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The global ocean absorbs roughly a quarter of carbon emissions from human activities, which is extremely important in helping to slow climate change. On the flip side, however, this benefit does come at a cost: as oceans take in more carbon, their waters become more acidic, endangering the health of marine ecosystems.
Enhancing our understanding of the complex processes driving sea/air carbon fluxes and refining estimates of how much carbon the global ocean sequesters are crucial for accurate carbon budget assessments and informed climate action.
Scientists have thought that the ocean skin—a 0.01 millimeter sliver of surface water, thinner than a human hair, which is typically fractionally cooler than the water below—should increase the amount of carbon dioxide being absorbed from the atmosphere.
This is because cooler water is more efficient at absorbing carbon dioxide. The gas concentration between this thin top layer and the water some 2 mm deeper is what controls the exchange of the gas between the atmosphere and the ocean.
However, this had never been extensively measured at sea, until now.
Thanks to research, which was partially funded by ESA, scientists from the UK’s University of Exeter, Plymouth Marine Laboratory and University of Southampton assessed in situ measurements taken from ships as they traversed the Atlantic Ocean (research ship RSS Discover pictured).
The measurements were taken by flux systems that detected tiny differences in carbon dioxide in air swirling towards the ocean surface and away again, along with precise temperature readings of the extremely thin ocean skin.
Based on these measurements, the new findings, published in the journal Nature Geoscience, confirm that that the temperature of the ocean skin increases carbon absorption.
