In Today’s Baffling Science News

Achilles’ heel of ice shelves is beneath the water, scientists reveal. First, let’s get this out of the way: Achilles’ Heel = fatal vulnerability in the otherwise invulnerable. Ice sheets are Achilles? And otherwise invulnerable? What could this even mean?

The calving front of the Filchner Ice Shelf, AntarcticaPetty, yes, but confusing. On to the real issues:

Iceberg production and melting causes 2,800 cubic kilometres of ice to leave the Antarctic ice sheet every year. Most of this is replaced by snowfall but any imbalance contributes to a change in global sea level.

So far, so good.

New research, led by academics at the University of Bristol with colleagues at Utrecht University and the University of California, has used satellite and climate model data to prove that this sub-shelf melting has as large an impact as iceberg calving for Antarctica as a whole and for some areas is far more important.

The findings, published today [15 September] in Nature, are crucial for understanding how the ice sheet interacts with the rest of the climate system and particularly the ocean.

So, ice sheets sometimes melt from the bottom, and this melting can be significant for the total amount of ice moving off Antarctica and into the ocean as water.  But:

Professor Jonathan Bamber, from the University of Bristol’s School of Geographical Sciences, said: “Understanding how the largest ice mass on the planet loses ice to the oceans is one of the most fundamental things we need to know for Antarctica. Until recently, we assumed that most of the ice was lost through icebergs.

“Now we realise that melting underneath the ice shelves by the ocean is equally important and for some places, far more important. This knowledge is crucial for understanding how the ice sheets interact now, and in the future, to changes in climate.

“By the ocean”? So, we’re not talking about melting on the underside of ice sheets up on land, but rather those already floating in the ocean? One itsy problem – if they are already floating in the ocean, then melting them doesn’t “contributes to a change in global sea level” much.* And does Bamber mean ‘ocean temperatures around Antarctica’ when he says ‘changes in climate’? Because unless there’s some other mechanism by which the climate causes floating ice to melt from the bottom, that has got to be what he means, right?

This bit of Science! reporting  isn’t helping anyone understand anything, or perhaps more accurately, is shedding more confusion than light.

* except for the possible expansion of the water if it gets warmer, which can be significant, maybe, but isn’t under discussion in this article. In general, melting ice that is already floating in the ocean is like melting the ice in your ice tea: you cup doesn’t overflow when the ice in it melts, unless the ice was somehow above the lip of the cup already.

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Author: Joseph Moore

Enough with the smarty-pants Dante quote. Just some opinionated blogger dude.

5 thoughts on “In Today’s Baffling Science News”

  1. Most kinds of ice actually have lower density than liquid water (that’s why it floats), so the mind reels wondering how melting the underside of land-locked ice shelves doesn’t decrease ocean levels.

  2. The story here is about ice shelves, the floating part of Antarctica. Ice shelves form as the inland ice flows (a bit like slow rivers) into the sea and start floating. So an ice shelf is inherently in contact with the ocean. These ice shelves melt from underneath until they brake into icebergs at their outer edge. This is the way Antarctic ice is lost into the Southern ocean (the way it gains mass is from snow fall in its interior). For many decades experts though the prevalent mechanism was calving (breaking of icebergs). What this study (http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12567.html) shows is that this calving mechanism is not 80% but only 50 percent of the story, the other half been due to the underside melting in contact with relatively warm oceanic waters.

    This is very important because it is crucial to understand how the ice shelves work if we are to understand how the ice sheet (ice sitting on the continent) works now and will react in the future. Indeed, ice shelves buttress the discharge of inland ice into the ocean. A loss of this buttressing effect means that the flow of inland ice accelerates and causes sea level rise. This importance of the melting process for the loss of ice shelves means that changes in ocean water temperature will have profound effect on the behavior of ice shelves and in the end of the ice sheet. On top of that, warmer water have been found in certain places around Antarctica causing the effects that I just mentioned. Finally, the occurrence of warmer waters around Antarctica could be linked to climate change through change in wind patterns.

    Hope that helps!

    1. Thanks, I appreciate the explanation, which is pretty much what I thought the article was referring to. However, my point is that you’d never reach that understanding unless you already knew what they were talking about – the article itself is worse than useless in this regard, as it sows only confusion.

      So, while I would absolutely be interested in (concerned about, even) evidence that the ice sheets in Antarctica are flowing more rapidly off the continent and into the ocean, nowhere in the original article I wrote about does it actually say that. Which is why I used the word ‘baffling’ in my post title – it’s not necessarily the science that’s baffling, but the reporting.

      I’ll check out the link you gave when I get the time.

      1. I am happy if my explanation helped clarify your understanding of the science we tried to convey. It is true than in this article, the distinction between ice shelf and ice sheet is not made clearly. This simplification for the reader was apparently a bad idea. It is a the difficult exercise to simplify without altering the message. If you feel you need a more detail explanation, please do have a look at the paper/abstract.

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