Ice melt changing ocean current ‘decades early’

Climate change-driven shifts in the circulation of waters to the deepest reaches of the ocean around Antarctica, which could reverberate across the planet and intensify global warming, are happening decades “ahead of schedule”, research shows.

Scientists said an acceleration of melting Antarctic ice and rising temperatures – driven by the emission of planet-warming gases – is expected to have a significant effect on the global network of ocean currents that carry nutrients, oxygen and carbon. This could threaten marine life and change the ocean’s crucial role in absorbing carbon dioxide and heat.

An earlier study using computer models suggested “overturning circulation” of waters in the deepest reaches of the oceans would slow by 40 per cent by 2050 if emissions remain high. But research released this week found it had already slowed 30 per cent between the 1990s and 2010s.

“Our data show the impacts of climate change are running ahead of schedule,” said lead author Kathryn Gunn of the CSIRO. The implications could be significant, with Antarctica’s deep ocean acting as a key “pump” for the global network of ocean currents.

“As the ocean circulation slows, more carbon dioxide and heat are left in the atmosphere, a feedback that accelerates global warming,” Ms Gunn said.

Oceans are a crucial regulator of the climate, absorbing large amounts of the additional planet-warming carbon that humans have pumped into the atmosphere since the 1800s, as well as more than 90 per cent of the increased heat.

The new research, published in journal Nature Climate Change, found less oxygen was reaching the deep ocean.