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

by Gareth on May 13, 2014

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 paper1 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 2 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…

That would add over 3 metres to future sea level, although Joughin et al find that Thwaites collapse is likely some way off in the future. Their paper concludes:

Nonetheless, the similarity between our highest melt rates and present observations suggests that collapse may be closer to a few centuries than to a millennium.

Rignot told Science that more realistic ocean modelling of the ocean’s effects on Thwaites could bring the date of collapse closer to the present.

Glaciologist Richard Alley told the New York Times that news of the two papers findings “shook me a little bit”:

“If we have indeed lit the fuse on West Antarctica, it’s very hard to imagine putting the fuse out,” Dr. Alley said. “But there’s a bunch more fuses, and there’s a bunch more matches, and we have a decision now: Do we light those?”

Rignot provides a more detailed explanation of the melting process in this video, also well worth watching:

The stability of the West Antarctic ice sheet has concerned scientists since the 1970s. There are multiple lines of evidence that it has collapsed in whole or in part during the last (Eemian) interglacial (LIG), and may have done so rapidly — on a timescale of decades to centuries. It now looks very likely that the processes that will lead to another collapse are well under way. There is a very real risk that they will continue whatever we do to restrain climate warming. We know from the LIG that sea levels were as much as 9m above present by the end of that warm period — with CO2 100 ppm lower than present.

The bottom line is clear: even if the global community succeeds in hitting a 2ºC target and the atmosphere stays under 450 ppm CO2 , we are going to have to say goodbye to the current coastline and everything built there. The long transition has begun in earnest. We can but hope that it is a process slow enough to allow us to adapt.

See also: New Scientist, Science Daily, BBC News, National Geographic, and the NASA JPL press release.

  1. 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 []
  2. 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. []

{ 35 comments… read them below or add one }

Kiwiiano May 13, 2014 at 9:18 pm

” The long transition has begun in earnest. We can but hope that its a process slow enough to allow us to adapt.”
I can’t see how we can adapt. How do we ‘manage’ the process of telling everyone with property below the 1-2-3-4-whatever metre contour that “Sorry but your property is doomed sometime in the next few decades and thus sharply devalued.” Resale values plummet, insurance cover falters, mortgages are unstable, maintenance spasmodic, services start to crumble, etc, etc.
Not that all of the above haven’t been on the cards since 1859 when we got our first heads-up on releasing fossil carbon.

bill May 13, 2014 at 10:44 pm

I really like the Richard Alley quote, since I’m sure the narcisso-Pollyannas will now announce that it’ll all happen long after they’re dead – and therefore no-one could reasonably expect them to contribute to any rectification – and, see, it’s too late to do anything about it anyway!

Rob Painting May 13, 2014 at 10:54 pm

Nice post Gareth. And the videos do a great job of explaining what’s going on.

John C May 14, 2014 at 9:23 am

Few centuries not decades Kiwi, big difference. We can’t even speculate as to what civilisation will look like in 2500. I doubt we will see more than 10 – 15 cm SLR in our lifetimes.

Gareth May 14, 2014 at 9:39 am

Depending on how old you are, of course.

It’s also worth considering that most climate projections have turned out to be too cautious (see this discussion in the New Yorker), and that this news from the WAIS will undoubtedly lead to an upward revision in SLR expectations and the rate at which it happens. More, sooner, in other words.

Kiwiiano May 14, 2014 at 10:10 am

And when combined with stronger storms & heavier rainfall even 10-15cm may be enough to cause significant coastal damage. In Christchurch for example, the South Shore area is extremely vulnerable. It’s a ‘temporary geological feature’ that should never have been built on, entirely sand. A strong off-shore depression combining with on-shore winds, heavy rains and a tide at the wrong time and hundreds of homes could be dog-tucker. When that happens, the ChCh Recovery will look very fragile.
It won’t require the sea to be lapping around Cathedral Square.

Macro May 14, 2014 at 10:21 am

You conveniently neglect storm surge John and have consistently in all your inane comments here.
Here is a quote from someone who knows far more about this than either you or I

“The report found the impact of climate change is leading to rising sea levels and will bring more flooding to low-lying areas.
“This report […] paints a very clear picture of what the future could hold for humanity if we don’t get on top of greenhouse emissions,” says Dr James Renwick of Victoria University’s school of Geography, Environment and Earth Science.
“Every 10cm of [sea level] rise triples the risk of a given inundation event, and we are expecting something like a metre of rise this century. That would mean today’s one-in-100 year event occurs at least annually at many New Zealand coastal locations. New Zealand has a great deal of valuable property and infrastructure close to the coast that will be increasingly at risk as time goes on.”
Dr Renwick calls the report, published by the UN’s Intergovernmental Panel on Climate Change, a “wake-up call” and says ecosystem biodiversity is also at risk – especially marine and alpine ecosystems.”

andyS May 14, 2014 at 11:03 am

Every 10cm of [sea level] rise triples the risk of a given inundation event

I’m not really sure what this statement means, but if we take it at face value, then the risk is 59,049 times (3^10) higher for 1m of SLR

Are we sure about this?

Macro May 14, 2014 at 10:32 pm

and why wouldn’t it be andy?
something that is only 0.5 m above sea level will be permanently inundated. you seem to think that every place is at least > 1 m above sea level when that is demonstrably not the case. Furthermore many seaside towns in nz and around the world are only protected by sand dunes which are highly susceptible to wave erosion and storm surges. Ohope is a clear case in point and New Brighton as I think you well know.
If no action is taken think how New Brighton would have faired in the recent cyclone and the high tide 1 m higher than it is today? I know at Whiritoa where i have a bach at high tide the dunes are well above my head ( i’m 1.82 m) when i stand at the high tide mark, but with a strong surf running the surge can run up the dunes on inundate the road washing the dunes away. The houses along the sea front are clearly in danger of their foundations being eroded with a 10 cm rise in sea level. and so for Ohope even more so! that settlement and it is quite substantial is clearly under threat. It has already suffered serious flooding in recent years.

John C May 14, 2014 at 11:45 am

If SLR continues obviously this will increase the flooding risk. Storm surges are nothing new, we get them now so a 15cm SLR will result in a similar level of flooding 15cm higher than now. My understanding was there was very little hard evidence to suggest storms are increasing in intensity.

As for your comment on the South Shore. I think mitigation is by far the most effective way to limit the effects of SLR, some roads may need to be raised, barriers constructed and in places land abandoned where it is clear defences are not viable.

Rob Painting May 14, 2014 at 12:42 pm

John C -“so a 15cm SLR will result in a similar level of flooding 15cm higher than now.

Bzzzzzt!! Wrong!!!

If you actually put some thought into this you’ll understand why.

Kiwiiano May 14, 2014 at 1:27 pm

Unfortunately when so many political leaders are studiously ignoring the problem, especially ours, mitigation ain’t gonna happen in time. Unless someone invents a time machine*.

Substantial lengths of SH1 would be candidates for raising, preferably by rerouting well inland. Barriers may help if the soils are suitable but at what cost and how high? Even the Netherlands didn’t plan on dykes needing to be added to every decade or so. Nth Canterbury is a classic example of unsuitable soils: a mix of sand and gravel with insufficient layers of loess/clay to ensure the sea won’t just bubble up behind any barriers.

Then there’s all the cities and towns built on the coast….. it’s hard to comprehend how our leaders can be so blasé about mitigation. Clearly whatever it might cost it will be small change compared to adaptation. I guess it’s the old story of it’s coming out of someone else’s budget.

(*which also ain’t gonna happen, or we would have armed troopers from the future shutting down the oil wells and coal mines and telling us to stop being so effin stupid.)

andyS May 14, 2014 at 1:52 pm

Humans will always have cities on coastlines. Sea trade is a fundamental part of our civilisation

Thomas May 14, 2014 at 3:59 pm

perhaps we will need to build floating harbour cities and infrastructure…
Andy, humans have not experienced anything like what we have ‘ordered’ for the coming generations, ever! Our brief history as a town and infrastructure building species has no precedent of having to deal with anything like this. We will need to develop whole new concepts of living in a world, which we have set onto a track of rapid change. Sorry to say but there is no ‘we have always done this….’ strategy to fall back on.

andyS May 14, 2014 at 4:03 pm

Wellington airport is fairly close to sea level
Apparently they are looking at extending the runway into Evans Bay to accommodate long haul flights.

NIWA (who also happen to be based on the shore of Evans Bay) are looking into the potential impact on marine life in the bay from this development.

Doesn’t stack up does it?

Thomas May 14, 2014 at 7:42 pm

Na, not long term. Hence this proposal may have merit:
http://tvnz.co.nz/national-news/proposal-move-wellington-airport-into-hills-5827535
and is supposedly cheaper than the extension anyway.

andyS May 14, 2014 at 7:50 pm

Personally, Thomas, I would treat anything that Gerry Brownlee describes as “an exciting idea” with a lot of skepticism

jh May 14, 2014 at 12:08 pm

Does this mean icebergs?

John C May 14, 2014 at 2:04 pm

Do you listen to yourself Kiwi? Bit hysterical.

A 1m SLR ain’t going to go far in N Canterbury, I can’t picture much land being lost at all. Christchurch is the sensitive area but even then it’s only areas next to the sea or rivers. Down town ChCh is many meters above sea level.

Excuse my ignorance but why would a 15cm SLR be worse than what is happening now, only 15cm higher?

Gareth May 14, 2014 at 2:52 pm

No need to guess, John, or accuse others of hysteria when you are wearing your blinders: this is what Christchurch and N Canterbury would look like at 2m SLR. Note that Kiaipoi is in trouble, as are any of the coastal communities with “beach” in their name. Dune systems would likely by breached and/or destroyed. In Christchurch the estuary is particularly vulnerable, with flooding extending into Burwood. Lake Ellesmere is beginning to head inland towards Lincoln. Salt water will be penetrating into groundwater well inland of any surface flooding, ruining drinking water and irrigation systems.

But bear in mind the longer term. Even if we manage to cap atmospheric GHGs at 450 ppm CO2e and restrain warming to 2ºC – which looks increasingly unlikely – then unless we start taking carbon out of the atmosphere rapidly, we are committed to eventual sea level rise of more than 20 metres. Trying setting that on the map page linked above, and see what happens to NZs coastline.

Living with continuously and rapidly rising seas is going to be a real challenge for everyone on the planet. Especially as it will come on top of all the other changes driven by warming…

andyS May 14, 2014 at 3:01 pm

Given that Christchurch has, in places, dropped by 50cm, it gives you a glimpse into the future of any potential scenario

One of the most obvious issues (other than the flooding) is the raising of the water table. Sea water encroachment into tree roots has killed off most of the trees in the South Brighton domain (the walkway by the estuary).

It has a bit of a “scorched earth” feel about it now that they have chopped down the trees

andyS May 14, 2014 at 3:17 pm

I don’t know if this street view works for you

The light coloured stuff in the foreground is sawdust. This was all trees not so long ago

Gareth May 14, 2014 at 3:31 pm

It does. Very depressing.

There a dairy farm on SH1 at Saltwater Creek which is having problems with salt incursion into the aquifer they’re tapping for irrigation, a neighbour told me a few years ago. That will only get worse.

georgedarroch May 14, 2014 at 2:53 pm

John C – you presume that you can disclaim the consequences of your actions.

A child born today will almost certainly be alive in 2100. Unless you are particularly old, this child will soon be old enough to press you on your responsibility, and your deliberate blocking of action.

Even I, given current life expectancies, will be alive into the 2070s. I will live to see these consequences. I hope you live long enough to realise the impact you will have on me, and my family.

andyS May 14, 2014 at 2:55 pm

It seems a bit harsh to blame John C for sea level rise

Thomas May 14, 2014 at 3:48 pm

Not at all Andy, and that goes for you too: People who today work to derail, confuse, divert and distract society from forming a firm and consolidated effort to address the core problems that are leading to this future have become culpable for the consequences of societies failure to act, just like the people who worked hard to prevent society from acting against smoking, have the blood of a significant number of people on their hands who could have been educated in time to stop smoking…

We need to get beyond the silly kindergarten games of denying what we are doing to the planet’s ecosystem and those who carry on doing so should have their mouth washed with soap… ;-)

andyS May 14, 2014 at 3:54 pm

Sounds a tad authoritarian, if you don’t mind me saying so. I think John C has been expressing the same uncertainty that is represented in IPCC reports.

As for me, I haven’t made any claims on SLR, to my knowledge, that anyone has taken issue with. So, I’ll pass on the mouth wash, thanks

georgedarroch May 14, 2014 at 10:52 pm

Authoritarian?

Not acting is a choice, and choices have consequences. Thanks to very robust science, we know what those consequences are. People like John C would like to make those decisions without acknowledging those consequences.

Talking about those consequences upsets them, as does telling them that without the opposition that they create action would be inevitable.

Imposing yourself on billions of people over the next several hundred years who will have to live with rising seas and advancing coasts? That’s authoritarian.

andyS May 14, 2014 at 10:59 pm

Ok,, so I agree with the IPCC as probably John C does. You wish to silence us

On what grounds, exactly?

Thomas May 14, 2014 at 11:07 pm

Andy: ” I haven’t made any claims on SLR, to my knowledge, that anyone has taken issue with..”, perhaps so, but your record on: “working to derail, confuse, divert and distract society from forming a firm and consolidated effort to address the core problems that are leading to this future..”, well that is legendary and etched into the archives of the Internet for all to see for a long time.
What type of soap would you like with that…. ;-)

John C May 14, 2014 at 5:09 pm

Is it just me or does your link not work Gareth?

Again it appears my abilities are being overestimated, and by quite a bit in this instance. I’m not sure there will be too many victims to apologise to, granted property may suffer in places but most people should be able to out run The ocean rising only a few mm/yr. That is pure alarmism.

To be fair to both of us, I’m sure we care equally about our country and the people in it. You appear worried about the potential effects of climate change while I’m more worried about the consequences of climate change regulations. Done poorly regulations could cripple the economy, putting thousands out of work. This has a massive personal cost for the people affected. Poor people could struggle to afford increased energy costs, etc, etc.

[Trolling removed. GR]

Gareth May 14, 2014 at 5:37 pm

Link fixed.

You may care to reflect on what happened at the end of the last ice age. During what’s known as Meltwater Pulse 1A, sea level is thought to have risen 20 metres in 200-500 years (4m to 10m per century). Granted there were much larger ice sheets around at the time, but there is also evidence for a rapid increase in sea level at the end of the Eemian (last) interglacial when ice sheets were about the same size as know (see link in post), and as discussed above the West Antarctic ice sheet is now committed to substantial melt.

Bottom line: it is not safe to assume that sea level rise will continue at “only a few mm/yr”.

Acknowledging the facts of the matter is not being alarmist: to any sensible person the facts are alarming in themselves.

eltoro May 14, 2014 at 10:30 pm

Thomas. I am 65 with a 5mth Granddaughter. I have seen enough and she will live long enough to know all to well the folly of denial in the current age.
I fear for her (and my children’s) future and am hugely frustrated by the denialist attitude of a few bloggers here and as deliberately perpetrated by vested interests in the wider world.
How much more evidence do they need. If this was a diagnosis of cancer by 9 of 10 specialist doctors on any one of these individuals the next of kin would be planning a funeral.
I fully endorse your sentiment. We will not get a second chance to make the right choices.

John C May 15, 2014 at 5:41 am

[Snipped: Saying that you "have not sighted evidence" of metres of sea level rise under a post discussing that very subject, and where I have gone to great lengths to show you evidence thereof, is what got you put on moderation in the first place. I will not pass comments that do not acknowledge the discussion you expect to take part in. GR]

Rob Painting May 15, 2014 at 9:29 am

John C – Isn’t there a bridge somewhere that is missing you?

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