Antarctica Melts Under Its Hottest Days on Record

ice melt in antarticaOn February 6, 2020, weather stations recorded the hottest temperature on record for Antarctica. Thermometers at the Esperanza Base on the northern tip of the Antarctic Peninsula reached 18.3°C (64.9°F)-around the same temperature as Los Angeles that day. The warm spell caused widespread melting on nearby glaciers.


The warm temperatures arrived on February 5 and continued until February 13, 2020. The images above show melting on the ice cap of Eagle Island and were acquired by the Operational Land Imager (OLI) on Landsat 8 on February 4 and February 13, 2020.

The heat is apparent on the map below, which shows temperatures across the Antarctic Peninsula on February 9, 2020. The map was derived from the Goddard Earth Observing System
https://earthobservatory.nasa.gov/images/44246/geos-5-a-high-resolution-global-atmospheric-model
(GEOS) model, and represents air temperatures at 2 meters (about 6.5 feet) above the ground. The darkest red areas are where the model shows temperatures surpassing 10°C (50°F).

Mauri Pelto, a glaciologist at Nichols College observed that during the warming event, around 1.5 square kilometers (0.9 square miles) of snowpack became saturated with meltwater (shown in blue above). According to climate models
http://climato.be/cms/index.php?climato=the-2020-melt-season-over-antarctica-as-simulated-by-marv3-10
, Eagle Island experienced peak melt-30 millimeters (1 inch)-on February 6. In total, snowpack on Eagle Island melted 106 millimeters (4 inches) from February 6- February 11. About 20 percent of seasonal snow accumulation in the region melted in this one event on Eagle Island.

 

Weddell Sea
Heat and Temperature measurements for the Weddell Sea in February 2020

The warm temperatures of February 2020 were caused by a combination of meteorological elements. A ridge of high pressure was centred over Cape Horn at the beginning of the month, and it allowed warm temperatures to build. Typically, the peninsula is shielded from warm air masses by the Southern Hemisphere westerlies, a band of strong winds that circle the continent. However, the westerlies were in a weakened state, which allowed the extra-tropical warm air to cross the Southern Ocean and reach the ice sheet. Sea surface temperatures in the area were also higher than average by about 2-3°C.

Dry, warm foehn winds also could have played a part. Foehn winds are strong, gusty winds that cause downslope windstorms on mountains, often bringing warm air with them. In February 2020, westerly winds ran into the Antarctic Peninsula Cordillera. As such winds travel up the mountains, the air typically cools and condenses to form rain or snow clouds. As that water vapour condenses into liquid water or ice, heat is released into the surrounding air. This warm, dry air travels downslope on the other side of the mountains, bringing blasts of heat to parts of the peninsula. The drier air means fewer low-lying clouds and potentially more direct sunlight east of the mountain range.

“Two things that can make a foehn-induced melt event stronger are stronger winds and higher temperatures,” said Rajashree Tri Datta, an atmospheric researcher at NASA’s Goddard Space Flight Centre. With warmer air in the surrounding atmosphere and ocean, the conditions were conducive this month for a foehn wind event.

This February heatwave was the third major melt event of the 2019-2020 summer, following warm spells in November 2019 and January 2020
https://earthobservatory.nasa.gov/images/146189/widespread-melt-on-the-george-vi-ice-shelf
. “If you think about this one event in February, it isn’t that significant,” said Pelto. “It’s more significant that these events are coming more frequently.”

Large Scale images of ice melt in Antarctica:
Before

Eagle Island before ice melt

 

After

Eagle Island after icemelt

 

Source
Image Source

 

 

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