![]() ![]() National Ice Center naming and size tracking conventions. Other satellite optical images are shown below. ![]() Here is a link to a NASA page showing recent optical images of the iceberg. It was much larger a few decades ago, but sections A and B have since collapsed and calved into icebergs such as Icebergs A20 and A68 as a result of warming conditions that weakened the ice shelf. The three sections (A, B, and C) of Larsen Ice Shelf existed on the east side of the Antarctic Penninsula for at least 10,000 years. ![]() The black "diamonds" are where the scatterometer did not collect measurements for that day. ![]() Because multiple orbit passes that are collected at different times during the day are combined to create the images there are lines corresponding to swath edges due to the changing wind conditions during the day. Scatterometers were designed to measure this roughness and determine the wind (speed and direction) over the ocean. Calm ocean is dark, but when wind blows, small waves are formed that "roughen" the surface and causes it to look brighter in the radar images. The ocean brightness is highly variable due the effects of the wind on the surface. Sea ice is not as bright, and can be seen moving in response to winds and ocean currents. When the surface melts, the backscatter turns dark. Glacial ice shows up very bright (white) due to volume scattering of the radar signal from the snow and ice. The grey level in the scatterometer images is proportional to the normalized radar cross section (sigma-0) derived from the ESA ASCAT-A and ASCAT-B scatterometers. Shorter movies of the A68 near South Georgia Island (July 2020 to present):įor comparison, here is a longer animation from July 1999 through 2007 that shows other large icebergs calving off the Ronne Ice Shelf and moving from the Weddell Sea into the South Atlantic: Movies of the full life (2017 to present) of A68: BYU repurposed the data to create images to study polar ice, including icebergs.) Several animations of these images are available. (A scatterometer is a type of satellite radar that was originally designed to measure ocean winds from space. Using satellite scatterometer data, the BYU Scatterometer Climate Record Pathfinder has been generating daily enhanced resolution radar images of the Earth and using the data to track the location of Iceberg A68 and its fragments. Iceberg A38B grounded for several months just west of South Georgia Island in 2004. Iceberg A43B, which was also from the Larsen C Ice Shelf, followed the same general path as Iceberg A68, and stalled just east of South Georgia for months in 2004. As large as A68 was, it is not exceptional either in size or path. Fragments moved east of South Georgia Island before melting by April 2021.Ī68 is a good example of an Antarctic tabular iceberg, which are produced when the end of a floating glacier or ah ice sheet breaks off-termed "calving". It closely approached the west coast of South Georgia before moving south, then east, and breaking up. Moving northward, it was caught in the Antarctic Circumpolar current and moved rapidly toward South Georgia Island. Finally, in 2018 it started moving northward, rotating several times. Iceberg A68 calved from the Larsen C Ice Shelf on the Antarctic Penninula in July 2017. ![]()
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