Antarctic ice going fast: Larsen C ice shelf primed for giant calving event

Analysis of rift propagation using Landsat data. Background image, in which the rift is visible, is from 4 December 2014. Inset graph shows the development of rift length with respect to the 2010 tip position, and rift width at the 2010 tip position, measured from 15 Landsat images (crosses). Circles and labels on the map, and dotted red lines on the graph, show the positions of notable stages of rift development.

The Larsen C ice shelf on the east coast of the Antarctic peninsula is primed for a giant iceberg calving event, and could be heading for total collapse — similar to the fate of the Larsen B ice shelf in 2002, according to scientists monitoring the ice. A huge crack (above: hover over the picture for the full caption from the paper) is propagating northwards at an accelerating rate, and could give birth to ice islands of between 4,600 km2 and 6,400 km2 — equivalent to three or four Stewart Islands floating out to sea — according to an open access paper, Jansen et al, Newly developing rift in Larsen C Ice Shelf presents significant risk to stability ((The Cryosphere Discuss., 9, 861–872, 2015)) (full pdf), published last month.

From the paper’s conclusions:

It seems inevitable that this rift will lead to a major calving event which will remove between 9 and 12 % of the ice shelf area and leave the ice front at its most retreated observed position. More significantly, our model shows that the remaining ice may be unstable. The Larsen C Ice Shelf may be following the example of its previous neighbour, Larsen B, which collapsed in 2002 following similar events.

The Larsen C ice shelf has been thinning over at least the last decade, and has shown signs of surface melting. Jansen et al developed two calving scenarios — shown below — and analysed the results with a model of the ice shelf.

Overview of the Larsen C Ice Shelf in late 2014 showing the contemporary location of the developing rift (red line), and a selection of previous and predicted future calving fronts. Background image is MODIS Aqua, 3 December 2014. Geographic features of interest are marked (R = Revelle Inlet, FI = Francis Island, TO = Tonkin Island, TI = Trail Inlet, SI = Solberg Inlet, K = Kenyon Peninsula) and the dashed box shows the extent of Fig. 2. The highlighted flow line indicates the location of the Joerg Peninsula suture zone.

For a good overview of the current state of our knowledge of Antarctic ice melt, see The big melt: Antarctica’s retreating ice may re-shape Earth from the Associated Press, which tipped me off to the Larsen C story. Larsen C is the most northerly of the remaining major Antarctic ice sheets, and the last remnant of an ice shelf that until 1995 stretched up to the tip of the east coast of the Antarctic Peninsula. After the collapses of Larsen A and B, the glaciers feeding the shelves were observed to speed up — increasing the overall ice sheet mass loss. While the loss of the ice shelf won’t itself cause any sea level rise — because it’s already floating — the resulting speed up will increase sea levels.

6 thoughts on “Antarctic ice going fast: Larsen C ice shelf primed for giant calving event”

  1. This is not good news. Pine Island glacier is also under threat and if others are not mentioned it is probably because they are remote and not monitored. Greenland is melting fast and so are most of the other land based glaciers around the world. If we get a one metre sea level rise the economic cost will be enough to collapse the economies of most countries including the USA and the UK. http://www.climateoutcome.kiwi.nz/blog/infrastructure-loss-in-new-zealand-due-to-sea-level-rise

  2. Can’t find it online in stuff.co.nz, but in this morning’s DominionPost, Bryan Leyland and Bob Carter are at it again with an OpEd titled “Hypothetical global warming: scepticism needed” in which among several distortions and untruths imply there is nothing wrong with ice sheets and glaciers at either pole. Also bring out the “no significant warming in last 18 years”, sea-level is not rising any faster than before, Polar Bears are doing OK, coral atolls are OK, some glaciers are advancing, Middle Ages was warmer, the oceans are not becoming acid, plants like CO2 and drought/flood numbers have hardly changed. Then finish it off with things will cool soon because of sun-spots.

    *Sigh* I wish these people would pay up their court costs rather than waste more time spouting nonsense.

    1. Precisely. The news media should treat Leyland like a pariah, not as a credible commentator.

      I can’t find it online, either. Any chance someone can let me have a scan?

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