We’ve known for decades that the oceans play a major role in Earth’s climate, not just because of the way they absorb heat and move it around, but also because they absorb CO2 from the atmosphere, and so play a role in mitigating our own carbon emissions.
The new study, led by the University of Exeter, includes this — and finds significantly higher net flux of carbon into the oceans.
It calculates CO2 fluxes from 1992 to 2018, finding up to twice as much net flux in certain times and locations, compared to uncorrected models.
“Half of the carbon dioxide we emit doesn’t stay in the atmosphere but is taken up by the oceans and land vegetation ‘sinks’,” said Professor Andrew Watson, of Exeter’s Global Systems Institute.
“Researchers have assembled a large database of near-surface carbon dioxide measurements — the “Surface Ocean Carbon Atlas” (http://www.socat.info) — that can be used to calculate the flux of CO2 from the atmosphere into the ocean.
“Previous studies that have done this have, however, ignored small temperature differences between the surface of the ocean and the depth of a few metres where the measurements are made.
“Those differences are important because carbon dioxide solubility depends very strongly on temperature.
“We used satellite data to correct for these temperature differences, and when we do that it makes a big difference — we get a substantially larger flux going into the ocean.
“The difference in ocean uptake we calculate amounts to about 10 per cent of global fossil fuel emissions.”
Dr Jamie Shutler, of the Centre for Geography and Environmental Science on Exeter’s Penryn Campus in Cornwall, added: “Our revised estimate agrees much better than previously with an independent method of calculating how much carbon dioxide is being taken up by the ocean.
“That method makes use of a global ocean survey by research ships over decades, to calculate how the inventory of carbon in the ocean has increased.
I suppose on the surface this seems like good news, but it honestly worries me. It means that as the oceans continue to absorb heat and consequently lose their ability to absorb more CO2, the rate of warming may increase faster than our previous understanding of oceanic carbon uptake would indicate. On the plus side, this may mean that if we reduce carbon emissions dramatically, the levels in the atmosphere will fall faster than previously expected, or at least rise more slowly than feared, as the result of the various feedback loops we’ve triggered. All in all, it’s good to know more about what’s happening, if we want to have a hope of changing course.
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As you say, it’s always good to know accurately what’s happening. That more CO2 than previously believed is dissolving in the oceans means that oceans will conitnue to acidify more rapidly, since it’s the dissolved CO2 that causes that. And, that we’ll have to move even more aggressively to save coral reefs and the ecosystem they sustain.
@ ^ garnetstar : Good points. Seconded.
To a degree, yeah.
Measurements of ocean pH are still accurate, as for as I know, so those changes were occurring with this higher rate of CO2 absorption, we just didn’t know the full picture. This is likely to give us a better understanding of how widespread the pH change is, but I don’t think it changes much for the locations that have been subject to intense monitoring – it just may explain why they’ve seen higher pH levels than one would expect with a presumption of lower CO2 uptake.
Things look bleak for tropical reefs either way, it’s just not clear to me whether this makes things actually look worse, on the pH front, vs explaining what we’ve already seen a bit better.