Icebergs B-42 and B-43 Icebergs Separate from Thwaites Glacier Calving Front

By Evelyn V. Bowens
U.S. National Ice Center
April 11, 2017

Suitland, MD — The U.S. National Ice Center (USNIC) identified two new icebergs that calved from Thwaites Glacier in the Amundsen Sea. The icebergs had been perched on the edge of Thwaites glacier for a few years, but finally began to separate from the ice shelf.

B-42 is located at 74°50’ South, 106°48’ West, in the Amundsen Sea. The iceberg measures 17 nautical miles on its longest axis and 5 nautical miles on its widest axis. B-43 is located at 7451’ South, 107°10’ West, in the Amundsen Sea. The iceberg measures 10 nautical miles on its longest axis and 5 nautical miles on its widest axis. USNIC analyst Chris Readinger confirmed B-42 and B-43 using the Sentinel-1A image shown below.

Iceberg names are derived from the Antarctic quadrant in which they were originally sighted. The quadrants are divided counter-clockwise in the following manner:

A = 0-90W (Bellingshausen/Weddell Sea)
B = 90W-180 (Amundsen/Eastern Ross Sea)
C = 180-90E (Western Ross Sea/Wilkesland)
D = 90E-0 (Amery/Eastern Weddell Sea)

When first sighted, an iceberg’s point of origin is documented by the USNIC. The letter of the quadrant, along with a sequential number, is assigned to the iceberg. For example, C-19 is sequentially the 19th iceberg tracked by the USNIC in Antarctica between 180-90E (Quadrant C). Icebergs with letter suffixes have calved from already named icebergs, where the letters are added in sequential order. For example, C-19D, is the 4th iceberg to calve off the original C-19 iceberg.

The National Ice Center is a tri-agency operational center represented by the United States Navy (Department of Defense), the National Oceanic and Atmospheric Administration (Department of Commerce), and the United States Coast Guard (Department of Homeland Security). The National Ice Center mission is to provide the highest quality strategic and tactical ice services tailored to meet the operational requirements of U.S. national interests and to provide specialized meteorological and oceanographic services to United States government agencies.

Satellite image of Iceberg B-42 and B-43
Figure 1: SENTINEL-1A image of B-42 and B-43 dated April 4 2017

For more information, please contact:
National Ice Center
Command Duty Officer
Voice: (301) 943-6977
Twitter: @usnatice
Facebook: @usnatice

The U.S. National Ice Center is a tri-agency center operated by the Navy, NOAA, and Coast Guard and provides global to tactical scale ice and snow products, ice forecasting, and related environmental intelligence services for the United States government.

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