As warming weakens ocean circulation, the seas may increasingly become a source of heat-trapping gas, a new study finds.
“Some climate models predict a 30% slowdown in ocean circulation due to melting ice sheets, especially around Antarctica,” said the study author Jonathan Lauderdale, environmental scientist at MIT.
Ocean currents transport carbon from the surface to the depths of the ocean, but they also bring carbon from these depths. Scientists have long assumed that slower circulation would decrease both the amount of carbon taken from the atmosphere and the amount taken from deep waters. In this scenario, the ocean would continue to be a global carbon sink.
But the new modeling study concludes that slowing currents can also disrupt the rise of nutrients from depths to the surface, depriving carbon-absorbing phytoplankton.
Phytoplankton declines would be self-reinforcing, since the small creatures also convert ocean iron into a form that other phytoplankton can consume. Decreased iron would cause an even greater decline in phytoplankton, meaning they would absorb less carbon from the atmosphere or depths. O discoveries were published in Nature Communications.
The result is that the ocean would not only absorb less carbon dioxide from the atmosphere, it would also release more carbon dioxide from its depths, leading to greater warming. Said Lauderdale: “We cannot count on the ocean to store carbon in the deep ocean in response to future changes in circulation.”
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New research raises concerns that ocean circulation will collapse
