Sea Ice Blues off the Antarctic Peninsula

Sea Ice Blues off the Antarctic Peninsula
Sea Ice Blues off the Antarctic Peninsula

With the arrival of summer in the southern hemisphere, sea ice that clung to the Antarctic Peninsula through austral winter 2023 is now letting go.

The seasonal transformation is visible in this pair of images, acquired by the MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA’s Aqua satellite on December 19, 2023 (top), and January 1, 2024 (bottom). The images are centered on the Larsen A and B embayments on the peninsula’s eastern side.

The embayments are named for the ice shelves that once floated here as part of the greater Larsen Ice Shelf. In the past three decades, two large sections of the ice shelf (Larsen A and B) have collapsed: Larsen A in 1995 and Larsen B in 2002. Larsen C, south of this image, still hangs on but its “coastline” changed dramatically in 2017 when it spawned a massive iceberg.

Instead of ice shelves—the floating extension of glacial ice from land—the Larsen A and B embayments now often contain seasonal sea ice—frozen seawater that floats on the ocean surface, often covered with snow. Much of this sea ice, known as “fast ice,” clings to coastlines and ice shelves. Fast ice can help resist against the seaward flow of glaciers on land and slow their contribution to sea level rise, though fast ice is less effective at this buffering effect compared to a much thicker ice shelf.

Sea ice that grows over the course of a single winter, also known as first-year sea ice, often breaks up and clears out of the Larsen A embayment in summer. (Note that there are exceptions, especially between 2011 and 2021.) This season, by December 19, the transition became noticeable when meltwater (blue) pooled atop parts of the fast ice. According to the National Snow and Ice Data Center, melt-related features did not extend onto the nearby ice sheet or ice shelf (as of December 15).

By January 1, the ice had fractured and drifted freely into the Weddell Sea. “The Prince Gustav Channel, Larsen Inlet, and Larsen A are all now clear of first-year sea ice, and the Larsen B embayment is getting chipped away at the front,” said Christopher Shuman, a University of Maryland, Baltimore County, glaciologist based at NASA’s Goddard Space Flight Center.

It remains to be seen if, and when, the remaining sea ice in the Larsen B embayment will clear out this summer. Sea ice in the embayment broke apart over the span of a few days in January 2022 after persisting there for more than a decade. It cleared out again in summer 2023.

NASA Earth Observatory images by Wanmei Liang, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview. Story by Kathryn Hansen.

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