Dense Antarctic water returning to the Atlantic surprises experts

Posted: September 4, 2019 by oldbrew in Natural Variation, Ocean dynamics, research
Tags: , , ,

Antarctica


The lead oceanographer in this research says: “The deep oceans have been warming across much of the world for decades, so we were surprised to suddenly see this trend reversing and stabilizing in the Scotia Sea.”
Carbon dioxide up, warming down – surprising to some it seems.

The supply of dense Antarctic water from the bottom of the ocean to the Atlantic has declined in recent years, says Phys.org.

However, a new study explains for the first time how since 2014 this has stabilized and slightly recovered due to the variability in upstream dense waters, with implications for the global climate.

The study, led by British Antarctic Survey, is published this week in the journal Nature Climate Change.

Seawater that has been cooled around Antarctica sinks to the bottom of the ocean forming Antarctic Bottom Water, which can be found across the deepest parts of most of the World Ocean. The volumes of the denser subsets of this water mass have been decreasing in the Scotia Sea, a key pathway from the Weddell Sea toward the rest of the global ocean over the last decades.

Using ship-based measurements of temperature and salinity (saltiness) spanning thirty years from British, German, and US research cruises from 1989-2018, researchers have tracked the changes in the Scotia Sea, and attribute them to changes happening upstream in the Weddell Sea, closer to Antarctica, possibly due to changes in winds, sea ice formation, or glacial ice melt on the continental margins.

These observations shed light on the links between the deep ocean near Antarctica and the large-scale global ocean circulation, which prevents rapid surface climate change by trapping a large portion of human-produced carbon and warming in the deep ocean.

Reduced density of deep water (caused by warmer temperatures and increased ice melt) is associated with a weakening of this ocean circulation, with implications for global climate.

Lead author Dr. Povl Abrahamsen, oceanographer at British Antarctic Survey, says:

“The deep oceans have been warming across much of the world for decades, so we were surprised to suddenly see this trend reversing and stabilizing in the Scotia Sea. While we do not know if this marks a reversal in the observed trends or merely a hiatus in the decline, this calls for better understanding of the ocean processes in the formation regions of these water masses nearer Antarctica.”

Full article here.
– – –
Study: Stabilization of dense Antarctic water supply to the Atlantic Ocean overturning circulation

Comments
  1. Phoenix44 says:

    Is it reversing or stabilising?

    More evidence of the warming trend reversing?

  2. oldbrew says:

    Another recent ‘surprise’…

    Growing Iceland, Greenland glaciers make scientists gasp
    Posted: May 20, 2019

    https://tallbloke.wordpress.com/2019/05/20/growing-iceland-greenland-glaciers-make-scientists-gasp/

  3. ivan says:

    Since we all know the definition of an expert (x is the unknown quantity and a spurt is a drip under pressure) is it any surprise that they should be caught out by the cold arriving. Maybe if some of these ‘experts’ got out of their ivory towers and actually looked at the real world rather than relying on unvalidated computer models they might start to understand but I doubt it because they rely on funding from the UN Church of Climatology and are blind to anything that doesn’t conform to that idiology.

  4. oldbrew says:

    ivan – the researchers are from the British Antarctic Survey, so they probably do go there sometimes 🙂
    – – –
    Quote: which prevents rapid surface climate change by trapping a large portion of human-produced carbon and warming in the deep ocean.

    This is ambiguous. Are they saying the warming is ‘human-produced’, or just the carbon (meaning carbon dioxide) – or leaving it to the reader to interpret?

    Carbon dioxide has always been absorbed by the oceans as part of the carbon cycle, regardless of how it arrived in the atmosphere. But for oceans that depends on the seawater being cooler than the atmosphere at the time, otherwise CO2 goes in the other direction i.e. sea to air – as the arrows next to CO2 (below) indicate.

  5. oldbrew says:

    Switching on the Atlantic Ocean heat pump

    Date: August 22, 2019
    Source: Stockholm University

    Summary:
    34 million years ago the warm ‘greenhouse climate’ of the dinosaur age ended and the colder ‘icehouse climate’ of today commenced. Antarctica glaciated first and geological data imply that the Atlantic meridional overturning circulation, the global ocean conveyor belt of heat and nutrients that today helps keep Europe warm, also started at this time. Why exactly, has remained a mystery.
    . . .
    The team of scientists, from the Bolin Centre for Climate Research, used a combination of geophysical data and climate modelling to show that the freshwater transport through the Arctic-Atlantic gateway plays a critical role in controlling the overturning circulation.

    https://www.sciencedaily.com/releases/2019/08/190822081156.htm
    – – –
    the colder ‘icehouse climate’ of today – not what climate miserablists want to hear 🤔

  6. cognog2 says:

    I’m not surprised that scientists these days get surprised.

  7. Coeur de Lion says:

    Whenever anyone says carbon when they mean CO2 they forfeit trust. I’m proud of my carbon footprint- zero! Oh, sorry, I do drawing with a pencil. Dammit I’ll have to stop.

  8. stpaulchuck says:

    so the experts were surprised… once again… Hmmm, I think I see a pattern here.

    —————
    “Meanwhile, conservatives are said to have rejected science if they won’t believe that taxes control the weather.” from moonbattery.com
    ———–
    “Science is the belief in the ignorance of the experts” – Richard Feynman

  9. David A says:

    Ice has increased in the SH until the last two years, so cold water melt should have been high each year.

    Would like to see the error bars on their studies, factoring in current shifts etc, TOB and seasonal flux.

  10. A better headline would’ve been “Antarctic… surprises dense ‘experts’.”

    2014-2018 ice was negatively affected by the post-SC24 solar maximum El Nino(s).

    The recent year’s Greenland and Antarctic ice growth confirm my 2018 conclusion that we have entered a ‘mini-ice age’, that will manifest as progressively harder winters, cooler NH summers, earlier falls, and later springs at high latitudes, glacial growth, thicker polar sea ice and growing ice extent. But it will only last a few more years until after the sun fires back up again.

    A lower solar cycle 25 would imply a sooner and progressively deeper return to these conditions.

    Excerpt from my AGU poster on how the sun’s TSI controls the ocean & climate:

  11. phil salmon says:

    This could be the most important climate news in a long time. The Antarctic is the “grand central station” of global 3D ocean circulation. Major changes in climate such as the termination of the last glaciation have been initiated in and by the Antarctic. If something changes there it’s worth paying attention.

    https://images.app.goo.gl/NDpqf7Mx5rqgdGeA9

  12. oldbrew says:

    David A – some error bars (bounds) here…

    Fig. 2: Area of LWSDW from hydrographic sections.

    Select the ‘Figures’ tab in the Study link at end of blog post.

  13. Jim says:

    Interested in their definition of terms. More water returning to the seas, usually implies warming. Lack of water from an ice system should imply cooling. I believe it would have been better yet, to investigate the sources of the water influx. The why, in that area. But, I would guess, that is another trip and needs funding.

  14. oldbrew says:

    Remember this one?

    JUNE 25, 2019

    Part of the Pacific Ocean is not warming as expected, but why?
    https://phys.org/news/2019-06-pacific-ocean.html

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