March of the Antarctic Icebergs

Antarctic Icebergs March 2022 Annotated

March 6, 2022

After nearly crushing the endangered Brunt Ice Shelf, a swarm of Antarctic icebergs settle down for the southern winter.

In the summer of 2019, a rift that began accelerating across the Brunt Ice Shelf threatened to release an iceberg about twice the size of New York City. But as another Antarctic summer comes to an end, the ice shelf stubbornly holds together. It has – so far – even avoided collisions with numerous icebergs floating nearby, threatening to smash the shelf like an icy wrecking ball.

During the southern summer of 2021-22, icebergs in the eastern Weddell Sea drifted south with the Antarctic Coastal Current. Iceberg A-23A – currently the world’s largest iceberg – has floated free after detaching itself from the sea floor where it had been “grounded” (stuck) for decades. And in January 2022, Iceberg D-28 rounded the Stancomb Wills Glacier Tongue, hovering about 4,300 kilometers (2,600 miles) from where it broke away from the Amery Ice Shelf in 2019.

Eventually, a mixture of large icebergs converged near the Brunt Ice Shelf. The image above, taken on March 6, 2022, with the Moderate Resolution Imaging Spectroradiometer (MODIS) turned on.[{” attribute=””>NASA’s Aqua satellite, shows the bergs as they neared the end of their summer migration.

The drift of the icebergs has slowed as daylight hours have waned and temperatures have dropped, allowing sea ice to start growing in earnest on the Weddell Sea. The bergs will eventually become fully encased in seasonal sea ice for the austral winter. But for now, their enormous size makes them effective bulldozers, still capable of plowing through the sea ice and leaving paths of open water behind them. Notice also the striking cloud bands near the sides of icebergs D-31A and D-28. These are likely the result of vortices in the air produced by the edges of the thick, table-like bergs.

More bands of clouds are visible north of the bergs. Clouds like these, known as cloud streets or convective roll clouds, often line up when strong, cold winds blow over comparatively warm ocean water. In this instance, the air blowing off Antarctica was “quite cold,” according to Bart Geerts, an atmospheric scientist at University of Wyoming. Geerts inferred from the ERA5, a reanalysis product from the European Centre for Medium-Range Weather Forecasts (ECMWF), that the winds that day were blowing from the southwest and would have been about -20°C (-4°F).

Antarctic Iceberg Thermal Signatures March 2022 Annotated

March 9, 2022

The relative warmth of seawater behind the icebergs and within leads in the sea ice is apparent in the second image, acquired on March 6 by the Landsat 8 satellite. The image is false-color, created by blending data from the satellite’s Operational Land Imager (for detail and texture) and its Thermal Infrared Sensor (TIRS). The warmest areas (yellow, orange, and red) depict open water and thin, newly formed sea ice. The coldest areas (blue and white) are older, thicker ice, including the icebergs and broken ice rubble in their paths.

NASA Earth Observatory images by Joshua Stevens, using Landsat data from the U.S. Geological Survey, and MODIS data from NASA EOSDIS LANCE and GIBS/Worldview. Story by Kathryn Hansen with image interpretation by Christopher Shuman, NASA/UMBC, and Bart Geerts, University of Wyoming. March of the Antarctic Icebergs

Tom Vazquez

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