Shrinking Iceberg A-76A

Shrinking Iceberg A-76A

In May 2021, Iceberg A-76 broke from the Ronne Ice Shelf in Antarctica. At the time, it was the largest iceberg floating anywhere in the world. Two years later, only fragments of the former berg remain.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired this image on May 24, 2023. It shows Iceberg A-76A, which broke from A-76 shortly after the initial calving and remains the event’s largest surviving berg. But its size has dwindled during the past month as pieces have splintered off in warmer, more northern waters.

At the time of this image, Iceberg A-76A and several newly separated pieces floated near the remote island of South Georgia. They were about 2,400 kilometers (1,500 miles) north of the berg’s origin near the Ronne Ice Shelf. “It is impressive to think it ‘sailed’ that far in about two years,” said Christopher Shuman, a University of Maryland, Baltimore County, glaciologist based at NASA’s Goddard Space Flight Center. “That obviously speaks to the force of powerful currents in this part of the Southern Ocean.”

By October 2022, Iceberg A-76A had likely escaped the clockwise circulation of the Weddell Gyre and entered the Drake Passage—a turbulent body of water between South America’s Cape Horn and Antarctica’s South Shetland Islands. More than a year into its voyage, the berg’s size had not changed much. It still measured 135 kilometers long and 26 kilometers wide—a total area about twice the size of London.

But the Drake Passage often marks a turning point for icebergs. From there, they typically whip north toward the South Atlantic and quickly melt in the region’s warmer—but still chilly—waters. Iceberg A-76A appears to be experiencing this same fate as it nears South Georgia late in the austral autumn. Around the time of this image, A-76A measured 78 kilometers long and 11 kilometers wide—an area about the size of Austin, Texas.

Other major icebergs have met their demise in a similar fashion. Notably, the Delaware-sized Iceberg A-68A that broke from Antarctica’s Larsen C Ice Shelf in July 2017 finally splintered apart in the waters around South Georgia in February 2021.

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

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