May saw above average temperatures over nearly all of the Arctic Ocean, Baffin Bay, and Greenland. Early sea ice retreat in the Bering Sea extended into the southern Chukchi Sea. Northern Baffin Bay and the Nares Strait have low ice cover. By month’s end, open water extended along the northeastern Alaskan and northwestern Canadian coasts, all well ahead of schedule. However, this was partly balanced by slower-than-average ice loss in the Barents Sea. At the end of May, Arctic sea ice daily extent stood at second lowest in the 40-year satellite record.

Overview of conditions

Figure 1. Arctic sea ice extent for May 2019 was 12.16 million square kilometers (4.70 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent averaged for May was 12.16 million square kilometers (4.70 million square miles). This is 1.13 million square kilometers (436,000 square miles) below the 1981 to 2010 average and 240,000 square kilometers (93,000 square miles) above the previous record low for the month set in May 2016. The month saw rapid ice loss in the Bering Sea and southern Chukchi Sea. During the second half of the month, an extended coastal polynya opened along the northwestern coast of the Beaufort Sea extending into the Mackenzie River Delta area. Visible MODIS imagery shows many large ice floes interspersed with open water along the ice edge and fracturing of ice further within the pack.

Although ice loss in the Barents Sea was rapid in early May, it subsequently slowed and extent slightly increased late in the month. There was nevertheless an overall ice retreat for May as a whole. Around mid-month, a polynya began to open at the north end of Baffin Bay, near the Nares Strait. At about this time, an ice arch that restrains southward ice drift in the Lincoln Sea began to fail, allowing transport of ice through the strait and creating a small polynya northwest of Greenland (discussed below). By the end of May, other polynyas started to form around the New Siberian Islands as well as Severnaya Zemlya, and open water began to develop along coastal regions in the Kara Sea and in northern Hudson Bay.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of June 3, 2019, along with daily ice extent data for four previous years and the record low year. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 in brown, 2015 in purple, and 2012 in dotted brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for May 2019. 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

Broadly following the pattern for April, air temperatures at the 925 hPa level (approximately 2,500 feet above the surface) for May were again well above average over nearly all of the Arctic Ocean. Along the western Greenland coast, a broad area north of Greenland, and westward north of the Canadian Archipelago, temperatures were as much as 7 degrees Celsius (13 degrees Fahrenheit) above the 1981 to 2010 reference average for the month. Over much of the remainder of the Arctic Ocean, temperatures were 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) above average. By contrast, over the Barents Sea as well as along the Laptev Sea coast, temperatures were near average or up to 2 degrees (4 degrees Fahrenheit) below average. As averaged for May, there was an area of high sea level pressure, an anticyclone, centered near the pole. This pattern drew warm air from the south into Baffin Bay and into the Arctic Ocean. Also, air under an anticyclone descends and warms. Both factors help to explain the unusually high temperatures over much of the Arctic Ocean.

May 2019 compared to previous years

Figure 3. Monthly May ice extent for 1979 to 2019 shows a decline of 2.74 percent per decade.

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

Overall, sea ice extent during May 2019 decreased by 1.49 million square kilometers (575,300 square miles). This was fairly close to the 1981 to 2010 average loss for the month. The linear rate of sea ice decline for May from 1979 to 2019 is 36,400 square kilometers (14,100 square miles) per year, or 2.74 percent per decade relative to the 1981 to 2010 average.

Ice arch break up in the Lincoln Sea

Figure 4. This NASA Worldview (download to view animation) image shows sea ice in the Nares Strait from April 19 to May 11. A new Worldview functions creates an animation using Aqua Moderate Imaging Spectroradiometer (MODIS) true color composite images.

Credit: NASA
High-resolution image

In most years (2007 being a notable exception), an ice arch forms during late autumn and winter at the north end of Nares Strait, the narrow passage that separates Greenland from Ellesmere Island. This arch acts as a barrier, preventing ice from the Arctic Ocean from drifting through the strait and into Baffin Bay. The arch typically breaks up in June or July, allowing ice to drift through the narrow channel. This year, the arch broke up by late March, much earlier than is typical. Since then, there has been a steady flow of ice through Nares Strait (download animation to view). Since 2000, only four other years appear to have had similar early breakups of the arch: 2007 (when no arch formed at all), 2008, 2010, and 2017 (Moore et al., 2018). Typically, strong wind events trigger the break up, but warm temperatures and thinner ice can also contribute.

Arctic sea ice variability linked to atmospheric temperature fluctuations

Figure 5. The top figure shows how the year-to-year sea ice area co-varies with mid-atmosphere temperatures (average of temperatures between 850 HPa to 400 HPa, or about 5,000 to 25,000 feet above sea level). The below bar graph provides the contributions of other suggested mechanisms. Combined, they account for about 25 percent of the sea ice variations. The direct influence of mid-atmosphere temperature fluctuations remains as the primary cause of year-to-year sea-ice variations.

Credit: NSIDC Sea Ice Index and ERA-Interim Reanalysis
High-resolution image

While Arctic sea ice extent is declining sharply, it is also highly variable from one year to the next. Scientists from the Max Planck Institute for Meteorology (MPI-M) and the University of Stockholm have proposed that this strong variability is closely related to fluctuations in the air temperature above the Arctic Ocean driven by atmospheric heat transport into the Arctic from lower latitudes. In contrast to previous assumptions, they argue that other factors, such as the ice-albedo feedback, cloud and water vapor feedbacks, and oceanic heat transported into the Arctic together explain only 25 percent of the year-to-year sea ice extent variations. Most of the sea ice variations are thus directly caused by mid-atmospheric temperature conditions; this is evident in both observational data and climate models. Their study implies that year-to-year fluctuations in sea ice extent are easier to understand than previously thought. However, their study also suggests that it may be more difficult to predict the summer extent of Arctic sea ice from one year to the next, because the problem of predicting atmospheric heat transport is closely related to the challenges of long-term weather forecasting.

Antarctic sea ice extent exceptionally low in the Weddell and Amundsen Seas

Figure 6. Antarctic sea ice extent for May 2019 was 8.80 million square kilometers (3.40 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Antarctic sea ice extent continues to climb toward its seasonal maximum, which is expected in late September or early October. At the end of May, Antarctic sea ice extent was very close to record daily lows over the period of satellite observations, previously set for the month in 1980. Unusually low ice extent in the eastern Weddell Sea and northern Amundsen Sea are responsible for the low overall total extent, with smaller areas of open water in the eastern Wilkes Land coastal region and southwestern Indian Ocean (Cosmonaut Sea). Slightly above average sea ice extent is present in the north-central Ross Sea and northwestern Weddell Sea.

References

Kwok, R., L. Toudal Pedersen, P. Gudmandsen, and S. S. Pang. 2010. Large sea ice outflow into the Nares Strait in 2007. Geophysical Research Letters. doi: 10.1029/2009GL041872.

Moore, G. W. K. and K. McNeil. 2018. The early collapse of the 2017 Lincoln Sea ice arch in response to anomalous sea ice and wind forcing. Geophysical Research Letters. doi:10.1029/2018GL078428.

Olonscheck, D., T. Mauritsen, and D. Notz. 2019. Arctic sea-ice variability is primarily driven by atmospheric temperature fluctuations. Nature Geoscience. doi:10.1038/s41561-019-0363-1.

April reached a new record Arctic low sea ice extent. Sea ice loss was rapid in the beginning of the month because of declines in the Sea of Okhotsk. The rate of ice loss slowed after early April, due in part to gains in extent in the Bering and Barents Seas. However, daily ice extent remained at record low levels throughout the month.

Overview of conditions

Figure 1. Arctic sea ice extent for April 2019 was 13.45 million square kilometers (5.19 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for April 2019 averaged 13.45 million square kilometers (5.19 million square miles). This was 1.24 million square kilometers (479,000 square miles) below the 1981 to 2010 long-term average extent and 230,000 square kilometers (89,000 square miles) below the previous record low set in April 2016.

Rapid ice loss occurred in the Sea of Okhotsk during the first half of April; the region lost almost 50 percent of its ice by April 18. Although sea ice was tracking at record low levels in the Bering Sea from April 1 to 12, the ice cover expanded later in the month. Elsewhere, there was little change except for small losses in the Gulf of St. Lawrence, the southern part of the East Greenland Sea, and southeast of Svalbard. In addition, open water areas developed along coastal regions of the Barents Sea. The ice edge expanded slightly east of Novaya Zemlya.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of May 1, 2019, along with daily ice extent data for four previous years and 2012. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 in brown, 2015 in purple, and 2012 in dotted brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for April 2019. 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

Air temperatures at the 925 hPa level (approximately 2,500 feet above the surface) were above average across the Arctic during the first two weeks of April, especially over the East Siberian Sea and the Greenland Ice Sheet where air temperatures were as much as 9 degrees Celsius (16 degrees Fahrenheit) above average (Figure 2b). Elsewhere, 925 hPa temperatures were between 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) above average, including the Sea of Okhotsk where ice loss early in the month was especially prominent. These relatively warm conditions were linked to a pattern of high sea level pressure over the Beaufort Sea paired with low sea level pressure over Alaska, Siberia, and the Kara and Barents Seas. This drove warm air from the south over the East Siberian Sea. Similarly, high pressure over Greenland and the North Atlantic, coupled with low sea level pressure within Baffin Bay, helped usher in warm air over southern Greenland from the southeast.

During the second half of the month, temperatures remained above average over most of the Arctic Ocean, and up to 8 degrees Celsius (14 degrees Fahrenheit) above average over the East Greenland Sea. However, temperatures were 1 to 5 degrees Celsius (2 to 9 degrees Fahrenheit) below average over the Bering Sea, and up to 8 degrees Celsius (14 degrees Fahrenheit) below average over the Canadian Arctic Archipelago. Air temperatures were slightly below average in the Kara Sea.

April 2019 compared to previous years

Figure 3. Monthly April ice extent for 1979 to 2019 shows a decline of 2.64 percent per decade.

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

The 1979 to 2019 linear rate of decline for April ice extent is 38,800 square kilometers (15,000 square miles) per year, or 2.64 percent per decade relative to the 1981 to 2010 average.

Sea ice age update

Figure 4. The top maps compare Arctic sea ice age for (a) April 8 to 14, 1984, and (b) April 9 to 15, 2019. The time series (c) of mid-April sea ice age as a percentage of Arctic Ocean coverage from 1984 to 2019 shows the nearly complete loss of 4+ year old ice; note the that age time series is for ice within the Arctic Ocean and does not include peripheral regions where only first-year (0 to 1 year old) ice occurs, such as the Bering Sea, Baffin Bay, Hudson Bay, and the Sea of Okhotsk.

Credit: W. Meier, NSIDC
High-resolution image

Younger sea ice tends to be thinner than older ice. Therefore, sea ice age provides an early assessment of the areas most susceptible to melting out during the coming summer. The Arctic sea ice cover continues to become younger (Figure 4), and therefore, on average, thinner. Nearly all of the oldest ice (4+ year old), which once made up around 30 percent of the sea ice within the Arctic Ocean, is gone. As of mid-April 2019, the 4+ year-old ice made up only 1.2 percent of the ice cover (Figure 4c). However, 3 to 4-year-old ice increased slightly, jumping from 1.1 percent in 2018 to 6.1 percent this year. If that ice survives the summer melt season, it will somewhat replenish the 4+ year old category going into the 2019 to 2020 winter. However, there has been little such replenishment in recent years.

The sea ice age data products were recently updated through 2018 (Version 4, Tschudi et al., 2019). Data is available here. In addition, an interim QuickLook product that will provide preliminary updates every month is in development.

Changing ice and sediment transport

Figure 5a. This map shows the main sea ice drift patterns.
Figure 5b. This illustration shows how sediments can be ingrained into the newly forming sea ice.
Figure 5c. This graph shows the probability that newly formed ice in the winter will survive the summer.

Credit: T. Krumpen
High-resolution image

Figure 5d. This image shows sediment-rich sea ice in the Transpolar Drift Stream. A crane lowers two researchers from the decks of the icebreaker RV Polarstern to the surface of the ice to collect samples.

Photo Credit: R. Stein, Alfred Wegener Institut
High-resolution image

Scientists from the Alfred Wegener Institut (AWI) monitored and analyzed sea ice motion using satellite data from 1998 to 2017 and concluded that only 20 percent of the sea ice that forms in the shallow Russian seas of the Arctic Ocean now reaches the central Arctic Ocean to join the Transpolar Drift Stream (Figures 5a and b). The Russian seas, including the Kara, Laptev, and East Siberian Seas, are considered the ice nursery of the Arctic. The remaining 80 percent of this first-year ice melts before it has a chance to leave this nursery. Prior to the year 2000, that number was about 50 percent (Figure 5c).

These conclusions find support from sea ice thickness observations in Fram Strait, which is fed by the Transpolar Drift Stream. AWI scientists regularly gather ice thickness data in Fram Strait as part of their IceBird program. The ice now leaving the Arctic Ocean through the Fram Strait is, on average, 30 percent thinner than it was 15 years ago. There are two reasons for this. First, winters are warmer and the melt season now begins much earlier than it used to. Second, much of this ice no longer forms in the shallow seas, but much farther north. As a result, it has less time to thicken from winter growth and/or ridging as it drifts across the Arctic Ocean.

These changes in transport and melt affect biogeochemical fluxes and ecological processes in the central Arctic Ocean. For example, in the past, the sea ice that formed along the shallow Russian seas transported mineral material, including dust from the tundra and steppe, to the Fram Strait (Figure 5d). Today, the melting floes release this material en route to the central Arctic Ocean. Far less material now reaches the Fram Strait and it is different in composition. This finding is based on two decades of data sourced from sediment traps maintained in the Fram Strait by AWI biologists. Instead of Siberian minerals, sediment traps now contain remains of dead algae and microorganisms that grew within the ice as it drifted.

Putting current changes into longer-term perspective

Figure 6. This map shows Arctic regions used in the Walsh et al. study and how much each area’s September extent contributes to the total September sea ice extent. The top number gives the percentage (as squares of correlations, or R2) when the raw 1953 to 2013 ice extent time series is used. The bottom number (bold) gives what the percentage drops to after the time series data have been detrended. For example, about 70 percent of the September Arctic-wide extent number is explained by the September extent in the seas north of Alaska, but that drops to about 20 percent once the trends have been removed.

Credit: Walsh et al., 2019, The Cryosphere
High-resolution image

While changes in sea ice extent over the past several decades are usually shown as linear trends, they can mask important variations and changes. A recent study led by John Walsh at University Alaska Fairbanks compared various trend-line fits to sea ice extent time series back to 1953, for the Arctic as a whole and various sub-regions. This data set extends the satellite record by using operational ice charts and other historical sources (Walsh et al., 2016). They found that a two-piece linear fit with a break point in the 1990s provides a more meaningful basis for calculations of sea ice departures from average conditions and their persistence, rather than a single trend line computed over the period 1953 to the present. Persistence of sea ice departures from average conditions represents the memory of the system, which can be used to forecast sea ice conditions a few months in advance. September Arctic-wide ice extent can also be predicted with some limited skill when the data include the trend. However, this apparent skill largely vanishes when the trend is removed from the data using the two-piece linear fit. This finding is consistent with the notion of a springtime predictability barrier, such that springtime sea ice conditions are usually not a strong predictor of the summer ice cover because atmospheric circulation patterns in summer erode this memory in the system. For example, despite the extensive coverage of fairly young—and hence thin—ice this spring, cool summer weather conditions may limit melt, leading to a higher September ice extent than might otherwise be expected.

April snow melt in Greenland—notable but not unusual

Temperatures were well above average over Greenland for much of April but were still below freezing except near the coast. Satellite data indicate that there was a small area surface melt on the southeastern coastal part of the ice sheet early in the month. In the last week of April, melt became more extensive, spreading further north on the east coast and starting on the west coast. While interesting, this is not especially unusual. Most years of the past decade have some surface melt in April. In 2012 and 2016, strong melt events occurred in April that covered a much larger area than in 2019. NSIDC is now tracking Greenland surface melt for 2019 on a daily basis.

Further reading

Krumpen, T., H. J. Belter, A. Boetius, E. Damm, C. Haas, S. Hendricks, M. Nicolaus, E.-M. Nöthig, S. Paul, I. Peeken, R. Ricker, and R. Stein. 2019. Arctic warming interrupts the Transpolar Drift and affects long range transport of sea ice and ice-rafted matter. Scientific Reports. doi:10.1038/s41598-019-41456-y.

Tschudi, M. A., W. N. Meier, and J. S. Stewart. 2019. An enhancement to sea ice motion and age products. The Cryosphere Discussion, in review. doi:10.5194/tc-2019-40.

Walsh, J. E., W. L. Chapman, and F. Fetterer. 2015, updated 2016. Gridded Monthly Sea Ice Extent and Concentration, 1850 Onward, Version 1. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi:10.7265/N5833PZ5.

Walsh, J. E., J. S. Stewart, and F. Fetterer. 2019. Benchmark seasonal prediction skill estimates based on regional indices. The Cryosphere. doi:10.5194/tc-13-1073-2019.

The Alfred Wegener Institute (AWI) IceBird Program

Arctic sea ice extent appears to have reached its maximum extent on March 13, marking the beginning of the sea ice melt season. Since the maximum, sea ice extent has been tracking at record low levels. In the Bering Sea, extent increased through the middle of March after setting record lows—only to drop sharply again.

Overview of conditions

Figure 1. Arctic sea ice extent for March 2019 was 14.55 million square kilometers (5.62 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for March averaged 14.55 million square kilometers (5.62 million square miles), tying with 2011 for the seventh lowest extent in the 40-year satellite record. This is 880,000 square kilometers (340,000 square miles) below the 1981 to 2010 average and 260,000 square kilometers (100,400 square miles) above the lowest March average, which occurred in 2017.

The Bering Sea, which had been nearly ice free at the beginning of March, saw gains in extent through the middle of the month. However, those gains were short lived as extent dropped sharply during the last week of March. The Bering Sea typically reaches its maximum ice extent in late March or early April. This year, the maximum occurred in late January and was 34.5 percent below the 1981 to 2010 average maximum. These late-March sea ice extent losses in the Bering Sea accelerated the decline of total Arctic sea ice extent. By April 1, Arctic extent was at a record low for that date.

Other signs of spring are emerging. A substantial amount of ice retreated in the Gulf of St. Lawrence and the Sea of Okhotsk, as well as in the Barents Sea. Late in the month, small areas of open water were observed in sea ice fields from the University of Bremen, particularly near the shores of the Laptev and Kara Seas, the Sea of Okhotsk, and off of northwestern Alaska.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of April 2, 2019, along with daily ice extent data for four previous years and the record low year. 2018 to 2019 is shown in blue, 2017 to 2018 in green, 2016 to 2017 in orange, 2015 to 2016 in brown, 2014 to 2015 in purple, and 2011 to 2012 in dotted brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for March 2019. 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

Overall, Arctic weather in March featured low pressure and above average temperatures. Two low pressure centers at sea level, one over the Bering Sea and the other over the Barents Sea, dominated the atmospheric circulation pattern. Low pressure over the Barents Sea brought cloudy and cool conditions to the immediate region, but also funneled warm air into the central Arctic Ocean. Air temperatures at the 925 mb level (about 2500 feet above sea level) were above average over most of the Arctic region, with the exception in the Atlantic sector of the Arctic Ocean. Temperatures were far above average, locally exceeding 10  degrees Celsius (18 degrees Fahrenheit), over the Beaufort Sea, northeast Alaska, and northwest Canada.

The pattern of overall low pressure across the Arctic in March was manifested as a persistent positive phase of the Arctic Oscillation (AO), a pattern that started during the second week of February. A positive AO in winter has in the past favored low September ice extent. This is in part due to a wind pattern tending to advect older, thicker ice out of the Arctic through the Fram Strait. The wind pattern associated with the positive AO also tends to pull ice away from the Siberian coast, resulting in thinner ice in the region that readily melts out during summer. However, with the overall thinning of the Arctic ice cover, the relationship between winter AO phase and September sea ice extent is not as clear as it used to be.

March 2019 compared to previous years

Figure 3. Monthly March ice extent for 1979 to 2019 shows a decline of 2.7 percent per decade.

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

The net change in sea ice extent between the beginning and end of March was small, which is typical for the month. Sea ice extent increased during the first part of the month to the annual maximum on March 13 and then declined through the remainder of the month.

The 1979 to 2019 linear rate of decline for March ice extent is 41,700 square kilometers (16,100 square miles) per year, or 2.7 percent per decade relative to the 1981 to 2010 average.

Winter recap

Figure 4. This plot shows average sea level pressure in the Arctic in millibars (hPa) from December 1, 2018 to March 31, 2019. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
High-resolution image

Moderation marked the 2018 to 2019 winter. Air temperatures at the 925 mb level were average to slightly above average over most of the Arctic Ocean, with only the southern Beaufort Sea being especially warm with temperatures 5 degrees Celsius (9 degrees Fahrenheit) higher than average.

Below average pressures at sea level dominated over the Bering Sea and much of the Eurasian side of the Arctic Ocean (Figure 4). Circulation patterns, however, were not especially unusual and there were no pronounced short-term heat waves of the type observed in recent winters. For much of the Arctic, sea ice extent was near average through most of the winter. As noted in a previous post, the most compelling feature of the winter was the substantial ice loss during February and early March in the Bering Sea, leading to nearly ice-free conditions.

Snow on sea ice

Figure 5a. This graph shows the annual volume of snow on sea ice from 1981 to 2016 based on reanalysis fields from NASA Modern-Era Retrospective analysis for Research and Applications-2 (MERRA-2) in blue and the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Intermin (ERA-I) in green.

Credit: J. Stroeve, NSIDC
High-resolution image

Figure 5b. The top map of the Arctic shows April trends in snow depth (in centimeters/year) from 1981 to 2016 based on NASA Modern-Era Retrospective analysis for Research and Applications-2 (MERRA-2). The bottom map of the Arctic shows April trends in snow depth (in centimeters/year) from 1981 to 2016 based on the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim (ERA-I). The total volume of accumulation is measured from August through July, starting in the 1980 to 1981 winter.

Credit: Stroeve et al., 2019, Journal of Geophysical Research-Oceans
High-resolution image

With a general trend toward later sea ice formation in autumn and winter and earlier melt in spring and summer, the time period for snow accumulation on the sea ice is changing. However, snow on sea ice is something that satellites do not measure well. As a result, several different approaches have been used to assess snow on sea ice, ranging from using atmospheric reanalysis precipitation forecasts and applying simple temperature thresholds to simulating physical processes impacting snow on sea ice (e.g., wind redistribution, melt, snow compaction) using sophisticated models. A new model (SnowModel) was recently developed for sea ice applications by colleagues at Colorado State University, and is now providing daily snow depth and density estimates from 1980 onwards. A key challenge is that different atmospheric reanalyses, which are used as input to the model, depict different amounts of precipitation. However, regardless of which reanalysis is used, from newer systems such as the NASA Modern-Era Retrospective analysis for Research and Applications-2 (MERRA-2) to older systems, such as the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim (ERA-I), the increasing open water season has reduced the amount of annual snow being accumulated on the sea ice (Figure 5a and 5b). However, there is a lot of spatial variability in trends. There are trends toward shallower April snow depth over the coastal seas and trends toward deeper snow  over the central Arctic Ocean. Snow on sea ice plays several important roles such as influencing rates of thermodynamic ice growth each winter, melt pond development in summer, and melt water input to the upper ocean. Snow on sea ice also has important biological consequences by changing the amount of sunlight able to penetrate the ice.

Antarctic autumn—slow rise

As noted in last month’s post, Antarctica’s annual minimum extent occurred on March 1, the seventh lowest in the satellite record. Since the minimum, ice extent has increased at a slower-than-average pace, remaining well below the inter-decile (10 to 90 percent) range of past early autumn extents. Sea ice growth during March 2019 has been greatest in the central Ross Sea and northeastern Weddell Seas, with significant ice retreat continuing in the southern Bellingshausen Sea. In keeping with the relatively slow ice growth, air temperatures at the 925 mb level have been 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) above the 1981 to 2010 average along much of the Antarctica coast from Wilkes Land eastward to the Ross, Amundsen, Bellingshausen, and Peninsula regions. Temperatures along the Dronning Maud Land coast have been 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) below average. The atmospheric circulation at sea level has been characterized by three regions of higher than average pressure interspersed with areas of lower than average pressure, termed a wave-3 pattern by climate scientists. In particular, low pressure in the Amundsen Sea area and high pressure in the Drake Passage (between South American and the Antarctic Peninsula) produced strong winds from the northwest along the southern Peninsula, driving sea ice retreat there while other regions generally saw growth in sea ice extent.

Further reading

Stroeve, J., G. E. Liston, S. Buzzard, A. Barrett, M. Tschudi, M. Tsamados and J. S. Stewart. 2019. A lagrangian snow-evolution system for sea ice applications. Journal Geophysical Research-Oceans, submitted.

Liston, G. E., C. Polashenski, A. Roesel, P. Itkin, J. King, I. Merkouriadi and J. Haapala. 2018. A distributed snow-evolution model for sea-ice applications (SnowModel). Journal Geophysical Research-Oceans. doi.org/10.1002/2017JC013706.

Arctic sea ice appears to have reached its annual maximum extent on March 13, tying with 2007 for seventh lowest in the 40-year satellite record. The 2019 maximum sea ice extent is the highest since 2014. NSIDC will post a detailed analysis of the 2018 to 2019 winter sea ice conditions in our regular monthly post in early April.

Overview of conditions

Figure 1. Arctic sea ice extent for March 13, 2019 was 14.78 million square kilometers (5.71 million square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

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

On March 13, 2019, Arctic sea ice likely reached its maximum extent for the year, at 14.78 million square kilometers (5.71 million square miles), the seventh lowest in the 40-year satellite record, tying with 2007. This year’s maximum extent is 860,000 square kilometers (332,000 square miles) below the 1981 to 2010 average maximum of 15.64 million square kilometers (6.04 million square miles) and 370,000 square kilometers (143,000 square miles) above the lowest maximum of 14.41 million square kilometers (5.56 million square miles) set on March 7, 2017. Prior to 2019, the four lowest maximum extents occurred from 2015 to 2018.

The date of the maximum this year, March 13, was very close to the 1981 to 2010 median date of March 12.

Table 1. Ten lowest maximum Arctic sea ice extents (satellite record, 1979 to present)

A recent paper (Meier and Stewart, 2019) describes the level of accuracy in NSIDC ice extent estimates, with the aim of improving annual minimum and maximum ranking of extents and to determine which years are close enough to be considered tied. For the Arctic maximum, which typically occurs in March, the uncertainty range is ~34,000 square kilometers (13,000 square miles), meaning that extents within this range must be considered effectively equal. The 2019 maximum extent is only 10,000 square kilometers (3,900 square miles) higher than the 2007 maximum, which is within this uncertainty range. Thus, we designate the 2007 and 2019 maximum extents as equal. As is shown in Table 1, other years have also been ascribed tied rankings. NSIDC scientists will rank future maximums and minimums using these criteria.

Final analysis pending

Please note this is a preliminary announcement of the sea ice maximum. At the beginning of April, NSIDC scientists will release a full analysis of winter conditions in the Arctic, along with monthly data for March.

Further reading

Meier, W. N., and J. S. Stewart. 2019. Assessing uncertainties in sea ice extent climate indicators. Environmental Research Letters, 14, 035005. doi:10.1088/1748-9326/aaf52c.

Arctic sea ice extent for February 2019 was the seventh lowest in the satellite record for the month, tying with 2015. So far this winter, sea ice extent has remained above the 2017 record low maximum. Extent in the northern Barents Sea, which has been quite low in recent years from “Atlantification,” is closer to average this February. Extent is very low in the Bering Sea at the end of February after unusual ice loss throughout the month. In Antarctica, the sea ice minimum may have been reached on both February 28 and March 1.

Overview of conditions

Figure 1a. Arctic sea ice extent for February 2019 was 14.40 million square kilometers (5.56 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for February 2019 averaged 14.40 million square kilometers (5.56 million square miles). This was 900,000 square kilometers (347,000 square miles) below the 1981 to 2010 long-term average extent, and 450,000 square kilometers (174,000 square miles) above the record low for the month set in February 2018. For the Arctic as a whole, February 2019 tied with 2015 for the seventh lowest average February extent in the 1979 to 2019 satellite record.

The daily average ice growth rate of 19,400 square kilometers (7,500 square miles) was near the long term average of 20,200 square kilometers (7,800 square miles). Ice growth during February primarily occurred in the Barents Sea and in the Sea of Okhotsk. Some ice growth was also observed in the Labrador Sea. Recent years have seen reduced ice coverage in the northern Barents Sea related to “Atlantification”—a greater influence of warm waters brought in from the Atlantic (see previous post). Sea ice extent toward the end of February 2019, however, was much closer to average in this region. By sharp contrast, sea ice extent drastically retreated in the Bering Sea in February and continues to as of this post.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of March 4, 2019, along with daily ice extent data for four previous years and the record low year. 2018 to 2019 is shown in blue, 2017 to 2018 in green, 2016 to 2017 in orange, 2015 to 2016 in brown, 2014 to 2015 in purple, and 2011 to 2012 in dotted brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for February 2019. 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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Arctic temperatures at the 925 hPa level (approximately 2500 feet above the surface) were from 4 to 10 degrees Celsius (7 to 18 degrees Fahrenheit) above the 1981 to 2010 average for a region extending from the Bering Sea, through the Beaufort Sea, and into the Canadian Arctic Archipelago (Figure 2b). This is consistent with a pattern for the month of low pressure at sea level centered over the western Bering Sea, and high pressure centered over northwestern Canada (Figure 4b). Low pressure dominated both the central Arctic Ocean and the northern North Atlantic. As such, it comes as no surprise that the Arctic Oscillation index was positive overall for the month.

February 2019 compared to previous years

Figure 3. Monthly February ice extent for 1979 to 2019 shows a decline of 3.0 percent per decade.

Credit: National Snow and Ice Data Center
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Overall, sea ice extent during February 2019 increased by 543,000 square kilometers (210,000 square miles). This was fairly close to the 1981 to 2010 average increase for the month. The linear rate of sea ice decline for February is 46,300 square kilometers (17,900 square miles) per year, or 3.0 percent per decade relative to the 1981 to 2010 average.

Ice loss in the Bering Sea

Figure 4a. This graph shows the sharp decline in sea ice extent in the Bering Sea starting at the end of January and continuing as of this post. The inset map in the top left compares sea ice extent at the beginning of January 27 and at the end of March 3, 2019.

Credit: W. Meier, National Snow and Ice Data Center
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Figure 4b. This plot shows average sea level pressure in the Arctic in millibars (or hPa) for February 2019. Yellows and reds indicate high air pressure; blues and purples indicate low air pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
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As noted above, sea ice in the Bering Sea region is the most remarkable Arctic feature this month. On average, Bering sea ice extent increases until late March or early April. The ice in the region is volatile, responding to winds and waves. Extent often fluctuates during the winter when thin ice near the edge moves north or south and melts or grows. However, this year is quite extreme. From January 27 through March 3, extent decreased from 566,000 square kilometers (219,000 square miles) to 193,000 square kilometers (74,500 square miles), roughly equivalent to the size of Montana (Figure 4). A similar ice loss occurred last year, but 2018 and 2019 appear to be extreme in the satellite record. As of the beginning of March, the 2019 Bering Sea ice extent was the lowest in the satellite record for this time of year.

A major cause of the ice loss is the strong low pressure in the Bering Sea and the high pressure over northwestern Canada (Figure 4b). Strong winds between these pressure centers drew warm air into the region from the south, inhibiting ice growth in the Bering Sea while also pushing ice to the north. Storms also broke up large areas of ice near the ice edge and reduced the sea ice extent. Warmer than average sea surface temperatures have also been observed in the region.

An early look at sea ice freeboard from ICESat-2

Figure 5. These maps show preliminary sea ice freeboard (height of snow or ice surface above the ocean) from two weeks of ICESat-2 data acquired in October 2018. Note that both the spatial scale and the vertical scale are different for the two maps.

Credit: R. Kwok, Jet Propulsion Laboratory
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Colleague Ron Kwok of the Jet Propulsion Laboratory in Pasadena, CA, provided a first look of Arctic sea ice freeboard from the NASA Ice, Cloud and land Elevation Satellite 2 (ICESat-2) at the Fall 2018 American Geophysical Union conference. Freeboard represents the height of the top of the ice or snow above the adjacent ocean surface. Figure 5 shows the maps produced for both the Arctic and the Antarctic from the first two weeks of preliminary data from the satellite, October 14 to 28, 2018.

Freeboard measurements can be used to estimate sea ice thickness and volume, given certain assumptions. While in general freeboard and ice thickness increase and decrease together, the exact conversion from one to the other depends very much on snow thickness, snow and ice density, and degree of surface melt (if any). These maps are based on ~210 orbits using a single laser track from one of the six ICESat-2 laser profiles, smoothed to a 25-kilometer (15.5-mile) running average of the difference between snow and sea ice cover height, and ocean surface height. The ocean surface height is measured in ice-free ocean areas in gaps, or leads, within the sea ice.

Note how for the Arctic ICESat-2 captures the expected pattern of higher freeboard (thicker ice) north of the coast of the Canadian Arctic Archipelago and Greenland and lower freeboard (thinner ice) on the Eurasian side of the Arctic. As also expected, there is little thick ice (i.e. few areas with high freeboard) in Antarctica which consists of mostly first-year ice (less than 1 year old); the obvious exceptions are the areas of high freeboard in the northwestern Weddell Sea and along the northern coast of West Antarctica (Bellingshausen and Amundsen seas) where some older sea ice persists.

ICESat-2 data will be distributed by the NASA Snow and Ice Distributed Active Archive Center (DAAC) at NSIDC and will be available to the public soon.

Antarctic minimum sea ice extent was likely reached on February 28 and March 1

After plummeting in late December to record daily lows in sea ice extent, Antarctica’s melt slowed significantly in January and February, reaching its likely minimum of 2.47 million square kilometers (954,000 square miles) on both February 28 and March 1. This is the seventh lowest extent in the satellite record.

Sea ice extent has been particularly low in the central and eastern Weddell Sea and in the eastern Ross Sea, but above average ice extent remains along the East Antarctic coastline and the Bellingshausen Sea. Temperatures in the sea ice areas surrounding Antarctica have been near average to slightly below average at 1 degree Celsius to -2 degrees Celsius (34 degrees Fahrenheit to 28 degrees Fahrenheit), except in the Central Pacific/Ross Sea region where temperatures have been up to 3 degrees Celsius (5 degrees Fahrenheit) above the 1981 to 2010 average.

Further reading

Anchorage Daily: “Bering Sea ice is at an ‘unprecedented’ low right now”

In January 2019, a pattern of high-altitude winds in the Arctic, better known as the polar vortex, weakened, sweeping frigid air over North America and Europe in the second half of the month. Arctic sea ice extent remained well below average, but temperatures in the far north were closer to average than in past years.

Overview of conditions

Figure 1. Arctic sea ice extent for January 2019 was 13.56 million square kilometers (5.24 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for January averaged 13.56 million square kilometers (5.24 million square miles). This was 860,000 square kilometers (332,000 square miles) below the 1981 to 2010 long-term average sea ice extent, and 500,000 square kilometers (193,000 square miles) above the record low for the month set in January 2018. January 2019 was the sixth lowest January extent in the 1979 to 2019 satellite record.

The average rate of daily ice growth of 51,200 square kilometers (19,800 square miles) was faster than the long-term average. Ice growth primarily occurred in the Bering Sea and Sea of Okhotsk in the Pacific sector as well as in the Labrador and Kara Seas. Some ice spread to the northeast of Svalbard, while retreating slightly to the northwest of these islands. Total ice extent was tracking at eighth lowest on January 31, with below average extent in nearly all sectors of the Arctic.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of February 5, 2019, along with daily ice extent data for four previous years and the record low year. 2018 to 2019 is shown in blue, 2017 to 2018 in green, 2016 to 2017 in orange, 2015 to 2016 in brown, 2014 to 2015 in purple, and 2012 to 2013 in dotted brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for January 2019. 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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Figure 2c. This plot shows average sea level pressure in the Arctic in millibars (hPa) for January 2019. Yellows and reds indicate high air pressure; blues and purples indicate low average air pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
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Arctic temperatures were only slightly above average, contrasting recent Januaries when very warm conditions prevailed. Daily 2 meter air temperatures for the Arctic averaged above 80 degrees North from the Danish Meteorological Institute were just a few degrees above the 1958 to 2002 average, whereas in 2018, temperatures ranged from 4 to 12 degrees Celsius (7 to 22 degrees Fahrenheit) above average. Looking at the 925 hPa level (approximately 2,500 feet above the surface; Figure 2b), temperatures of 1 to 2.5 degrees Celsius (2 to 4.5 degrees Fahrenheit) above the 1981 to 2010 average were the rule over the Beaufort Sea and Canadian Arctic Archipelago, and over the Bering Sea. However, part of the Atlantic side of the Arctic had temperatures near or slightly below average for the month. The atmospheric circulation pattern was unusual, with above average pressure at sea level over a broad area including northern Canada, Greenland, and the northern North Atlantic, and a broad area of below average pressure along the Russian and Siberian Arctic coast. Low pressure also prevailed over the northern Pacific and Bering Sea (Figure 2c).

January 2019 compared to previous years

Figure 3. Monthly January ice extent for 1979 to 2019 shows a decline of 3.2 percent per decade.

Credit: National Snow and Ice Data Center
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Overall, sea ice extent during January 2019 increased by 1.59 million square kilometers (614,000 square miles). This was 270,000 square kilometers (104,000 square miles) above the 1981 to 2010 average rate for the month. The linear rate of sea ice decline for January was 46,700 square kilometers (18,000 square miles) per year, or 3.2 percent per decade relative to the 1981 to 2010 average.

Cold shoulder

Figure 4. The left image shows atmosphere winds (70 millibars, about 60,000 feet altitude) on January 15, 2019. North America is in the center of this view. The right image shows surface air temperatures on January 30, 2019. For reference, Chicago was -26 degrees Celsius (-15 degrees Fahrenheit) on this morning (dark blue color)

Credit: earth.nullschool.net
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When well developed, the upper atmosphere circumpolar wind pattern, or polar vortex, isolates cold Arctic air in the far north, strengthens the mid-latitude jet stream, and reduces the frequency of frigid air outbreaks into lower latitudes. Early in January 2019, the polar vortex split into several separate closed streams. There was an outbreak of bitter cold air crossing southern Canada, the US Midwest, and the East Coast, during the last week of January. Such events have been popularly termed “invasions of the polar vortex.”

Conditions in the upper US Midwest were colder than any previous winter period in the past two decades. Low temperatures in northern Minnesota and all of Wisconsin on January 30 and 31 were in the -27 to -35 degrees Celsius range (-17 to -31 degrees Fahrenheit). Large areas of Michigan, Ohio, Indiana, Iowa, and the Dakotas reached temperatures below -20 degrees Celsius (-4 degrees Fahrenheit). However, few all-time low temperature records were set during the cold snap. Very mild conditions followed the cold snap in early February.

Arctic change: Fast and furious…and urgent

In a recent review paper (Overland et al., 2019), colleagues from a spectrum of polar geophysics disciplines summarized the many facets of the Arctic’s ongoing transformation, noting that this region, perhaps foremost in the globe, requires a quick adjustment to the pace of climate change. The amplification of global climate change in the Arctic, and the emerging potential for long-term atmospheric and ocean circulation changes, permafrost greenhouse gas release, and the effects of changing snow cover and snowmelt timing, point to serious but hard-to-forecast impacts on global society and infrastructure by the second half of this century.

Antarctic notes

After a rapid December loss and record low extent in early January, Antarctic sea ice extent declined at a slower-than-average rate. On January 31, Antarctic sea ice extent dropped to third lowest on record, tying with 2006 and bested by 2017 and 2018. Sea ice extent was particularly low in the eastern Weddell Sea and the eastern Ross Sea. Over the satellite record, Antarctic January sea ice was increasing at 4,400 square kilometers (1,700 square miles) per year or 0.9 percent per decade, although this was not statistically significant at the 95 percent confidence level. The Antarctic minimum for the year is typically in late February. The Southern Annular Mode, similar to the polar vortex for the southern hemisphere, was in its positive phase, favoring westerly winds around the continent and cool conditions over its ice sheet. This was indeed the case for East Antarctica, where temperatures were 2 to 6 degrees Celsius (4 to 11 degrees Fahrenheit) below the 1981 to 2010 mean, but other parts of Antarctica and the surrounding sea ice areas were near average.

References

Danish Meteorological Institute Arctic temperatures

Overland, J., E. Dunlea, J. Box, R. Corell, M. Forsinus, V. Kattsov, M. S. Olsen, J. Pawlak, L-O Reirson, and M. Wang. 2019. The urgency of arctic change. Polar Science. doi:10.1016/j.polar.2018.11.008

As 2018 came to a close, Arctic sea ice extent was tracking at its third lowest level in the satellite record, while sea ice in the Antarctic remained at historic lows. Slightly faster growth in the first few days of the new year, mostly in the Pacific sea ice areas, has the daily sea ice extent at fifth lowest as of this post.

Overview of conditions

Figure 1. Arctic sea ice extent for December, 2018 was 11.86 million square kilometers (4.60 million square miles). The magenta line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

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

Arctic sea ice extent for December averaged 11.86 million square kilometers (4.60 million square miles). This was the fourth lowest December average in the 1979 to 2018 satellite record, falling 980,000 square kilometers (378,000 square miles) below the 1981 to 2010 average, and 400,000 square kilometers (154,000 square miles) above the record December low set in 2016. However, slow ice growth during the second half of the month resulted in an ice extent that was tracking third lowest for December 31. Since then, growth has sped up, especially within the Sea of Okhotsk and to a lesser degree in the southwestern Kara Sea, bringing the daily sea ice extent up to the fifth lowest in the satellite record.

As has been typical the last few winters, sea ice extent remained below average within the Kara and Barents Seas, tracking third lowest in the Barents Sea as of December 31 and second lowest for the month of December as a whole. December extent in the Kara Sea was the fifth lowest for the month. Much of the area around Svalbard remains ice free. Elsewhere, ice extent tracked near average for this time of year, including in the Chukchi Sea where the ice was slow to form this past winter.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of January 7, 2018, along with daily ice extent data for four previous years and the record low year. 2018 to 2019 is shown in blue, 2017 to 2018 in green, 2016 to 2017 in orange, 2015 to 2016 in brown, 2014 to 2015 in purple, and 2012 to 2013 in dotted brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. About the data

Credit: National Snow and Ice Data Center
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Figure 2b. This graph shows daily air temperatures at 2 meters for the Arctic averaged above 80 degrees North from Zachary Labe, using ERA40 for the 1958 to 2002 climatology (blue line) and the operational European Centre for Medium-Range Weather Forecasts (ECMWF) for the current year (in red).

Figure is modified from the Danish Meteorological Institute
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Unfortunately, as a result of the partial government shutdown, we are unable to access the National Oceanic and Atmospheric Administration (NOAA) pages to retrieve information on atmospheric air temperatures and sea level pressure patterns. Instead, we turn to daily (2 meters above the surface) mean air temperatures north of 80 degrees North from the European Centre for Medium-Range Weather Forecasts (ECMWF) operational model. This analysis shows that air temperatures remained above the 1958 to 2002 average for all of December (Figure 2b).

December 2018 compared to previous years

Figure 3. Monthly December ice extent for 1979 to 2018 shows a decline of 3.7 percent per decade.

Credit: National Snow and Ice Data Center
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Overall, sea ice extent during December 2018 increased 1.63 million square kilometers (629,000 square miles). This is 358,000 square kilometers (138,000 square miles) less ice gained than the December 1981 to 2010 average. The linear rate of sea ice decline for December is 47,200 square kilometers (18,200 square miles) per year, or 3.7 percent per decade relative to the 1981 to 2010 average.

Southern exposure

As noted in our post last week, Antarctic sea ice declined at a rate well above the 1981 to 2010 average for the last three weeks of December, leading to record low extent for this time of year. This pattern has continued through the first week of 2019, with areas of the northern and eastern Weddell Sea and the central Ross Sea losing ice extent.

2018 year in review

Figure 4. This graph shows the Bering Sea ice extent for 2017 to 2018 (blue) compared to the 1979 to 2017 median (black) and the 1979 to 2017 minimum to maximum range (gray shading).

Credit: W. Meier, NSIDC
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Figure 5. This figure shows departures from average sea ice extent in the Arctic Ocean relative to 1981 to 2010 from 1850 to 2018. Above average extent is shown by red and orange colors, while below average extent is shown in blue colors.

Credit: Updated from Walsh et al., 2015. Gridded Monthly Sea Ice Extent and Concentration, 1850 Onward, Version 1
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January 2018 began the year with record low sea ice extents for the Arctic as a whole. Regionally, below average ice extent characterized both the Kara and Barents Seas and the Chukchi and Bering Seas. This pattern continued into February and early March. The low sea ice conditions in the Bering Sea persisted throughout the entire winter and were the lowest ever recorded during the satellite record (Figure 4). In particular, the ice in the region significantly declined in February—normally the time when extent is reaching its seasonal maximum. As reported in the NOAA Arctic Report Card, during a two and a half week period in mid-February, the Bering Sea ice extent dropped by over 225,000 square kilometers (87,000 square miles), an area roughly the size of Idaho.

The seasonal maximum, reached on March 17, 2018, was the second lowest in the satellite record. While low extent persisted through April and May, sea ice loss during early summer was unremarkable despite above average 925 hPa air temperatures over the Arctic Ocean and Eurasia. Antarctica reached its second-lowest annual minimum on February 20 and 21, and extent remained low throughout the year. However, the locations of the regional departures from average shifted during the year, as is often the case. Extent in the northern and eastern margins of the Weddell Sea were persistently low.

Air temperatures over the Arctic Ocean in July were below average, followed by above average temperatures in August. In fact, on average, August temperatures were higher than July temperatures in 2018. This is highly unusual in the Arctic and something not seen in at least 40 years. Overall the June, July, and August mean 925 hPa air temperatures over the Arctic Ocean ranked as the sixth highest since 1979.

The September 2018 seasonal minimum extent ended up slightly above the long-term linear trend line, tying with 2008 for the sixth lowest in the satellite record. After the minimum, the ocean was slow to freeze up, and October sea ice extent ended up as the third lowest. However, ice growth was very rapid in November, such that November 2018 extent approached the interquartile range of the 1981 to 2010 median. Nevertheless, large amounts of open water remained in the Barents and Chukchi Seas. By the end of December, ice conditions in the Chukchi Sea were back to average, while extent remained unusually low in the Barents Sea.

Coverage of old ice (greater than 4 years old) over the Arctic continued to decline. Such old ice covers only 5 percent of the area it used to in 1980s.

It is interesting to compare these conditions to historical reconstructions. Today’s departures from average conditions are quite remarkable when viewed over the last 160+ years (Figure 5). While some lower than average (computed 1981 to 2010) winter and summer sea ice conditions occurred prior to the satellite data record, they were not as large in magnitude or as persistent as recent departures have been. Further, recent years have shown unusually low sea ice extent persisting well into autumn and winter, reflecting a distinct change in seasonality in the Arctic compared to earlier years with low summer ice conditions.

As of January 1, 2019, Antarctic sea ice extent had experienced several days of record lows. These record-low extents, which followed a period of rapid ice loss in December, exemplify the high seasonal and year-to-year variability in Antarctic sea ice. With six to eight weeks remaining in the melt season, it remains to be seen whether the present situation will persist and lead to a record-low annual minimum. A discussion of Arctic conditions will be posted next week.

Overview of conditions

Figure 1. Antarctic sea ice extent for January 1, 2019 was 5.47 million square kilometers (2.11 million square miles). The orange line shows the 1981 to 2010 average extent for the month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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On January 1, Antarctic sea ice extent stood at 5.47 million square kilometers (2.11 million square miles), the lowest extent on this date in the 40-year satellite record. This value is 30,000 square kilometers (11,600 square miles) below the previous record low for January 1, set in 2017, and 1.88 million square kilometers (726,000 square miles) below the 1981 to 2010 average. Extent declined at a rate of 253,000 square kilometers (97,700 square miles) per day through December, considerably faster than the 1981 to 2010 mean for December of 214,000 square kilometers (82,600 square miles) per day. Indeed, the rate of Antarctic ice extent loss for December 2018 is the fastest in the satellite record, albeit close to 2010 and 2005.

Conditions in context

Figure 2: Derived from NSIDC’s Charctic tool, this time series compares the six lowest December extents for Antarctic sea ice. For the 40-year satellite record, the years coming closest to the 2018 extent are 1979 and 2016. Note that the extent lines for 1979 and 1982 end on December 30 because older satellite sensors only collected data every other day. The absence of any late or early tendency in the lowest December extents indicates the lack of an overall trend in Antarctic sea ice.

Credit: W. Meier, NSIDC
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On December 26, Antarctic sea ice extent fell below the low mark for this date, set in 2016, and has continued to track below all other years. Notably, the November to December 2016 period was considered an extreme excursion of Antarctic sea ice at the time. However, since then Antarctic sea ice extent has continually remained below the 1981 to 2010 median and mostly below the interquartile extent (below 75 percent of the 30-year range of values). This change in behavior, which began during the austral spring of 2016, contradicts prior characterizations of Antarctic sea ice cover as slowly expanding, yet highly variable. Instead, another strong decline through late December 2018 has taken the extent below the November and December 2016 levels to new record lows. Antarctica’s high year-to-year variability (record high extents for December were observed as recently as 2014 and 2007) suggests that a conclusive sea ice trend associated with the warming air and ocean around Antarctica has yet to reveal itself.

Spatial patterns of loss

Figure 3a. This maps shows the difference between Antarctic sea ice extent on December 1, 2018, and January 1, 2019.

Credit: W. Meier, NSIDC
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The rapid ice loss through December 2018 and into early January 2019 has exposed large areas of the Southern Ocean that are typically ice-covered at this time of year. At the beginning of December 2018, a substantial band of ice ringed most of the Antarctic continent, although regions of open water had begun to appear along portions of the coast near the Amery Ice Shelf and within the ice pack to the east of the Weddell Sea (Figure 3a). Despite being ice-covered at the beginning of the month, concentrations were quite low in the eastern Weddell, eastern Ross Sea, and the region north (and to either side) of the Amery. These areas have since melted out completely. Many other areas of low concentration ice remain, particularly in the northeastern Weddell Sea and the northern Ross Sea (Figure 3b). These areas are expected to melt out soon.

Six to eight weeks remain in the Antarctic melt season. Whether the record low daily extents now being seen will persist and lead to a record seasonal minimum cannot be predicted.

Figure 3b. These maps show sea ice concentration (left) and sea ice concentration anomaly, or difference from average (right), for December 31, 2018. In the right map, blues indicate higher than average sea ice concentrations; reds indicate lower than average concentrations.

Figure courtesy of Phil Reid, Australian Bureau of Meteorology. Sea ice concentration data from NSIDC.
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Although it is too soon for us to isolate what caused the rapid December decline and recent record low extents, it is likely that unusual atmospheric conditions and high sea surface temperatures—important factors in the 2016 and 2017 record lows—are playing a role. Unfortunately, as of this post our usual source of atmospheric data is not accessible due to the US government shutdown. NSIDC will continue to monitor the low ice conditions in the Antarctic and will provide updated analyses through the austral summer.