early in 2015

melt onset maps

Figure 5. The map at left shows melt onset dates for 2015. The map at right shows anomalies (departure from average) compared to the 1981 to 2010 long-term average. Data are from the Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave Imager (SSM/I) passive microwave time series.

Credit: Jeff Miller, NASA Goddard Space Flight Center
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The timing of seasonal melt onset plays an important role in the amount of ice that can be melted each summer. When melt begins, the surface albedo drops, meaning that more of the sun’s energy is absorbed by the surface, favoring further melt and a further decline in albedo. Because microwave emissions are sensitive to liquid water in the snowpack, the timing of melt onset can be detected using the same satellite passive microwave data that is used for determining the sea ice extent, but with a different algorithm. This summer, melt began a month earlier than average in the Kara Sea, where the ice cover retreated early in the summer, and in the southern Beaufort Sea, where the ice cover is now very diffuse. In contrast, melt came later than average in Baffin Bay where the ice has been slow to completely melt out this summer. Melt also came later than average in parts of the East Siberian and Laptev seas.

Breakup of old, thick ice in the Beaufort Sea

Figure 6. The map at top, left shows ice age, in years, for the beginning of July 2015 (Week 27, June 29 to July 5). The MODIS satellite image (bottom, left) of the Beaufort Sea area, from July 22, 2015, shows a mélange of very large and smaller multiyear ice floes surrounded by open water. The AMSR-2 satellite image from July 22 (top, right) shows ice percent concentration. Ice age data are from C. Fowler and J. Maslanik, University of Colorado Boulder. MODIS data are from the Land Atmosphere Near-Real Time Capability for EOS (LANCE) System, NASA/GSFC. Sea ice concentration image courtesy University of Bremen from the JAXA AMSR-2 sensor.

Credit: National Snow and Ice Data Center
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Multiyear ice, which is ice that has survived at least one melt season, tends to be fairly thick. The location of multiyear ice and its age can be determined through tracking the ice motion from year to year. Ice age data from the beginning of July show a tongue of old multiyear ice extending from the southern Beaufort Sea towards Alaska into the Chukchi Sea. However, passive microwave imagery from AMSR-2 reveals that the ice pack has become very diffuse within the Beaufort Sea, with ice concentrations dropping below 50%. Corresponding visible-band imagery from MODIS shows a mélange of very large and smaller multiyear ice floes surrounded by open water. The presence of open water surrounding the floes allows for enhanced lateral and basal ice melt, raising the possibility that much of the multiyear ice in this region will melt out during the remainder of the summer.

Antarctic sea ice extent pauses, still high

Figure 2. The graph above shows Arctic sea ice extent as of XXXXX XX, 20XX, along with daily ice extent data for four previous years. 201X is shown in blue, 201X in green, 201X in orange, 201X in brown, and 20XX in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 6. The graph above shows Antarctic sea ice extent as of August 3, 2015, along with daily ice extent data for 2010, 2013, and 2015. 2015 is shown in solid blue, 2014 in green, 2013 in dashed blue, and 2010 in pink. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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July average extent for Antarctica was 17.06 million square kilometers (6.59 million square miles). Sea ice extent grew at approximately 150,000 square kilometers per day (58,000 square miles per day) for the first half of July, but then growth slowed to just 10,000 square kilometers (3,900 square miles) per day for much of the rest of the month. The change was due to regional ice retreats in the northern Weddell Sea and northwestern Ross Sea,  almost balanced by continued growth in the northern Bellingshausen Sea west of the Antarctic Peninsula. The slower growth in sea ice extent places 2015 now at around 4th highest in terms of daily extent, below 2014, 2013, and 2010.

Relatively warm conditions prevailed for much of the month in the two regions of ice edge retreat, the northern Weddell Sea and northwestern Ross Sea, with average air temperatures at the 925 hPa level (3,000 feet above sea level) at approximately 4 degrees Celsius (7 degrees Fahrenheit) above average. However, sea surface temperatures just north of the ice edge were 0.5 to 1 degree Celsius (1 to 2 degrees Fahrenheit) cooler than average, raising the potential for rapid ice growth through the remainder of the winter season.

May in decline

Melt season is underway, and sea ice in the Arctic is retreating rapidly. At the end of May, ice extent was at daily record low levels. By sharp contrast, sea ice extent in the Southern Hemisphere continues to track at daily record high levels.

Overview of conditions

sea ice extent

Figure 1. Arctic sea ice extent for May 2015 was 12.65 million square kilometers (4.88 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Arctic sea ice extent for May 2015 averaged 12.65 million square kilometers (4.88 million square miles), the third lowest May ice extent in the satellite record. This is 730,000 square kilometers (282,000 square miles) below the 1981 to 2010 long-term average of 13.38 million square kilometers (5.17 million square miles) and 70,000 square kilometers (27,000 square miles) above the record low for the month, observed in 2004.

The below average extent for this month is partly a result of early melt out of ice in the Bering Sea and the persistence of below-average ice conditions in the Barents Sea. Early breakup of sea ice in the Bering Sea also occurred last spring. Elsewhere, ice is tracking at near-average levels. By the end of May, several openings had appeared in the ice pack, most notably in the southern Beaufort Sea near Banks Island, off the coast of Barrow, Alaska, and in the Kara Sea. Now that we are entering the month of June, the rate of ice loss is likely to quicken, but how fast will depend on the weather conditions and the date of ice surface melt onset across the high Arctic.

Conditions in context

sea ice extent graph

Figure 2a. The graph above shows Arctic sea ice extent as of June 1, 2015, along with daily ice extent data for four previous years. 2015 is shown in blue, 2014 in green, 2013 in orange, 2011 in brown, and 2011 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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Figure 2b. In this satellite image, captured on June 2, 2015, broken up ice over the eastern Beaufort Sea is apparent. Eastern Russia is snow covered, while the Seward Peninsula is relatively snow free. Sea level pressures were high over the Arctic Ocean at this time. Greenland is seen clearly at the lower left. Image from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the NASA Terra satellite.

Credit: Land Atmosphere Near-Real Time Capability for EOS (LANCE) System, NASA/GSFC
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Overall, May was cooler than average over the central Arctic Ocean, the East Greenland Sea and the East Siberian and Laptev seas, notably north of the Greenland Ice Sheet where air temperatures at the 925 millibar level (about 3,000 feet above the surface) were 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) below average. However, temperatures were 4 to 8 degrees Celsius (7 to 14 degrees Fahrenheit) above average in the Beaufort Sea and the Barents and Kara seas, with surface temperatures rising above the freezing point in Barrow, Alaska. These temperature patterns were linked to below-average sea level pressures over the Bering Sea, Baffin Bay and the North Atlantic, coupled with above average pressures over Siberia, Alaska, and Canada. Associated wind patterns also helped to push ice offshore from the coast of Alaska, leading to the formation of open water off the coast of Barrow, Alaska.

Temperature conditions during May may prove to be important, given the potential role that melt ponds in spring play in the evolution of the ice cover throughout summer. For example, during years with fewer melt ponds in May, September sea ice extent tends to be higher than during years with more melt ponds. (See our May 2014 discussion of the importance of spring melt ponds.)

Overall the total ice extent for May 2015 declined at a fairly rapid pace, losing 1.69 million square kilometers (653,000 square miles). This was slightly faster than the 1981 to 2010 average rate of decline of 1.41 million square kilometers (544,000 square miles). The ice extent is now tracking at more than two standard deviations below the 1981 to 2010 long-term average.

May 2015 compared to previous years

Figure 3. Monthly XXXXX ice extent for 1979 to 201X shows a decline of X.X% per decade relative to the 1981 to 2010 average.||Credit: National Snow and Ice Data Center|  High-resolution image

Figure 3. Monthly May ice extent for 1979 to 2015 shows a decline of 2.33% per decade relative to the 1981 to 2010 average.

Credit: National Snow and Ice Data Center
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Arctic sea ice extent averaged for May 2015 was the third lowest in the satellite record for the month. Through 2015, the linear rate of decline for May extent is 2.33% per decade.

Weather versus preconditioning

Figure 4. The images above compare patterns of winter (January-February-March) sea ice concentration anomalies (SIC, in percent concentration) with sea surface temperature anomalies (SST, in Kelvin) and sea level air pressures (SA, in pressure altitude), for a pre-industrial control model simulation.

Credit: M. Bushuk et al., Geophys. Res. Lett.
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The shrinking summer sea ice cover has fostered increased socioeconomic activity in the Arctic, such as resource extraction and ship traffic, leading to a focus on developing reliable methods to predict the summer minimum sea ice extent several months in advance.

Key to improving our ability to accurately forecast September sea ice conditions is a better understanding of the physical mechanisms underlying sea ice variability from year to year. An area of growing interest is sea ice reemergence: the observation that lower-than-average or higher-than-average sea ice extent tends to recur at time lags of 5 to 12 months. This reemergence phenomenon appears to be related to sea surface temperatures in the seasonal ice zones (from melt season to growth season), sea ice thickness in the central Arctic (from growth season to melt season) and atmospheric circulation (from melt season to growth season).

For example, a new study shows that when winter sea ice concentrations are above average in the East Greenland, Barents and Kara seas, ice concentrations tend to be below average in the Bering Sea. This spatial pattern of anomalies linking the North Atlantic and North Pacific is related to the sea level pressure pattern that drives surface winds and their associated movement of atmospheric heat. These conditions are in turn linked to cooler or warmer than average sea surface temperatures that provide memory, influencing regional sea ice concentrations the following autumn. Thus, while the atmosphere is critical in setting the spatial patterns of sea ice variability, the ocean provides the memory for reemergence.

Figure 4 shows the leading winter (January-February-March) patterns of sea ice reemergence in the Arctic, based on model output from a pre-industrial control simulation of the Community Climate System Model version 4 (CCSM4). The reemerging sea ice concentration (SIC) pattern is characterized by below-average SIC in the Bering Sea and above-average SIC in the Barents-Greenland-Iceland-Norwegian (Barents-GIN) seas. Local sea surface temperature anomalies (SSTs) have the opposite sign and provide memory that allows melt season SIC conditions to reemerge the following growth season. The sea level pressure (SLP) pattern drives winds that provide for communication between the North Atlantic and North Pacific.

The Sea Ice Prediction Network provides a forum for the sea ice forecasting community to share predictions of September mean sea ice extent using a variety of methods.

Down below, Antarctica above

Figure 1. Arctic sea ice extent for XXXX 20XX was X.XX million square kilometers (X.XX million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole.  Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 5. The graph above shows Antarctic sea ice extent as of June 1, 2015, along with daily ice extent data for four previous years. 2015 is shown in blue, 2014 in green, 2013 in orange, 2012 in brown, and 2011 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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Beginning in late April, Antarctic sea ice extent surpassed the previous satellite-era record set in 2014, and for the entire month of May it has set daily record high ice extents. This makes May 2015 the record high month for the 1979 to 2015 period. As has been the case for several months, ice extent is unusually high in areas of the eastern Ross Sea – western Amundsen Sea, and in the northern and northeastern Weddell Sea. Unusually high extent has developed over the Davis Sea area of the far southern Indian Ocean.

Antarctic sea ice extent for May 2015 averaged 12.10 million square kilometers (4.67 million square miles). The linear rate of increase for May is now 2.88% per decade for the period 1979 to 2015.

Despite the record sea ice extent, air temperatures at the 925 millibar level (about 3,000 feet above the surface) remained generally above average for most of the continent and coastal areas of the surrounding ocean. Air temperatures were as much as 5 degrees Celsius (9 degrees Fahrenheit) above the 1981 to 2010 average over the West Antarctic ice sheet and central Ross Sea. The region of high ice extent near the northeastern Ross Sea had near-average air temperatures in the vicinity of the ice edge. Cooler than average temperatures were observed near the ice edge in the northeastern Weddell Sea (2 degrees Celsius, or 4 degrees Fahrenheit, below average) and Davis Sea (4 degrees Celsius, or 7 degrees Fahrenheit, below average). Air circulation patterns were variable for the month. The Southern Annular Mode, a north-south movement of the westerly wind belt that circles Antarctica, was in a near neutral state for the month as a whole.

Further reading

Bushuk, M., D. Giannakis, and A. J. Majda (2015). Arctic sea-ice reemergence: The role of large-scale oceanic and atmospheric variability. J. Climate, doi:10.1175/JCLI-D-14-00354.1, in press.

Bushuk, M. and D. Giannakis (2015). Sea-ice reemergence in a model hierarchy. Geophys. Res. Lett., doi:10.1002/2015GL063972, in press.

Schroeder, D., D.L. Feltham, D. Flocco and M. Tsmados, (2014). September Arctic sea ice minimum predicted by spring melt pond fraction. Nature Climate Change, doi:10.1038/nclimate2203.

Stroeve, J., E. Blanchard-Wrigglesworth, V. Guemas, S. Howell, F. Massonnet and S. Tietsche, (2015). Developing user-oriented seasonal sea ice forecasts in a changing Arctic. EOS, doi:10.1175/JCLI-D-14-00354.1, in press.

 

A double dip

After reaching its seasonal maximum on February 25, the beginning of the melt season was interrupted by late-season periods of ice growth, largely in the Bering Sea, Davis Strait and around Labrador. Near the end of March, extent rose to within about 83,000 square kilometers (32,000 square miles) of the February 25 value. The monthly average Arctic sea ice extent for March was the lowest in the satellite record.

Overview of conditions

sea ice extent map

Figure 1. Arctic sea ice extent for March 2015 was 14.39 million square kilometers (5.56 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Arctic sea ice extent for March 2015 averaged 14.39 million square kilometers (5.56 million square miles). This is the lowest March ice extent in the satellite record. It is 1.13 million square kilometers (436,000 square miles) below the 1981 to 2010 long-term average of 15.52 million square kilometers (6.00 million square miles). It is also 60,000 square kilometers (23,000 square miles) below the previous record low for the month observed in 2006.

Conditions in context

sea ice extent timeseries

Figure 2. The graph above shows Arctic sea ice extent as of April 5, 2015, along with daily ice extent data for four previous years. 2015 is shown in blue, 2014 in green, 2013 in orange, 2012 in brown, and 2011 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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The change in total Arctic sea ice extent for March is typically quite small. It tends to increase slightly during the first part of the month, reach the seasonal maximum, and then decline over the remainder of the month. Following the seasonal maximum recorded on February 25, this year instead saw a small decline over the first part of March, and then an increase, due largely to periods of late ice growth in the Bering Sea, Davis Strait and around Labrador. On March 26, extent had climbed to within 83,000 square kilometers (32,000 square miles) of the seasonal maximum recorded on February 25. Despite this late-season ice growth, analysts at the Alaska Ice Program report in their April 3 post that ice in the Bering Sea was very broken up.

March 2015 compared to previous years

sea ice trend graph

Figure 3. Monthly March ice extent for 1979 to 2015 shows a decline of 2.6% per decade relative to the 1981 to 2010 average.

Credit: National Snow and Ice Data Center
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The monthly average Arctic sea ice extent for March was the lowest in the satellite record. Through 2015, the linear rate of decline for March extent is 2.6% per decade.

Overview of the winter season

Figure 4. The plot shows Arctic air temperature anomalies at the 925 hPa level in degrees Celsius for March 2015. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division|  High-resolution image

Figure 4. The plot shows Arctic air temperature anomalies at the 925 hPa level in degrees Celsius for March 2015. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
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As discussed in our previous post, the winter of 2014/2015 was characterized by an unusual pattern of atmospheric circulation, with the jet stream lying well north of its usual location over Eurasia and the North Pacific, and then plunging southwards over eastern North America. This pattern was associated with unusually warm conditions extending across northern Eurasia, the Bering Sea and Sea of Okhotsk, Alaska and into the western part of the United States, contrasting with cold and snowy conditions over the eastern half of the United States. The record low seasonal maximum in ice extent recorded on February 25, 2015 was largely due to low extent in the unusually warm Bering Sea and Sea of Okhotsk. This pattern of atmospheric circulation and temperatures largely continued through March.

Recent work by Dennis Hartmann of the University of Washington suggests that this unusual jet stream pattern was driven, at least in part, by a particular configuration of sea surface temperatures over the tropical Pacific known as the North Pacific Mode, or NPM. The NPM pattern consists of above-average sea surface temperatures in the western Tropical Pacific that extend north and east towards the California coast and across the far northern Pacific Ocean. While the better-known El-Nino-Southern Oscillation (ENSO) pattern has been in a neutral state for the past few winters, the NPM has been in an extreme positive state since the summer of 2013.

The pattern of air temperatures seen this past winter has persisted through March; note the unusually warm conditions over northern Eurasia, Alaska and western North America, contrasting with unusually cold conditions over eastern North America.

Snow cover update

http://nsidc.org/arcticseaicenews/files/2015/04/snow.png

Figure 5. This map shows the rank of snow water equivalent measured at SNOTEL sites across the western U.S. A rank of 1 (black dots) corresponds to the lowest SWE in the SNOTEL record; a rank of 31 (magenta dots) is the highest.

Credit: Andrew Slater, NSIDC
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The unusual atmospheric circulation pattern just discussed also helps to explain the snow drought over the western United States. NSIDC scientist Andrew Slater maintains regular updates of western U.S. mountain snowpack conditions using data from the SNOTEL (snowpack telemetry) system – a network of automated sensors that measure snow water equivalent. The automated SNOTEL sites are complemented by snowcourses, where snow water equivalent is measured manually on a periodic basis.

Typically, the snowpack peaks around April 1. As seen in Figure 5, the April 1 snowpack over most of the western United States is far below average. At many sites, snow water equivalent is at historic lows for this time of year. Conditions are somewhat better along the Front Range of Colorado and in Arizona, Wyoming and Montana.

Record warmth in Antarctica

Air temperatures reached record high levels at two Antarctic stations last week, setting a new mark for the warmest conditions ever measured anywhere on the continent. On March 23, at Argentina’s base Marambio, a temperature of 17.4° Celsius (63.3° Fahrenheit) was reached, surpassing a previous record set in 1961 at a nearby base, Esperanza. The old record was 17.1° Celsius (62.8° Fahrenheit). However, Esperanza quickly reclaimed the record a few hours later on March 24, reaching a temperature of 17.5° Celsius (63.5° Fahrenheit).

The cause of these warm conditions is familiar to people living in mountainous regions: a foehn or chinook wind, in which air flows up and over a steep mountain ridge. On the windward side, moisture is wrung out of the air mass in the form of rain or snow. As the air descends on the leeward (downwind) side, it compresses and warms.

This airflow pattern is a key part of the climate conditions that led to past ice shelf disintegrations in the region, such as the dramatic break-up of the Larsen B Ice Shelf in 2002. Air pressure patterns during the event indicated a near-stationary high pressure center in the Drake Passage north of the Antarctic Peninsula, and a strong area of low pressure at the base of the Peninsula, favoring the foehn pattern. Events like this have been recorded by a network of sensors installed by the National Science Foundation LARISSA project.  This network recorded temperatures as high as 16.9° Celsius (62.4° Fahrenheit), westerly winds up to 23 meters per second (45 miles per hour), and a ~100 hour period of temperatures above freezing over the Larsen B area. A recent publication by a colleague at the Scripps Institute of Oceanography describes the impact of foehn or chinook patterns on ice shelf and sea ice stability in the region, making use of the network of Automated Meteorology-Ice-Geophysics Observing Systems (AMIGOS) and other weather sensors in the region.

Further reading

Cape, M., M. Vernet, P. Skvarca, S. Marinsek, T. Scambos, and E. Domack. 2015. Foehn winds link climate-driven warming to coastal cryosphere evolution in Antarctica. Jour. Geophys. Res., Atmospheres, submitted.

Scambos, T., R. Ross, T. Haran, R. Bauer, D.G. Ainley, K.-W. Seo, M. Keyser, A. De, Behar, D.R. MacAyeal. 2013. A camera and multisensor automated station design for polar physical and biological systems monitoring: AMIGOS. Journal of Glaciology, 59 (214), 303-314, doi: 10.3189/2013JoG12J170.

Vary January

Arctic sea ice extent was the third lowest for the month of January. Ice extent remained lower than average in the Bering Sea and Sea of Okhotsk, while ice in the Barents Sea was near average. Antarctic sea ice extent declined rapidly in late January, but remains high.

Overview of conditions

map of sea ice extent

Figure 1. Arctic sea ice extent for January 2015 was 13.62 million square kilometers (5.26 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Sea ice extent in January averaged 13.62 million square kilometers (5.26 million square miles). This is 910,000 square kilometers (351,000 square miles) below the 1981 to 2010 long-term average of 14.53 million square kilometers (5.61 million square miles), and 50,000 square kilometers (19,000 square miles) above the record low for the month observed in 2011.

This below-average Arctic extent is mainly a result of lower-than-average extent in the Bering Sea and the Sea of Okhotsk. On the Atlantic side, Barents Sea ice extent is near average. This is in sharp contrast to the general pattern seen since 2004 of below average extent in this region, but above average extent in the Bering Sea. Ice extent is also near average in the East Greenland Sea, Baffin Bay and the Labrador Sea.

Conditions in context

comparison of Arctic sea ice extent

Figure 2. The graph above shows Arctic sea ice extent as of February 2, 2015, along with daily ice extent data for four previous years. 2014 to 2015 is shown in blue, 2013 to 2014 in green, 2012 to 2013 in orange, 2011 to 2012 in brown, and 2010 to 2011 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

During most of January, the Arctic Oscillation (AO) was in a strongly positive phase. When the AO is in a positive phase, sea level pressure in the Arctic is particularly low, and sea level pressure is relatively high in the middle latitudes of the Northern Hemisphere. Variability in Arctic sea ice conditions is strongly influenced by the phase of the AO. Typically, during the positive phase of the AO, surface winds push ice away from the shores of Siberia, leading to the formation of more young, thin ice that is prone to melting out in summer. The positive phase also tends to increase the transport of thick, multiyear ice out of the Arctic through Fram Strait.

Air temperatures (at the 925 millibar level, about 3,000 feet above the surface) were mostly above average over most of the Arctic Ocean, with positive anomalies of 4 to 6 degrees Celsius (7 to 11 degrees Fahrenheit) over the Chukchi and Bering seas on the Pacific side of the Arctic, and also over the East Greenland Sea on the Atlantic side.

January 2015 compared to previous years

average monthly arctic sea ice extent

Figure 3. Monthly January ice extent for 1979 to 2015 shows a decline of 3.2% per decade relative to the 1981 to 2010 average.

Credit: National Snow and Ice Data Center
High-resolution image

Arctic sea ice extent for January was the third lowest in the satellite record. Through 2015, the linear rate of decline for January extent over the satellite record is 3.2% per decade.

Barents Sea ice variability

Barents Sea Ice Area and Ocean Tempearture

Figure 4. The graph shows Barents Sea ice area (blue line) and ocean temperatures in the Barents Sea Opening (red line) from 1980 to 2015. The sea ice area tends to be smaller for higher Atlantic water temperatures, with a lag of 1 to 2 years (note the reversed scale for Atlantic water temperatures). The data are based on Årthun et al. (2012), who find that the ocean temperature largely reflects changes in volume of Atlantic water inflow. Sea ice area anomalies are from the NASA Team algorithm (Cavalieri et al., 1996), provided by the National Snow and Ice Data Center. Ocean temperature has been sampled by the Institute of Marine Research (IMR), Norway, and is a section between Norway and Bear Island (BSO; 71.5-73.5N, 20E).

Credit: Ingrid Onarheim, Bjerknes Centre for Climate Research
High-resolution image

Variability in winter sea ice in the Barents Sea largely reflects ocean heat transport. The inflow of Atlantic water between Norway and Bear Island (the Barents Sea Opening or BSO) is the Barents Sea’s main oceanic heat source. Because there are no significant freshwater sources reaching the central Barents Sea, this warm Atlantic water extends to the surface and readily impacts the sea ice. This contrasts with the rest of the Arctic Ocean, where the Atlantic water lies well beneath the slightly fresher polar surface layer. The import of sea ice in the northern straits is also small, around 20% of the sea ice area exported southwards in the Fram Strait, meaning that the Barents Sea primarily consists of thin, first-year ice. Thus, periods with large volumes of warm Atlantic water entering into the Barents Sea are correlated with less sea ice formation and overall less sea ice extent.

Variations in winter ice extent in the Barents Sea are well correlated with variations in overall Arctic sea ice extent, as assessed over the satellite record. This winter is an exception. Sea ice extent in the Barents Sea is fairly high compared to recent years, while it is low for the Arctic as a whole. According to colleagues at the University of Bergen, this is due to a reduced overall inflow of Atlantic waters. A maximum in the ocean heat transport occurred in the mid 2000s, yet since then, the inflow has in general lessened, both along the Norwegian coast, through the Fram Strait, and through the Barents Sea Opening between Norway and Bear Island. Variations in Atlantic inflow is a focus of ongoing research at the Bjerknes Centre in Bergen, as well as in other research centers in Europe.

Antarctic sea ice declines rapidly, still high

Antarctic sea ice extent as of 2/2/2015

Figure 5a. The graph above shows Antarctic sea ice extent as of February 2, 2015, along with daily ice extent data for four previous years. 2014 to 2015 is shown in blue, 2013 to 2014 in green, 2012 to 2013 in orange, 2011 to 2012 in brown, and 2010 to 2011 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Antarctic sea ice extent reached record high levels for late December 2014 and early January 2015, peaking around January 10 at more than 2.5 million square kilometers (965,000 square miles) above the 1981 to 2010 average, and 1.05 million square kilometers (580,000 square miles) above the previous record (2014) for that date. As noted last month, the largest excursions are occurring in the northern Weddell Sea and the northern Ross Sea. After January 10, and particularly after January 19, sea ice extent dropped rapidly (~250,000 square kilometers, or 96,500 square miles, per day), and large areas of the northern Ross Sea became ice free. The northern Weddell region still has a very large ice extent relative to average conditions.

Antarctic wind and air temperature anomalies

Figure 5b. These images show Antarctic wind vector (top) and air temperature (bottom) anomalies for late December 2014 to early January 2015, compared to 1981 to 2010 averages.

Credit: NOAA ESRL Physical Sciences Division
High-resolution image

Weather conditions during late December and January help to explain these changes. In the northern Weddell Sea, southerly winds (more so than average) and cool conditions relative to the 1981 to 2010 average prevailed for late December and all of January, and sea ice there remained high relative to long-term averages for the month. For the northern Ross Sea, air temperatures at the 925 hPa level have been slightly above average for the entire period, but winds in this area shifted during January, from southerly (pushing ice outward) to northwesterly. The combination of northerly winds and slightly warm conditions seems to have reduced the ice extent anomaly significantly in this sector.

Further reading

Smedsrud, L.H., I. Esau, R. B. Ingvaldsen, T. Eldevik, P. M. Haugan, C. Li, V. S. Lien, A. Olsen, A. M. Omar, O. H. Otterå, B. Risebrobakken, A. B. Sandø, V. A. Semenov, and S. A. Sorokina. 2013. The role of the Barents Sea in the Arctic climate system.
Reviews of Geophysics, 51, doi:10.1002/rog.20017.

Årthun, M., T. Eldevik, L. H. Smedsrud, Ø. Skagseth, and R. B. Ingvaldsen. 2012.
Quantifying the Influence of Atlantic Heat on Barents Sea Ice Variability and Retreat. Journal of Climate, Volume 25, pp. 4736-4743, doi:10.1175/JCLI-D-11-00466.1.

Schauer, U. and A. Beszczynska-Möller. 2009. Problems with estimation and interpretation of oceanic heat transport – conceptual remarks for the case of Fram Strait in the Arctic Ocean, Ocean Sci., 5, 487–494.

Extremely ordinary

While the U.S. experienced extreme weather in November, conditions in the Arctic were fairly ordinary. Arctic sea ice in November followed a fairly average growth pace. Ice extent was near average over much of the Arctic with only the Chukchi Sea and Davis Strait showing below average ice conditions.

Overview of conditions

Arctic sea ice extent map

Figure 1. Arctic sea ice extent for November 2014 was 10.36 million square kilometers (4.00 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Sea ice extent in November averaged 10.36 million square kilometers (4.00 million square miles). This is 630,000 square kilometers (243,000 square miles) below the 1981 to 2010 long-term average of 10.99 million square kilometers (4.24 million square miles) and 520,000 square kilometers (201,000 square miles) above the record low for the month observed in 2006.

Arctic sea ice extent continued to increase throughout the month of November. By the end of the month, most of the Arctic Ocean was covered by ice, the exception being the Chukchi Sea that remained unusually ice free for this time of year. Ice also began to extend into Hudson Bay and Baffin Bay, although ice growth was slower than average in Davis Strait. The near-average ice conditions in the East Greenland, Barents and Kara seas have not been seen in the last few winters, and is the reason that overall extent for November is higher than in recent years.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of XXXXX XX, 20XX, along with daily ice extent data for four previous years. 201X is shown in blue, 201X in green, 201X in orange, 201X in brown, and 20XX in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2. The graph above shows Arctic sea ice extent as of November 30, 2014, along with daily ice extent data for four previous years. 2014 is shown in blue, 2013 in green, 2012 in orange, 2011 in brown, and 2010 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Sea ice extent grew 2.15 million square kilometers (830,000 square miles) during the month of November. This was about average for the month and substantially slower than observed in 2012. While the month started with 1.17 million square kilometers (452,000 square miles) more ice in 2014 than on November 1, 2012, by the end of the month, the difference between 2014 and 2012 had closed to only 416,000 square kilometers (161,000 square miles). The difference in November ice growth between 2012 and 2014 reflects the larger area of open water at the end of summer 2012. With more open water, there was a larger area for new ice to grow.

November 2014 compared to previous years

extent trend graph

Figure 3. Monthly November ice extent for 1979 to 2014 shows a decline of 4.7% per decade relative to the 1981 to 2010 average.

Credit: National Snow and Ice Data Center
High-resolution image

Arctic sea ice extent for November was the 9th lowest in the satellite record. Through 2014, the linear rate of decline for November extent over the satellite record is 4.7% per decade.

Arctic amplification and mid-latitude weather extremes

surface air temperatures

Figure 4. This plot of average surface air temperatures from November 17 to 19, 2014 over North America during a polar outbreak shows unusually cold air reaching down into the U.S. Temperatures are in degrees Kelvin. Blues and purples indicate sub-freezing temperatures.

Credit: NSIDC/NOAA ESRL Physical Sciences Divisionr
High-resolution image

Last month we discussed how the extra heat stored in ice-free areas of the ocean during recent summers is released back to the atmosphere as the ice begins to re-form, leading to amplified warming in the Arctic atmosphere. The impact of this warming and its potential impacts on mid-latitude weather patterns and extreme weather events is an active area of research.

This November has been particularly notable for severe weather in the U.S., with a very strong storm in the Bering Sea affecting the Aleutian Islands of western Alaska* (a remnant of Typhoon Nuri that tracked from the tropics through the Aleutians), record-setting low temperatures in the upper plains, and epic lake-effect snow near Buffalo, N.Y. Such individual events cannot be directly linked to climate change, let alone specifically to sea ice loss.

*Correction, December 16, 2014: Adjusted the wording here to make clear that the storm did not affect mainland Alaska, but only the Aleutians.

New research this year from Japanese scientists (Mori et al., 2014) provides support for the hypothesis, put forward by Jennifer Francis of Rutgers University and Steve Vavrus of the University of Wisconsin, that the warming Arctic is contributing to an increasing waviness of the jet stream with the potential for more extreme weather events, including cold outbreaks in the lower 48 U.S. and Eurasia that have been seen in recent years. However, while there is some evidence of this connection, it is not conclusive and many scientists remain skeptical of a link between Arctic sea ice and mid-latitude weather.

Antarctica watch

antarctic extent map

Figure 5. Antarctic sea ice extent for November 2014 was 16.63 million square kilometers (6.42 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic South Pole. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Antarctic sea ice has continued to decline at a faster-than-average pace (approximately 122,000 square kilometers, or 47,100 square miles per day through the month of October, compared to the average rate of 112,000 square kilometers or 43,200 square miles per day), and is now about 650,000 square kilometers (251,000 square miles) below the level for the date recorded in 2013. Currently ice extent remains about 700,000 square kilometers (270,000 square miles) higher than the 1981 to 2010 average for this time of year. Large reductions in the Bellingshausen Sea and the southern Indian Ocean were the main causes of the Antarctic-wide decrease, driven in large part by persistent northerly winds. Air temperatures over the Southern Ocean for the month were near average in nearly all areas. On the icy continent itself, cool conditions prevailed over the Antarctic Peninsula and West Antarctica (1 to 2 degrees Celsius, or 1.8 to 3.6 degrees Fahrenheit below average) while warm conditions were the rule in the Eastern Hemisphere section (2 to 4 degrees Celsius, or 3.6 to 7.2 degrees Fahrenheit above average).

 

Reference

Mori, M., M. Watanabe, H. Shiogama, J. Inoue, and M. Kimoto, 2014. Robust Arctic sea-ice influence on the frequent Eurasian cold winters in past decades. Nature Geoscience, vol. 7, pp. 869-873.