November 9, 2020 - A-68-A iceberg headed toward South Georgia Island

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   A68 iceberg headed toward South Georgia Island
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   A large Antarctic iceberg is drifting towards South Georgia Island,
   giving scientists and ecologists pause as they ponder potential impacts
   of a grounding of a massive ‘berg on the island’s population of seals,
   penguins, and birds.

   The birth of iceberg A-68 occurred in July 2017, and NASA satellites
   captured early images of the massive iceberg shortly after it broke
   away from the Larsen C ice shelf. A-68 was one of the largest on
   record, spanning a surface area larger than the state of Delaware with
   estimated weight of about one trillion tons. After spending most of its
   first two years floating in the Weddell Sea close to the Larsen C ice
   shelf, by September 2018 the ‘berg began to float northward roughly
   parallel to the Antarctic Peninsula, all under the watchful eye of NASA
   satellites.

   On November 5, 2020, the Moderate Resolution Imaging Spectroradiometer
   on the Terra satellite spotted iceberg A68-A approaching South Georgia
   Island.

   Although the original A-68 lost two large chunks during the long
   northward journey, causing it to be renamed A-68-A, the iceberg remains
   sizable. Estimated to measure about 98 mi (138 km) by 29 mi (48 km),
   A-68-A is currently similar in size to South Georgia Island itself.
   South Georgia measures104 miles (167.4 km) long and—at the widest
   point—23 miles (37 km).

   South Georgia Island lies in the path of icebergs drifting northward
   from Antarctica, and several large ones have ended up carried by the
   strong currents of the Weddell-Scotia Confluence to ground on the broad
   continental shelf that surrounds the island. When the blocks of ice
   catch their keel on the continental shelf, they grind to a halt and
   slowly melt, dumping frigid, fresh water into the saline ocean. The
   dump of freshwater changes the structure of the water column, and this
   can change the currents across the continental shelf. The cooler,
   fresher water and the shifting currents can strongly impact the
   ecosystem, including the presence of krill, a tiny shrimp-like
   planktonic crustacean that is vital food for many marine organisms that
   feed the wide diversity of seabird colonies, seals, and penguins. As
   one of the bases of the marine food web, decreasing populations of
   krill could also impact the rich commercial fisheries found off of
   South Georgia Island.

   Despite the already-close approach of A-68-A to South Georgia Island
   and a real risk of grounding, the scenario is not yet set in stone (or
   ice). Icebergs very often make near-misses of the island and its broad
   continental shelf only to drift northward. Once in the warmer waters,
   even the largest ‘bergs then begin to melt.

   Image Facts
   Satellite:  Terra
   Date Acquired: 11/5/2020
   Resolutions:  1km (260 KB),  500m (824.4 KB),  250m (2.2 MB)
   Bands Used: 1,4,3
   Image Credit: MODIS Land Rapid Response Team, NASA GSFC



https://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2020-11-09
 
