Large ice loss on the Greenland ice sheet in 2019

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Low winter snow cover, springtime heat waves, and a sunny summer led to a large runoff of meltwater from the Greenland ice sheet in 2019, primarily from its western side.

Overview of conditions

Figure 1. At top left, a map of the total number of days of surface melting for the Greenland Ice Sheet spanning the full summer season. At top right, the difference between 2019 total melt days and the 1981-2010 average number of melt days. Lower panel shows the daily area of surface melting for 2019 and several recent years.

Figure 1. The top left map shows the total number of days of surface melting in the summer season for the Greenland ice sheet. The top right map shows the difference between 2019 total melt days and the 1981 to 2010 average number of melt days. The lower panel shows the daily area of surface melting for 2019 and several recent years. Data courtesy of Thomas Mote, University of Georgia. About the data

Credit: National Snow and Ice Data Center/T. Mote, University of Georgia
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Figure 2. Bar chart showing the total melt-day extent (the sum of the daily melt area for the season) for 2019 and the preceding 20 years.

Figure 2. This bar chart shows the total melt-day extent, or the sum of the daily melt area during the melt season, for 2019 and the preceding 20 years.

Credit: T. Scambos/NSIDC
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Figure 3. This graph shows the total surface mass balance (SMB) for the Greenland ice sheet from September 2018 to August 2019, relative to the 1981 to 2010 average, which is represented by the 0 line in black.

Credit: X. Fettweis, Université of Liège, Belgium/MAR regional climate model
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Surface melting on the Greenland ice sheet ramped down at a near-normal pace in the weeks following the major melt event of early August (Figure 1). Only a few minor late-season melt events occurred in September and October. Overall, melting on the Greenland ice sheet for 2019 was the seventh-highest since 1978, behind 2012, 2010, 2016, 2002, 2007, and 2011 (Figure 2). Since 2000, the ice sheet has experienced a general increase in melting, with melt-day area for 2019 totaling 28.3 million square kilometers (10.9 million square miles) for the season. Melting was observed over nearly 90 percent of the island on at least one day, reaching the Summit Station and much of the high-altitude areas. It was particularly intense along the northern edge of the ice sheet, where compared to the 1981 to 2010 average, melting occurred for an additional 35 days. The number of days with melting was slightly above average along the western flank of the ice sheet as well, with about 15 to 20 more days of melting than average. In the south and southeast, melting was slightly less than average by a few days.

Despite the less-than-record number of melt days, models show that 2019 had very large net ice loss for the year, at slightly more than 300 Gt, nearly equal to the intense melt year of 2012. Results of the University of Liege’s MAR 3.10 model (here using weather reanalysis data from NCEP-NCARv1; the ERA5 reanalysis data provides similar results) confirms that the 2018 to 2019 surface mass balance (SMB) departure from average is very close to the previous 2011 to 2012 record of surface mass loss (Figure 3). SMB is the net result of total snowfall and rainfall minus runoff and evaporation. This does not include the imbalance in discharge, or the extent to which glacier outflow exceeded remaining snowfall input, which is significant although smaller than earlier in the decade. The main area of mass loss was the western side of the ice sheet.

Conditions in context

Figure 4. The top plot shows air pressure difference from average, relative to 1981 to 2010. This is shown as the height difference from average of the 700 mb pressure level (about 10,000 feet), in meters. The bottom plot shows air temperature difference from average at the same altitude, in degrees Celsius.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
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Figure 5. The left maps shows total snowfall and rainfall, if any, minus runoff or evaporation, which is the Surface Mass Balance (SMB) for the Greenland ice sheet. SMB spans from September 2018 to August 2019, shown in number of millimeters (0.04 inches) of equivalent water amount on the surface. The right map shows the difference from average snowfall input (SMB) for the same period, again shown in millimeters of water equivalent on the surface.

Credit: X. Fettweis, Université of Liège, Belgium/MAR regional climate model
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The key factors for surface mass loss and melting for Greenland in 2019 included: 1) exceptional persistence of anticyclonic conditions (high pressure) during the 2019 summer, promoting dry and sunny weather that enhanced the surface melt thanks to the melt-albedo feedback, and 2) low snowfall in the preceding fall-winter-spring, particularly in the high-melt areas of western Greenland.

High pressure was dominant along the northwestern side of Greenland and Baffin Bay for the core of the melt season in June, July, and August this year, driving warmer air toward the northern region of the ice sheet and leading to clear sky conditions that promoted solar-driven surface melting (Figure 4). As the thin winter snow cover melted away early in the summer, darker older ice was exposed. Clear sunny weather led to a very high run-off rate, resulting in large mass losses. Persistent high pressure over Baffin Bay drove some downsloping wind events along the southwestern coasts. Melting along the northern coast as simulated by MAR was the highest recorded since 1978.

The summer months were only moderately warmer than average relative to 1981 to 2010, roughly 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) higher along the western coast. This confirms that the main driver of surface melt in 2019 was above average cloud-free days, not warm air temperatures as in the 2012 summer melt. This also explains the exceptional dry and sunny conditions at the south.

 

Acknowledgements

Xavier Fettweis, Université of Liège in Belgium, providing the MAR 3.10 model results

Jason Box, Geological Survey of Denmark and Greenland (GEUS) in Copenhagen, Denmark

Europe’s warm air spikes Greenland melting to record levels

Warm air from Europe’s heat wave reached Greenland on July 29 and 30, setting temperature records at Summit Station and melting about 90 percent of the ice sheet surface from July 30 to August 3. Melt runoff was estimated at 55 billion tons during the interval, or about 40 billion tons more than the 1981 to 2010 average for the same time period. Overall, melting this July was much higher than average, leading to more extensive bare ice and flooded snow areas.

Overview of conditions

Figure 1a. The top left map shows melt extent for Greenland on July 31, the peak of the recent warm event. The map includes temperatures at local noon for that day from several Programme for Monitoring of the Greenland Ice Sheet (PROMICE) weather stations. The top right map shows the total number of melt days for January 1 to August 3, 2019. The bottom panel shows the melt area day-by-day for 2019 (blue) and several other high-melt years.

Credit: National Snow and Ice Data Center
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Figure 1b. This graph shows the cumulative surface melting area for 2019 and several of the most recent years.

Credit: National Snow and Ice Data Center
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A rapid increase in surface melting on the Greenland ice sheet began on July 30 and continued through August 3, covering primarily the central and northern areas of the ice sheet on both the east and west ice sheet slopes. On July 30 and 31, melting reached the Summit Camp area of the ice sheet, corroborated by both air temperature from the National Oceanic and Atmospheric Administration (NOAA) weather station at Summit and the passive-microwave melt analysis. Peak melt area occurred on July 31, with just over 60 percent of the ice sheet surface experiencing melt (Figure 1a). Over the course of the five-day event approximately 90 percent of the surface of Greenland reached the melting point at least once.

The daily sum of melt area in July was 397,560 square kilometers (154,500 square miles), well above the 1988 to 2017 average of 337,945 square kilometers (130,481 square miles). The 1988 to 2017 range is a 30-year record of daily melt mapping for Greenland in summer. Melt area mapping from 1979 to 1987, on the other hand, recorded every other day, using a earlier passive microwave satellite.

Cumulatively, the 2019 season sum of melt area for every day is tracking well behind 2012, the satellite-era record for total melt-day area, and slightly behind 2016 (Figure 1b). However, total ice mass loss for 2019 is nearly equal to 2012 because of low winter snowfall. Early melting of the surface in 2019 quickly removed the snow accumulation from winter, and deeper melting this month has eroded older snow and ice over large areas of the western side of Greenland.

Conditions in context

Figure 2a. Top, Average air temperature difference from the 1981-2010 average at the 700 hPa level, or about 10,000 feet above sea level, for 30 July – 03 August, 2019. Bottom, average sea level pressure (estimated over land areas) for the same period. (NCEP Reanalysis data, National Center for Atmospheric Research)

Figure 2a. The top plot shows air temperature as a difference from average for the 1981 to 2010 reference period at the 700 hPa level (about 10,000 feet above sea level) for July 30 to August 3, 2019. The bottom plot shows the average sea level pressure (estimated over land areas) for the same period.

Credit: National Centers for Environmental Prediction (NCEP) Reanalysis data, National Center for Atmospheric Research
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Evolution of heat wave from Europe to Arctic

Figure 2b. This series of images from the atmospheric circulation model shows the evolution of a weather pattern from July 25 to July 31, 2019.

Credit: Global Forecast System (GFS)/National Centers for Environmental Prediction (NCEP)/US National Weather Service
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Surface air temperatures during the warm event over Greenland peaked to 12 degrees Celsius (22 degrees Fahrenheit) above the 1981 to 2010 reference period, and averaged 3 to 9 degrees Celsius (5 to 16 degrees Fahrenheit) above the reference period over nearly the entire ice sheet for the five-day period. High pressure was centered over the ice sheet during the event.

Extreme warm air conditions were present over western Europe in late July, as desert air from the Sahara moved northward. Following the record high temperatures in France, the Netherlands, and Germany, counterclockwise airflow around a low pressure in the North Atlantic brought the warm air mass from Scandinavia to Iceland and then to Greenland. As warm air arrived at Summit Station, Greenland, a prolonged period of near-freezing to above-freezing temperatures occurred on July 30 and 31. In a place where the sun sits low on the horizon at night, these temperatures are unprecedented in the period of observations for this site, which began in 1987. Temperatures dropped further on the night of July 31, but came close to melting again on August 1. With air incoming from the east and some cloudiness in the south of Greenland, melting was amplified on the western side by heating from air compression in downslope winds, increasing the surface melting and runoff. The westward movement of the warm air mass is unusual. Most recent warm events, such as the widespread melting earlier this year, and in July and August of 2012, were a result of air masses coming from the southwest and up along the western Greenland coast.

Losing billions of tons of ice per day

Figure 3. Top graph, estimated snow and ice gain or loss for the Greenland Ice Sheet for several recent years, in billions of tons, relative to the average of the reference period, 1981-2010; lower two graphs show estimated melt runoff (upper graph) and total amount of melt (lower graph), in billions of tons per day for several recent years. Dashed lines indicate forecast values for early August. Model results from the MAR 3.9 model provided by Xavier Fettweis.

Figure 3a. The top graph shows estimated snow and ice gains or losses for the Greenland ice sheet for several recent years, in billions of tons, relative to average for the 1981 to 2010 reference period.

Credit: X. Fettweis, Université of Liège, Belgium/MAR regional climate model
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Figure 3b. lower two graphs show estimated melt runoff (upper graph) and total amount of melt (lower graph), in billions of tons per day for several recent years. Dashed lines indicate forecast values for early August. Model results from the MAR 3.9 model provided by Xavier Fettweis.

Figure 3b. These two graphs show estimated melt runoff, for the upper graph, and total amount of melt, for the lower graph, in billions of tons per day for several recent years. Dashed lines indicate forecast values for early August. Total melt amount over the ice sheet is higher than melt runoff because in many areas high up on the ice sheet, small amounts of melt seep into the snow and re-freeze, leaving the mass of the ice sheet unchanged.

Credit: X. Fettweis, Université of Liège, Belgium/MAR regional climate model
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Our colleague, Xavier Fettweis at the Université of Liège, Belgium, developed a Greenland ice and climate model that provides estimates of mass gained or lost by snowfall and melt (not including ice lost from the outflow of glaciers) (Figure 3a). To date, 2019 is tracking the record high melt volume and ice loss of 2012 almost exactly, with about 40 days left in the melt season. At present, Greenland has lost a total of over 250 billion tons from melt runoff (and low total snowfall earlier in the season). Daily melt amounts were 12 to 24 billion tons through the five-day event, about 6 to 18 billion tons above the rates typical of the 1981 to 2010 reference period for these days. Total runoff for the five-day period was 10 to 12 billion tons per day, or 5 to 7 billion tons per day above average rates (Figure 3b). The ice sheet lost approximately 55 billion tons through melt runoff during the event.

At summit: The highest temperatures in the past 12 years

Air temperatures at Summit Station, Greenland

Figure 4. This graph shows temperatures at 2 meters (6.5 feet) above the snow surface from Summit Station, Greenland, for the past 12 years (2008 to 2019, inclusive) for June 1 to August 15. Above-freezing temperatures over a ten-minute period have only been reached at Summit Station on three days during this period: July 11, 2012, and July 30 and 31, 2019. Data provided by NOAA’s Earth System Research Laboratory, Global Monitoring Division.

Plot prepared by Christopher Shuman and Michael Schnaubelt, University of Maryland Baltimore County
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The NOAA 2-meter air temperature data from Summit Station on the July 30, 2019 was at or above freezing for more than 11 hours, a record in the last 12 years, which has seen a period of increased temperatures overall. Furthermore, this melting event on July 30 also sets the record for the preceding century. Prior to 2012, melt layers at summit have been absent since 1889, and only appear again 680 years earlier.

Only two other melt events occurred here in the last 12 years, both shorter: On July 11, 2012 melting lasted for about 6.5 hours and on July 31, 2019 for more than five hours. The highest 1-hour average of above-freezing temperatures were set in 2012 at 0.79 degrees Celsius (33.4 degrees Fahrenheit) and in 2019 at 0.92 degrees Celsius (33.7 degrees Fahrenheit). Cooling on the evening of July 30 to 31 was minimal, to approximately -2.5 degrees Celsius (27.5 degrees Fahrenheit), and an unprecedented second day of above-freezing maximum temperatures occurred on July 31, 2019, when temperatures were above freezing for more than five hours and reached a maximum of 1.1 degrees Celsius (34.0 degrees Fahrenheit).

Deep blue ice and darker snow

Figure 5a. These maps of Greenland show albedo, or the brightness and reflectivity, of the ice sheet surface (blue-white areas) on July 29 and August 1, 2019, using Sentinel-3 Ocean and Land Color Instrument (OLCI).

Credit: Jason Box, Geological Survey of Denmark and Greenland (GEUS)
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Figure 6. Landsat 8 of an area of the western Greenland Ice Sheet on August 2nd in the Jakobshavn area near the upper edge of the bare ice region, showing dark exposed ice, melt ponds, some residual winter snow, and tundra near the coast. Enhanced true color image from Path 009, Row 011, 180 km (112 miles) on a side; north is marked.

Figure 5b. This enhanced true-color Landsat 8 image shows an area of the western Greenland ice sheet on August 2 in the Jakobshavn area near the upper edge of the bare ice region. Dark exposed ice, melt ponds, some residual winter snow, and tundra are visible near the coast. The image is of Path 009, Row 011, 180 kilometers (112 miles) on a side; north is marked.

Credit: US Geological Survey and NASA
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As the melt event progressed, a wider area of dark bare ice was exposed (Figure 5a). However, a brief snow event just prior to the major melt period left some areas slightly brighter and more reflective, reducing the total area that melted relative to the 2012 event (60 percent in 2019 versus 70 percent of the ice sheet in 2012). Jason Box of the Geological Survey of Denmark and Greenland (GEUS) provided the new albedo, or solar reflectance, mapping product.

A Landsat image of the western flank of Greenland acquired on August 2 shows dark blue exposing older bare ice, with a darker band of dust-laden ice—formed during the last ice age—and wet snow and melt ponds at higher elevations along the right side of the image. 

July run-off: whitewater

Figure 7. Top, runoff from the ice sheet near the Greenland capital of Nuuk. The bottom image shows the location of the monitoring station.

Figure 6. The top photograph shows runoff from the Greenland ice sheet near the Greenland capital of Nuuk. The bottom image shows the location of the monitoring station.

Credit: Irina Overeem
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Water from the Greenland ice sheet contains rock flour, or very finely ground mineral dust, from bedrock erosion by the flowing ice. In the Naajatkuat River, a meltwater river in the Nuuk fjord region, a measurement station above the rapids monitors river levels (Figure 6). The image of runoff was taken during an earlier warm week, July 12 to 14, in southwest Greenland when daytime high temperatures at this low coastal elevation were 19 degrees Celsius (66 degrees Fahrenheit).

Irina Overeem has been monitoring river levels at the flood station at this location since 2011. At the time the picture was taken, the river level was 5.3 meters (17 feet) below the sensor. At the highest level during the exceptional melt in 2012, the water reached to 2.5 meters (8.2 feet) below the sensor. As of this post, water levels for the peak of the July to August 2019 event had not been recovered from the station. 

Further reading

Hanna, E., X. Fettweis, S. H. Mernild, J. Cappelen, M. H. Ribergaard, C. A. Shuman, K. Steffen, L. Wood, and T. L. Mote. 2013. Atmospheric and oceanic climate forcing of the exceptional Greenland ice sheet surface melt in summer 2012. International Journal of Climatology, 34, 4, 1022–1037. doi:10.1002/joc.3743.

Shuman, C. A., K. Steffen, J. E. Box, and C. R. Stearns. 2001. A dozen years of temperature observations at the summit: Central Greenland automatic weather stations 1987–99. American Meteorological Society, 741-752. doi:10.1175/1520-0450(2001)040<0741:ADYOTO>2.0.CO;2.

Trusel, L. D., Das, S. B., Osman, M. B., Evans, M. J., Smith, B. E., Fettweis, X., McConnell, J. R., Noël, B. P. and van den Broeke, M. R. 2018. Nonlinear rise in Greenland runoff in response to post-industrial Arctic warming. Nature, 564(7734), 104. doi:10.1038/s41586-018-0752-4.

Acknowledgements

Xavier Fettweis, Université of Liège in Belgium, for providing the MAR 3.9 model results.

Christopher A. Shuman (University of Maryland Baltimore County (UMBC) Joint Center for Earth Systems Technology at NASA Goddard Space Flight Center (GSFC)) and Mike Schnaublet (UMBC Physics) for producing the “Air Temperatures at Summit, Greenland” graph from data provided by NOAA’s Earth System Research Laboratory, Global Monitoring Division.

Jason Box, Geological Survey of Denmark and Greenland (GEUS) in Copenhagen, Denmark, for producing albedo measurements from a variety of sources for the Greenland ice sheet.

Irina Ovreem and Jasmine Hansen,The Institute of Arctic and Alpine Research (INSTAAR) and the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder (CU). The Research and Innovation Office (RIO), INSTAAR, and CU Boulder funded this field season.

A record melt event in mid-June

Between June 11 and 20, an extensive area of the Greenland ice sheet surface melted. At its peak on June 12, thawing climbed from the western and eastern coasts to elevations above 3,000 meters (9,800 feet). High air pressure and clockwise circulation around the island brought warm air from the south and sunny conditions. While several recent years have had similar early widespread melt events, the event of June 11 to 20 reached a peak of just over 700,000 square kilometers (270,000 square miles), setting a record for this early in the melt season. Models estimate the amount of melted ice at approximately 80 billion tons for that period.

Overview of conditions

Figure 1. The top left map shows the melt extent on June 12, the peak of the recent warm event. The top right map shows the difference between the average number of melt days for January 1 to June 20, relative to the 1981 to 2010 average, and the amount of melting that has occurred this year. The lower panel shows the melt area day-by-day for 2019 and several other years with mid-June excursions in melting, showing that the event of 2019 was a record surface melt area for June 12. Data are from the MEaSUREs Greenland Surface Melt Daily 25km EASE-Grid 2.0 data set. About the data

Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
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Following a relatively dry winter and warm spring for Greenland, a major surface melt episode occurred between June 11 and 20. The maximum area of melt occurred on June 12, at 712,000 square kilometers (275,000 square miles). Melting was detected around the entire coast except the far southern tip of the ice sheet, and extended well inland in both the west central and east central regions, nearly to the summit. The eastern and northeastern coastal areas also melted extensively.

Melting in Greenland through the end of spring has been significantly higher than the 1981 to 2010 average, with several areas exceeding 10 days of additional melt above the average, and a few regions with more than 20 days. Only the southernmost tip of the island and a region along the southwestern side of the ice sheet are below the average to date.

Conditions in context

Figure 2a. The top plot shows differences in air temperature relative to the 1981 to 2010 average at the 700 hPa level, or about 10,000 feet above sea level, for June 11 to 20. The bottom plot shows the average sea level pressure (estimated over land areas) for the same period.

Credit: NCEP Reanalysis data, National Center for Atmospheric Research
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Figure 5.

Figure 2b. These true-color images from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) sensor show sunny conditions over Greenland on June 11 to 13, left to right. The band of greyish-white along the western coast is the ablation area, or exposed bare ice area where the ice sheet is losing mass, as seen in the NASA WorldView MODIS corrected reflectance true-color images.

Credit: NASA WorldView
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During the June 11 to 20 melt event, warm conditions extended over the entire island and particularly along the eastern coast with temperatures up to 9 degrees Celsius (16 degrees Fahrenheit) above the 1981 to 2010 average. High air pressure across the island drew warm air from northeastern Canada across the island. Along the eastern coast, warm winds from the west flowed downhill. Sunny conditions across nearly the entire island were seen on June 11, 12, and 13 (Figure 2b), increasing melt.

Rapid drop in albedo along the western flank

GT_JuneMeltSpike_CSfig3

Figure 3. Surface brightness in the top two images, derived from the Moderate Resolution Imaging Spectroradiometer (MODIS), shows the rapid darkening of the western edge of the ice sheet. The left image shows May 15, while the right June 17. The recent extensive melt event exacerbated early melting in the ablation area, where bare ice becomes exposed by early warming. Shortwave ‘white sky’ albedo, or the fraction of light reflected upward from the surface, for the wavelength range is 0.3 to 5.0 micrometers. Credit: C. Schaaf and A. Elmes, University of Massachusetts Boston.

The bottom photograph shows dark exposed ice, melt ponds, and residual winter snow on June 12 near the upper edge of the bare ice region on the Greenland ice sheet.

Credit: K. Atkinson
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In our previous post, we noted that low snowfall over western Greenland and early spring warming led to an early beginning to the 2019 melt season. Loss of this thin snow cover has rapidly darkened the surface of the western coast by exposing the bare ice of the ablation area of the ice sheet earlier than usual (Figure 3). The ablation area is the area of a glacier where more glacier mass is lost than gained, and where old snow has eroded leaving bare ice. Fresh powdery snow reflects about 80 percent of solar energy, while bare clean ice reflects between 40 to 50 percent, depending on the dust content, which can darken its surface. This early exposure of bare ice increases the pace of meltwater production by allowing the darker ice surface to absorb more solar radiation. An image acquired by one of our readers from a commercial jet crossing southern Greenland shows the edge of the bare ice zone, with darkened snow and bare ice, along with some remaining snow from the previous winter.

A very warm spring

Figure 4. The graph shows air temperature for spring 2019 from the EastGRIP Automated Weather Station compared to the average of the preceding three years. Although the EastGRIP station was not in the area of surface melting in June melt event, the trend shows the unusually warm conditions for this spring.

Credit: J. Box, Programme for Monitoring of the Greenland Ice Sheet (PROMICE)
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A warm spring has heated the Greenland snowpack, preconditioning it for early melting. Although early-season melting (prior to the June 12 event) was not record breaking, the upper snow layers are more likely to thaw as summer proceeds.

Estimated total melt and meltwater runoff from a climate model

Figure 5. The upper plot estimates meltwater runoff from the Greenland ice sheet for several warm years and the 1981 to 2010 reference period average and maximum, in billions of tons per day. Model estimate for 2019 is plotted through 28 June. The lower plot estimates the total melt for the same years and reference period. Total melt is greater because a large fraction of the melt over snow-covered areas drains into the snow and refreezes.

Credit: X. Fettweis, Université of Liège, Belgium/MAR regional climate model
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A model of Greenland climate, using inputs of weather data and forecasts as well as the physical properties of the ice sheet, has estimated the total amount of melt during the extensive melt event. The model also estimated the total amount of melt that flowed off the ice sheet and into the ocean (Figure 5). Both total melt and meltwater runoff set new records for several of the melt event dates. Total melt from June 11 to 20 was about 80 billion tons, of which approximately 30 billion tons ran off the ice into the ocean (or was stored temporarily in lakes).

Further reading

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 (PROMICE)

April and May: Above average, but nothing to write Nome about

Surface melting on the Northern Hemisphere’s largest mass of ice began during the second week of April, with several significant melting episodes at the end of the month and into early May. Warm conditions over the ice sheet and winds from the east were prevalent for the two-month period. While significant, and above average for the 1981 to 2010 reference period, the melting extent has been comparable to previous years spanning 2010 to 2018.

Overview of conditions

Figure 1. The number of melt days in 201X on the Greenland Ice Sheet exceeded XXX for low elevation areas along the southwestern coast, and values above XXXdays were seen in the far north and southeastern coastal areas. Data are from the MEaSUREs Greenland Surface Melt Daily 25km EASE-Grid 2.0 data set. . About the data||Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia|High-resolution image

Figure 1. This map shows the cumulative melt days for the 2019 melt season through May 31, 2019. Data are from the MEaSUREs Greenland Surface Melt Daily 25km EASE-Grid 2.0 data set. About the data

Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
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Figure 2. The graph above shows the daily extent of melt during 2013 on the Greenland Ice Sheet surface as a percentage. The 1981 to 2010 average is shown by a blue dashed line. The gray area around this average line shows the two standard deviation range of the data. Data are from the MEaSUREs Greenland Surface Melt Daily 25km EASE-Grid 2.0 data set. About the data||Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia|High-resolution image

Figure 2. The top plot shows Greenland’s daily melt extent with the percentage of the ice sheet experiencing melt for each day in 2019. The red line depicts April 1 to May 31, the dashed blue line the 1981 to 2010 average, and the grey areas show the range of 90 percent (pale grey) and 50 percent (dark grey) of all years during that period. The bottom plot shows daily melt areas in square kilometers from April 1 to May 31 for 2010 (black), 2011 (light green), 2012 (light orange), 2013 (lavender), 2014 (red), 2015 (purple), 2016 (brown), 2017 (dark orange), 2018 (dark green), and 2019 (blue). Data are from the MEaSUREs Greenland Surface Melt Daily 25km EASE-Grid 2.0 data set. About the data

Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia
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Fig3_ClimateReanalzer_12Apr

Figure 3. This map shows precipitation on April 12, spanning the North Atlantic, Arctic Ocean, and adjacent continental areas. This basic pattern recurred several times in late April and May.

Credit: NOAA, Climate Analyzer
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The number of surface melting days was well above the 1981 to 2010 average for the beginning of the 2019 Greenland melt season, particularly along the southeastern coast. Surface melting was detected up to 26 out of the 61 days between April 1 to May 31. A narrow band of melting was also present along the western coast, from the southern tip of Greenland to the region around Thule in the northwest, exceeding 20 days in some locations. This represents an early onset, but not an unprecedented extent or intensity relative to recent years.

On May 6, melt extent was the highest observed for that day in the 40-year satellite record by a small margin. However, greater melt events—both earlier and later than May 6—have been observed in the past. The May 6 event extended over the southeastern flank of the ice sheet.

More extensive melt periods were seen from mid- to late April and again in early May when clouds bringing warm air and moisture blanketed the southeastern coast. This was attributed to low pressure in the Irminger Sea, between Iceland and Greenland, driving air from the east and south onto the steeply sloping ice sheet, resulting in snowfall and sometimes rain.

 

Conditions in context

Figure 4. The top plot shows the departure from average air temperature over Greenland at the 700 hPa level, or about 10,000 feet above sea level, for April and May 2019 as compared to the 1981 to 2010 average. The bottom plot shows average sea level pressure (estimated over land areas) for the same period.

Credit: NCEP Reanalysis data, National Center for Atmospheric Research
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Figure 5. These maps are the result of a climate model simulating surface mass balance (SMB) departure from average for Greenland up to June 2, 2019. SMB is the net sum of snowfall and rainfall, minus any evaporation or runoff. The reference period is 1981 to 2010.

Credit: Xavier Fettweis, Université of Liège, Belgium/MAR regional climate model
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It was unusually warm over nearly the entire ice sheet relative to the 1981 to 2010 reference, notably over the northern half of the island, where temperatures were more than 4 degrees Celsius (7 degrees Fahrenheit) above average. Over most of the island, this still means conditions were well below freezing, but along the western coast and southeastern coast, temperatures rose to the melting point frequently. Sea level pressure was higher than average along the northeastern coast, with low pressure centered (on average for the two months) off the southeastern tip of the island, and southwest of Iceland. This set up a pattern of winds blowing from the east, off the ocean, and supported significant water vapor transport and large snow accumulations. Winds from the east are not unusual for this region, and tend to bring warm and snowy conditions, and sometimes rain.

Snowfall and surface mass balance, or the combination of snow and rain, minus any evaporation or runoff, are near average, recovering from a relatively dry winter. This recovery is related to a strong influx of moisture-carrying air from the south and east of Greenland to its southeastern coast. However, the recovery is limited to that area, and the rest of Greenland to the north and west are well behind their typical snowfall totals for this time of year. Notably, some net runoff (ice loss for the ice sheet) has already begun along the central western coast resulting from the early onset of the melt season and the low winter snowfall.

Slowing of Greenland’s largest glacier

Figure 6. Ice flow speed for a point near the front of Jakobshavn Isbrae, the largest glacier in Greenland, derived from a number of satellite data sets; and ocean temperatures from 250 m depth (about 825 feet below the surface) measured in Disko Bay, located just in front of the glacier fjord. Jakobshavn Isbrae is near the center of the western coast of Greenland.

Figure 6. The top graph shows ice flow speed for a point near the front of Jakobshavn Isbrae, the largest glacier in Greenland, derived from a number of satellite data sets. The bottom graph shows ocean temperatures from 250 meters depth (about 825 feet below the surface) measured in Disko Bay, located just in front of the glacier fjord. Jakobshavn Isbrae is near the center of the western coast of Greenland.

Credit: Khazendar et al., 2019 Nature Geoscience
High-resolution image

A recent paper documents that Greenland’s largest glacier, Jakobshavn Isbrae, has slowed dramatically in recent years in response to cooling of ocean temperatures in the waters near the coast. The study uses ice flows determined from satellite spanning 19 years (2000 to 2018) and ocean temperature from a number of measurements over that time. Ice flow speeds in the selected location peaked at 7 kilometers per year (4.3 miles per year) in late 2013, and slowed thereafter to a summertime peak of just 5 kilometers per year (3.1 miles per year) in 2017. At the same time, ocean temperatures in a deep bay near the glacier fjord entrance dropped dramatically, from 3.5 degrees Celsius (38.3 degrees Fahrenheit) to 1.5 degrees Celsius (34.7 degrees Fahrenheit) as a cool pulse of water displaced warmer water that had previously persisted in the area. The authors of the study pointed out that, while it may appear that ice loss from the ice sheet is slowing, their results merely show how critical the interaction is between deep glacier ice and warm ocean water, and that it is inevitable, given a generally warming ocean, that rapid ice loss will again occur. However, the slowdown of ice flow at Jakobshavn Isbrae (and for other glaciers) for the past two years may imply slowing of mass loss, which may persist for several more years.

Early warmth, early melting, and early darkening in western Greenland

Fig7_NUUK_PromiceData

Figure 7. The top graph shows weather and snow measurements for a site on the Greenland Ice Sheet east of the coastal city of Nuuk (NUUK_U, 72.39 degrees North, 27.26 degrees West, 988 meters or 3,240 feet elevation). The top graph illustrates how a drop in snow reflectance (albedo) coincided with early melting in May 2019, as air temperatures surged above freezing. Both graphs show the average conditions for albedo and air temperature for the preceding 11 years.

Credit: Jason Box, Programme for Monitoring of the Greenland Ice Sheet (POMICE)
High-resolution image

Low snowfall over western Greenland, combined with the early warming, has resulted in an early onset of the melt season at several automated weather stations (AWS) managed by Programme for Monitoring of the Greenland Ice Sheet (PROMICE), a Danish ice and climate research site. The stations have been maintained for the past 12 years, providing a record that permits comparison of 2019 to the recent past. Colleague Jason Box of the Danish Geological Survey produced these graphics and has also compiled a video on current conditions in Greenland and the likelihood of an extensive melt year in 2019.

Further reading

Khazendar, A., Fenty, I. G., Carroll, D., Gardner, A., Lee, C. M., Fukumori, I., … & Noël, B. P. 2019. Interruption of two decades of Jakobshavn Isbrae acceleration and thinning as regional ocean cools. Nature Geoscience,12; 277-283, doi:10.1038/s41561-019-0329-3.

The 2019 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 for winter

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 2019. 

Greenland melt in July and August: Three spikes and out

Three major melt events during late July and August brought the 2018 Greenland melt season to a close. Overall, conditions on the ice sheet were slightly warmer than average for the second half of the summer. From October 2017 to September 2018, continued heavy snowfall on the southeastern coast resulted in near-record snow mass added to the ice sheet.

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 maps show the cumulative melt days for the 2018 melt season through September 15, upper left, and the difference from the average, upper right, for July and August combined, as referenced to the 1981 to 2010 period. Below is a plot of daily melt area for the 2018 season through September 15, compared with melt extents for 2017, 2016, and the 1981 to 2010 period. The three warm periods of increased melt in July and August 2018 are labelled. Data courtesy of Thomas Mote, University of Georgia. About the data

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

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

Figure 2. This graph shows the cumulative melt area (the running sum of the daily area experiencing melt) in millions of square kilometers for 2018 through September 15, 2017, 2016, and the 1981 to 2010 reference period. The graph shows the pace of melting for the respective periods, and a brief increase in cumulative area growth during the three warm spikes in melt area. About the data

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

In July and August, the number of surface melt days was above average along the southwestern coast, reaching well up into the ice sheet. Surface melt was below average in the northwestern and northeastern areas of the ice sheet, but melting in the southeast increased after the early season.

Three significant melt events peaked on July 17, July 31, and August 9. While none of these were exceptional, they were among the highest melt extents for those dates in the satellite record, at or above 500,000 square kilometers (193,000 square miles)—roughly a third of the ice sheet. High atmospheric pressure contributed to the melt events on July 31 and August 9. Strong winds from the southeast were linked to the melt events on July 17 and July 31, and from the southwest on August 9. Surface temperatures during the events were generally 2 to 5 degrees Celsius (4 to 9 degrees Fahrenheit) above the 1981 to 2010 average. Overall, higher-than-average temperatures of 0.5 to 1.2 degrees Celsius (0.9 to 2.2 degrees Fahrenheit) above the 1981 to 2010 mean characterized the second half of summer. The only exception was the northwestern area near Thule, where temperatures were as much as 0.5 degrees Celsius (0.9 degrees Fahrenheit) below average.

High snowfall and moderate melt runoff in 2018

Figure 3. Model results for the Greenland Ice Sheet snowfall and melt runoff since 1960. The model (MAR 3.9) was run using input from NCEP weather reanalysis data. SMB stands for ‘surface mass balance’, the net difference between snowfall input and meltwater runoff (or evaporation) loss. The bars show the relative difference from a reference period of observations and modelling (1981-2010). Source is Dr. Xavier Fettweis, MAR 3.9 model, see http://climato.be/melt

Figure 3. This chart shows the model results for the Greenland Ice Sheet snowfall and melt runoff since 1960. The model (MAR 3.9) was run using input from National Centers for Environmental Prediction (NCEP) weather reanalysis data. The surface mass balance (SMB) refers to the net difference between snowfall input and meltwater runoff, or evaporation, loss. The bars show the relative difference from the 1981 to 2010 reference period of observations and modeling.

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

As noted in the previous post, exceptional winter snow accumulation and heavy, summer snowfall, drove the net snow input mass to 130 billion tons above the 1981 to 2010 average. This was followed by a near-average melt and runoff period, resulting in a large net mass gain for the ice sheet in 2018 of 150 billion tons. This is the largest net gain from snowfall since 1996, and the highest snowfall since 1972. However, several major glaciers now flow significantly faster than in these earlier years. The net change in mass of the ice sheet overall, including this higher discharge of ice directly into the ocean, is not clear at this point but may be a smaller loss or even a small gain. This is similar to our assessment for 2017, and in sharp contrast to the conditions for the preceding decade.

Persistent winds from the northeast triggered high snowfall for 2017 to 2018 along the eastern Greenland coast. These winds blew across open ocean areas allowing the atmosphere to entrain moisture and deposit it as heavy snowfall on the ice sheet.

Bright summer

Figure 4. The top graph shows the trend of reflectivity for the entire Greenland Ice Sheet for 2018 through September 15, and four reference years: 2000, 2010, 2012, and 2017. The grey band represents the 5-to-95 percentage range for the 2000 to 2009 reference period. The maps below show average monthly albedo, or reflectance, for July 2018, on the left, and August 2018, on the right.

Figure 4. The top graph shows the 2018 reflectivity trend for the entire Greenland Ice Sheet through September 15, and four reference years: 2000, 2010, 2012, and 2017. The grey band represents the 5-to-95 percent range for the 2000 to 2009 reference period. The maps below show average monthly albedo, or solar reflectivity, for July 2018, on the left, and August 2018, on the right.
High-resolution image

High winter and spring snowfall, and a moderate initial pace of melting, resulted in a more reflective (higher albedo) surface for the ice sheet than in past summers. Since bright, fresh snow blanketed areas that were once darker, such as dirty snow or bare ice, July’s average albedo for the ice sheet was 5 to 9 percent above the 2000 to 2009 reference period.

Wet snow also has a darker surface, or lower albedo. Increased surface melting, above-average temperatures, and the three spikes in melting, August’s albedo decreased to more average values. However, the albedo along the western coast remained above average.

Further reading

The annual publication of the Arctic Report Card is expected in December, which will include more details of all aspects of the 2017 to 2018 period for Greenland’s climate and ice sheet.

Box, J. E., D. van As, and K. Steffen, 2017. Greenland, Canadian and Icelandic land ice albedo grids (2000-2016). Geological Survey of Denmark and Greenland Bulletin, 38, 53-56

The 2018 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

2018 melt season halftime assessment

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
High-resolution image

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 courtesy NCEP NOAA
High-resolution image

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

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
High-resolution image

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
High-resolution image

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)
High-resolution image

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
High-resolution image

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
High-resolution image

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