Today’s Image of the Day from NASA Earth Observatory features the massive iceberg A-23A and its offspring near South Georgia, a remote island in the South Atlantic Ocean. 

The natural-color image was captured by NASA’s Aqua satellite on July 22, 2025, as sunlight returned to Antarctica after months of polar night.

By this time, the main iceberg still covered an impressive 969 square miles, while the smaller iceberg fragments measured 62 and 28 square miles.

The journey of iceberg A-23A 

A-23A has been on a long journey since breaking away from Antarctica’s Filchner Ice Shelf nearly four decades ago. Now drifting about 1,500 miles north of where it started, the iceberg is showing its age. 

Once a giant of the southern ocean, A-23A is steadily losing large chunks of ice as it moves through the warmer waters near South Georgia.

Icebergs born in the frigid waters around Antarctica usually spend years drifting on the cold currents. But once they move north toward warmer seas, they face a tough fight against melting caused by higher temperatures, rough waves, and seasonal weather changes. 

These natural forces slowly chip away at the ice, shrinking these floating giants over time.

The iceberg’s slow breakup

Around March 1, 2025, A-23A became lodged on the shallow continental shelf near South Georgia.

This stopover wasn’t permanent. By late May, the iceberg had broken free from the shelf, continuing its drift eastward along currents that also carried the famous A-68A iceberg in 2020.

The winter months in the southern hemisphere brought harsher conditions. The iceberg endured rough seas and freezing air, causing more ice to break off its edges. 

Two of these newly formed icebergs were large enough to earn their own names and tracking status: A-23D and A-23E.

The role of radar technology 

Radar technology played a key role in spotting and tracking these pieces. Jan Lieser from Australia’s Bureau of Meteorology first spotted the new icebergs using radar data from NovaSAR-1. 

These observations were later confirmed by the U.S. National Ice Center with radar images from the European Space Agency’s Sentinel-1 satellite.

“Radar satellites can take images of the Earth at polar night and through all weather conditions, including heavy clouds and even smoke,” noted Lieser.

Life cycle and climate impact

Even after losing significant ice, A-23A remains the largest free-floating iceberg in the world’s oceans. Another iceberg, D-15A, is larger but grounded off East Antarctica’s Amery Sea. 

As longer daylight hours brighten the South Atlantic, scientists expect A-23A to lose even more ice while it travels farther north.

Icebergs like A-23A serve as floating records of Antarctica’s changing climate. Their journeys help scientists learn how ocean currents and temperatures influence iceberg lifespans. 

When icebergs drift into warmer waters, melting accelerates, contributing freshwater to the ocean. This influx can affect local marine ecosystems and even influence global ocean circulation patterns.

Cascading effects of icebergs

The breakup of large icebergs also releases nutrients trapped in the ice, feeding marine life and sometimes causing bursts of plankton growth. 

These blooms can have cascading effects through the food chain, supporting fish and other wildlife around remote islands like South Georgia.

Tracking icebergs has become more precise thanks to advancements in satellite technology. Radar satellites provide consistent monitoring, unaffected by darkness or bad weather. 

Visible light sensors complement these efforts during clear conditions. Together, they give scientists a clearer picture of iceberg movements and breakups.

Iceberg tracking in a changing world

The story of A-23A is more than just the tale of a drifting iceberg. It reflects broader changes happening in polar regions due to climate shifts. 

Ice shelves in Antarctica are breaking off more frequently, and giant icebergs are becoming common visitors to subantarctic waters.

Monitoring these icebergs helps researchers understand how warming oceans affect ice melt and the resulting impacts on sea levels and ecosystems. This knowledge is vital for predicting future changes and preparing for their consequences.

In the end, A-23A is a powerful reminder of nature’s slow but relentless changes. From its breakaway in Antarctica to its current fate in the South Atlantic, this iceberg’s path tells a story about time, climate, and the forces shaping our planet.

Image Credit: NASA Earth Observatory 

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