Deep ocean currents around Antarctica set to slowdown the Antarctic overturning circulation

March 26, 2023

A new paper by members of the ACCESS Community, shows how meltwater increases around Antarctica are set to dramatically slowdown the Antarctic overturning circulation, with a potential collapse this century.  

The researchers found that when simulations include upcoming meltwater changes around Antarctica, the abyssal overturning cell declines by more than 40% by 2050. This is an alarming result, as a slowing or collapse of the overturning circulation would change our climate and marine environment in profound and potentially irreversible ways.

Recent and projected bottom water property changes from the main perturbation run

The study, published in the journal Nature last March, used the ACCESS Ocean Model version 2 (ACCESS-OM2), with the ocean model component Modular Ocean Model Version 5.1 (MOM5.1), coupled to the Los Alamos sea-ice model version 5.1.2 (CICE5.1.2). 

“When I first looked at the Antarctic overturning circulation back in the 1990s, it was clear that models could not resolve dense shelf water formation around the Antarctic margin. Fast forward to today, and coupled climate models have improved considerably, but they still struggle to capture localised regions of Antarctic Bottom Water formation around the continental margin,” says Professor Matthew England, one of the authors of the study. 

“It has taken decades to get to this point, but now using the models built by the COSIMA community over many years, we have been able to successfully capture the dense water flows from Antarctica,” says Professor England. 

The work was undertaken by a group of collaborators including Qian Li (formerly based at UNSW now at MIT), Adele Morrison, Andy Hogg and Steve Rintoul. The successful model development is the result of a longstanding partnership between COSIMA, The Geophysical Fluid Dynamics Laboratory (GFDL), in partnership with the National Computational Infrastructure (NCI) and the Australian Earth System Simulator (ACCESS-NRI) infrastructures. 

The next critical step for this research is to include ice-shelf feedbacks in the analysis. The researchers are concerned about the deep warming that results at the West Antarctic margin, which threatens further ice melt. Including ice-shelf feedbacks will be essential to improve the model simulations, but this needs a coordinated model development effort across all the organisations and infrastructures involved.  

Read more about this research here:  

To read the full article: Li, Q., England, M.H., Hogg, A.M. et al. Abyssal ocean overturning slowdown and warming driven by Antarctic meltwater. Nature 615, 841–847 (2023). 



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