Expansion of Antarctic Bottom Water driven by Antarctic warming in the last deglaciation

Overview

Past fluctuations in atmospheric CO₂ are believed to be closely connected to changes in global ocean circulation, particularly those involving the Southern Ocean and the North Atlantic. These regions played pivotal roles in regulating carbon exchange between the atmosphere and the deep ocean.

Antarctic Bottom Water Dynamics

During the last deglaciation, warming in the Antarctic region triggered a significant expansion of Antarctic Bottom Water (AABW). This water mass, formed around the Antarctic continental shelves, influences the global deep ocean circulation by transporting cold, oxygen-rich water into the ocean’s abyssal layers.

According to recent findings, the rise in temperature around Antarctica accelerated the melting of ice shelves, increasing the freshwater input into surrounding seas. This process modified the density structure of the water column, promoting deeper convection and enhanced AABW formation.

Global Climate Connection

Such changes had wide-reaching consequences. The strengthened AABW flow affected global thermohaline circulation patterns, redistributing carbon and heat between the hemisphere’s oceanic basins. The interplay between AABW expansion and atmospheric CO₂ regulation may help explain major carbon cycle shifts during the transition from the last glacial maximum to the present interglacial.

Interpretations and Implications

Researchers suggest that Antarctic warming acted as a key driver of global ocean reorganization during deglaciation periods. Understanding this feedback between polar processes and atmospheric CO₂ provides essential insight into future climate responses under ongoing Antarctic warming.

“Past atmospheric CO₂ fluctuations are thought to be intricately tied to ocean circulation changes involving Southern Ocean and North Atlantic dynamics.”

Author’s Summary

Antarctic warming during the last deglaciation intensified the formation of bottom waters, reshaping global ocean circulation and influencing Earth’s carbon cycle balance.

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Nature Nature — 2025-12-01

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