Early Slowdown of Antarctic Deep Ocean Currents

• 30 May 2023

Recently, a new research revealed that deep ocean currents in Antarctica are slowing down much earlier than previously predicted.

Key findings of the research are:

• Early Slowdown: Deep ocean currents in Antarctica, known as the overturning circulation, are slowing down earlier than predicted, with a 30% slowdown observed over the past three decades.
• Cause: The slowdown is attributed to the melting of Antarctic ice, which is disrupting the formation of Antarctic bottom water, a dense and oxygen-rich water mass that drives the overturning circulation.
• Reduced Supply of Oxygen: The decline in Antarctic bottom water formation reduces the supply of oxygen to the deep ocean, leading to a decrease in deep ocean oxygen levels.
• The reduction in oxygen-rich bottom water allows warmer, oxygen-depleted waters to replace it, further reducing oxygen levels in the deep ocean.
• Impact on Deep-Ocean Organisms: The slowdown in the overturning circulation and declining oxygen levels have significant implications for marine life, as even small changes in oxygen can impact deep-ocean organisms' behaviour and habitat availability.
• May Intensify Global Warming: The slowdown may also intensify global warming as the overturning circulation transports carbon dioxide and heat to the deep ocean, and reduced ocean storage capacity leads to more carbon dioxide and heat remaining in the atmosphere.
• Increase in Sea Levels: The reduction in Antarctic bottom water reaching the ocean floor increases sea levels due to thermal expansion of warmer waters.