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posted by Fnord666 on Saturday August 10 2019, @06:18PM   Printer-friendly
from the because-Florida dept.

Arthur T Knackerbracket has found the following story:

The Gulf Stream, the warm current that brings the east coast of Florida the mixed blessings of abundant swordfish, mild winters and stronger hurricanes, may be weakening because of climate change.

Visible from the air as a ribbon of cobalt blue water a few miles off the coast, the Gulf Stream forms part of a clockwise system of currents that transports warm water from the tropics up the east coast and across the Atlantic to northwestern Europe. In the frigid climate near Greenland, the water cools, sinks and flows south again, rolling through the deep ocean toward the tropics.

This marine circulatory system has reached its weakest point in 1,600 years, recent studies show, having lost about 15% of its strength since the mid-20th century. Scientists disagree on whether climate change or natural cycles account for the slowdown. But a consensus has emerged that climate change will lead to a slower Gulf Stream system in the future, as melting ice sheets in Greenland disrupt the system with discharges of cold fresh water.

A weaker Gulf Stream would mean higher sea levels for Florida's east coast. It could lead to colder winters in northern Europe (one reason many scientists prefer the term climate change to global warming). And it could mean that a lot of the heat that would have gone to Europe would stay along the U.S. east coast and in Florida.

"If you slow down the sinking of water in the North Atlantic, that means you have a pileup of waters along the eastern seaboard of the United States and the Gulf of Mexico," said Brenda Ekwurzel, director of climate science for the Union of Concerned Scientists, an environmental group. "That means that you have increased regional sea level rise just from that ocean circulation change. So that's not good for New York City, Norfolk or along Florida."

-- submitted from IRC


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  • (Score: 2) by dry on Monday August 12 2019, @03:02AM (4 children)

    by dry (223) on Monday August 12 2019, @03:02AM (#879046) Journal

    Perhaps you're thinking of before the isthmus of Panama closed and the Atlantic and Pacific were connected. That and when Antarctica separated from S. America were the most recent big changes in ocean circulation, besides the melting glaciers.

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  • (Score: 2) by HiThere on Monday August 12 2019, @03:33AM (3 children)

    by HiThere (866) Subscriber Badge on Monday August 12 2019, @03:33AM (#879063) Journal

    I don't *think* it was quite that long ago, but Greenland was definitely in a different position.

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    • (Score: 2) by dry on Monday August 12 2019, @04:20AM (2 children)

      by dry (223) on Monday August 12 2019, @04:20AM (#879079) Journal

      Well according to wiki, https://en.wikipedia.org/wiki/Isthmus_of_Panama [wikipedia.org]

      The isthmus formed around 2.8 million years ago,[1] separating the Atlantic and Pacific Oceans and causing the creation of the Gulf Stream.

      I'm no expert and even wiki seems to disagree with itself further down the page. It does also seem that Greenland has been there for quite a few 10's of million years.
      I find it interesting as continental drift seems to be one of the big drivers of climate change over geological time scales.

      • (Score: 2) by HiThere on Monday August 12 2019, @07:50PM (1 child)

        by HiThere (866) Subscriber Badge on Monday August 12 2019, @07:50PM (#879347) Journal

        Looking at a map of the plates, it seems that you are right and I am wrong. It must have been the entire North American plate moving. But I don't think the time I'm remembering is as recent as the connection of North and South America. That was recent enough that saber-tooth tigers around.

        So you're noting a more recent event that shaped the current gulf-stream. I was remembering a reference to an earlier one (which must have been called something different).

        But the point is that even though the oceanic currents are all connected, diverting one of them doesn't shut down everything, it just changes the pattern of flows...with, of course, connected influences on climate. The current gulf stream depends on Arctic subduction currents, but those don't happen if the colder water at the top of the ocean is lighter than the water in the depths of the ocean, and fresher water, even when cold, is lighter than saltier water. So Greenland melting could shut down, or *severely* slow the gulf stream, but this wouldn't shut down all the ocean currents. The main Pacific currents would probably barely be touched, and the South Atlantic currents, though modified, would probably continue.

        OTOH, I'm *NOT* an expert in this area. I've taken a couple of classes multiple decades ago. Someone pointing a link to a real source of knowledge would be useful. My references are all to the kind of popular science source that a non-expert can read, and which come up quickly on Google. (Like " https://www.livescience.com/37529-continental-drift.html [livescience.com] ", which is what convinced me that my memory of Greenland rotating was false.)

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        • (Score: 2) by dry on Monday August 12 2019, @11:30PM

          by dry (223) on Monday August 12 2019, @11:30PM (#879412) Journal

          The only earlier event that changed all the oceans circulation that I know off, without going way back when N. America was half under water was the formation of the Drake passage and Tasmanian Seaway maybe 30 million yrs back (20-40 Ma). https://en.wikipedia.org/wiki/Antarctic_Circumpolar_Current#Formation [wikipedia.org]
          I'm also far from an expert and might be missing something like the melting ice caps forming huge inland freshwater lakes then breaking free to the ocean which introduced a huge amount of fresh water and set the end of the last ice age back.
          I'm inclined to agree that the Gulf stream stopping wouldn't have much affect on the Pacific. Still if you look at this map, https://en.wikipedia.org/wiki/File:Thermohaline_Circulation_2.png [wikipedia.org] everything is connected. Be nice to know more and it's a shame that dating some of this stuff is so inaccurate.