The Pine Island Glacier quickly drops another iceberg
The Pine Island Glacier quickly drops another iceberg
The Pine Island glacier in western Antarctica is known to dispense icebergs in the Amundsen Sea, but the frequency of these events appears to be increasing. The most recent delivery occurred at the end of October 2018, when the Sentinel-1 satellite observed that the glacier was detached from about 300 square kilometers of ice. The largest piece, called Iceberg B-46, represented 226 square kilometers.
the Operational Earth Imager (OLI) in Landsat 8 acquired this image (left) of the new iceberg on November 7, 2018. By way of comparison, the second OLI image shows the same area on September 17, 2018, before a crack propagated rapidly through the glacier and generate bergs
By the time the image was acquired on November 7, some pieces had already been detached from the B-46 and reduced in size to about 185 square kilometers, still large enough to be tracked by the National Ice Center of the United States. Also note that the edges of the bergs are high enough and the angle of the sun low enough to cast dramatic shadows on the sea ice.
The Pine Island Glacier is composed of ice that formed in the earth as part of the ice sheet of West Antarctica. Ice from the glacier flows into the sea and extends over Pine Island Bay as a floating ice shelf. The open water areas, or polinias, are visible as the dark areas in the image on the left. This is where the relatively warm water accumulation has prevented sea ice from forming.
The birth of B-46 is the latest in a series of almost annual events; Pine Island Glacier has thrown icebergs in 20132015 2017, and 2018. (The icebergs of 2015 stopped in the midst of the darkness of the southern winter.) Before 2013, such events occurred every six years.
According to Joe MacGregor, glaciologist and project scientist for NASA's Operation IceBridge, the change in calving frequency is probably related to the thinning of the ice shelf. The thinning can destabilize the shelf because it loses contact with the "anchor points" that strongly influence how the calves of the platform.
Given the thinning, retreat and contribution of the Pine Island Glacier to sea level rise, scientists are watching it closely. Operation IceBridge He routinely examines the glacier during its annual missions on the continent. The mission most recently flew over Pine Island on November 7, 2018, giving those on board a first-hand view of the new iceberg. Brooke Medley, assistant scientist for the IceBridge project, took this picture and showed a view to the north of the Pine Island Glacier (right) and B-46 (left).
Images from the NASA Earth Observatory by Lauren Dauphin, using Landsat data from the United States Geological Survey. Photo by Brooke Medley / NASA. History of Kathryn Hansen with the interpretation of the image of Chris Shuman and Joe MacGregor, GSFC of NASA.
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