Tag: Pine Island Glacier

Postcards from La La Land: the Cnut conundrum

New Zealand’s merry little band of climate deniers are turning out to be a right bunch of Cnuts. Sea level rise and its implications for Christchurch and the wider world have been making news in recent weeks — as have new projections of rapid sea level rise over the remainder of this century. So what does a good climate denier do? To stay faithful to their core belief — that climate change isn’t happening, or isn’t going to be bad — they have to argue against policies designed to deal with its impacts, as well as those intended to cut carbon emissions. Sea level rise? Like Cnut, they line themselves up against the waves.

I’ve blogged many times on the challenge sea level rise poses for post-quake Christchurch. The 2011 quakes caused large parts of the city to drop by up to half a metre — effectively delivering decades of sea level rise in a matter of minutes. For some areas of the city tidal and run-off flooding are now commonplace.

The current debate on sea level issues has been prompted by the city council’s long term planning process — which recommends ((Based on a revised report (pdf) developed from consultants Tonkin & Taylor’s 2014 work.)) that development should be restricted in areas where future sea level rise is expected to cause problems. Not surprisingly, this has some owners of coastal properties concerned that they will lose out. The council has also looked at the idea of building a tidal barrier across the Avon-Heathcote estuary to protect the city.

Local politics and property owner self-interest is bumping into the harsh realities of climate change, leading to a wide variety of responses — including “it isn’t happening”.

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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.

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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TDB today: Goodbye coastline – we are beyond the point of no return

In which I pull together the strands of the recent bad news from Antarctica and Greenland, and lament the loss of the coastline we all grew up with — no longer a theoretical possibility but a long term certainty. Check out Goodbye coastline – we are beyond the point of no return, this week’s post at The Daily Blog, and start planning for all our watery futures.

PIG and pals pass point of no return – West Antarctic ice melt inevitable

Two new papers published this week suggest that the West Antarctic glaciers draining into the Amundsen Sea — the Pine Island, Thwaites, Haynes, Pope, Smith and Kohler glaciers — are melting rapidly and are now committed to collapse, adding up to 1.2 metres to future sea level rise. In the NASA JPL video above, Eric Rignot, lead author of a paper ((E. Rignot, J. Mouginot, M. Morlighem, H. Seroussi, B. Scheuchl. Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith and Kohler glaciers, West Antarctica from 1992 to 2011. Geophysical Research Letters, 2014; DOI: 10.1002/2014GL060140)) examining how the glaciers’ “grounding lines” — the point where the bottom of the glacial ice leaves the bedrock and starts to float — have retreated very significantly over the last 20 years explains how they are now melting back unstoppably. Another paper modelling ice loss from the Thwaites glacier ((Ian Joughin, Benjamin E. Smith, Brooke Medley. Marine Ice Sheet Collapse Potentially Underway for the Thwaites Glacier Basin, West Antarctica, Science, DOI: 10.1126/science.1249055.)) finds that it is committed to retreat and collapse via the same mechanism. Lead author Ian Joughin of the University of Washington, told Science magazine:

The next stable state for the West Antarctic Ice Sheet might be no ice sheet at all…

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