2018 melt season halftime assessment

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May and June were markedly cooler than the average, although total melt-day area for the ice sheet is near average as of early July. Winds from the south and high air pressure over Iceland caused a spike in melt area in early July. To date, heavy winter snowfall along the eastern side of the island and a near-average melt season means that the ice sheet has gained a large amount of mass. However if the melting intensifies, ice sheet mass could rapidly decline in the second half of the month.

Overview of conditions

Figure 1. The top map shows the cumulative melt days for the 2018 melt season through July 7 (upper left) and the difference from the average (upper right) for May and June combined, referenced to the 1981 to 2010 period. Below is a plot of daily melt area for the 2018 season through July 7, compared with melt extents for 2017, 2016, and the 1981 to 2010 period. Data courtesy of Thomas Mote, University of Georgia. About the data||Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia|High-resolution image

Figure 1. The top map shows the cumulative melt days for the 2018 melt season through July 7 (upper left) and the difference from the average (upper right) for May and June combined, referenced to the 1981 to 2010 period. Below is a plot of daily melt area for the 2018 season through July 7, compared with melt extents for 2017, 2016, and the 1981 to 2010 period. Data courtesy of Thomas Mote, University of Georgia. About the data

Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
High-resolution image

Figure 2. Cumulative melt area graph for 2018 to date, 2017, 2016 and the 1981-2010 period showing the pace of melting for the respective periods. he bottom chart shows the cumulative melt area (the running sum of the daily area experiencing melt) in millions of square kilometers for the three most recent melt seasons: 2015, 2016, and 2017.

Figure 2. Cumulative melt area graph for 2018 to date, 2017, 2016, and the 1981 to 2010 period showing the pace of melting for the respective periods. he bottom chart shows the cumulative melt area (the running sum of the daily area experiencing melt) in millions of square kilometers for the three most recent melt seasons: 2015, 2016, and 2017. About the data

Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
High-resolution image

So far, overall melting on the Greenland Ice Sheet has tracked at a slightly above average pace. Surface melting has been slightly below average in the northwest and far southern coastal areas, and slightly above average in the central southern region. A small area of significantly higher-than-average melting has occurred along the northeast coast, where some melt ponds have formed.

A spike in surface melt extent occurred from June 2 to June 9, tying records set on June 4 and 6 in 2010 and 2016. The melt extent reached over 375,000 square kilometers (145,000 square miles), or just over 20 percent of the ice sheet. The main area of increased melting was along the southeastern side of Greenland, extending well inland to regions close to the ice ridge in the southern ice sheet.

Conditions in context

Figure 3

Figure 3a. The top plot shows the air pressure anomaly (altitude departure from average at a 500 millibar pressure level) for May and June, 2018 (at approximately 16,000 feet above sea level). The bottom plot shows the temperature departure from average at the 700 millibar level (approximately 10,000 feet above sea level) for the same period. The reference period for both plots is 1981 to 2010.

Credit: NSIDC courtesy, NOAA ESRL Physical Sciences Division
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Figure 3b. This plot shows the 3-month running average of the North Atlantic Oscillation (NAO) index for the current decade thorough June, 2018.

Figure 3b. This plot shows the 3-month running average of the North Atlantic Oscillation (NAO) index for the current decade through June 2018.

Credit: Data coutesy NCEP NOAA
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Low air pressure across the island, but particularly to the southeast, characterized the first half of the melt season. This pattern coincided with temperatures of 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) below average from the southeast to the summit area at the center of the ice sheet, and near-average temperatures near the northern coast.

During the main snow accumulation period from October 2017 to April 2018, higher-than-average pressure in the northeast drove air from the Greenland Sea in the northern North Atlantic onto the eastern and northeastern coast. Last year from October 2016 to April 2017, a strong gradient between high pressure over Britain and low pressure over the southeastern coast created a more southerly flow, leading to high snowfall along the southeastern part of the ice sheet.

The 2018 hydrological year, or October 2017 to September 2018, has so far seen an unusually long period of North Atlantic Oscillation (NAO) conditions in the strongly-positive phase, indicating lower-than-average pressure over the North Atlantic. This drives warmer-than-average conditions over northwestern Europe and leads to heavy snowfall over eastern Greenland. England and Scandinavia have seen heat waves and forest fires.

Heading for a rise?

Figure 4

Figure 4. The top graph shows weather model results of estimated total accumulation of snow in Greenland for the 2017 to 2018 winter, spring, and summer season. The bottom maps show total snowfall amount (left) and departure from average of snowfall (right) for the same period. The two maps are the result of a climate model simulating surface mass balance (SMB) departure from average for Greenland as of September 1, 2017, based on weather data. Surface mass balance is the total net new material added (or lost) from the ice sheet surface from snowfall, rain, evaporation, and wind. Units are millimeters of water equivalent (1 millimeter is about 0.04 inches; for reference, 500 millimeters is about 19 inches).

Credit: Xavier Fettweis, Université of Liège, Belgium/MAR regional climate model
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As with last year, large snowfall events in October and February led to pronounced mass accumulation on the Greenland Ice Sheet for the 2017 to 2018 winter, along the eastern and northeastern coast. High snowfall early in the autumn and winter seasons is likely related to both onshore, or upslope, winds on the eastern side of the island and low sea ice concentration off the eastern side of the island after the sea ice extent minimum in September. The higher-than-average input of snow, which continued into June, combined with the near-average melt season to date has pushed the estimated mass gain for the ice sheet very high—more than 200 billion tons above the 1981 to 2010 model average (MAR 3.9 model, X. Fettweis), and above last year’s high values for the same time period. Other models, such as the HIRHAM Regional Climate Model Version 5, place the extra snow mass for early July at 130 billion tons. More of the 2018 melt season is to come, so this net mass uptake may be reduced in the remainder of July and August.

Most melting since 1550 C.E.

Figure 5. The top chart shows melt feature percent (MFP) records from GreenTrACS firn cores (numbered points on inset map) across the upper ice sheet areas of southwest Greenland. A deeper core was acquired at the location marked in red, which preserved a record of similar melt features for the years 1547 to 1989. The bottom graph shows record melt from two west Greenland ice cores, showing that modern melt rates, in red, are higher than at any time in the record since at least 1550 Common Era (CE), in black. The record is plotted as the percent of each year's layer represented by refrozen melt water.

Figure 5. The top chart shows melt feature percent (MFP) records from GreenTrACS firn cores (numbered points on inset map) across the upper ice sheet areas of southwest Greenland. A deeper core was acquired at the location marked in red, which preserved a record of similar melt features for the years 1547 to 1989. The bottom graph shows record melt from two west Greenland ice cores, showing that modern melt rates, in red, are higher than at any time in the record since at least 1550 Common Era (CE), in black. The record is plotted as the percent of each year’s layer represented by refrozen melt water.

Credit: Graeter, K. A., et al., 2018, Geophysical Research Letters
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A recent study has looked at shallow ice cores in Greenland acquired in 2016 that extend back 20 to 50 years. The study used these frozen records of climate history as a way to count melt-related features found in the snow layers, and compare them with climate and melting information from a much deeper core stretching back over 470 years. The shallow ice cores are from the high-elevation areas just west of the central ridge of the ice sheet, south of the Summit area. In this region, melting is frequent but not so intense that melt events in one year erase the previous year’s events. The shallow cores show a general increase in melt features since the 1990s over nearly all of the southern part of the ice sheet. A deeper ice core near one of the sites had a much longer record of melt event features, covering 1547 to 1989. By comparing the records in the adjacent cores, the study determined that the recent level of annual melt events has not occurred in the past 500 years at least.

Further reading

Graeter, K. A., E. C. Osterberg, D. G. Ferris, R. L. Hawley, H. P. Marshall, G. Lewis, T. Meehan, F. McCarthy, T. Overly and S. D. Birkel. 2018. Ice core records of West Greenland melt and climate forcing. Geophysical Research Letters, 45(7), 3164-3172, doi:10.1002/2017GL076641.

The 2017 Greenland Ice Sheet SMB simulated by MARv3.5.2 in real time

Polar Portal’s Greenland surface conditions

Programme for Monitoring of the Greenland Ice Sheet

2017 review and 2018 season kick-off

In 2017, the cumulative daily melt area for the Greenland ice sheet was the smallest since 1996, yet still higher than any year between 1979 and 1994 (1995 was a high melt season). The 2017 melt season was also notable for its late melt events, one of them occurring on October 29 to 31, tied for the latest for any year in the satellite record.

We have re-started daily monitoring for 2018 and will be providing periodic discussions as conditions warrant. Early melting in 2018 has been confined to a few points along the eastern coast.

Overview of conditions

. Cumulative melt days for the 2017 melt season (upper left) and melt day anomaly, or difference from the average (upper right) for the same period, referenced to 1981-2010. Below is a plot of daily melt area as a percentage of the ice sheet for the entire season.

Figure 1. The top map shows the cumulative melt days for the 2017 melt season (upper left) and the departure from the 1981-to-2010 average melt days (upper right). A time series of daily melt area as a percentage of the ice sheet extent for the entire season is shown in the bottom panel.

Data courtesy of Thomas Mote, University of Georgia.
About the data
Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
High-resolution image

Figure 2. Total melt area for the entire annual melt season (April through October) for all 39 years in the satellite record. Units are tens of millions of square kilometers, or about 3.861 million square miles. The mean for 1981-2010, of 18.4 million square kilometers (7.143 million square kilometers) is shown as a red line.

Figure 2. The top chart shows the total melt area for the annual melt season (April through October) over 39 years of the passive microwave satellite record. Units are tens of millions of square kilometers. The mean for the 1981 to 2010 average of 18.4 million square kilometers (7.143 million square kilometers) is shown as a red line. The bottom chart shows the cumulative melt area (the running sum of the daily area experiencing melt) in millions of square kilometers for the three most recent melt seasons: 2015, 2016, and 2017.

About the data
Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
High-resolution image

The 2017 melt season was less intense than recent years, and was below average melt in the 1981 to 2010 reference period. Surface melting was particularly low in southeastern Greenland. In general, melting was limited to low elevations (below 1500 meters or 4900 feet) along the western and northeastern coastlines. Fewer melt days than average occurred along the Davis Strait and the interior melt pond region along the central western coast. As discussed below, the melt year ended with two significant late melt events in southeastern Greenland. The final 2017 melt event occurred at the end of October, covering the southeastern coast.

Overall, the 2017 melt season was the lowest since 1996. Although it began and ended with a few large melt events, the middle of the melt season through mid-July was below average—only briefly picking up intensity late in July through mid-August.

Conditions in context

Figure 3. Air pressure differences (top) and air temperature differences (bottom) are shown at the 700-millibar pressure level in the atmosphere (approximately 10,000 feet above mean sea level), relative to the 1981 to 2010 reference period for June, July, and August 2017.

Credit: NSIDC courtesy, NOAA ESRL Physical Sciences Division
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Lower-than average atmospheric pressure southeast and north of Greenland was present during the height of the summer melt season. Near the summit in central Greenland, the average air temperature for the summer melt season was more than 1 degree Celsius below the 1981 to 2010 average. Temperatures were about 1 degree Celsius (2 degrees Fahrenheit) above average along the southwestern tip and northeastern coastline.

The late late show

Figure 4. Greenland daily melt area for all years with an October melt events exceeding 50,000 square kilometers (19,305 square miles).

Figure 4. The top image shows the temperature departure from average at the 700-millibar level (approximately 10,000 feet above sea level) from October 27 to 31, 2017, relative to the 1981 to 2010 reference period. The bottom graph shows Greenland daily melt area for all years with October melt events exceeding 50,000 square kilometers (19,305 square miles).

Credit: NSIDC courtesy, NOAA ESRL Physical Sciences Division (top); NSIDC courtesy, University of Colorado Boulder (bottom)
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The 2017 melt year ended with two extreme spikes in melt area, one in mid-September and one at the end of October. While not unprecedented, such events are unusual. The 2017 late October event was notable for its duration (4 days with melt area above 25,000 square kilometers (10,000 square miles)). As with many warm events during the winter, a surge of warm air along the eastern coast was responsible for the melting. In 2003, a much larger melt event occurred in late October.

Did the Greenland ice sheet grow in 2016 to 2017?

Figure 5. Top graph, daily net snow-rain-melt changes in mass for the Greenland Ice Sheet (in gigatons/day) for the 2016-2017 season and the 2017-2018 season to date. Gray band and dark grey line show the 1981-2010 range A large and prolonged addition of mass occurred in October-November of 2016. A similar, but briefer mass increase is seen for mid-February of 2018. Lower graph, cumulative net mass change for the record melt year of 2011-2012, and for 2016-2017 and 2017-2018 to date.

Figure 5. The top graph shows daily net snow-rain-melt changes in mass for the Greenland ice sheet (in gigatons/day) for the 2016 to 2017 season and the 2017 to 2018 season to date. The grey band and dark grey line show the 1981 to 2010 range. A large and prolonged addition of mass occurred in October to November 2016. A similar, but briefer mass increase is seen for mid-February 2018. The bottom graph shows cumulative net mass change for three melt years: 2011 t0 2012, 2016 to 2017, and 2017 to 2018 to date.

Credit: polarportal.org
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Figure 6. This graph shows

Figure 6. This graph shows Greenland’s total mass balance from snowfall, rainfall, and melt runoff (surface mass balance or SMB) during the melt year (September to August) for all 39 years in the passive microwave satellite record.

Credit: Xavier Fettweis, Université of Liège, Belgium/MAR regional climate model
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A model-based assessment of Greenland’s total net mass balance from snowfall, rainfall, and melt runoff (surface mass balance or SMB) shows large snow input in fall and winter 2016, followed by low surface melting in summer 2017. Relative to the 1981 to 2010 reference period, the ice sheet accumulated just under 200 billion tons more snow than typical. This value does not include the mass lost through ice flow to the ocean that produces icebergs, or to melting on the underside of the ice as it first flows into the ocean. Compared with 2014 to 2015 and 2016 to 2017 melt years, where mass loss ranged between -190 and -270 billion tons, it is likely that 2016 to 2017 was very close to a zero net mass gain, and possibly positive. If so this would be the first time since the late 1990s that the ice sheet increased in size. Unfortunately, the best satellite for making such assessments, the Gravity Recovery and Climate Experiment (GRACE), ceased to operate prior to summer 2017. The replacement satellite, GRACE-Follow-On (GRACE-FO), is scheduled to launch this spring.

Early trends in the 2017 to 2018 season show a smaller but still above-average snowfall input to the season so far, with an intense storm depositing a significant amount of snow in mid-February. Early melt events prior to April 1, have been minor, but a few areas of melting occurred on February 18, along the eastern coastline. The eastern coastline is also the main region of above-average snow input to date.

Further reading

The 2017 Greenland ice sheet surface mass balance (SMB)

Greenland ice loss 2002 to 2016

Greenland surface conditions

2017 Arctic Report Card

Late season melt in southern Greenland

Surface melt spiked in mid-September in southern Greenland. A surge of warm air from the central Atlantic fueled the late melt event, which was confined to the southwestern and southeastern coasts and peaked on September 15, 2017. The late season spike is one of the largest to occur in September on satellite record (since 1978). The event was not related to the recent hurricanes.

Overview of conditions

Figure 1. This map shows the 15 September 2017 melt day for the Greenland ice sheet relative to the 1981 to 2010 average for the same period.

Figure 1. This map shows the daily melt extent for September 15, 2017, on the Greenland ice sheet.

Data courtesy of Thomas Mote, University of Georgia.
About the data
Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
High-resolution image

Figure 2. This chart shows the daily melt extent as a percentage of the ice sheet area through 24 September 2017.

Figure 2. This chart shows the daily melt extent as a percentage of the ice sheet area through 24 September 2017.

Data courtesy of Thomas Mote, University of Georgia.
About the data
Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
High-resolution image

Beginning September 13, 2017, the southern peripheral regions of the Greenland ice sheet began to show significant surface melt, an unusual event for this late in the season. The total melt area rapidly increased before culminating on September 15, when more than 15 percent of the ice sheet surface (263,000 square kilometers; 101,500 square miles) had satellite evidence of snowmelt. By September 18, surface temperatures fell back below freezing across the island.

Conditions in context

Figure 3. This plot shows the daily average surface air temperature in degrees Celsius for the KAN_U weather station in Greenland.

Figure 3. This plot shows the daily average surface air temperature in degrees Celsius for the KAN_U weather station in Greenland.

Credit: PROMICE, Programme for Monitoring of the Greenland Ice Sheet
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Figure 4. Animation x: The animation above shows mean daily air temperatures at 925hPa (~2,500 feet above sea level). A large plume of warm air covers southern Greenland on September 15. Shades of blue show air temperatures lower than freezing (0C = 273K) and yellows through reds show air temperatures higher than freezing.

Figure 4. This animation shows mean daily air temperatures at 925 hectopascals (at about 2,500 feet above sea level). A large plume of warm air covers southern Greenland on September 15, 2017. Shades of blue show air temperatures lower than freezing (zero degrees Celsius is equal to 273 Kelvin) and yellows through reds show air temperatures higher than freezing.

Data Courtesy of NOAA
About the Data

Figure 5. NOAA Weather Prediction Center surface analysis at 0900 Greenwich Mean Time (GMT)/Coordinated Universal Time (UTC) on Thursday, 14 September 2017. Low pressure system located off the coast of Newfoundland with warm front approaching southern Greenland.

Figure 5. This map shows the NOAA Weather Prediction Center surface analysis at 0900 Greenwich Mean Time (GMT)/Coordinated Universal Time (UTC) on Thursday 14 September 2017. A low pressure system located off the coast of Newfoundland with a warm front approaches southern Greenland.

Credit: NOAA
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The mid-September spike is not the latest melt event recorded in the 38-year period of Greenlandic melt observations. September of 2000, 2002, and 2006 were also marked by similar episodes of surface area melt of nearly equal magnitude. In 2003, a melt event occurred on October 25, and impacted 174,000 square kilometers (67,000 square miles) of the ice sheet.

The 2017 late melt event, peaking on September 15, can be attributed to a mid-latitude frontal system moving off the coast of Newfoundland on September 14 (Figure 4). The cyclone’s warm sector brought surface air temperatures well above freezing for Greenland’s southern coast in addition to steady rainfall. Several weather stations on the Greenland ice sheet recorded above-freezing temperatures, notably including the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) KAN-U station at nearly 2,000 meters (6,600 feet) elevation (Figure 3).

Connection to Atlantic hurricanes

hurricanes

Figure 6. In this Moderate Resolution Imaging Spectroradiometer (MODIS) true color image, remnants of Hurricane Irma pass over southeastern United States. Meanwhile, a warm air mass south of Greenland is causing surface air temperatures to rise.

Credit: NASA Worldview
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The 2017 Atlantic hurricane season has been energetic, with Hurricanes Harvey and Irma making landfall on the continental United States. The heat transported by the two large tropical systems, however, is not directly linked to the large September 15 spike. Hurricane Harvey made landfall on August 25, and Irma on September 10. Figure 6 shows the remnants of Irma over southeastern United States on September 13, after the warming event began in southern Greenland.

Late summer melting spike for 2017 melt season; Greenland ice may increase

Extensive and persistent melt in northern Greenland characterized late July to early August. A brief high pressure pattern centered on the west coast led to similar conditions that made 2015 a record melt year for the ice sheet’s northern sections. Overall, however, reduced melting and heavy early springtime snowfall may result in a net increase in Greenland’s ice mass this year for the first time this century.

Overview of conditions

The map on the top left shows the cumulative melt days for the 2017 melt season through August 17, 2017; and the map on the top right shows the departure from average for melt days relative to the 1981 to 2010 average for the same period.

Figure 1. The map on the top left shows the cumulative melt days for Greenland’s 2017 melt season through August 17, 2017; and the map on the top right shows the departure from average for melt days relative to the 1981 to 2010 average for the same period.

Data courtesy of Thomas Mote, University of Georgia.
About the data

Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
High-resolution image

Figure 2. The top chart shows the daily melt extent as a percentage of the ice sheet area through 30 June 2017. The bottom chart shows the cumulative melt area (the running sum of the daily area experiencing melt) in millions of square kilometers for certain years between 2000 to 2017.

Figure 2. The top chart shows the daily melt extent as a percentage of the ice sheet area through 17 August 2017. The bottom chart shows the cumulative melt area (the running sum of the daily area experiencing melt) in millions of square kilometers for certain years between 2000 to 2017.

Data courtesy of Thomas Mote, University of Georgia.
About the data

Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
High-resolution image

The 2017 melt season has been less intense than recent years, and is below average melting for the 1981-to-2010 reference period. Surface melting has been low in the southeast, and has been limited to coastal regions at low elevations. The western and northeastern coastal areas have a slightly higher-than-average number of melt days through mid-August.

Beginning on July 16, a broader area of northern Greenland began to melt, spreading and persisting until August 3. Both the northeastern and northwestern coastal areas were affected. At its peak, July 22 to 24, over 30 percent of the ice sheet experienced some surface melting each day, although several recent years had similar or larger melt areas on those days. The higher-than-average-melt-days area was confined to lower elevations of the ice sheet.

Conditions in context

here

Figure 3a. This plot shows the air pressure anomaly (altitude departure from average at a 500 millibar pressure level) for July 15 to August 15, 2017.
Figure 3b. This plot shows temperature departure from average at the 700 millibar level (approximately 10,000 feet above sea level) for July 15 to August 15. The reference period for both plots is 1981 to 2010.

Credit: NSIDC courtesy, NOAA ESRL Physical Sciences Division
High-resolution image

The surge in surface melt extent coincided with a period of high air pressure centered over Greenland’s western coast, with below-average pressure areas on all sides. This produced strong southerly winds along the western flank, increasing that area’s air temperature and surface melt extent. This warm pulse of air traveled northward and around the northern coast of Greenland. However, in the far north, sharply cooler conditions surrounding the strong melt event led to below-average temperatures for the 31-day period in the island’s north-central parts.

Fires around the ice

While the ice sheet melt has been unremarkable, wild fires on the coastal tundra have made news this season. Wild fires in Greenland are rare with only a handful detected in a typical year by the Fire Information for Resource Management System (FIRMS). FIRMS uses the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) data to detect fires worldwide. In 2017 the number of fires in Greenland spiked. The fire triggers are unknown but NSIDC researchers Jeff Thompson and Lora Koenig have been investigating vegetation change over the past fifteen years around the Greenland ice sheet. Their research shows a complicated pattern of vegetation change that makes the land areas surrounding the ice sheet more prone to large fires. In some regions, warming leads to increased plant productivity by providing more growing days; however, in other areas an earlier drying of the soil and early browning of the vegetation result in a landscape more susceptible to fire. This research is ongoing but highlights how warming in the Arctic can have both a positive and negative effect on vegetation.

Field notes: Greenland’s percolation zone, then and now

Scientists at work

Figure 4. In the top photograph, a ground-penetrating radar system glides over the Greenland ice sheet. Designed by students at Dartmouth’s Thayer Engineering School, the system runs on a solar-recharged power system, which is operational all season long with no need for backup power.
In the bottom left photograph, Karina Graeter collects density samples in a shallow snow-pit prior to core drilling.
In the bottom right photograph, Karina Graeter and Bob Hawley show a high-quality core section, drilled with the Ice Drilling and Design Operations (IDDO) Sidewinder system during the Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) traverse.

Credit: Gabe Lewis, GreenTrACS
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The Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) team completed a successful eight-week snowmobile traverse across the western side of the Greenland ice sheet, through a region where extensive surface melt refreezes in the snow below the surface. This area is called “the percolation zone” of the ice sheet. The collaborative project, funded by the National Science Foundation (NSF), involved professors and students from Dartmouth College, Boise State University, and the University of Maine. This year’s field team drilled nine 25 to 33 meter (82 to 108 feet) ice cores (totaling 260 meter or 853 feet), and collected about 3000 kilometers (1864 miles) of Global Positioning System (GPS) elevation data and ground-penetrating radar profile data. The team also measured albedo at 34 sites, conducted several kite-borne aerial photography surveys, and measured surface density, temperature profiles, and snow grain size in 25 snowpits.

Several ice cores were collected at locations that the Program for Regional Climate Assessment (PARCA) had measured in the 1990s to compare changes in accumulation and meltwater retention. The cores were photographed in the field and will be analyzed for the number of refrozen melt layers, and overall snow accumulation, at Dartmouth College.

Greenland’s ice sheet may grow in 2017

The NASA Gravity Recovery and Climate Experiment (GRACE) satellites detect changes in Earth's gravity, gravitational-change-based monthly estimate of the net mass change of Greenland’s ice sheet since 2000. Credit: climate.nasa.gov

Figure 5. The NASA Gravity Recovery and Climate Experiment (GRACE) satellites detect changes in Earth’s gravity, gravitational-change-based monthly estimate of the net mass change of Greenland’s ice sheet since 2000.
Credit: climate.nasa.gov
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Figure 6. The top graph shows weather model results of estimated total accumulation of snow in Greenland for 2010, 2012, and 2017 between September 1, 2016 and August 26, 2017. The two maps are the result of a climate model simulating surface mass balance (SMB) departure from average for Greenland as of September 1, 2016, based on weather data. Surface mass balance is the total net new material added (or lost) from the ice sheet surface from snowfall, rain, evaporation, and wind. Units are millimeters of water equivalent (1 millimeter is about 0.04 inches; for reference, 500 millimeters is about 19 inches).

Credit: climate.be, and Xavier Fettweis, Université of Liège, Belgium/MAR regional climate model
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Figure 7. These maps show the ice flow speeds for points near the ice front of five major Greenland glaciers for the period 2013 through August 2017 from the Global Land Ice Velocity Extraction (GoLIVE) project. Locations on Greenland are clockwise from the upper left: Peterman Glacier, Zacharaie Isstrom, Kangerdlugssuaq Glacier, Helheim Glacier, and Jacobshavn Glacier.
Credit: NSIDC/Global Land Ice Velocity Extraction (GoLIVE) project
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For at least the past seventeen years (since probably 1996, according to recent publications) the Greenland ice sheet has been losing ice on an annual basis. This is best illustrated by data from the Gravity Recovery and Climate Experiment (GRACE) satellite, which measures the change in mass over the entire ice sheet through changes in Earth’s gravitation. Some years, such as 2012, have much larger losses, and others like 2013 lost little, but every year in recent decades has had at least a slight net reduction in ice. Overall the trend has been 286 ± 21 billion tons of ice per year, equal to about 0.8 millimeter sea level rise (0.03 inches). However, the events of the 2016-to-2017 annual snowfall and melt cycle suggest that this year will see a net gain for the ice sheet.

The low melt for the 2017 summer, and the greater-than-average snowfall for the southeastern coastal area, added a net amount of snow and ice to the island’s ice sheet. This combination of surface melting, evaporation, runoff, and the snowfall (and rain) is called the surface mass balance (SMB). It represents all the components from the atmosphere that contribute ice and snow to the ice sheet. As of late August, model estimates of the remaining snowfall on the Greenland ice sheet showed about 70 billion tons more snow than the 1981-to-2010 average, and roughly 400 billion tons more than the record 2012 loss. This is primarily due to excess accumulation in southeastern Greenland in the past winter and spring. Several major accumulation events in October, February, and May, led to a snowpack roughly 500 millimeters (20 inches) thicker than average in the areas near Kangerlugssuaq and Helheim Glaciers. Observations at automatic weather stations sites along Greenland’s southeastern coast confirm model results.

For the balance of mass and volume for the entire ice sheet, the SMB is combined with total ice loss from ice flowing through outlet glaciers into the ocean. Given that Greenland has retained more snow input this year, ice export would need to increase to bring the ice sheet into balance or continue with annual ice loss. To estimate recent changes in ice flow, we used near-real-time measurements of the surface speed of some major ice outlets for the Greenland ice sheet from the GoLIVE data set. For five major Greenland outlets, ice speed has varied since 2016, but a significant slowing of the largest glacier Jacobshavn has offset small increases of this subset. It is likely that 2017 will see a net increase in Greenland’s ice mass for the first time this century. However, a more detailed analysis of all the island’s glaciers and surface elevation changes will be needed to confirm this.

Further reading

Fahnestock, M., T. Scambos, T. Moon, A. Gardner, T. Haran, and M. Klinger. 2016. Rapid large-area mapping of ice flow using Landsat 8. Remote Sensing of Environment185, pp.84-94. doi.org/10.1016/j.rse.2015.11.023.

Shepherd, A., E. R. Ivins, A. Geruo, V. R. Barletta, M. J. Bentley, S. Bettadpur, K. H. Briggs, D. H. Bromwich, R. Forsberg, N. Galin, and M. Horwath. 2012. A reconciled estimate of ice-sheet mass balance. Science338. Issue 6111, pp.1183-1189. doi: 10.1126/science.1228102.

Thompson, J.A. and L. Koenig. 2016, February. Evidence for increasing desiccation of vegetation in Greenland. In AGU Fall Meeting Abstracts.

Thompson, JA and L. Koenig. 2017, in revision. Land surface phenology in Greenland and links to cryospheric change. Earth and Space Science.

The Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) blog
The 2017 Greenland ice sheet SMB simulated by MARv3.5.2 in real time
Polar Portal’s Greenland surface conditions

Slow start to the 2017 melt season

Despite moderately higher-than-average air temperatures and high air pressure over Greenland, the 2017 melt season began modestly. As of June 30, total melt area was the lowest since the 2009 melt season.

To update the Greenland Today site, the team has improved the graphics and land masking; archived records reflect the new values.

Overview of conditions

Cumulative and anomaly melt days

Figure 1. The map on the top left shows the cumulative melt days for the Greenland Ice Sheet through June 30, 2017; and the map on the top right shows the departure from average for melt days relative to the 1981 to 2010 average through June 30 for the reference period.

Data courtesy of Thomas Mote, University of Georgia. About the data

Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
High-resolution image

Daily and cumulative melt extent charts

Figure 2. The top chart shows the daily melt extent as a percentage of the ice sheet area through 30 June 2017. The bottom chart shows the cumulative melt area (the running sum of the daily area experiencing melt) in millions of square kilometers for certain years between 2000 to 2017.

Data courtesy of Thomas Mote, University of Georgia. About the data

Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
High-resolution image

Two significant melt events marked the early part of Greenland’s 2017 melt season, but overall melt extent was low through the end of June. Total cumulative melt extent for 2017 is the lowest in the satellite record since 2009. Only 2009, 2006, and 2000 had less melt at this point since 2000. Daily melt extent through June 30 of this year has yet to surpass 20 percent of the ice sheet in any single day, and melting has been confined to lower elevations. Melting occurred much less frequently than average (relative to the early melt seasons spanning 1981 to 2010) in much of the ice sheet, especially in the southern and northwestern regions, while western low-elevation areas and the far northeastern ice edge had slightly higher-than-average melting.

Conditions in context

Air pressure and temperature anomaly charts

Figure 3. The top plot shows the air pressure anomaly (altitude departure from the average of the 500 millibar pressure level) for May to June 2017. This is equivalent to the variation in air pressure, with higher levels indicating high pressure; note that the typical altitude of 500 millibars pressure is about 18,000 feet. The bottom plot shows temperature departure from average at the 700 millibar level (approximately 10,000 feet above sea level) for May to June 2017. The reference period for both plots is 1981 to 2010.

Credit: NSIDC courtesy, NOAA ESRL Physical Sciences Division
High-resolution image

A pattern of slightly higher-than-average pressure over most of central and northern Greenland for May and June brought southerly and southwesterly winds along the western edge of the ice sheet, where most of the melt days have occurred. Temperatures in that area were about 1.5 to 2 degrees Celsius (2.7 to 3.6 degrees Fahrenheit) higher than average, and similar warmth on average covered the northeastern coast. However, much of the southeast and northwest of the island were near average temperatures for May and June.

Unusually heavy snow last autumn

Map showing surface mass balance changes

Figure 4. These maps are the result of a climate model simulating surface mass balance departure from average for Greenland as of June 27, 2017, based on weather data. Surface mass balance is the total net new material added (or lost) from the ice sheet surface from snowfall, rain, evaporation, and wind. Units are millimeters of water equivalent (1 millimeter is about 0.04 inches; for reference, 500 millimeters is about 19 inches).

Credit: Xavier Fettweis, Université of Liège, Belgium/MAR regional climate model
High-resolution image

Snowfall in eastern and southeastern Greenland through the 2016 to 2017 autumn and winter was far above average, adding 500 millimeters water equivalent to some areas. Much of this occurred during a series of storms in October, when a large persistent low-pressure pattern southeast of Greenland pushed warm moist air onto the eastern and southeastern mountains. This additional snowfall increased the overall mass of the ice sheet by about 150 billion tons more than average prior to the start of the melt season. However, melting and run-off, though off to a slow start, will reduce this excess mass through the course of the summer. As the season progresses, we will evaluate whether the total effect of the full annual climate led to mass gain or mass loss for the ice sheet.

Soot in the pristine snow

Smoke plume from Canadian Arctic

Figure 5. An observed smoke plume above the western Canadian Arctic drifted toward Greenland from 18 to 21 June 2014. Aerosol optical thickness (AOT) in yellow light (550 nanometer) measured the degree to which aerosols prevented the transmission of light. This soot was identified in a snow pit in Greenland during field work two years later. A value of 1 indicates that 37 percent (1/e where e is Euler’s number) of light can pass through the aerosol layer. A value of 0 indicates no absorption by the aerosol.

Credit: Modified from figure 4 in Khan et al., 2017.
High-resolution image

For years it has been suspected that increasing forest burning in the high Arctic has brought soot to the Greenland ice sheet, darkening the snow and  increasing melting. Now two recent studies have identified levels of black carbon in snow—not just in Greenland, but across many parts of the cryosphere. Among other results, the studies showed that indeed soot from fires in northwestern Canada was deposited within days in Greenland, thousands of miles away. Although sunlight quickly modifies the chemical components of soot, once deposited it is stable, and can remain for many years. Thus, as the ice sheet accumulates more soot from fires and manmade causes, its melting in the succeeding summers accelerates due to the persistent presence of black particles in the snow and ice.

New data, new tools, new look for Greenland Today

Greenland Today has introduced improvements to the site in the past two weeks. Changes in supporting data sets and graphics have both enhanced the accuracy of the product and the interactivity of the site.

The ice sheet mask has been updated to restrict the melt determination more closely to the ice edge. In particular, areas along Greenland’s northeastern side, where scattered small ice masses and heavy seasonal snow cover exist, have been masked out. This part of the island is primarily bare ground in late summer, and was frequently mis-mapped as an ice sheet melt area, often with a persistent reading well into autumn. An improved mask has also been applied to other areas with similar issues, to both the historical data and daily near-real-time coverage. Note that while this has reduced the overall ice sheet area and melting area, the update more accurately reflects ice sheet melt; but in doing so, does not impact the trends or discussion of Greenland’s conditions under a changing climate.

Color schemes for several of the graphics have also been adjusted. The interactive chart of daily melt extent has been updated to better represent data from the earlier sensor (Scanning Multichannel Microwave Radiometer (SMMR), the main sensor from 1979 to 1987). During the SMMR years, data was collected every other day. To compensate for the missing days, current climatology is computed by averaging the daily melt on days void of data. This new approach has allowed the Greenland Today team to show more precise cumulative melt plots and to correctly compute the cumulative melt climatology.

In the past, the daily melt plot applied a 5-day average to the climatology. This has been removed to present the day-to-day volatility in the interquartile and interdecile ranges. It also corresponds better with the interactive melt plot, which in the past did not apply a 5-day average to the climatology.

In addition, two computer glitches have been fixed on the interactive plot. In the past, statistics could mix, but now users can clearly see either mean and standard deviation, or median and interquartile and interdecile ranges. And finally, the SVG file now downloads properly.

Further reading

Khan, A. L., S. Wagner, R. Jaffe, P. Xian, M. Williams, R. Armstrong, and D. McKnight. 2017. Dissolved black carbon in the global cryosphere: Concentrations and chemical signatures. Geophys. Res. Lett., 44. doi:10.1002/2017GL073485.

Thomas J. L. et al. 2017. Quantifying black carbon deposition over the Greenland ice sheet from forest fires in Canada. Geophys. Res. Lett., 44. doi:10.1002/2017GL073701.

The 2017 Greenland Ice Sheet SMB simulated by MARv3.5.2 in real time
Polar Portal’s Greenland surface conditions
Programme for Monitoring of the Greenland Ice Sheet

Melt calibration, suspension of daily images

Daily melt extent mapping is suspended for the winter. Calibration of yearly melt detection requires analysis of the springtime snow conditions by a separate program. See our March 18, 2013 post for more discussion of melt calibration.

Our new interactive chart supports a retrospective look at past Greenland melt seasons. This will remain active for our users.

We will resume the daily image updates in April 2017. 

2016 melt season in review

Melt extent in Greenland was above average in 2016, ranking tenth highest (tied with 2004) in the 38-year satellite record. Melt area in 2016 was slightly greater than in 2015, which ranked twelfth. However, near-average to below-average coastal snowfall levels that exposed bare ice earlier in the melting season, combined with warm and sunny conditions at lower elevations, led to high overall ice loss from runoff.

Overview of conditions

map of cumulative melt days

Figure 1. The map on the top left shows the cumulative melt days for the 2016 Greenland melt season (through 17 October). The map on the top right shows the melt day anomaly for 2016 relative to average number of melt days for the 1981 to 2010 average. The bottom graph shows the summer melt extent on the Greenland Ice Sheet for 2016.

Data courtesy of Thomas Mote, University of Georgia. About the data

Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
High-resolution image

Seasonal surface melt began early in 2016, with extensive melt events in southwest Greenland in the second and fourth week of April. Greater than average melt was observed in western and northeastern Greenland, as was also seen in 2015. A few areas along the eastern and southeastern coast near Helheim and Kangerdlugssuaq glaciers, saw frequent melting in 2016, resulting in increased ice exposure. Dark ice, typical along the central western Greenland coast, also appeared near Helheim and Kangerdlugssuaq glaciers. Common during any melt season, a series of warm events caused brief spikes of high melt area during the summer. Summer daily melt extent rarely fell below the 1981 to 2010 average. Peak melt extent occurred on July 19, when our passive microwave analysis method mapped surface melting on 43 percent of the ice sheet.

Conditions in context

Figure 2. The left plot shows air pressure anomaly (height anomaly of the 500 mbar pressure level, in meters) and the right plot shows air temperature anomaly (in degrees Celsius) for June, July, and August 2016 combined, relative to the 1981 to 2010 average.

Credit: NSIDC courtesy, NOAA ESRL Physical Sciences Division
High-resolution image

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Figure 3. The top left map shows cumulated snowfall (water equivalent) in millimeters, while the right shows anomaly of snowfall for Greenland from 2015 to 2016. The bottom maps show the net change in water equivalent thickness in millimeters (negative values, in blue, mean mass loss) for Greenland from 2015 to 2016.

Credit: Xavier Fettweis, Université of Liège, Belgium/MAR regional climate model
High-resolution image

Warm weather conditions and higher-than-average air pressure prevailed for June, July, and August in 2016 (compared to the three month average for 1981 to 2010). The tendency for higher-than-average pressure over the island continues a trend seen for several recent summers. This year, the pressure pattern center hovered above Baffin Island, inducing drier and sunnier conditions along the western coast, raising its temperatures up to 2 degrees Celsius (4 degrees Fahrenheit) higher than average for the summer. This caused frequent surface melting along the western flank of the ice sheet where dark, older, interior ice became exposed. Cooler and cloudier conditions prevailed in northeastern Greenland (less than 1 degree Celsius or 2 degrees Fahrenheit above average). However, on both the eastern and western coastal areas of the ice sheet, the exposure of dark ice combined with more sunshine led to intense melting during the observed melt days. High levels of run-off on the western coast, and eastern coast ‘hot spots’ of frequent and intense melting led to a high estimated mass loss. One model (MAR 3.5.2 from Xavier Fettweis, Université de Liège, forced by NCEP reanalysis data) estimates a net extra surface mass loss of water with respect to the 1981 to 2010 average at 144 gigatons. This is the third highest surface mass loss since observations began in 1979, trailing the warm summers of 2010 and 2012.

Greenland in 2016 compared to other years

cumulative and anomaly melt day areas

Figure 4. The top graph shows the average daily melt area anomaly for Greenland, 1979 to 2016. The graph compares melt area in thousands of square kilometers for June to August each year, to the average for 1981 to 2010 for these same months. The bottom graph shows the cumulative melt day area for 2016, 2015, 2012, 2010, and 2007.

Credit: National Snow and Ice Data Center, University of Colorado Boulder
High-resolution image

The 2016 total summer melt extent area (the sum of surface melt area for each day for June, July, and August) was 36 million square kilometers (13.9 million square miles), tenth largest in the 1978 to 2015 period (tied with 2004). While significantly higher than the 1981 to 2010 average, the 2016 melt season was typical for Greenland summers in the past decade. Comparing the progression of melt area for 2016 with the three highest melt extent years (2012, 2010, and 2007) shows that while 2016 had a high early-season melt area, the pace slowed in mid-July relative to the warmest years. Greenland’s 2016 daily melt extent area anomaly (difference from the daily extent average extent for the 1981 to 2010 average) was approximately 90,000 square kilometers (34,800 square miles) per day.

Dark ice, high melt, warm air

Figure 5. The top map shows the summer albedo (reflectivity) anomaly for Greenland in 2016. The inset map is a closer look at a region of unusually low albedo (e.g., dark ice). A nearby Greenlandic town, Tasiilaq, had record warm air temperatures in the summer of 2016 with records stretching 121 years from 1895 (bottom graph).

Credit: Jason Box, Geological Survey of Denmark
High-resolution image

Greenland’s warm summer, with significant coastal melting, led to darker-than-average areas with more bare ice as opposed to snow on ice. Albedo refers to the reflectivity of Earth surfaces; it is also a measure of the amount of light scattered and reflected in all directions from a surface. Areas of dark ice, or low albedo, are common along the western coast, but albedo values during the past summer were exceptionally low. This summer also experienced new areas of dark ice in isolated patches along the southeastern coast. Near the village of Tasiilaq, a strong positive melt-day anomaly exposed a large area of darker deep ice, and a weather station reported the warmest summer on record there (records since 1895). Narsarsuaq, near the southern tip of the island, also had the warmest summer on record (records since 1961), and the capital city of Nuuk along the southwestern coast recorded the second-warmest summer (records since 1873). The area near Kangerlussuaq (‘Kanger’ on the map) did not set a record, but recorded a much warmer-than-average summer, with some areas setting daily records in April (records since 1958).

Melting, melting

Figure 6. This graph shows a comparison of measured and modeled elevation loss due to surface melt for several Danish-operated weather stations (solid lines) and the MAR model at those sites (dashed lines). The locations of the stations are shown in Figure 5. || Credit: Dr. X. Fettweis, University of Liege, Belgium|High-resolution image

Figure 6. This graph shows a comparison of measured and modeled elevation loss due to surface melt for several Danish-operated weather stations (solid lines) and the MAR model at those sites (dashed lines). The locations of the stations are shown in Figure 5.

Credit: Dr. X. Fettweis, University of Liege, Belgium
High-resolution image

Melting leads to a lowering of the ice sheet surface, and the scale can be significant. Moreover, the climate community relies on climate models to conduct forecasts and estimates, since data from the ice sheet or from satellites can be sparse. By comparing the results of the MAR 3.5.2 model of the Greenland Ice Sheet with weather and surface measurement data from the network of automated weather stations operated by the Geological Survey of Denmark (GEUS), called Programme for the Monitoring of the Greenland Ice Sheet (PROMICE), we can evaluate the accuracy of the model. The data and model both show that several meters of ice melted during the summer of 2016 around the perimeter of Greenland and that, except for two low sites (not well resolved at the 20-kilometer MAR resolution), the MAR model compares well with observations.

Thanks to X. Fettweis, J. Box, T. Mote, D. van As, and C. Shuman for contributions to this post.

Further reading

MAR climate model of Greenland
Geological Survey of Denmark (GEUS) Greenland weather network
Dr. Jason Box’s site discussing reflectivity and albedo on Greenland

Warm spell, cold snap

July 2016 had warm conditions and frequent melting in northern Greenland, similar to 2015 but not as extreme. However, last winter’s low snowfall in the south meant that July’s near-normal melting and slightly cool weather still produced above average melt water runoff, resulting in mass loss from the ice sheet. At month’s end, clear skies and a northerly wind led to a record low evening temperature at Summit Camp.

Overview of conditions

July anomaly maps for 2016, 2012, and 2015

Figure 1. These maps show the Greenland Ice Sheet’s cumulative melt day anomalies for July 2016 (top), July 2012 (bottom left), and July 2015 (bottom right) relative to the July average for 1981 to 2010.

Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
High-resolution image

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Figure 2. The top chart shows the daily melt extent as a percentage of the ice sheet area through August 9.
The bottom chart shows the cumulative melt area (the running sum of the daily area experiencing melt) in millions of square kilometers.

Data courtesy of Thomas Mote, University of Georgia. About the data

Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
High-resolution image

Although nearly keeping pace with 2012 in May and June, surface melting on Greenland in July did not match the extreme area of melting seen in 2012, and has generally remained near the 2015 levels. Melting occurred more frequently than average (relative to Julys spanning 1981 to 2010) along the northern half of the ice sheet. Meanwhile, the southern half had above-average melt near the coast, and less frequent surface melting in higher elevations. However, in mid-August several days of extensive southern melting have been observed, which will add to that melting total at season’s end. The largest melt extent observed (using the Mote method based on satellite data) was 43 percent of the ice sheet, on July 19. As of August 15, the 2016 cumulative melt area was just over half of the 2012 area at the same date.

Conditions in context

Figure 3a. A plot of pressure anomaly. Figure 3b. A plot of temperature anomaly.

Figure 3a. This plot shows the air pressure anomaly (altitude departure from the average of the 500 millibar pressure level) for July 2016.
Figure 3b. This plot shows temperature departure from average at the 700 millibar level (approximately 10,000 feet above sea level) for July 2016. The reference period for both plots is 1981 to 2010.

Credit: NSIDC courtesy, NOAA ESRL Physical Sciences Division
High-resolution image

In 2016, a pattern of higher-than-average pressure over central Greenland continued the summer circulation trend, bringing southerly winds along the western and northern parts of the ice sheet. While similar to the 2015 patterns, the surface air pressure departure from average was about half of that seen last year. Temperatures were higher than average (1 to 2 degrees Celsius or 2 to 3.6 degrees Fahrenheit) over the northern and northeastern ice sheet. However, temperatures were average to slightly below average in the southernmost part of the island and the eastern peninsula near Scoresbysund.

Less snow last winter means more ice sheet loss in Southern Greenland

maps showing surface melt change and snow and rain input

Figure 4. Left, this map shows the model result simulating surface mass change of Greenland as of August 9, 2016. The graph shows a blue (negative) ring around the perimeter of Greenland indicating the effect of summer melt and run-off.
Right, this map shows total snow and rain input, mostly from the preceding winter.

Credit Dr. X. Fettweis, University of Liege, Belgium (www.climato.be) and the MAR 3.5.2 model
High-resolution image

Greenland’s net ice mass loss for 2016 is large, even though the number of melt days is below average in some areas. This is because snowfall input to some parts of Greenland was below average. With low winter and spring snowfall input in these areas, any present snow melts away sooner, and subsequently the melting of underlying glacier ice begins earlier, causing the ice sheet to lose mass. The lower-than-average mass input to the southern part of Greenland, and in the northeast, means that a significant net loss of ice happened in these areas, even though the number of melt days in the south has been slightly below average.

Western Greenland darkness: how low can you go?

Albedo anomaly map

Figure 5. Left, This map shows Greenland’s departure from its average reflectivity (whiteness or albedo) for the first few days of August 2016, based on a ten-year reference period (2000 to 2009). Yellow colored regions indicate areas that are more than 15 percent darker than average.
Right, MODIS satellite image from 07 August, 2016 of the central west coast of Greenland (area in black outline on map).

Credit: J. Box, Geological Survey of Denmark and Greenland (GEUS)
High-resolution image

Bare ice areas are much darker than new dry snow areas. Once melting removes winter snow, older coarse snow from previous years, called firn, exposes bare and contaminated glacier ice (from dust, soot, or algae). In western Greenland, a band of dark glacier ice becomes exposed in late summer, and a band of melt-saturated snow is present farther up on the dome-shaped ice sheet. With less solar energy reflected, melting in these darker areas increases. A map of the departure from the average reflectivity (whiteness or albedo) relative to the period 2000 to 2009 indicates areas of significantly darker-than-average surface near the perimeter of the ice sheet. Only a few areas of recent snowfall are brighter than the average from the same reference period.

Cold snap

air temperatures from summit camp

Figure 6. This plot shows air temperatures from Summit Camp in Greenland for the period of July 11 to August 11.

Credit: T. Oetiker, RRDTOOL
High-resolution image

Clear skies, high pressure, and northerly winds lowered nighttime temperatures at the very end of July, resulting in the lowest July air temperature on record for the Summit Camp in Greenland at the top of the ice sheet (10,550 feet, or 3216 meters, above sea level). Near midnight on July 31, the temperature reached 23 degrees Fahrenheit below zero (-30.7 degrees Celsius). Air temperatures have been recorded at Summit since about 1990, a short reference period. Dry clear air and a long sunset allowed the surface air to cool rapidly as heat radiated away overnight.

Firn Aquifer Research—notes from the field team

Figure 7. This photograph shows researchers conducting an aquifer test. In the foreground, tubing is used to pump water from the borehole, drillte to about 20 meters below the surface into the aquifer. A blue hose connected to the PVC pipe releases the water downslope from the pumping borehole. In the far background, flow rate is measured (~1 liter per second) by filling a bucket of known volume. The rate indicates very permeable firn in the aquifer. A second hole (below the second plywood board) holds a pressure transducer to record the lowering of the water table and then monitor water level recovery in the 5 hours following the flow the test. |Credit: Nick Schmerr .

Figure 7. This photograph shows researchers conducting an aquifer test. In the foreground, tubing is used to pump water from the borehole, and drill down to the aquifer, about 20 meters below the surface. A blue hose connected to the PVC pipe releases the water downslope from the pumping borehole. In the far background, flow rate is measured (about 1 liter per second) by filling a bucket of known volume. The rate indicates very permeable firn in the aquifer. A second hole (below the second plywood board) holds a pressure transducer to record the lowering of the water table, and then monitor water level recovery in the 5 hours following the flow the test.
Credit: Nick Schmerr
High-resolution image

The high pressure system that persisted over southern Greenland throughout the end of July has brought good weather to the Greenland Aquifer Expedition Team south and upstream of Helheim Glacier (team members: Rick Forster, Kip Solomon, Clement Miege, and Olivia Miller, University of Utah; Nick Schmerr, University of Maryland, and Stefan Ligtenberg, University of Utrecht). This region is notorious for heavy snowfall, often hindering field work, but this year’s sunny, warm weather has allowed the team to work quickly and effectively. Temperatures at the field site have been above freezing day and night, with daylight lasting up to 18 hours a day. Significant surface melt, which feeds the aquifer, is eroding snow around the tents. After a few days the tents appear to rest on pedestals.

Melt water in Southeast Greenland percolates into the snow, like a sponge, and in many coastal areas the meltwater penetrates to depths of 10 to 20 meters (33 to 66 feet) and is stored year round in firn aquifer systems. Unlike southwestern Greenland, where meltwater enters river systems and then quickly drains to the ocean, the meltwater in southeastern Greenland is retained for some period in the aquifer before reaching the ocean. The exact path is still uncertain. The team is drilling ice cores, measuring water flow rates, and using seismic and radar measurements to look at the structure of the aquifer. These measurements will determine the quantity and duration of water being stored in the aquifer system. Due to the good weather, the team is a few days ahead of schedule, completing field work at two sites and starting on the third and final site. The team drilled into the water table at a depth of about 20 meters (66 feet) at the first two sites and has conducted dye tests to watch water percolate into the aquifer.

Further reading

Blog from Greenland Aquifer Expedition
The 2016 Greenland ice sheet SMB
Polar Portal’s Greenland surface conditions for June 2016
PROMICE: Programme for Monitoring of the Greenland Ice Sheet