Greenland melt

You may have seen images like this before, demonstrating the progressive summer melting of the Greenland ice sheet:


Then in July 2012 this happened:


The image on the left represents melting on 8 July. By 12 July some 97% of the ice sheet surface was melting. The Carbon Brief (a quality blog) has the story.

Yes, it was unusual, but not unprecedented. Ice cores show that this happens every 150 years or so, and it last happened in 1889. That said, weather patterns have been unusual at high latitudes in the northern hemisphere, and these changes have been linked with climate change. In this case it was a combination of warmer weather and cloud cover that did the trick.

In terms of ice mass loss, a few days is not going to make much difference. The ice sheet is up to three kilometres thick and at high altitude the water will refreeze. Near the edges the water may end up in the ocean. This can happen through moulins, where the water falls down into the ice sheet via a crevasse, typically to the base of the sheet, which can lubricate the gradual movement of the ice. This is a classic photo of a moulin:

hansenFigure7 small p

Not sure I’d stand where those blokes are standing! This diagram shows how it works:

MoulinFeatures irf

The underlying topography of Greenland is not conducive to losing the whole ice sheet. In the centre it’s below sea level and has jagged mountains around the edges, a bit like a saucer. This NSIDC image gives the basic idea.


Of course the ‘mountains’ are vastly smaller than that in true scale.

Graphs like this one from Hansen can get us excited:


Certainly the mass loss is worrying. In terms of the next century, however, it is too early to tell how fast the rate of loss will increase. James Hansen shows the effect that a 10-year exponential doubling of ice sheet melting can have late in this century:

Hansen_Screen shot 2012-01-03 at 8.27.18 AM

The shape of what’s to come is likely to be somewhere between the two, but less than either.

The IPCC report of 2007 showed the relative contribution of the four main sources of sea level rises – thermal expansion, glaciers and ice-caps, Greenland, and Antarctica. So far the ice sheets are playing a minor role. This is certain to change, but gradually. Here is the table from the IPCC report:

IPCC sea level p_cropped_again_580

In 1993-2003 Greenland accounted for only 0.21mm in annual sea level rise of 3.1mm.

As we saw at Climate Clippings 73 item 5, the indications are that Greenland’s ice loss may slow before it speeds up.

It is likely, though, that we are getting into the zone where the Greenland ice sheet will be seriously compromised as we move above CO2 concentrations of 400 ppm.

Just in, the north pole is now making a beeline towards Greenland, courtesy of melting and ice loss. That’s impressive even though it’s only moving a couple of centimetres per year!

Late press:

New Scientist has an article (paywalled) telling us that sea level changes will be quite uneven around the world. If all the ice on Greenland melts, for example, sea level will actually fall in that area! Two reasons are given. First, the lifting the weight of the ice will see the land surface rise. Secondly, there is a gravitational pull between an ice mass and the surrounding water in the ocean which pulls the water towards the ice!

The way things are expected to work, Europe will benefit, but the east coast of the US will be unlucky with sea level rises up top 25% higher than expected. The water from melted ice has to go somewhere. South America will be adversely affected.

There is a copy of the text of the article here without the pictures.

10 thoughts on “Greenland melt”

  1. Chris Uhlmann raised an interesting point:
    What about border protection? The Pacific Solution was a totemic Howard Government policy. More than anything else in Labor’s wilderness years, it energised its base because it was seen by the faithful as immoral.

    In May 2003 Julia Gillard described it as “costly, unsustainable and wrong as a matter of principle”.

    It was dismantled with the best of intentions. No matter what is now claimed, that was done against the advice of the experts in government agencies. The then immigration minister would describe the end of offshore processing of asylum seekers as one of his proudest moments.

    “The Rudd Government pledged to dismantle the Pacific solution and we have moved quickly on that front,” Senator Chris Evans said. “The Pacific solution was a cynical, costly and ultimately unsuccessful exercise introduced on the eve of a Federal election by the Howard Government.”

    Then the boats came, in their hundreds, and the retreat began. Almost every brick in the Pacific Solution wall has been rebuilt. On Thursday, on the eve of a federal election, the Government’s bill excising Australia from its own migration zone passed.

    What does Labor believe in now?

  2. Brian, your climate science briefings are among the best produced offerings on the Internet. Congratulations.

  3. Not sure I’d stand where those blokes are standing!

    That was exactly the first thought that came into my head when I saw the photo, Brian. I got a feeling of vertigo just looking at it.

    I think I’d be standing 50 or 500 metres back.

  4. I second that, as I follow climate science on several diverse sources, imho non have the eloquence and diligence to summ up a particular aspect and place it into context, as Brian’s offerings. This particular OP made me reflect on how detailed our knowledge has become and the depth of understanding which has been achieved. The picture has become remarkably clearer, thus scenarios and probabilities start to firm up.

  5. Thanks, Katz, and Ootz. I try, and sometimes I get lucky.

    Actually there’s more, but I’ll have to do Climate clippings first.

    It’s always quite possible I’ll miss something important, though.

  6. Looking at the sea level rise graph I was musing that one could view this as though global politicians took out a 100 year lease on the planet in 2000 thinking that the terms of the lease were a “too good to be true” very favourable deal till 2080, and the they could renegotiate for the next 100 years.

    Problem is that it was a once off deal with unspecified consequences.

    I have been working on a new affordable accommodation housing design in which one of the parameters is that these buildings need to last for a minimum one hundred and fifty years. With that criterion climate change and sea level rise are vitally important considerations.

    Location, location, location, as they say.

    With our preoccupation of living for the moment we have completely lost sight of longevity of situation, even though we seek to live longer.

    I’d like to flesh this out a lot further and lead into what might be the instruments of our survival. Another day.

  7. Excellent piece, Brian. Thank you. Now if you could only add some mindless contrarian naysaying for balance we could publish it in the MSM.

  8. “Greenland Melt”

    When I saw this thread I thought it was about the meltdown in Milne’s office lol.

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