Antarctic Deep Ocean Currents on the Brink of Collapse, Researchers Warn

Date: March 30, 2023

Source: University of New South Wales

Summary

Researchers have found that Antarctic deep ocean circulation could decline by over 40% in the next 30 years, posing significant threats to the world's oceans and climate.

Full Story

Scientists warn that the deep ocean currents surrounding Antarctica are at risk of collapsing, which could lead to stagnant ocean floors and significant consequences for the climate and marine ecosystems for centuries to come.

Scientia Professor Matthew England, Deputy Director of the ARC Centre for Excellence in Antarctic Science (ACEAS) at UNSW Sydney, coordinated a new study published in Nature. The research team included lead author Dr. Qian Li, formerly from UNSW and now at MIT, as well as co-authors from ANU and CSIRO.

The world's oceans are connected through an overturning circulation driven by cold water that sinks near Antarctica. This circulation carries heat, carbon, oxygen, and nutrients around the globe, playing a crucial role in regulating climate, sea level, and the productivity of marine ecosystems.

Prof. England stated, "Our modelling shows that if global carbon emissions continue at the current rate, then the Antarctic overturning will slow by more than 40% in the next 30 years -- and on a trajectory that looks headed towards collapse."

Unprecedented Modelling Techniques

The international team of scientists used advanced modelling techniques to estimate the amount of Antarctic deep water produced under the IPCC 'high emissions scenario' until 2050. The model captures details of ocean processes not previously accounted for in other models, including the potential influence of meltwater from ice on circulation.

While the deep ocean current has remained relatively stable for thousands of years, increasing greenhouse gas emissions may cause the Antarctic overturning circulation to slow down significantly in the coming decades.

The Impact of Reduced Antarctic Overturning

If the deep ocean current collapses, ocean waters below 4,000 meters will stagnate, trapping nutrients in the deep ocean and reducing their availability for marine life near the surface. This could lead to severe consequences for marine ecosystems and the climate.

Co-author Dr. Steve Rintoul of CSIRO and the Australian Antarctic Program Partnership noted that direct measurements confirm the warming of the deep ocean is already underway. Melting ice around Antarctica is making nearby ocean waters less dense, which in turn slows the Antarctic overturning circulation.

Dr. Adele Morrison, from ACEAS and the ANU Research School of Earth Sciences, highlighted the significant impact of melting ice sheets on the overturning circulation that regulates Earth's climate. As the planet warms, the Antarctic and Greenland ice sheets are expected to continue melting at an accelerated rate.

Prof. England warned, "We are talking about the possible long-term extinction of an iconic water mass. Such profound changes to the ocean's overturning of heat, freshwater, oxygen, carbon, and nutrients will have a significant adverse impact on the oceans for centuries to come."

Related Topics

• Earth & Climate
• Global Warming
• Oceanography
• Climate
• Geography
• Fossils & Ruins
• Early Climate
• Origin of Life
• Fossils
• Ancient DNA

Related Terms

• Global climate model
• Climate
• Greenland ice sheet
• Climate model
• Antarctic krill
• Global warming
• Deforestation
• Antarctic Circle

Story Source

Materials provided by University of New South Wales. Original written by Melissa Lyne. Note: Content may be edited for style and length.

Journal Reference

Qian Li, Matthew H. England, Andrew McC. Hogg, Stephen R. Rintoul, Adele K. Morrison. Abyssal ocean overturning slowdown and warming driven by Antarctic meltwater. Nature, 2023; 615 (7954): 841 DOI: 10.1038/s41586-023-05762-w