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Climate Hustle

New study shows warm waters are melting Antarctica from below

Posted on 13 November 2014 by John Abraham

Just this week, a new study has appeared which describes a clever method for measuring the flows of ocean currents and their impacts on ice shelves. This study has identified a major mechanism for melting ice in the Southern Hemisphere.

The paper, co-authored by Andrew Thompson, Karen Heywood, and colleagues is very novel. The scientists used sea gliders to identify water flows that bring warm waters to the base of ice shelves in Antarctica. As I’ve written before, ocean currents are complex; you cannot neglect their impact on the Earth’s climate.

In some parts of the ocean, dense waters near the surface fall to the ocean floor and spread across the globe. In other regions, waters from the deep rise to the surface. Similarly, waters move horizontally and carry their heat with them. In some cases the surface waters and the mid-depth waters flow in different directions.

But regardless of the direction of flow, these waters carry energy with them. This process, often called “advection,” results in a major redistribution of heat across the globe. Sometimes, warm waters flow into cold regions, transferring heat, and melting ice. It is this phenomenon that was at the center of the current paper.

Fluids sometimes move as large directional masses (sometimes called bulk motion) caused by some agent of motion, for instance winds that blow over the surface and drag waters. Other motions are characterized by swirls and eddies – not unidirectional flow. This type of motions is called eddy-induced transport. A determination of which type of transport dominates and where they dominate is important to understanding Antarctic ice melt.

The Caltech and UEA scientists used sea gliders to make their measurements. Sea gliders are devices that move up and down in the ocean waters, taking samples of water properties, while they glide. Sea gliders are a relatively new measurement tool and they provide high-resolution, high-quality data.

A sea glider. A sea glider. Photograph: Marine Insight

Three such gliders were deployed in the Weddell Sea in early 2012. Together, the gliders made 750 dives to depths of 1000 meters or to within 20 meters of the sea floor. They completed their dives every four hours, making measurements of temperature, salinity, oxygen levels, and optical properties every five seconds. The data was then transmitted wirelessly to a data collection station.

The data showed that eddy-transport and surface-wind-caused motion are comparable in their contribution to water circulation. They showed however, that the eddy motion is largely confined to the warm intermediate water layers. The penetration of the warm waters to the ice shelves is believed to be responsible for the dramatic ice loss that has been observed in the Antarctic.

I asked Dr. Heywood about her research and she told me,

Click here to read the rest

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Comments

Comments 1 to 10:

  1. Thanks for another great article from JA. Toward the end he says: " I have a paper in press with Dr. Ted Scambos that identifies the potential for rapid sea level rise based on Antarctic melting."

    I, for one, look forward for this update, though not without some dread!

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  2. Dusty Schroeder, lead author of the article announcing the results, helped lead a team that used aerial surveys to create radar maps capable of penetrating the surface of the ice. They found two bodies of water under the glacier which interacted with each other, distributing heat in the process.

    The source of heating is believed to be a tearing apart, or rifting, of the crust under the Antarctic ice sheet. This allows movement of magma and creates volcanic eruptions, melting the ice. Liquid water and geological activity under the sheet allows the massive feature to slip off the continent.

    http://www.techtimes.com/articles/8278/20140610/underwater-volcanoes-climate-change-reason-melting-west-antarctic-ice.htm#ixzz3Jec2ZNjB

    …………………………………………………………………………………………….

    In 2007, oceanographers Hillier and Watts surveyed 201,055 submarine volcanoes. “From this they concluded an astounding total of 3,477,403 submarine volcanoes must reasonably exist worldwide,” said this article by John O’Sullivan.

    Hillier and Watts “based this finding on the earlier and well-respected observations of Earth and Planetary Sciences specialist, Batiza (1982) who found that at least 4 per cent of seamounts are active volcanoes.”

    According to Batiza’s survey, the Pacific mid-plate alone contains an incredible 22,000 to 55,000 underwater volcanoes, with at least 2,000 of them considered active. http://www.themoralliberal.com/2011/05/09/volcano-heats-high-mountain-lake-to-108-degrees/

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  3. Sorry dorje... But the actual Schroeder paper makes none of the assertions you or "tech times" claim.

    http://www.pnas.org/content/111/25/9070.long

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  4. Same with the Hillier and Watts paper. Neither of these have any relation to climate change or changes in ice mass loss rates in Antarctica.

    LINK

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  5. Schroeder paper states:  We also observe high geothermal flux in the upper reaches of the central tributaries that are relatively close to the site of the WAIS Divide ice core (Fig. 3, location B), where unexpectedly high melt and geothermal flux have been estimated.* We estimate a minimum average geothermal flux value of about 114 mW/m2 with a notional uncertainty of about 10 mW/m2 for the Thwaites Glacier catchment with areas exceeding 200 mW/m2 (Fig. 3). These values are likely underestimates due to the low uniform geothermal flux value used in the ice sheet model (9) and the compensating effect of enhanced vertical advection of cold shallow ice in high-melt areas.

    As for Hillier and Watts--the point of course is heat, ocean warming; the source in this case of heat are submarine volcanoes, alot of them.

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  6. dorje...  Neither of these papers say anything that would suggest that heat from submarine volcanoes is responsible for the warming of the past 50-100 years.

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  7. Abstract/Summary of "Heat flux variations beneath central Greenland's ice", 2013:
    At the Earth’s surface, heat fluxes from the interior1 are generally insignificant compared with those from the Sun and atmosphere2, except in areas permanently blanketed by ice. Modelling studies show that geothermal heat flux influences the internal thermal structure of ice sheets and the distribution of basal melt water3, and it should be taken into account in planning deep ice drilling campaigns and climate reconstructions4. Here we use a coupled ice–lithosphere model driven by climate and show that the oldest and thickest part of the Greenland Ice Sheet is strongly influenced by heat flow from the deep Earth. We find that the geothermal heat flux in central Greenland increases from west to east due to thinning of the lithosphere, which is only about 25–66% as thick as is typical for terrains of early Proterozoic age5. Complex interactions between geothermal heat flow and glaciation-induced thermal perturbations in the upper crust over glacial cycles lead to strong regional variations in basal ice conditions, with areas of rapid basal melting adjoining areas of extremely cold basal ice. Our findings demonstrate the role that the structure of the solid Earth plays in the dynamics of surface processes.  http://nora.nerc.ac.uk/503004/

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  8. dorje...  Do you understand that these paper are not claiming that heating from below the ice sheets has changed any time in recent history, that would explain what we attribute to changes in greenhouse gas concentrations? They are merely quantifying the effect, which has likely been unchanged over the past century.

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  9. dorje @7.

    Further to Rob Honeycutt @8, the temperature profile of Greenland shows only static heat fluxes from below. The changes are all from above and their impact can be used to plot Greenland surface temperatures at the summit of the ice cap back into the last ice age. And this would not be possible if the flux from below were changing with time.

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  10. dorje - Another collection of seemingly random facts, again lacking content or direction. What are you trying to say (if anything)?

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    Moderator Response:

    [RH] dorje's comments have been deleted for failing to indicate that they are actually just quotations from the papers he's citing without adding any additional original commentary.

    [PS] Not to mention being totally off topic.

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