Iceberg A-23A has had a more eventful run than most of the large Antarctic icebergs that have calved from the continent’s ice shelves in recent decades. Over its winding, 40-plus-year journey, the “megaberg”spent decades grounded in the Weddell Sea before drifting north, twirling in an ocean vortex for months, and nearly colliding with an island in 2025.
By 2026, the iconic iceberg, sopping with meltwater and shedding smaller bergs as it moved into warmer ocean waters, put on one more show. The chunks of ice and frigid glacial meltwater left in its wake appear to have fueled a surge in phytoplankton abundance, known as a bloom, observed in surface waters by NASA satellites.
On Jan. 25, 2026, the OCI (Ocean Color Instrument) on NASA’s PACE (Plankton, Aerosol, Cloud, Ocean Ecosystem) satellite detected plumes of chlorophyll-a drifting around the remaining bergs and debris field. Researchers use chlorophyll concentrations as a marker of phytoplankton abundance.
Image credit: NASA Earth Observatory images by Michala Garrison, using PACE data from the NASA Ocean Biology Distributed Active Archive Center OB.DAAC, and Landsat data from the U.S. Geological Survey.
