Get information about melting on the Antarctic Ice Sheet. We post analysis periodically as conditions warrant.
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Daily data images return for Greenland Ice Sheet soon
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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 in mid April 2023.
A crumbling ice shelf edge after a warm summer and low sea ice
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
High-resolution image
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
High-resolution image
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
High-resolution image
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
High-resolution image
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
High-resolution image
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.
Widespread melting and ponded water on the Peninsula Ice Shelves
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
High-resolution image
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
High-resolution image
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
High-resolution image
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
High-resolution image
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
High-resolution image
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
High-resolution image
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.
Acknowledgements: Greenland Ice Sheet Today is produced at the National Snow and Ice Data Center by Ted Scambos, Julienne Stroeve, and Lora Koenig with support from NASA. NSIDC thanks Jason Box, Xavier Fettweis, and Thomas Mote for data and collaboration.
