North Atlantic is getting less salty, but it's too soon to blame climate change

March 14, 2018 by Kim Martineau, Columbia University
Researchers report a sharp drop in salinity in the North Atlantic Ocean over the last decade, providing the most detailed look yet at changing ocean conditions in the region. Credit: Argo project

Salinity in the North Atlantic dropped dramatically over the last decade, according to a new study that used data from a floating network of sensors to get the most detailed picture yet of changing ocean conditions in the region.

But researchers say it's too soon to say whether the decline is due to an influx of freshwater from melting ice on land or sea, or part of a natural, longer term cycle. A research team at Columbia University's Lamont-Doherty Earth Observatory and Johns Hopkins University published the results in the Journal of Climate's April issue.

Between 2004 and 2015, salinity fell by as much as half a gram of salt per kilogram of seawater in the sub-polar North Atlantic, a region that includes the Labrador Sea dividing Canada and western Greenland. That's the equivalent of diluting the area with 5,000 cubic kilometers of freshwater, says the study's lead author Jan-Erik Tesdal, a PhD student at Columbia.

Though many forces cause salinity to rise and fall, the researchers attribute the immediate cause for the decline to changes in ocean circulation. A large system of circulating currents that deliver freshwater to the region, the sub-polar gyre, appears to be moving faster, propelled by stronger winds tied to the North Atlantic Oscillation climate pattern.

To put the changes in context, salinity fell twice as much in the early 1970s, equivalent to about 10,000 square kilometers of freshwater flooding the North Atlantic, suggesting that a natural cycle is at play. The drop, however, comes as Greenland's glaciers slide into the sea at a faster rate, and summer sea ice reaches record lows. Researchers haven't seen freshwater fluxes out of the Arctic Ocean increase much yet, but that could change soon.

"My suspicion is that we might soon see the outflow of fresher Arctic water to increase, which will eventually reach the sub-polar North Atlantic and cause a further decline in salinity," said Tesdal.

If climate change is causing the ocean freshening trend, that should become clear within the next 10 years, said study coauthor Thomas Haine, an oceanographer at Johns Hopkins University. "Right now it's ambiguous because of natural variability."

Oceanographers are keenly interested in the North Atlantic for its role in regulating Earth's climate and circulating the nutrients that feed , from plankton to predator fish. Its dense, salty waters draw carbon dioxide from the air and send it deep into the ocean. In the process, nutrients mix through the water column, sustaining marine life. If were to drop too far, some of this mixing would stop, reducing the North Atlantic's carbon dioxide uptake and nutrient cycling which would in turn influence climate and the food web.

Explore further: Warm summers could weaken ocean circulation

More information: Jan-Erik Tesdal et al. Salinity Trends within the Upper Layers of the Subpolar North Atlantic, Journal of Climate (2018). DOI: 10.1175/JCLI-D-17-0532.1

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11 comments

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SamB
1.3 / 5 (13) Mar 14, 2018
Well, since you have indicated where you are going with this, 'too soon' becomes a moot point.
tblakely1357
1.7 / 5 (12) Mar 14, 2018
It's never too soon to blame anything on GW even if you have to make shit up. That narrative ain't gonna push itself.
thefurlong
4.7 / 5 (15) Mar 14, 2018
It's nice to see that even when science reporting is extra-cautious, and makes a point of not necessarily blaming denialists' cause celebre, the latter still can't help themselves, but spray their disinformation fueled lick-spittle all over the comments section.
szore88
1 / 5 (8) Mar 14, 2018
You Marxists want to destroy American manufacturing so bad you can taste it. Thank GOD Trump won...
szore88
1 / 5 (7) Mar 14, 2018
It's nice to see that even when science reporting is extra-cautious, and makes a point of not necessarily blaming denialists' cause celebre, the latter still can't help themselves, but spray their disinformation fueled lick-spittle all over the comments section.


https://www.youtu..._UOjEir0
Bogie99
1 / 5 (9) Mar 14, 2018
^Climate scientists overplayed their hand with doomsday scenarios, creating an unnecessary emotional divide. The blame falls on them for being so loose with an important topic as to treat it as a plaything.
leetennant
5 / 5 (8) Mar 15, 2018
Climate change dumps freshwater into ocean
Salinity declines
Too soon to blame climate change!
Really?
leetennant
5 / 5 (9) Mar 15, 2018
You Marxists want to destroy American manufacturing so bad you can taste it. Thank GOD Trump won...


All these things are just so weirdly specific. Like, Marxism is a really really specific niche set of beliefs and American manufacturing is so small globally. I'm trying to imagine a world where a set of Marxists really were set on destroying specifically US manufacturing. This would be, like, what? Five people trying to destroy something that employs 15?
yep
5 / 5 (9) Mar 15, 2018
You Marxists want to destroy American manufacturing so bad you can taste it. Thank GOD Trump won...

Noam Chompsky laid the blame in his last documentary on blowback from civil rights and questioning why we were in Vietnam. Destroy the middle class by out sourcing manufacturing and devaluing labor. Turning us into a service economy. Then you have no power base to question the oligarchy and the military industrial complex.

Trump is the piece of shit that ripped off all those families in Atlantic city by not paying for services rendered. Basically sucked the marrow from the bones and threw it in the trash heap.
Is that what you hope Trump does for the country, bankrupts us to get rid of debt?

Was it the Marxists who bailed out the banks and GM a few years ago or were they Socialists.
To big to fail? Is that Facism?
HeloMenelo
5 / 5 (8) Mar 15, 2018
It's never too soon to blame anything on GW even if you have to make shit up. That narrative ain't gonna push itself.


Correction: The Sh$t you make up to deny it. Scientific Evidence for Global Warming is everywhere, you're
stuck in a cave and cannot see what goes on outside of it. Your own dumbfounded cause is an insult onto yourself and those who oppose reality.
HeloMenelo
4.4 / 5 (9) Mar 15, 2018
Climate change dumps freshwater into ocean
Salinity declines
Too soon to blame climate change!
Really?


tblakely mackit, bohie,szore et al above which is simply antigorale's sockpuppets showing everyone that get this, they cannot even make sense of normal common sense, hilarious, let alone begin to undertsand the word science and less of what it possibly mean and what the consequences are.

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