The scientists utilized satellite information to document changes in the icebergs thickness, location, volume, and mass from the time it broke from the ice shelf in July 2017 until it started to rapidly break down in January 2021.
About 85 percent of an iceberg lies listed below the waters surface area– less than suitable for measuring its overall density. Scientists can now approximate the thickness by determining elements of the iceberg that are above the water. Researchers can then convert this height into thickness by accounting for the densities of the iceberg, the snow layer on top, and the surrounding sea water.
Thinning and fragmentation both increased as the iceberg wandered north, but fragmentation finally controlled as the iceberg broke down in the Northern Scotia Sea.
Iceberg A-68A thickness. 2017– 2021.
Researchers recently chronicled the death throes of A-68A, one of the worlds largest-known icebergs.
As soon as an iceberg is born it starts to die. Waves chip away at its edges, air defrosts it from above, and water melts it from below. Researchers recently recorded such death throes for one of the worlds largest-known icebergs.
In July 2017, Iceberg A-68 broke from the Larsen C Ice Shelf, along the east coast of the Antarctic Peninsula. At the time, it was the largest iceberg on the planet and the sixth-largest berg in 3 years of records. It determined nearly 5,800 square kilometers (2,200 square miles), or about the size of the state of Delaware. In other words, A-68 had a lot to lose. Throughout three and a half years, the berg disintegrated and melted, leaving its mark on the ocean environment, specifically near the remote island of South Georgia.
” Icebergs give cold fresh water and nutrients in the Southern Ocean,” stated Anne Braakmann-Folgmann, a doctoral candidate at the University of Leeds. “However, where and how much of this is launched is not effectively studied and not included in ocean models yet, particularly for the largest icebergs.”
Braakmann-Folgmann and coworkers set out to chart the journey of A-68A. (The brand-new name was provided to the primary berg after a couple of small pieces broke off.) The researchers used satellite data to document changes in the icebergs density, area, volume, and mass from the time it broke from the ice rack in July 2017 up until it started to rapidly break down in January 2021.
When the iceberg thinned as it drifted north from the Weddell Sea into the Scotia Sea, the maps above show where and. The first map (left) reveals the bergs thickness in July 2017, when it was still near the Larsen C Ice Shelf. Notification that it is thicker on its left side, where it was connected to the ice shelf, and thinner on the ideal side, where it was exposed to the ocean. Its overall average density was 235 meters at the time. As the berg drifted north, it met warmer air and water temperatures, which sped up melting. By January 2021, when the berg surrounded South Georgia, it had thinned to an average density of 168 meters.
About 85 percent of an iceberg lies below the waters surface– less than perfect for measuring its overall density. However researchers can now approximate the density by measuring parts of the iceberg that are above the water. Information from NASAs Ice, Cloud, and land Elevation Satellite 2 (ICESat-2) and the European Space Agencys CryoSat-2 (laser and radar altimeters, respectively) can show the distance from the satellite to the surface of the iceberg and to the surface of the sea. The distinction between these measurements is called the icebergs “freeboard”– the height of the ice that increases above the water. Researchers can then convert this height into thickness by accounting for the densities of the iceberg, the snow layer on top, and the surrounding sea water.
Iceberg A-68A map. 2017– 2021.
The scientists revealed that from July 2017 till January 2021, melting from the bottom of the iceberg represented 32 percent of its loss. Melting peaked near South Georgia, where the scientists approximated that 152 billion metric heaps (152 billion cubic meters) of fresh water was contributed to the ocean– the equivalent of 61 million Olympic swimming pools– over the span of three months. Researchers are still examining the result of all this fresh water on local ocean homes. If the additional nutrients provided to the ocean by the melting iceberg promoted any biological production, they likewise desire to understand.
When big pieces broke away from the sides of the berg, other ice losses happened. This was particularly the case when A-68A left the protective sea ice near Antarctica and transferred to the north, where it was exposed to the devastating waves of the open ocean. Thinning and fragmentation both increased as the iceberg wandered north, but fragmentation finally controlled as the iceberg broke down in the Northern Scotia Sea.
NASA Earth Observatory images by Joshua Stevens, using information courtesy of Braakmann-Folgmann, A. et al. (2022) and The Antarctic Iceberg Tracking Database at Brigham Young University.