Featured Science Paper
Localized subduction of anthropogenic carbon dioxide in the Southern Hemisphere oceans
This paper greatly advances our understanding of how carbon emissions are drawn deep into the Southern Ocean, slowing the rate of global climate change. A few regions around the world are key in overturning deep and shallow layers of the ocean, and allow carbon to be locked away from the atmosphere for centuries. The Southern Ocean in particular is known to be a significant oceanic carbon sink, and accounts for 40% of all carbon entering the deep oceans. And yet, until now, no-one could quite work out how the carbon gets there from the surface waters. This paper resolves this, and shows the importance of 1000km-wide plunging “funnels”.
The analysis is based around a decade’s worth of data from thousands of robotic floats, and hundreds of ships spread across the southern hemisphere oceans. It has shown that carbon capture process occur in well-defined regions of the Southern Ocean, which Sallee et al. mapped. They pinpointed five such zones in the Southern Ocean, including one off the southern tip of Chile and another to the south-west of New Zealand. They found that certain combinations of winds and currents are required to pump carbon dioxide into the deep ocean, where much of it stays locked away for thousands of years. Mesoscale ocean eddies have a primary role in this process.
The importance of ocean eddy processes in the global carbon cycle, demonstrated by these new results, raises the question of how well coarse resolution climate models represent the relatively fine-scale eddy processes. This work lays down some very significant challenges to the developers of climate and Earth System models, but also shows the way forward in evaluating and improving model performance.
Sallee, Jean-Baptiste et al. 2012
Nature Geoscience, 5. 579-584. 10.1038/ngeo1523