Iceberg A-76 Calves into A-76A, A-76B, and A-76C as it slowly moves away from the Ronne Ice Shelf

By LT Falon M. Essary, USN
U.S. National Ice Center
May 26, 2021

Suitland, MD — The U.S. National Ice Center (USNIC) has confirmed A-76 has calved two large icebergs. A-76 is now known as A-76A. The icebergs which formed are named A-76B, and A-76C. As of May 26th, A-76A was centered at 75° 05' South, 59° 29' West and measures 73 nautical miles on its longest axis and 14 nautical miles on its widest axis. A-76B was centered at 75° 22' South, 57° 07' West and measures 20 nautical miles on its longest axis and seven nautical miles on its widest axis. Iceberg A-76C was centered at 75° 37' South, 57° 22' West and measures 16 nautical miles on its longest axis and seven nautical miles on its widest axis.

The new icebergs were first spotted by Dr Jan Lieser of Australia’s Bureau of Meteorology and confirmed by USNIC Ice Analyst Christopher Readinger 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 A-76A, A-76B, and A-76C
Figure 1: Sentinel-1A image of icebergs A-76A, A-76B, and A-76C from May 26, 2021 (Sentinel-1A courtesy of ESA)

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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