Iceberg A-74 Calves into A-74A and A-74B as it slowly moves away from the Brunt Ice Shelf

By LT Jacquelyn Putnam, NOAA
U.S. National Ice Center
Jun 10, 2022

Suitland, MD — The U.S. National Ice Center (USNIC) has confirmed that iceberg A-74 (figure 1, below) has calved into two icebergs A-74A and A-74B near Berkner Island in the Weddell Sea. As of June 07, A-74A was centered at 76° 55' South and 45° 54' West and measured 28 nautical miles on its longest axis and 18 nautical miles on its widest axis. A-74B was centered at 76° 45' South and 44° 54' West and measured 9 nautical miles on its longest axis and 4 nautical miles on its widest axis. A-74 first calved from the Brunt Ice Shelf in March 2021 and has drifted 90 nautical miles westward in the 15 months since.

The calving event was first spotted by USNIC Analyst Katherine Quinn, and confirmed by USNIC Analyst Christopher Readinger using the Sentinel-1A image 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.

Iceberg positions are analyzed weekly and are available on the USNIC webpage at:

Satellite image of Iceberg A-74A and A-74B
Figure 1: Sentinel-1A image of icebergs A-74A and A-74B from June 07, 2022

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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