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from the buffers-work-up-to-a-point-and-then-all-hell-breaks-loose dept.
If circulation of deep waters in the Atlantic stops or slows due to climate change, it could cause cooling in northern North America and Europe – a scenario that has occurred during past cold glacial periods.
Now, a Rutgers coauthored study suggests that short-term disruptions of deep ocean circulation [also] occurred during warm interglacial periods in the last 450,000 years, and may happen again.
Ironically, melting of the polar ice sheet in the Arctic region in a warmer world, resulting in more fresh water entering the ocean and altering circulation, might have caused previous coolings.
[...] The study, published in the journal Science and led by scientists at the University of Bergen in Norway, follows a 2014 study on the same topic.
"These findings suggest that our climate system, which depends greatly on deep ocean circulation, is critically poised near a tipping point for abrupt disruptions," said coauthor Yair Rosenthal, a distinguished professor in the Department of Marine and Coastal Sciences and Department of Earth and Planetary Sciences at Rutgers University–New Brunswick. "Although the disruptions in circulation and possible coolings may be relatively short-lived – lasting maybe a century or more – the consequences might be large."
The warm North Atlantic Current -- the northernmost part of the Gulf Stream -- flows into the Greenland Sea. It becomes progressively colder and saltier due to heat loss to the air, eventually sinking and forming the North Atlantic Deep Water formation -- a mass of deep, cold water that flows southward. Melting of the polar ice sheet in the Arctic region would result in more fresh water entering the ocean and disrupting that circulation pattern, potentially causing cooling in northern areas of Europe and North America.
[...] The latest study covers three other warm interglacial periods within the past 450,000 years. During all of them, regardless of the degree of global warming, the scientists found similar century-long disruptions of the North Atlantic Deep Water formation. And they found that such disruptions are more easily achieved than once believed and took place in climate conditions similar to those we may soon face with global warming.
Journal Reference:
Eirik Vinje Galaasen, Ulysses S. Ninnemann, Augustin Kessler, et al. Interglacial instability of North Atlantic Deep Water ventilation. Science, 2020 DOI: 10.1126/science.aay6381
(Score: 3, Interesting) by Anonymous Coward on Saturday March 28 2020, @02:48AM (3 children)
Thank you for posting a non-troll comment. As a meteorologist, I'll take a swing at this.
My guess is that the short term effect from lower emissions due to COVID-19 is actually an increase in temperature. If we kept up this reduction in travel for a quite awhile, I think we'd see a cooling effect, or at least a decrease in the rate of warming.
There are two factors I'm considering: greenhouse gases and aerosols. When you're burning gasoline, you're producing carbon dioxide, but you're also producing very small particulates, or aerosols. The direct effect of adding more greenhouse gases to the atmosphere is warmer temperatures. However, most aerosols other than soot tend to scatter some sunlight back into space, leading to cooler temperatures.
Greenhouse gases like carbon dioxide have very long residence times in the atmosphere. The residence time of carbon dioxide in the atmosphere is on the order of a century. However, aerosols are readily removed from the atmosphere on a much shorter time scale. Water vapor tends to condense around many types of aerosols. Aerosols that seed droplet formation are called cloud condensation nuclei. And if the droplet merges with other droplets and becomes large enough to fall to the ground, all of those aerosols will be removed from the atmosphere along with any other aerosols the droplet collects on the way down. In short, aerosols don't stay in the atmosphere very long and are removed much quicker than carbon dioxide and other greenhouse gases.
In the short term, the warming from fewer aerosols in the atmosphere probably has a larger effect than the reduction in greenhouse gas emissions. I expect in the short term, we'd actually see warmer temperatures. If the pause was for a longer period of time, long enough that the reduction in greenhouse gases has a bigger effect, we'd probably see a cooling. We may see a bigger impact in the short term from decreased emissions of other greenhouse gases with much shorter residence times. But for a pause of a few months, I suspect the reduction in aerosols more than offsets the impact on greenhouse gases. I don't have the data to know for sure, but that's what I expect would occur.
(Score: 2) by MostCynical on Saturday March 28 2020, @10:08AM (2 children)
Nitrogen has dropped over Italy [phys.org], but what that will mean for the climate is not clear.
"I guess once you start doubting, there's no end to it." -Batou, Ghost in the Shell: Stand Alone Complex
(Score: 2) by maxwell demon on Saturday March 28 2020, @11:52AM
No, nitrogen still makes up about 80% of the atmosphere in Italy. The article you linked talks about nitrogen dioxide, a very different substance that actually contains more oxygen than nitrogen.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 0) by Anonymous Coward on Saturday March 28 2020, @02:33PM
Dusts haven't, but the agency did not release dust particle data fearing it might be misinterpreted. https://www.qualenergia.it/articoli/quali-relazioni-tra-coronavirus-e-inquinamento-atmosferico/ [qualenergia.it]
Not very sciencey of them...