As of 12-15-2023, the 2023 melt season has impacted East Antarctica’s Amery Ice Shelf, and the Dronning Maud Land Ice Shelf has above-average melting. But the Antarctic Peninsula has had exceptional melt this summer, a/k/a The Midnight Sun that runs from October to February.
The 2022-2023 melt season made news after Nature published a study titled Record-high Antarctic Peninsula temperatures and surface melt in February 2022: a compound event with an intense atmospheric river.
Research teams are only beginning to accumulate data as most scientists have only recently arrived in various regions of the world’s largest ice cap. As a result, research is still underway for the 2023-2024 melt season.
Startling news for the 2022-2023 melt season and the Antarctic Peninsula, where the Antarctic Peninsula had experienced a “new extreme warm event and record-high surface melt in February 2022, rivaling the recent temperature records from 2015 and 2020, and contributing to the alarming series of extreme warm events over this region showing stronger warming compared to the rest of Antarctica.” The northern and northwestern AP was impacted by an Atmospheric River that had attained a Category Three on the Atmospheric River Scale (AR). According to the study abstract, the river brought anomalous heat and rainfall to the peninsula’s tip. “The event was triggered by multiple large-scale atmospheric circulation patterns linking the AR formation to tropical convection anomalies and stationary Rossby waves, with an anomalous Amundsen Sea Low and a record-breaking high-pressure system east of the AP.” Circulation analysis linked climate change directly to the storms' powerful amplification impacts while increasing the probability of the storm even occurring.
The melting of the AP in 2022-2023 has resulted in a mind-boggling increase in speed and significant ice loss at three glaciers. The Hectoria Glacier quadrupled its sliding speed and lost 15 miles of ice at its front over 16 months, according to a must-read article by Douglas Fox in Science Direct. He found that the sea ice loss enabled massive heavy waves of ocean water to smash into areas protected by sea ice. The same phenomenon occurred at Thwaites Glacier in December 2022 after Iceberg B22a moved from a sea mount, exposing the calving front to wave action.
I am not aware of any major calving event anywhere in Antarctica. There were, however, multiple minor calving events at Getz Ice Shelf.
Hektoria Glacier, Green Glacier, and Crane Glacier sit near the tip of the Antarctic Peninsula, which reaches up toward South America. The crescent moon–shaped bay, called the Larsen B Embayment, once seemed stable. As these glaciers oozed off the coastline, their ice used to merge into a floating slab around 200 meters thick. This slab, called the Larsen B Ice Shelf, was about the size of Rhode Island and filled the entire bay.
Don’t let the YouTube screen capture scare you away. The animation opens.
The Larsen ice shelves existed for over 12,000 years, buttressing the land glaciers from dumping into the sea and raising sea levels. The shelf was exposed to warm surface temperatures, which warmed the surface enough for meltwater streams and lakes to pound over the shelf and weigh it down, with warming currents melting the underbelly of Larsen B, creating swiss-cheesification of the shelf underside, the massive shelf shattered into icebergs. The three glaciers noted by Fox in his story were no longer hindered by the ice shelf thinned, draining the melt into the ocean.
In 2011, however, the thinning slowed as thin sea ice-strengthened, became thick, and lasted year-round, stabilizing the glaciers while providing a backstop until 2022. Last year, the 2011 fast ice shattered, drifted away
Then, starting in 2011, the hemorrhaging slowed down. The thin veneer of sea ice that forms over the bay each winter began to persist year-round, preserved by a series of cold summers. This “landfast ice,” attached firmly to the coastline, grew five to 10 meters thick, stabilizing the glaciers. Their floating tongues gradually advanced back into the bay. But things changed abruptly in early 2022. On January 19 and 20, the landfast ice disintegrated into fragments, which drifted away. The shelves were once again exposed to fierce ocean storms.
Using data from ocean buoys farther north, Ochwat and colleagues determined that a series of powerful waves, higher than 1.5 meters, had swept in from the northeast — cracking apart the landfast ice. Those waves were highly unusual for this area.
The Southern Ocean, which encircles Antarctica, holds some of the world’s roughest waters. The Antarctic Peninsula extends up into this turbulent region, but its east side, where the Larsen B Embayment sits, rarely feels the waves. It is normally protected by several hundred kilometers of pack ice — floes of sea ice, pressed together by ocean currents — that dampen the waves, leaving the waters near Larsen as flat as a mirror.
In 2022, water temperatures near the surface of the Southern Ocean rose several tenths of a degree Celsius higher than normal, causing pack ice to shrink and peel away from the peninsula. This exposed the area to waves, which then broke up the landfast sea ice.
The glacier tongues all accelerated as a result. Fox noted that Crane’s tongue essentially vanished. Green Glacier lost all floating ice, as did Hectoria. Hectoria also lost six miles of grounded ice.
The National Snow and Ice Center reports on the melting of Antarctica and Greenland so far this year. (The link includes reporting on Antarctic snowfall and a Greenland update.)
As of December 15, the Antarctic Ice Sheet had above average melt in the Amery and Dronning Maud Land Ice Shelf regions, with significant melting on the Antarctic Peninsula. Greenland’s 2023 melt season was the third highest on record with persistent high melt extents in late June through mid-July, with a late August melt spike.
Antarctic surface melting through December 15 was above average in nearly all the regions with high annual melting totals relative to the 1991 to 2020 reference period. Melt Days were five to eight days above average over the Larsen C and northern George VI Ice Shelves, and a few days above average in the Amery, Roi Baudouin, and Brunt Ice Shelves. While a few melt-related features appeared on landfast sea ice in the Larsen A embayment (not pictured), no melt was apparent on the nearby ice sheet or ice shelf region as of December 15.
Satellite imagery of Larsen B collapse.
