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On January 15, 2025, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured the world’s largest iceberg drifting towards South Georgia Island. In this image, the bright white rectangular-shaped Iceberg A23A floats roughly 250 kilometers (155 miles) off the southern tip of crescent-shaped South Georgia Island. Clouds swirl around both the island and the iceberg while brilliant streaks and swirls of blue and green color the waters of the South Atlantic Ocean.
After breaking from the Filchner-Ronne Ice Shelf in 1986, Iceberg A23A spent decades stuck to the floor of the southern Weddell Sea. It began to wiggle loose in the early 2020s, and by March 2023 the Rhode Island-sized iceberg floated unencumbered. But such freedom lasted only a year. As it drifted northward in March 2024, the berg became ensnared by a rotating vortex of water, or Taylor column, caused by currents encountering a bump on the seafloor. It continued to spin in that location until, after making 15 rotations, the ‘berg broke out of the spin-cycle in November 2024. It has been drifting freely since, floating on currents that transport roughly 90 percent of icebergs from the Weddel Sea toward the South Atlantic Ocean.
Currents also shape the streaks of color north of South Georgia Island. The blues and greens mark the location of a large phytoplankton bloom. These microscopic plant-like organisms thrive in the cold, nutrient-rich water near the southern tip of South America, which is located 1,340 miles (2,157 km) west of South Georgia Island. Phytoplankton blooms float freely in the upper levels of the ocean, pushed and pulled by currents.
Image Facts
Satellite:
Aqua
Date Acquired: 1/15/2025
Resolutions:
1km (763.6 KB), 500m (1.7 MB),
Bands Used: 1,4,3
Image Credit:
MODIS Land Rapid Response Team, NASA GSFC