Iceberg D-33D Has Calved from Iceberg D-33A in the Weddell Sea

By LT Jared Doris, USN
NIC.cdo@noaa.gov
U.S. National Ice Center
June 21, 2026

SUITLAND, MD — The U.S. National Ice Center (USNIC) has confirmed that iceberg D-33D (figure 1, below) calved from iceberg D-33A in the Weddell Sea. As of June 21, D-33A was centered at 64°12' South and 55°40' West and measured 19 nautical miles on its longest axis and 10 nautical miles on its widest axis. D-33D was centered at 64°25' South and 55°44' West and measured 15 nautical miles on its longest axis and 6 nautical miles on its widest axis. The break was first seen on satellite imagery on June 20. D-33A first calved from the Borchgrevink Ice Shelf in August 2023.

The calving event was spotted by Dr. Klaus Strübing and confirmed by USNIC Master Ice Forecaster Britney Fajardo using the Sentinel-1 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 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 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.

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.

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