On February 6th of this year, weather stations registered the hottest temperature in recorded history for Antarctica. Thermometers at the Esperanza Base on the northern region of the Antarctic Peninsula showed 18.3°C (64.9°F), which is about the same temperature as Los Angeles registered that day.
The warm conditions triggered widespread thawing on nearby glaciers, arriving on February 5th and continuing until February 13th of this year. Mauri Pelto, a glaciologist at Nichols College, noticed that, throughout the period of warming, approximately .9 square miles (1.5 square kilometers) of snowpack become drenched in meltwater.
The Hottest Day Ever in Antarctica
As per climate standards, Eagle Island experienced peak melt: one inch (30 millimeters) on February 6th. Altogether, snowpack on Eagle Island thawed four inches (10 millimeters) from February 6th to February 11th. Approximately 20 percent of seasonal snow mass in the area melted in this one incident on Eagle Island.
Pelto said: “I haven’t seen melt ponds develop this quickly in Antarctica. You see these kinds of melt events in Alaska and Greenland, but not usually in Antarctica.”
He also utilized satellite observations to identify widespread surface melting close to Boydell Glacier. Pelto said that such rapid thawing is triggered by sustained high temperatures well above freezing. Such continual warmth was not usual in Antarctica until the 21st century, but it has become more regular in the last few years.
The warm temperatures during this month were caused by a mix of meteorological aspects. A ridge of high pressure was placed over Cape Horn at the beginning of February, and it enabled warm temperatures to accumulate. Usually, the peninsula is protected from warm air quantities by the Southern Hemisphere westerlies, a series of powerful winds that rotate around the continent.
Even so, the westerlies were allegedly in a limp state, which enabled the extra-tropical warm air to pass through the Southern Ocean and get to the ice sheet. Sea surface temperatures in the region were also leveled up than average by about two to three degrees Celsius.
Foehn Winds Might Also Affect the Temperatures
Dry and warm foehn winds could have also been the culprit. Foehn winds are powerful, gusty winds that trigger downslope windstorms on mountains, usually bringing warm air along. In February of this year, westerly winds approached the Antarctic Peninsula Cordillera, and because such winds get to the peak of the mountains, the air usually cools and presses to create rain or snow clouds.
As the water vapor transforms into liquid water or ice, heat is freed into the atmosphere. The warm, dry air then moves downslope on the other side of the mountains, causing explosions of heat to regions of the peninsula. The drier air means less low-lying clouds, and eventually more direct sunlight east of the mountain extent.
Rajashree Tri Datta, an atmospheric researcher at NASA’s Goddard Space Flight Center, said: “Two things that can make a foehn-induced melt event stronger are stronger winds and higher temperatures.”
This month’s heatwave was the third significant melt event of the 2019-2020 summer after warm spells happened in November 2019 and January 2020.
Pelto said: “If you think about this one event in February, it isn’t that significant. It’s more significant that these events are coming more frequently.”