Icebergs A-23G and A-23H Have Calved from Iceberg A-23A in the northern Weddell Sea

By LTJG Jared Doris, USN
NIC.PAO@noaa.gov
301-943-6977
August 18, 2025

Suitland, MD — The U.S. National Ice Center (USNIC) has confirmed that icebergs A-23G and A-23H calved from A-23A in the northern Weddell Sea. As of August 30, A-23A was centered at 53° 17' South and 36° 51' West and measured 33 nautical miles on its longest axis and 30 nautical miles on its widest axis. A-23G was centered at 53° 09' South and 37° 10' West and measured 20 nautical miles on its longest axis and 8 nautical miles on its widest axis. A-23H was centered at 53° 22' South and 37° 11' West and measured 13 nautical miles on its longest axis and 3 nautical miles on its widest axis. A-23A first calved from the Ronne Ice Shelf in 1986.

The new icebergs were first spotted by Dr. Jan Lieser of Australia’s Bureau of Meteorology and Christopher Shuman of University of Maryland, and confirmed by USNIC Master Ice Forecaster, Britney Fajardo, using the MODIS image below.

Iceberg names are derived from the Antarctic quadrant in which they were originally calved. 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.

Iceberg positions are analyzed weekly and are available on the USNIC webpage at: https://usicecenter.gov/Products/AntarcIcebergs

The U.S. National Ice Center (USNIC), in collaboration with its global partners, empowers mariners and Naval forces operating in polar, subpolar, and Great Lakes regions with authoritative and timely snow, sea- and lake-ice products and forecasts. USNIC safeguards life and property at sea, defends access and commerce, and further enhances Naval maneuver and superiority. To access daily products, weekly products, archival data and much more of USNIC data in various formats, visit the USNIC webpage at: https://usicecenter.gov/Products.

For more information, please contact:
U.S. National Ice Center
Command Duty Officer
Voice: (301) 943-6977
E-mail: nic.cdo@noaa.gov
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.