Late June ushered in a significant shift in weather and melting for Greenland, particularly for the southern portion of the ice sheet, known as South Dome, where melting is currently on a record pace. Melting along the northern rim of the ice sheet is also greater than average. These changes are a result of a shift in the air circulation, associated to negative North Atlantic Oscillation (NAO) index values. High air pressure now covers the island, bringing warm winds from the southwest and favoring sunnier condition enhancing the surface melt in the ablation zone, for which the extent is now close to the previous records in the summers of 2012 and 2019.

Overview of conditions

Figure 1. The top left map illustrates cumulative melt days on the Greenland Ice Sheet for the 2023 melt season through July 12. The top right map illustrates the difference from the 1981 to 2010 average melt days for the same period. The bottom graph shows the daily melt area for Greenland from April 1st through August 6th for 2023 and several of the near-record melt years in this century. The gray lines and bands depict the average daily melt area for 1981 to 2010, the interquartile range, and the interdecile range.

Credit: National Snow and Ice Data Center/T. Mote, University of Georgia
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Beginning around June 23, the areal extent of Greenland’s surface melting and runoff increased significantly. Several widespread melting events covering about 800,000 square kilometers (302,000 square miles) or up to 50 percent of the ice sheet occurred on June 27, July 6 to 7, and July 11, as several pulses of warm air swept across the southern portion of the ice sheet and northward around the northern coast. The total number of days with melting are now well above average throughout the southern and southwestern portions of the ice sheet by up to 5 to 15 days, and along its northern flank by about 10 days. Total melt-day extent, the sum of daily melt extents for the season so far, is now sixth highest overall. Melt-day extent over the southern portion of the ice sheet is now at a record high for the 45-year satellite record.

A significant increase in the estimated (modelled) run-off has occurred in the South Dome and Zachariæ Isstrøm Glacier regions, exacerbated by the below-average net accumulation in the southern and northeastern portions of the ice sheet at the end of spring. Moreover, at least some melting has now occurred over most of the ice sheet, even at high elevations, and this preconditions the snow for further melting by warming and darkening the upper layers.

We have in part corrected the parameters for determining melt from the satellite data by adjusting the baseline reference period used to characterize the pre-melting springtime snowpack. However, somewhat unusual conditions in the upper Jakobshavn Gletscher region, inferred to be due to a heavy surface frost event sometime earlier in the spring, prevent a complete removal of the anomalous early-melt area. This remaining possible inaccuracy is now a small fraction of the total melt-day mapping for the year (less than 5 percent).

Conditions in context

Figure 2a. The above plot illustrates average surface air temperature as a difference from the 1991 to 2020 mean for the period of June 21 to July 12, 2023, for Greenland and the surrounding areas. Warmer-than-average conditions are now present across nearly all of the ice sheet.

Credit: National Centers for Environmental Prediction (NCEP) Reanalysis data
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Figure 2b. This plot shows the difference from average of the height of the 700-millibar level (about 3 kilometers or 10,000 feet above sea level), an indication of the mean air pressure, for Greenland and the surrounding areas for June 21 to July 12. High pressure to the southwest of Greenland drove warm air along the western coast and across the ice sheet.

Credit: National Centers for Environmental Prediction (NCEP) Reanalysis data
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Figure 3. The top graph shows melt run-off and the bottom graph shows daily surface melt total from the Modèle Atmosphérique Régional (MAR) model for May 1 through July 18. The last few days are based on a forecast.

Credit: X. Fettweis, University of Liège and MAR3.12
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Air temperatures across Greenland have been above average over the past several weeks, by up to 1.5 to 2 degrees Celsius (3 to 4 degrees Fahrenheit) in the south and over 3 degrees Celsius (5 degrees Fahrenheit) in the north-central area. Air pressure patterns have changed markedly since the May-June period, with higher-than-average pressure both to the southwest and the northeast of the island. This pattern has brought a series of warm air pulses across the island from the southwest.

Both melt volume and surface meltwater run-off have increased since the weather pattern change. Daily estimated totals of melt have been about 15 billion tons per day for the first half of July, and estimated melt run-off about 10 billion tons per day. These anomalies have been two standard deviations above average since the end of June. Negative NAO conditions are expected to continue through the end of July, and we expect the total July runoff at South Dome to exceed the previous record years of 2002, 2007, 2012, and 2019. Given the below-average snowfall in the southern and northeastern areas, and the frequent occurrence of rainfall this July, the surface is pre-conditioned for further melting, exposing more ice-covered ablation areas especially near the coast. Further melting in July and early August will be enhanced by sunnier conditions as a result of negative NAO condition and will lead to high melt run-off.

Record pace of melting at South Dome

Figure 4. At top left, melting degree days total for 2023 up to July 14 for 2006 through 2023 for the Northeast Eemian (NEM) automatic weather station (AWS) site; at top left melting degree days up to July 14 for 1996 through 2023 for South Dome (SDM) AWS. Melting degree days are the sum of the number of degrees above melting at the peak daily temperature for days with melt in a summer season. The bottom graph is a plot of hourly air temperature for the SDM AWS for 2023 showing the persistent period of melting during July 6 to 12.

Credit: J. Box and the Geological Survey of Denmark and Greenland (GEUS), PromIce GC-Net
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Figure 5. This graph shows surface mass balance, the sum of snow and rainfall minus evaporation and run-off, difference from the 1981 to 2010 average for the South Dome area for the 2022 to 2023 hydrological year and several recent years through mid-July.

Credit: J. Box and the Geological Survey of Denmark and Greenland (GEUS), PromIce GC-Net
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Figure 6. National Oceanic and Atmospheric Administration Global Monitoring Laboratory temperature data from the Summit Observatory, initially transmitted at 1-minute average resolution, are plotted here at 10-minute averages for the month of June (late June 2008 through 2023). The previous record high temperature for June was on June 12, 2019, briefly at 0.1 degrees Celsius (32 degrees Fahrenheit). On June 26, 2023, a temperature of 0.4 degrees Celsius (33 degrees Fahrenheit) was seen during a several-hour stretch of near or above freezing conditions at the Summit weather station.

Credit: Christopher A. Shuman, University of Maryland, Baltimore County at NASA Goddard Space Flight Center and Michael Schnaubelt, Johns Hopkins University, using data from NOAA’s Global Monitoring Laboratory
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Warm conditions in both the northern and southern sections of the island have led to a record high melt-degree-day index for weather stations in those areas for the periods when they have operated. For all days in a season where the maximum temperature is above freezing, the melting degree day index sums the total number of degrees above freezing for each day. At both the Northeast Eemian automatic weather station (NEM) and the South Dome automatic weather station (SDM), the total melting degree day index is ahead of the past record melt season, 2012 (Figure 4). At South Dome, an extended period of above-freezing temperatures occurred from July 6 to 12, pushing its total melting degree-days index rapidly higher (Figure 5). However, both 2019 and 2012 had very intense melting in the second half of July and in early August.

At Summit Station, we have been monitoring the reported air temperature, and on several occasions in June and into July the air temperatures have been very close to or slightly exceeding the melting point. The above freezing temperatures on June 26 (Figure 6) represents a record warm air temperature for June at Summit.

Greenland catches the wave

Figure 7. This figure shows example days of the mapping of air-flow waviness over the study area used in the Preece et al., 2023 study. The top map shows airflow contours with low sinuosity (waviness) on August 16, 2001. The bottom map shows a strong waviness pattern on July 11, 2012.

Credit: Modified from Preece et al., 2023, Nature Communications
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Air circulation in the Arctic is dominated by westerly winds that encircle the Pole, driven at a fundamental level by the difference in temperature between the tropics and the high latitudes. The boundary of these eastward-flowing winds is marked by the polar jet stream. As Arctic and Greenland air temperatures have warmed, with strongly decreased sea ice and springtime snow cover and increased surface melting, the notion has been forwarded that the jet stream could become more sinuous, or ‘wavier’, leading to weather extremes of persistent warmer or cooler than average conditions. This is one of the more debated potential aspects of Arctic Amplification, that is, the processes that seem to amplify the pace of warming in the high northern latitudes.

A new study supports this hypothesis based on the observed summertime waviness of the airflow over northern Canada, Greenland, and the North Atlantic for 1979 through 2022. During the months of June, July, and August there has been a small but statistically significant increase in the waviness of air circulation in the region of Greenland. Since the mid-2000s, waviness of the airflow has increased in concert with a strong decrease in the June snow cover for North America and Europe. Moreover, this is associated with high pressure over Greenland, creating a ‘blocking high’ that can remain fixed for extended periods (weeks to months). High pressure conditions in Greenland are associated with increased warmth and melting and increased solar energy input to the ice sheet. Given the low June snow cover for 2023, and the emergence of above average pressure over Greenland in June and the first half of July, there is a strong possibility that this pattern will persist through this year as well.

Ice Art

Figure 8. This digital image shows melting ice and ice mélange near Qaanaaq, Greenland.

Credit: Sebastian Copeland
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On June 26, photographer and explorer Sebastian Copeland captured this image of an ice cliff during the widespread melting event at that time.

Further reading

Preece, J. R., T. L. Mote, J. Cohen, L. J. Wachowicz, J. A. Knox, M. Tedesco and G. J. Kooperman. 2023. Summer atmospheric circulation over Greenland in response to Arctic amplification and diminished spring snow cover. Nature Communications, 14(1), 3759. doi:10.1038/s41467-023-39466-6

The melt season for the Greenland Ice Sheet has been near-average so far, with cool conditions in northern Greenland despite warm weather in nearby Arctic Canada. A small region of the ice sheet may not be properly mapped as it shows a higher number of melt days than is likely considering the observed weather for that area. The team will be re-evaluating the melt algorithm for this region in the coming weeks. As of the post, record or near-record heat is being observed at the Greenland Summit, and is forecast to continue through the week. A following report in July will cover this event.

Overview of conditions

Figure 1. The top left map illustrates the cumulative melt days on the Greenland Ice Sheet for the 2023 melt season through June 15. The top right map illustrates the difference from the 1981 to 2010 average melt days for the same period. The bottom graph shows daily melt area from April 1 to June 15, 2023, with daily melt area for the preceding four years, plus the record high year of 2012. The gray lines and bands depict the average daily melt area for 1981 to 2010, the interquartile range, and the interdecile range. The circled area has only reached the melting point a few times in the early season. The team is evaluating the need for a mid-season correction.

Credit: National Snow and Ice Data Center/T. Mote, University of Georgia
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As of June 15, Greenland has had a near-average melt year. Total melt-day area ranked twenty-third in the 45-year-satellite record with the present data, which includes a small region near Jakobshavn Glacier that is over-reporting melt in an area with below-freezing air temperatures (Figure 1). Surface melting can occur when air temperatures at 2 to 3 meters (7 to 10 feet) above the surface (the average height of sensors on a weather station) are within a few degrees of melting, but we are re-evaluating the melt algorithm in this region. Melting is slightly above average in both southeastern and southern Greenland, and slightly below average along most of the rest of the western coast. As of June 15, neither the South Summit nor any regions along the northwestern, northern, or northeastern coast have experienced significant surface melting.

Conditions in context

Figure 2. The top plot illustrates average surface air temperature as a difference from the 1991 to 2020 average for the period April 1 to June 15, 2023, for Greenland and surrounding areas. The lower plot is the height of the 700 millibar level in the atmosphere, a measure of high or low pressure. Cool conditions and relatively low pressure have characterized the weather in the early period for the 2023 Greenland melt season.

Credit: National Centers for Environmental Prediction (NCEP) Reanalysis data
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Figure 3. This graph shows the difference from average cumulative Surface Mass Balance (SMB) (the total of snow and rain, minus any runoff or evaporation) for the Greenland Ice Sheet since September 1, 2022, to June 20, 2023, relative to several other years that illustrate the range of snowfall (plus rainfall) and late season runoff.

Credit: MARv3.12, X. Fettweis, University of Liège 
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Figure 4. The left map shows cumulative total surface mass balance for the Greenland Ice Sheet for the period September 1, 2022, to June 20 2023, shown as millimeters of water equivalent on the surface. The map on the right shows the difference from average of the surface mass balance for the 1981 to 2010 reference period. Ten millimeters is about 0.4 inches.

Credit: MAR 3.12, X. Fettweis, University of Liège

Air temperatures near the southern tip of Greenland have been 1 degree Celsius (2 degrees Fahrenheit) above average, but temperatures elsewhere on the island have been at or below average (Figure 2). The Summit area and northward have recorded temperatures about 1.5 degrees Celsius (3 degrees Fahrenheit) below average. Winds from the north along the western coast of the island brought cooler conditions, driven by generally low air pressure centered on Greenland’s north coast. The slightly warmer conditions and more frequent melting along the southern and southeastern coast were a result of winds coming from the south over that region.

Total surface mass balance, which at the beginning of the melt season is mostly winter snowfall accumulation, is now slightly above the 1981 to 2010 reference period by about 50 billion tons (Figure 3). However, winter snowfall accumulation has been below average along the southern coastal area, by as much as 800 millimeters (32 inches) of water equivalent (Figure 4). Along the western coast, snowfall accumulation is above average. Combined with the cool conditions, thicker accumulated winter snowpack may slow the progression of melt in this otherwise high melt area of the ablation, or exposed ice and run-off, region. With persistent winter snowfall, the surface remains bright longer, and therefore reflects more of the incoming sunlight. However, along the entire southern coast, lower winter snowfall followed by above average surface melt will promote increased runoff as the melt season progresses.

Early trends in temperature

Figure 5. This graph shows the air temperature record at the Crawford Point PromIce weather station for 2023 from mid-May to June 20, 2023, near the region of overly high melt-days from the satellite mapping. Air temperatures had not yet reached the melting point as of June 15.

Credit: J. Box and Geological Survey of Denmark and Greenland (GEUS), PromIce GC-Net
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Figure 6. These graphs show air temperature as a difference from average at two stations, near Jakobshavn (JAR station) and Qassimiut (QAS station), since the beginning of the year. The graphs illustrate the different recent trends of cool conditions (JAR) and warm conditions with surface melting (QAS). Note that the red or blue deviations from the horizontal line represent the differences from the average temperature for that day over the reference periods for the two stations.

Credit: J. Box and Geological Survey of Denmark and Greenland (GEUS), PromIce GC-Net
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Air temperatures for the potentially over-estimated melt area discussed above has been below freezing for the entire May to June period, with a maximum temperature of -0.9 degrees Celsius (30 degrees Fahrenheit) (Figure 5). As of this post, extensive melting has now reached the area. A comparison of the difference from average conditions for two regions through June 20 indicates that the area near Jakobshavn Isbrae has had below temperatures since about May 10, whereas Qassimiut has had above average temperatures since mid-February (Figure 6).

As the sun is dipping lower into the horizon in the Southern Hemisphere, the melt season for the Greenland Ice Sheet has begun. Daily melt extent mapping will resume for the Greenland Ice Sheet at the beginning of May 2023.

The Antarctic Peninsula has had an intense melt season with above average melting persisting through much of February. Saturated snow from a high melt year and low sea ice in Bellingshausen Sea have led to a series of minor calving events on the Wilkins Ice Shelf. Elsewhere in Antarctica, melting was near average.

Current conditions

Figure 1a. The upper maps of the Antarctic Ice Sheet on the left and the Antarctic Peninsula on the right show the total melt days for areas experiencing surface melting from November 1, 2022, to March 15, 2023. The graph on the bottom shows daily melt extent for the Antarctic Ice Sheet as a percentage of ice sheet area for the same time period in red and the 1990 to 2020 average in blue. The interquartile and interdecile ranges appear as grey bands.

Credit: E. Cassano and M. MacFerrin, CIRES; and T. Mote, University of Georgia
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Figure 1b. This map shows the number of melt days from November 1, 2022, to March 15, 2023, as a difference from average relative to the 1990 to 2020 reference period. Reds indicate more melt; blues indicate less melt.

Credit: E. Cassano and M. MacFerrin, CIRES and T. Mote, University of Georgia
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Figure 1c. These maps show the number of melt days from February 1 to March 15, 2023, as a difference from average relative to the 1990 to 2020 reference period. Reds indicate more melt than average; blues indicate less melt.

Credit: E. Cassano and M. MacFerrin, CIRES and T. Mote, University of Georgia
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Melting of the Antarctic Ice Sheet from November to mid-March followed a pattern, where both sides of the Antarctic Peninsula had extensive and frequent melting while elsewhere along the coast patches of melt rarely exceeded 10 days for the season (Figure 1a). However, these small totals represent an above average melt season for the Getz and Roi Baudoin Ice Shelves. In the Peninsula, the northern half of the Larsen C Ice Shelf experienced up to 60 days of melt between November 1 and March 15. During that same time period, some areas of the Larsen C Ice Shelf showed more than 30 days of melt above the average melt days for the 1990 to 2020 reference period (Figure 1b). The Wilkins Ice Shelf, southwest of the Peninsula, had over 70 days of surface melting for the same time period. Overall, Antarctica’s seasonal melt-day total was slightly higher than the 1990 to 2020 average, with significant melt extent events (exceeding the upper decile range) around December 20, January 20, and February 5. Although some groups reported high temperatures and melting over the Ross Ice Shelf in early January, satellite measurements reported no evidence of melting there at that time.

In the latter part of the melt season, melting was limited almost entirely to the Peninsula areas. The northern Larsen C continued to see above-average melting, with 10 days more than average in the 45-day window (Figure 1c). However, the frequency of melting slightly for the Wilkins and George VI Ice Shelf areas, and the extensive melt ponding seen in December and January slowly froze over.

Conditions in context

Figure 2. The top plot shows the departure from average air temperature in Antarctica at the 925 hPa level, in degrees Celsius, from February 1, 2023, to March 15, 2023, relative to the 1991 to 2020 reference period. The bottom plot shows the departure from average air temperature from November 1, 2022, to March 15, 2023. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: National Centers for Environmental Prediction (NCEP) Reanalysis data, National Center for Atmospheric Research
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For the February to mid-March period, relatively warm conditions were present in many parts of the ice sheet (Figure 2, top). However, even in mildly warm summers, temperatures still remain below the melting point on most of the continent. The exception is the Peninsula area where average temperatures were near or above the melting point with temperatures up to 1.5 degrees Celsius (3 degrees Fahrenheit) above average, leading to extensive melting in some areas. Above average temperatures for much of the coastline reflected the extremely low sea ice extent as Southern Ocean sea ice reached a new record low.

Looking at the season overall, while the Peninsula had 0.5 to 1.5 degrees Celsius (1 to 3 degrees Fahrenheit) above average temperatures between November 1, 2022 to March 15, 2023, most of the Antarctic interior had below average temperatures (Figure 2, bottom). While brief periods of melting occurred along the East Antarctic coast and parts of West Antarctica along the Amundsen Sea, in general melting was infrequent in all regions except the eastern and western sides of the Antarctic Peninsula.

Wilkins Ice Shelf calving events

Figure 3. This series of NASA Worldview images of the Wilkins Ice Shelf from the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) instrument was acquired from December 24, 2022, to March 10, 2023, showing retreat of sea ice and calving events along the western and southern edge of the ice shelf. A Sentinel-1a time series shows the northwestern ice front calving events in more detail. The image series is comprised of modified Copernicus Sentinel-1a data from 2022 to 2023, processed by the European Space Agency (ESA).

Credit: C. Shuman, University of Maryland, Baltimore County at NASA/Goddard Space Flight Center (GSFC); Animation provided by M. Fahnestock, University of Alaska Fairbanks
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During the austral summer of 2022-2023, the Wilkins Ice Shelf, located on the southwestern side of the Antarctic Peninsula, lost a significant area of mélange, which is a mix of icebergs and sea ice. The ice edge retreated along both the western ice edge (between Rothschild Island and Latady Island) and the southern ice edge (between Latady Island and Eroica Peninsula). Total area lost was approximately 160 square kilometers (62 square miles), although much of the loss along the western edge was mélange that had formed from past break-up events in 1998, 2008 and 2009, as mapped earlier by our colleagues Mathias Braun and Angelika Humbert.

Retreat occurred along four areas of the Wilkins mélange and ice shelf front. In the most northern area of shelf ice loss, retreat proceeded to the Mozart Ice Piedmont coast, and in the other regions along the western edge retreat, calvings removed a maximum of 5 kilometers (3 miles) from the previous mélange or ice shelf edge.

The warm conditions of the 2022-2023 summer, with above average melt days, and the extended period of very low sea ice in the Bellingshausen Sea, likely contributed to the series of small ice loss events.

References

Braun, M., A. Humbert, A. and Moll. 2009. Changes of Wilkins Ice Shelf over the past 15 years and inferences on its stability. The Cryosphere, 3(1), 41-56, https://doi.org/10.5194/tc-3-41-2009.

Humbert, A. and M. Braun. 2008. The Wilkins Ice Shelf, Antarctica: break-up along failure zones. Journal of Glaciology, 54(188), 943-944, https://doi.org/10.3189/002214308787780012.

Surface melting over Antarctica was near-average through January, but above average surface melting occurred on both the northeastern and southwestern areas of the Antarctic Peninsula. This has led to extensive ponding of melt on the surface in several areas. Elsewhere, surface melting lagged behind the average pace in January with the exception of the Roi Baudouin Ice Shelf.

Current conditions

Figure 1a. The upper left map of the Antarctic Ice Sheet shows the total melt days for areas experiencing surface melting from November 1, 2022, to January 31, 2023. The upper right map shows total melt days for the Antarctic Peninsula for the same time period. The graph on the bottom shows daily melt extent for the Antarctic Ice Sheet as a percentage of ice sheet area for the same time period in red and the 1990 to 2020 average in blue. The interquartile and interdecile ranges appear in grey bands.

Credit: E. Cassano and M. MacFerrin, CIRES and T. Mote, University of Georgia
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Figure 1b. This map shows the number of melt days from November 1, 2022, to January 31, 2023, as a difference from average relative to the 1990 to 2020 reference period. Reds indicate more melt; blues indicate less melt.

Credit: E. Cassano and M. MacFerrin, CIRES and T. Mote, University of Georgia
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Figure 1c. This map shows the number of melt days for January 2023, as a difference from average relative to the 1990 to 2020 reference period. Reds indicate more melt; blues indicate less melt.

Credit: E. Cassano and M. MacFerrin, CIRES and T. Mote, University of Georgia
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At the end of January, the warmest month for the Antarctic continent, surface melting was slightly above average overall (Figure 1a). Warm conditions and frequent foehn events persisted for the Peninsula after earlier strong melting along the West Antarctic northern coast abated. Despite this slowdown, the early-season melting on the Getz Ice Shelf led to above average melting for the season in that area. Surface melting on the northern Larsen Ice Shelf (Larsen B and C areas together) occurred on 45 days as of this post; for the elongated George VI Ice Shelf, melting occurred up to 40 days in some areas, and on the adjacent Wilkins Ice Shelf, the surface melted about 65 days during this season. So far, all three regions have experienced about 15 to 20 days more melt than average (Figure 1b). This above average surface melting for the Peninsula regions continued in January, but nearly all other areas experienced little or no melting, several days less than the average for the month (Figure 1c). By contrast, the Roi Baudouin Ice Shelf, south of the southern tip of Africa, had significant surface melting with roughly 10 more days than average and a total of 15 days of melt.

Conditions in context

Figure 2. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for January 2023, relative to the 1991 to 2020 reference period. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: National Centers for Environmental Prediction (NCEP) Reanalysis data, National Center for Atmospheric Research
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Antarctica’s air temperature in January 2023 in the coastal areas, where melting generally occurs, was near-average to below average except for the Peninsula, which was around 1 degree Celsius (2 degrees Fahrenheit) above average relative to the 1991 to 2020 period (Figure 2). The interior of the continent was much colder than average, as much as 5 degrees Celsius (9 degrees Fahrenheit) below the 1991 to 2020 reference period in the interior of East Antarctica. This pattern of temperatures reflects strong circumpolar winds, which tend to isolate the continental interior, but drive warm moist air, sometimes as rain events, to the western side of the Peninsula. This airflow leads in turn to warm foehn events (chinook winds) that induce extensive melting on the eastern side of the Peninsula.

Extensive melt ponds on the George VI Ice Shelf

Figure 3. This image of George VI Ice Shelf from the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) instrument was acquired on January 29, 2023, showing extensive melt ponding (deep blue speck and linear features) and saturated snow (grey surface near the ponds). Credit: NASA Worldview
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Extensive surface melt ponding on the George VI shelf is a result of the above average melting along the western Peninsula for November through January (Figure 3). This pattern rivals the record extent seen in 2019 to 2020 discussed in Banwell et al., (2021). While extensive melt ponding can lead to ice shelf hydrofracture and disintegration, the George VI Ice Shelf tolerates extensive melting because its confined nature—sandwiched between the peninsula and an island—inhibits internal fracturing.

New iceberg calving and recent changes to the Brunt Ice Shelf

Figure 4. The image on top shows a Landsat 8 panchromatic band composite from January 7 and 19, 2021, shortly before the calving of Iceberg A-74. The bottom image shows a Landsat 8 panchromatic band composite from January 20 and 25, 2023, shortly after the calving of Iceberg A-81. An additional satellite radar image, acquired by the SAOCOM 1A satellite (Satélite Argentino de Observación COn Microondas, Spanish for Argentine Microwaves Observation Satellite), which the European Space Agency launched in 2018, shows the calving event. Satellite radar imagery is relatively unaffected by clouds, and images of ice areas highlight both crevasses and rifting, and surface snow effects caused by melting and refreezing.

Credit: C. Shuman, University of Maryland, Baltimore County at Code 615 NASA Goddard Space Flight Center
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On January 22, 2023, a 1,550 square kilometer (580 square mile) iceberg calved from the southwestern side of the Brunt Ice Shelf near the British Antarctic base Halley VI. The iceberg has been named A-81 by the US National Ice Center. This calving had been anticipated for several years because of the reactivation of a rift nicknamed Chasm 1, which began in 2012. The steady growth of Chasm 1 since then prompted a move of the Halley VI research base to a safer location in 2016, known as Halley VIa. A rapidly-developing new rift east of an ice rise (McDonald Ice Rumples) released a 1,270 square kilometer (490 square miles) iceberg, A-74, two years ago. A pair of Landsat 8 images reveals the overall changes in the ice shelf since early 2021.

Calving of this type is generally unrelated to climate change because it arises from stresses acting upon the outflowing ice plate as it encounters a bedrock feature in the seabed. Such calving is often semi-cyclical, as the shelf periodically encounters the feature, fractures and breaks up, then reforms and grows outward until encountering the bedrock obstruction to flow again. Similar calving processes were in play for the final breakup of the Conger Ice Shelf last year although that ice shelf is unlikely to expand in the years ahead.

Further reading

Banwell, A. F., R. T. Datta, R. L. Dell, M. Moussavi, L. Brucker, L., G. Picard, C. A. Shuman, and L. A. Stevens. 2021. The 32-year record-high surface melt in 2019/2020 on the northern George VI Ice Shelf, Antarctic Peninsula. The Cryosphere, 15(2), pp. 909-925. doi:10.5194/tc-15-909-2021.

NASA Earth Observatory: Clear Days for Iceberg Spotting

As the peak of Antarctica’s melt season approaches, surface snow melting has been widespread over coastal West Antarctica, with much of the low-lying areas of the Peninsula and northern West Antarctic coastline showing 5 to 10 days more melting than average. However, much of the East Antarctic coast is near average. Snowfall in Antarctica for the past year has been exceptionally high as a result of an above average warm and wet winter and spring.

Overview of conditions

Figure 1a. The upper maps of the Antarctic Ice Sheet (left) and the Antarctic Peninsula (right) show the total melt days for the areas from November 1, 2022 to January 10, 2023. The graph on the bottom shows daily melt extent for the Antarctic Ice Sheet as a percentage of ice sheet area for the same time period in red and the 1990 to 2020 average in blue. The interquartile and interdecile ranges appear in grey bands. 

Credit: E. Cassano and M. MacFerrin, CIRES and T. Mote, University of Georgia
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Figure 1b. This map shows the number of melt days from November 1, 2022 to January 10, 2023, as a difference from average relative to the 1990 to 2020 reference period. Reds indicate more melt; blues indicate less melt.

Credit: E. Cassano and M. MacFerrin, CIRES and T. Mote, University of Georgia
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Antarctic surface snow melting through January 10 is above average and reached near-record extent in late December. A significant melt event spread over the Peninsula and across much of the West Antarctic Ice Sheet northern coast and into the Ross Ice Shelf area (Figure 1a). Melting has been moderately above average for the Peninsula areas, but unusually high in the Getz Ice Shelf area, where melting is less frequent. The Larsen Ice Shelf area has seen up to 25 days of melting, about 5 more than average, and the Wilkins region up to 30 days, again about 5 more than average (Figure 1b). The Getz and Sulzberger Ice Shelves (to the lower left of the Antarctic maps) have seen 10 melt days this season, about double the average for this time of year. East Antarctic Ice Shelves—Fimbul, Roi Baudouin, and Amery—have had near-average to slightly above-average melting of 5 to 10 days each.

Conditions in context

Figure 2. These plots show weather conditions as a difference from average relative to the 1991 to 2020 reference period for Antarctica and the surrounding coastal areas. The top plot shows air temperature at the 925 millibar level, in degrees Celsius, for December 1, 2022 to January 10, 2023. Yellows and reds indicate higher-than-average temperatures; blues and purples indicate lower-than-average temperatures. The bottom plot shows sea level pressure for the same period. Yellows and reds indicate higher-than-average air pressure; blues and purples indicate lower-than-average pressure.


Credit: National Centers for Environmental Prediction (NCEP) Reanalysis data, National Center for Atmospheric Research
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Antarctica’s weather for December through January 10, 2023, was warm in a broad area from the northern Ross Sea and along the northern West Antarctic coast to the northern tip of the Peninsula. Central West Antarctica had temperatures up to 2.5 degrees Celsius (4.5 degrees Fahrenheit) above average. Temperature differences from average were generally 1.5 degrees Celsius (3 degrees Fahrenheit) above average over parts of the Ross Sea and about 1 to 1.5 degrees Celsius (2 to 3 degrees Fahrenheit) above average through the northern West Antarctic coastal and Peninsula areas.

Air pressure was below average throughout most of the continent and adjacent Southern Ocean, with above-average pressures generally near 50 degrees South latitude. This creates stronger than average eastward-flowing winds around the continent, creating warm conditions in areas where the direction is southeastwards (i.e. the Peninsula), and in particular, causing strong foehn winds on the lee side (east side) of the Peninsula. Cool conditions in the high-altitude parts of East Antarctic are a result of strong circumpolar winds generally isolating this region from warmer air to the north.

Snow globe Antarctica

Figure 3. The top graph shows accumulated surface mass balance (total snowfall minus minor melt run off and snow evaporation) in billions of tons (Gtons) for the Antarctic continent from March 1, 2022, to January 10, 2023 (red line), along with several recent years, presented as a difference from the 1981 to 2010 average. The grey band is the standard deviation (66 percent of all years in 1981 to 2010 fall within the grey band). The bottom left map shows the total surface mass balance for the period. The bottom right map show SMB as a difference from average, shown in millimeters of water equivalent for the accumulated snow. These estimates are from the MARv3.12 model forced by the ERA5 reanalysis until December 2022 and by Global Forecast System (GFS) afterwards.

Credit: X. Fettweis, University of Liège, Belgium
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Snowfall over Antarctica has been significantly above average over these last weeks, continuing a trend that began in November 2021. Several recent hydrological years (March 1 to February 28) for Antarctica have had up to 200 billion tons more snow than average, but the 2022 to 2023 year has reached nearly 300 billion tons as of January 10, 2023. This is in line with some future projections that suggest larger accumulation with a warmer climate until warming reaches above 7.5 degrees Celsius (13.5 degrees Fahrenheit). This very high deviation from average snow input suggests that the Antarctic Ice Sheet could gain mass this year. Snowfall amounts have been especially high along the western edge of the Peninsula and the Bellingshausen coast, where persistent southeastward-flowing winds push marine air against a series of mountain ranges and the ice ridge along the spine of the Peninsula. However, the biggest contribution to the above average total snow input occurs in East Antarctica, and specifically Wilkes Land and the interior of Antarctica. Overall, high snowfall in Antarctica may completely offset recent net ice losses from faster ice flow off the ice sheet for this assessment period. Most of the past decade has seen annual net losses of 50 to 150 billion tons.

Melt ponds and glacier retreat in the Peninsula

Figure 4. This true color image shows several melt ponds on the northern part of the Antarctic Peninsula (see inset map) on January 10, 2023. The image is from the Moderate-resolution Imaging Spectroradiometer (MODIS) sensor aboard the NASA Aqua satellite. For reference, North is towards the upper right, and the image is 312.5 by 187.5 kilometers in size (about 180 x 120 miles).

Credit: NASA Worldview
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Above average surface melting over the northern Peninsula is evident in the accumulation of surface meltwater in several areas of the eastern side of the Peninsula. The Larsen C Ice Shelf, and the SCAR Inlet Ice Shelf, a remnant of the former Larsen B shelf, are all showing significant areas of accumulated meltwater on their surfaces. Meltwater on ice shelves can pose a threat to ice shelf stability through a process called hydrofracture, where water fills pre-existing cracks in the shelf and forces the crack to open further as water pressure increases inside the crack.

The warm conditions have also triggered several rapid tidewater-style retreats in the area this season, most noticeably for Hektoria/Green/Evans glacier system in the northwestern Larsen B embayment. The glacial ice front of Hektoria has retreated roughly 5 kilometers (3 miles) in the past two months. A similar outflow can be seen in the Moderate Resolution Imaging Spectroradiometer (MODIS) data to the north near the Sobral Peninsula from the Bombadier/Edgeworth/Dinsmore glacier system (not shown). The Seal Nunataks Ice Shelf remnant, which is between the Larsen A and Larsen B Ice Shelves, is also degrading since the sea ice minimum of early 2022.

Further reading

Kittel, C., C. Amory, C. Agosta, N. C. Jourdain, S. Hofer, A. Delhasse, S. Doutreloup, P.-V. Huot, C. Lang, T. Fichefet, T., and X. Fettweis. 2021. Diverging future surface mass balance between the Antarctic ice shelves and grounded ice sheet. The Cryosphere, 15, 1215–1236, https://doi.org/10.5194/tc-15-1215-2021

NASA Earth Observatory Article: Clear days for iceberg spotting

The melt season for the Antarctic Ice Sheet has begun. Mapping for the Greenland Ice Sheet 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 interactive chart supports a retrospective look at past Greenland melt seasons. This will remain available for our users.

Daily image updates will resume for the Greenland Ice Sheet in April 2023.

Daily monitoring of surface melting in Antarctica resumes for the 2022-2023 season. Early melting through November has been limited to the region near the northern Larsen Ice Shelf, the Wilkins Ice Shelf, and an unusual melt event in Wilkes Land and Northern Victoria Land. Total melt area is ahead of the average pace at this point in the season.

Current conditions

Figure 1a. The top left map shows the total melt days for the Antarctic Ice Sheet from November 1, 2020 to February 16, 2021. The top right map shows the difference from average relative to the 1990 to 2020 reference period. The bottom graph shows daily melt extent as a percent of the ice cap for the 2022-2023 melt season through November 28, and the average values and ranges for the reference period.

Credit: M. MacFerrin, CIRES and T. Mote, University of Georgia
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Figure 1b. This map of the Antarctic Peninsula shows total melt days from November 1 to 30, 2022.

Credit: M. MacFerrin, CIRES and T. Mote, University of Georgia
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Antarctic surface snow melting through December 1, 2022, has been limited in scope but is generally ahead of the 1991 to 2020 reference period (Figure 1a). The area at the northern end of the Larsen C, and the remnant ice shelf within the Larsen B Embayment (called the Scar Inlet Ice Shelf) saw above average melting in November for 5 to 10 days, most of it occurring November 4 to 7 and again around November 15 (Figure 2b). While the northern edge of the Wilkins Ice Shelf saw about five days as well, this is a bit less than has been typical for the previous few decades. Unusually, the region of Cook Inlet in the eastern Wilkes Land Coast and the mountainous region of Northern Victoria Land had two significant melt events in late November.

Conditions in context

Figure 2a. The top plot shows the departure from average air temperature over Antarctica at the 925 hPa level, in degrees Celsius, from November 1 to 30, 2022. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures. The bottom plot shows the departure from average sea level pressure in the Antarctic in millibars from November 1 to 30, 2022. Yellows and reds indicate higher than average air pressures; blues and purples indicate lower than average air pressures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
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Figure 2b. This plot shows wind speed, wind direction, and air temperature from nullschool.net for November 21, 2022, covering West Antarctica, the Ross Sea, and Wilkes Land. Strong wind streaklines are visible from the north (bottom of the image) that led to surface melting in the eastern Wilkes Land and Northern Victoria Land areas. Temperatures range from a few degrees above freezing as depicted in green to -45 degrees Celsius (-49 degrees Fahrenheit) over the plateau as depicted in purple.

Credit: nullschool.net
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Antarctica’s weather for November had moderately above average temperatures in the Peninsula, and very warm conditions in the northern Ross Sea and eastern Wilkes Land coast, both of the areas where melting occurred (Figure 2a). Overall, the air circulation pattern showed a clear wave-3 pattern, in which the Southern Ocean surrounding Antarctica is characterized by three high air pressure areas and three low air pressure zones between them.

The specific events that led to melting along the eastern side of the Antarctic Peninsula and in the northern Larsen region in particular were two strong foehn events one between November 4 and 7 and one in mid-November. A foehn is a warm wind blowing down an incline. The event leading to surface melting on Northern Victoria Land and eastern Wilkes Land in the last ten days of the month was more unusual, related to a very strong and persistent wind pattern from the north that brought slightly above-freezing conditions and strong precipitation, likely a mix of rain and snow (Figure 2b).

While most of the 2022 Greenland melt season was near average, September set records for high temperatures, melt extent, and ice loss. A persistent high air pressure pattern off the southeastern tip of the island, and low air pressure over the Canadian Archipelago—and remnants from Hurricane Fiona—drove the unusual conditions.

Overview of conditions

Figure 1a. The top left map illustrates cumulative melt days on the Greenland Ice Sheet for the 2022 melt season. The top right map illustrates the difference from the 1981 to 2010 average melt days for the same period. The bottom graph illustrates daily melt area for Greenland from April 1 through October 31, 2022, with daily melt area for the preceding five years. The gray lines and bands depict the average daily melt area for 1981 to 2010, the interquartile range, and the interdecile range.

Credit: National Snow and Ice Data Center/T. Mote, University of Georgia
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Figure 1b. This bar graph shows the daily cumulative melt area for the summer seasons over the 43-year satellite record. Average totals for the 1981 to 2010 30-year reference period, and for the most recent 21 years, 2001 to 2022 are shown as horizontal blue lines.

Credit: National Snow and Ice Data Center/T. Mote, University of Georgia
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For the melt season as a whole, ice sheet melting was well above average across the southwest and northeast while slightly below average in the northwest and southeast (Figure 1a). However, much of the above average seasonal melting resulted from an unusually warm September, particularly for the southwestern ice sheet. A major melting event took place at the beginning of September, with another significant melt spike in late September resulting from the remnants of Hurricane Fiona as an extra-tropical cyclone. Another period of above-average melt extent occurred in mid-July.

The 2022 melt season in Greenland overall (April 1 to October 31) had a cumulative total of 22.1 million square kilometers (8.53 million square miles) of melt, placing it at nineteenth highest in the 43-year satellite record (Figure 1b). While this is 18.1 million square kilometers (6.99 million square miles) above the 1981 to 2010 average, it is below the average for the twenty-first century years of 2001 to 2022 by 26.3 million square kilometers (10.2 million square miles). Though recent years have not reached or exceeded the extreme melting totals of 2010, 2012, or 2016, the past two decades continue to have consistently more melting than earlier years.

Conditions in context

Figure 2. The top plot illustrates surface air temperatures as a difference from the 1990 to 2020 average for June 1 to to August 31, 2022, for Greenland and surrounding areas. The bottom plot shows the air pressure as indicated by the height difference from average of the 700 millibar level (about 10,000 feet above sea level) for Greenland and the surrounding region for the same period.

Credit: National Centers for Environmental Prediction (NCEP) Reanalysis data, National Center for Atmospheric Research
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Conditions for the core of the melt season from June to August, were not far from the long-term average, with slightly above average temperatures in the northern part of the ice sheet and its southern tip, but below average temperatures in its central area, especially the east-central coast (Figure 2). Low atmospheric pressure between Iceland and the eastern Greenland coast—a pattern termed the Icelandic Low—brought mostly westward-flowing winds in the north and cool winds from the northwest for the western and southern areas.

Record September

Figure 3a. The map in the upper left shows melt days as a difference from average on the Greenland Ice Sheet for September 2022, and shows the location of the Swiss Camp research station. The top right graph shows automatic weather station air temperatures at Swiss Camp, which were above melting for much of the month. The bottom plot illustrates the air pressure as indicated by the height difference from average of the 700 millibar level (about 10,000 feet above sea level) for Greenland and the surrounding region for the same period.

Credit: National Centers for Environmental Prediction (NCEP) Reanalysis data, National Center for Atmospheric Research; Swiss Camp data are from the Geological Survey of Denmark and Greenland (GEUS) Greenland Climate Network (GC-Net) station, graph by Jason Box, GEUS
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Figure 3b. These graphs show meltwater runoff at the top and total melt production at the bottom per day for the Greenland Ice Sheet from June to September 2022, along with 2020 and 2012. The blue dashed line represents the maximum daily value for any year between 1981 and 2010; in gray line and area depict the average amount and the typical range of values (standard deviation). These estimates are from the MAR 3.12 reanalysis model.

Credit: Xavier Fettweis, University of Liège
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September 2022 conditions were very different from earlier months, notably the June to August period (Figure 3a). A strong and persistent high air pressure pattern was present off of Greenland’s southeastern coast coupled with low air pressure in the Canadian Archipelago, resulting in a transfer of warm air from the southeast onto the ice sheet. This set record warm conditions and unprecedented surface melt extents through the month relative to the 40+ year satellite record. In most years, the September cumulative melt area totals do not exceed 1 million square kilometers (386,000 square miles). The 1981 to 2010 average is 486,000 square kilometers (188,000 square miles). By contrast, the 2022 cumulative melt area total was 3.9 million square kilometers (1.51 million square miles), more than doubling the previous record September melt. The record September prior to 2022 was 2010, with 1.6 million square kilometers (618,000 square miles).

Air temperatures for Greenland overall were 6 degrees Celsius (11 degrees Fahrenheit) above average at the 700 millibar level, roughly 10,000 feet above sea level. This is more than 3 standard deviations above the typical range, making it the warmest September on record since 1950 in the MAR 3.12 reanalysis record. Conditions at a weather station near Swiss Camp in Greenland show near-continuous melting conditions through the month, much warmer than the previous two years.

September 2022 had an unusual amount of melt and meltwater runoff (Figure 3b). The total amount of meltwater produced during the month was 57 billion tons, a record for September, compared to the 1981 to 2010 average September total of 9 billion tons—according to MARv3.12 forced by the ERA5 reanalysis. Runoff total was also a record at 55 billion tons. Total runoff in September was a high fraction of the total produced melt because warm events and rainfall occurred during the period of maximum bare ice exposure at the end of summer. Overall, the estimated total change in surface mass of the ice sheet surface (not considering the outflow of glaciers) was only -8 billion tons, a smaller number than melt and runoff because of the high amounts of rainfall that fell on the ice sheet (again a record for September since 1950), some of which freezes onto the snow or firn surface.

Exposed

Figure 4. This graph shows the extent of exposed bare ice on the Greenland Ice sheet for 2022 and the preceding five years from Sentinel 3 data.

Credit: Jason Box, Geological Survey of Denmark and Greenland (GEUS); Adrien Wehrlé, University of Zurich; and European Space Agency Earth Observation (ESA EO) Science For Society, ESA Contract Change Notice (CCN) 4000125043/18/I-NB
High-resolution image

The unusual timing of warm and rainy conditions throughout the month of September led to a jump in the amount of exposed bare ice on the ice sheet. In most years, snowfall begins to cover the icy edges of the ice sheet in September, but this year exposed bare ice increased to typical mid-summer levels. This has an effect on both melt, since darker bare ice absorbs more solar energy, and run-off, as the ice surface cannot absorb water.

Break-up of the last large ice shelf in Greenland

Figure 5. These Landsat images span 22 years, showing the retreat and breakup of the Zachariae Isstrøm Ice Shelf. The upper right inset map shows the location of the ice shelf in northeastern Greenland. An animation by Christopher Shuman shows a longer series of images.

Credit: Christopher Shuman, University of Maryland, Baltimore Campus (UMBC) at NASA Goddard Space Flight Center (GSFC); data are from US Geological Survey
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Recently published research on the Zachariae Isstrøm (ZI) outlet glacier describes how this glacier’s floating ice shelf began to break apart early this century and is continuing to retreat under warming ocean and air conditions. As a result of the loss of the floating shelf, the grounded area of the glacier has accelerated and thinned, and it is now contributing more ice to the ocean.

Landsat data collected over the past 50 years indicates the floating ice in front of this outlet was relatively stable until late 2002. However, the loss of contact between the adjacent islands east of the ice shelf front initiated a break up in August 2002. This has proceeded with rapid ice front collapse events for the past several years.

References

Satellite Image Atlas of Glaciers of the World: Greenland