Tag: Antarctica

Totten hots up, ice shelves melting: it’s grim down south

AntarcticaCryosat2Much news in recent weeks from Antarctica, and none of it good. An Argentinian base on the tip of the Antarctic Peninsula recently reported a new high temperature record for the continent — 17.5ºC. A team of scientists has discovered that East Antarctica’s Totten Glacier — which drains a catchment that contains enough ice to raise sea levels by 3.5 metres — is vulnerable to melting caused by warm ocean water lapping underneath the ice and reaching inland ((Greenbaum JS et al, (2015), Ocean access to a cavity beneath Totten Glacier in East Antarctica, Nature Geoscience, doi:10.1038/ngeo2388)). Another group has stitched together satellite data on ice shelf thickness gathered from 1994 to 2012 and found that the ice shelves — mostly stable at the beginning of the period, are now losing mass fast ((Paolo, F.S. et al, (2015), Volume loss from Antarctic ice shelves is accelerating, Science, doi/10.1126/science.aaa0940)). From the abstract:

Overall, average ice-shelf volume change accelerated from negligible loss at 25 ± 64 km3 per year for 1994-2003 to rapid loss of 310 ± 74 km3 per year for 2003-2012. West Antarctic losses increased by 70% in the last decade, and earlier volume gain by East Antarctic ice shelves ceased. In the Amundsen and Bellingshausen regions, some ice shelves have lost up to 18% of their thickness in less than two decades.

The Amundsen region is home to the Pine Island Glacier, notorious for its current rapid loss of mass, and probably already past the point of no return for long term total melt. The map below shows the big picture: large red dots are ice shelves losing mass. Blue dots are shelves gaining mass.

Antarcticiceshelves

Ice shelves are important features of the Antarctic cryosphere. They buttress the ice piled up on the land, slowing down the flow of ice into the ocean. As the shelves lose mass, the flow of ice from the centre of the continent can speed up, adding to sea level rise. There’s a very good overview of the process — and the findings of the Paulo et al paper — in this excellent Carbon Brief analysis.

The study of the Totten Glacier — one of the fastest thinning glaciers in East Antarctica — is the first to look at the detail of the sea floor and ice thickness in the area. The study finds that there are “tunnels” under the ice leading into a deep trough inland that cold convey warm water inland — the same process that has destabilised the Pine Island Glacier in West Antarctica. As the authors suggest, rather drily, “coastal processes in this area could have global consequences”.

These signs of rapid changes around the coasts of Antarctica, together with hints that large parts of the huge East Antarctic ice sheet are at risk of following West Antarctica into the sea, suggest that even if sea levels only rise by a metre by the end of this century as the IPCC projected last year, the longer term picture will be a great deal wetter than that. After all, there is the equivalent of 60 metres of sea level rise locked up in East Antarctica.

For a very good overview of the state of our understanding of what’s going on in Antarctica, I recommend a listen to VUW’s Professor Tim Naish being interviewed by Radio New Zealand National’s Kim Hill last Saturday. Naish even covers what’s happening to the sea ice down there, but a longer term study of the sea ice is getting under way, led by another VUW prof — Jim Renwick.

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.

Climate documentary Thin Ice raising money for US broadcast

Thin Ice, the superb documentary about climate science and scientists filmed and produced by New Zealand and British climate scientists, has launched a Kickstarter crowdfunding campaign to finance a new edit of the film so that it can be shown on public TV in the US. From the Kickstarter page:

Why do we need help? The global screening on Earth Day, 2013, reached over 200 locations worldwide, and many others have seen it since. Now we have a chance to re-edit the film for screening on American Public Television – if we can raise the NZ$27,500 (US$22,000) in 30 days needed for the re-edit and promotion.

We want the film to be seen by as many people as possible on TV in Europe, Asia, Africa and South America. We already have subtitles in 8 languages, so with the shortened film Thin Ice will be that much more accessible to schools and communities worldwide.

With 14 days to go, the project still needs to raise NZ$20,000, so if you can spare a few dollars go to Kickstarter, make a few climate scientists happy, and help to get this excellent film put in front of a wider audience.

Friday melts, weird weather and whales (it’s been a long time…)

It’s been a long time since my last post: apologies for that. You may blame a bad cold, an urgent need for root canal work, the peak of the truffle season (and truffle tours for culinary heroes ((See also: why.)) ), the start of pruning and political distractions for the drop off in activity here. Normal service should resume in the near future, but meanwhile here are a few of the things that have caught my eye over the last week or two. You may therefore consider this an open thread – and given what follows, somewhat more open than usual…

The political distraction, of course, has been the response to Nicky Hager’s book, Dirty Politics. I haven’t yet read the book — it’s queued up on the iPad — but as everyone now knows, it concerns the sordid activities of right-wing attack blogger Cameron Slater, and in particular his close ties with senior government politicians. Slater has a long record of climate denial — often lifting material from µWatts or the Daily Mail to support his ignorant bluster — but the revelation that he published paid material for PR companies masquerading as his own opinion begs a question: was there a similar motivation for his climate denial posts?

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Antarctica: An Intimate Portrait of a Mysterious Continent

Science journalist Gabrielle Walker’s book Antarctica: An Intimate Portrait of a Mysterious Continent (Bloomsbury, 2012) tells an absorbing story of the wide variety of scientific work undertaken in Antarctica and the support services that maintain it. It also attempts to capture the human fascination of the continent, not least for the author herself in her five sojourns there. She provides close-up observations of some of the specialist teams working on an array of investigations: penguins, seals, under-ice sea creatures, meteorites, astronomy, paleoclimatology, the dynamics of ice movement and loss, and more. Stories of the early explorers find a place, and the psychology which motivates people to undertake sometimes long scientific enterprises in such a demanding environment.   Her book is striking and highly readable, often gripping.

It’s the climate change aspects of the book that I want to highlight here. Walker, who has a strong academic science background, specialises in energy and climate change. She co-authored a book on climate change with Sir David King a few years ago. I reviewed it at the time. Her knowledgeable familiarity with the subject is often in evidence in Antarctica.

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