Recent Amundsen Sea Embayment Research

-- UPDATED 11 June 2014 --

This post got the dreaded TL; DR on Reddit - but at least "they" acknowledged it was useful. Since it takes someone else to pick out the value in your work I offer this tweet from Jason Major.

@JPMajor tweet

- ORIGINAL POST

A significant area of Antarctic glaciological interest is the West Antarctic Ice Sheet (WAIS) and where it discharges into the Amundsen Sea Embayment.

Amundsen Sea Embayment
Amundsen Sea Embayment: Source Wikipedia

It is a research focus (e.g. iSTAR) because it is the region where the glacier ice is melting very rapidly.

A great research article by Dustin Schroeder (The University of Texas at Austin) has just been published in PNAS which presents evidence for the geothermal heat flux beneath the Thwaites Glacier.

Title page of Schroeder et al 2014

The paper is available on the PNAS site and it is open access.

Schroeder and colleagues use radio echo sounding to detect the bed of the glacier. They see water beneath the ice. In 2013 they published a paper in PNAS interpreting these observations as a vast subglacial water system under West Antarctica's Thwaites Glacier. (There is a nice EurekAlert about the under ice “river” system).

In this current 2014 paper about geothermal heat, they interpret some of their water observations as being due to heat from the Earth’s core. The paper has some beautiful (to me!) figures including Figure 3 a map of geothermal flux required to produce the melt water they observed:

Figure 3 of Schroeder et al 2014
Figure 3 of Schroeder et al 2014

This is brilliant because not only did they show there was an active water system in 2013, but they are now using their data to understand the nature of the water system beneath the ice sheet.

People tend to think “frozen” as stationary, and they can understand Antarctica as a static system – but in reality there are hundreds of under ice lakes like Vostok, There is - in places - extensive melting and refreezing of water going on under the ice – as pointed by out Robin Bell and colleagues in 2011.

Plus the under ice “river” system Schroeder and colleagues identified in 2013.

It is a very exciting time in polar research and I am looking forward to what this group publishes next.

Now some context

Schroeder and colleagues Figure 3 (above) shows geothermal flux (that is heat from the Earth) and a conversion to basal melt rates of the glacial ice. Their scale shows it goes up to 6 mm/yr.

Is this a big number?

The picture below was taken from a preprint of Hofmann and Morales Maqueda (2009).

Hofmann and Morales Maqueda (2009) Figure 1(a)
Hofmann and Morales Maqueda (2009) Figure 1(a)

This picture shows the oceanic geothermal heat flow data from Pollack et al (1993).

So Schroeder and colleagues derive a geothermal heat flow that is similar to that you find at the edges of tectonic plates – the brightest red in Schroeder and colleagues work (130 to > 200 mW/m2) is equivalent to green to yellow in the picture from Hofmann and Morales Maqueda (2009).

But it is much bigger than the values in that region of the Earth in the Pollack et al (1993) data.

Is the geothermal heat significant for melting the West Antarctic Ice Sheet?

Take Pine Island – which is adjacent to the Thwaites.

Pierre Dutrieux and colleagues had this to say in 2013 of the basal melt rates.

“At the broad scale [basal], melt rates of up to 100 m/yr occur near the grounding line [where the ice meets the ocean], reducing to 30 m yr/ just 20 km downstream [over the ocean]."

So 100 metres per year from the ocean verses 6.3 millimetres per year from the geothermal heat.

And the geothermal heat is clearly extremely variable in space.

And if you want go one step further then Park and colleagues said that this basal melt rate due to the ocean was increasing at an accelerating rate of 0.53 ± 0.15 m / yr−2.

Schroeder and colleagues work is, in my view, excellent and very significant. It demonstrates a hidden component for glacier hydrology.

But it is not the reason for the observed melt of the WAIS.

So...

climate depot headlineandWUWT

Are a very bad attempt of interpreting the significance of Schroeder and colleagues 2014 research.

(I am not going to link directly to those articles but if you insist then google can find them.)

References

Dutrieux, P., D. G. Vaughan, H. F. J. Corr, A. Jenkins, P. R. Holland, I. Joughin, and A. H. Fleming (2013), Pine Island glacier ice shelf melt distributed at kilometre scales, The Cryosphere, 7(5), 1543-1555.

Hofmann, M., and M. A. Morales Maqueda (2009), Geothermal heat flux and its influence on the oceanic abyssal circulation and radiocarbon distribution, Geophysical Research Letters, 36(3), L03603.

Park, J. W., N. Gourmelen, A. Shepherd, S. W. Kim, D. G. Vaughan, and D. J. Wingham (2013), Sustained retreat of the Pine Island Glacier, Geophysical Research Letters, 40(10), 2137-2142.

Pollack, H. N., S. J. Hurter, and J. R. Johnson (1993), Heat flow from the Earth's interior: Analysis of the global data set, Rev. Geophys., 31(3), 267-280.

Schroeder, D. M., D. D. Blankenship, and D. A. Young (2013), Evidence for a water system transition beneath Thwaites Glacier, West Antarctica, Proceedings of the National Academy of Sciences, 110(30), 12225-12228.

Schroeder, D. M., D. D. Blankenship, D. A. Young, and E. Quartini (2014), Evidence for elevated and spatially variable geothermal flux beneath the West Antarctic Ice Sheet, Proceedings of the National Academy of Sciences, 111(25), 9070-9072.

6 thoughts on “Recent Amundsen Sea Embayment Research

  1. hunter

    Which is the poorer interpretation: quoting the article on gethermal heating correctly and linking to it? Or claiming that CO2 has heated the bottom of the glaciers and is leading to the collapse- without acknowledging the time scales or the well documented long term movement the study on the collapse was based on?

    Reply
    1. Mark Brandon

      Post author

      Thanks for your comment @hunter

      I’ll stick to what I wrote about rather than what I didn’t.

      It’s not the quoting and linking for me which is so painful – but the wrapper around the article which creates an atmosphere which in my view ridicules scientific effort.

      So we start with an attempt to suggest that this great research somehow negates our understanding of the climate system
      From the University of Texas at Austin and the “you can stop your wailing now” department, comes this really, really, inconvenient truth.
      Why would someone think such research wasn't welcome?

      Then after the copy and paste of the press release are the comments.
      So we have...
      Accusations of corruption e.g:
      Just like every other controversial subject in this country, there is normally corrupt lobbying power behind it for one reason or another
      If I can suggest it’s even worse than we could imagine can I get some grant money? ……..100K sounds about right. Does anyone know a good financial expert who can hide the money?

      And just general patronising rubbish e.g:
      " “…Schroeder, who received his Ph.D. in May,..” Sigh, another baby scientist"
      The latter I find really funny since the “I am older than you therefore I must know better” is truly a Victorian idea.

      Reply
  2. Jeffronicus

    A block of ice placed on a floor slightly above freezing will slide faster than a block of ice placed on a floor at 0 degrees, but it's still the 50-degree room that's melting the block.

    It's bizarre -- and quite telling -- how quickly and firmly the denialist movement will latch onto something like the Daily Caller interpretation of the UTIG study, which even the lead author says has nothing to do with refuting climate change.

    Reply
    1. Mark Brandon

      Post author

      I share your pain at the sometimes (IMO) willful misinterpretation of a great piece of polar glaciological research.
      No doubt people will blame the authors for the way they have chosen to frame it.

      Reply
  3. Sheldon

    I'm always intrigued by the denialist "argument" that scientists are motivated by "pulling down grants", as though research funding translated into, or was in some way equivalent to, personal wealth. My reply used to be along the lines of "go look in any institution's staff car park". Nowadays I think more about the person commenting. The sphere of their perceptions must be so small (i.e. they have such tiny minds) that they can conceive of no motivation beyond the financial. In the words of the noted philosopher Mr. T, I pity the fools.

    Reply

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