Iceberg A-23B Has Calved from Iceberg A-23A in the northern Weddell Sea

By LTJG Garner Fleming, US Navy
NIC.PAO@noaa.gov
301-943-6977
January 31, 2025

Suitland, MD — The U.S. National Ice Center (USNIC) has confirmed that iceberg A-23B calved from A-23A in the northern Weddell Sea. As of January 31, A-23A was centered at 56° 47' South and 40° 19' West and measured 40 nautical miles on its longest axis and 32 nautical miles on its widest axis. A-23B was centered at 56° 47' South and 40° 52' West and measured 10 nautical miles on its longest axis and 4 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 confirmed by USNIC Analyst Britney Fajardo using the Sentinel-1 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

USNIC is a multi-agency center—subordinate to Naval Meteorology and Oceanography Command—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.

Naval Meteorology and Oceanography Command directs and oversees more than 2,500 globally-distributed military and civilian personnel who collect, process and exploit environmental information to assist Fleet and Joint Commanders in all warfare areas to make better decisions faster than the adversary.

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.