Western Antarctica ice sheet collapse now unstoppable, will cause up to 4m sea-level rise

Climate news, and not good news at all. Two separate studies confirm that one of the key ice shelves in Western Antarctica is collapsing. The loss of the ice sheet is inevitable — it can’t be stopped.

The analysis suggests that “up to 4 meters of sea-level rise” is inevitable, but I think they’re being — again — optimistic. See below for more on that. There’s much more ice available.

Here’s the news via the Guardian (my emphasis and paragraphing):

The collapse of the Western Antarctica ice sheet is already under way and is unstoppable, two separate teams of scientists said on Monday. The glaciers’ retreat is being driven by climate change and is already causing sea-level rise at a much faster rate than scientists had anticipated.

Antarctica (click to enlarge)

Antarctica (click to enlarge). The ice shelves mentioned are in the Amundsen Sea bay.

The loss of the entire western Antarctica ice sheet could eventually cause up to 4 metres (13ft) of sea-level rise, devastating low-lying and coastal areas around the world. …

The two studies, by Nasa and the University of Washington, looked at the ice sheets of western Antarctica over different periods of time. The Nasa researchers focused on melting over the last 20 years, while the scientists at the University of Washington used computer modelling to look into the future of the western Antarctic ice sheet.

But both studies came to broadly similar conclusions – that the thinning and melting of the Antarctic ice sheet has begun and cannot be halted, even with drastic action to cut the greenhouse gas emissions that cause climate change.

There are many ice sheets in Western Antarctica (see map), which the article says account for (just) 4 meters of potential sea level rise. The National Geographic points out:

[S]ix big glaciers in the Amundsen Sea “have passed the point of no return”[.]

There’s an excellent graphic here that shows the extent of the ice loss caused by these glacial melts.

How much ice is there to melt?

When it all goes, all the ice on the planet, we’re looking at a minimum of 65 meters of sea-rise. Thanks to the always helpful Greg Laden, we found this USGS page that gives the number as 80 meters, and accounts for it in these cold locations:

Table 1. Estimated potential maximum sea-level rise from the total melting of present-day glaciers.
Location
Volume (km3)
Potential sea-level rise, (m)
East Antarctic ice sheet
26,039,200
64.80
West Antarctic ice sheet
3,262,000
8.06
Antarctic Peninsula
227,100
.46
Greenland
2,620,000
6.55
All other ice caps, ice fields, and valley glaciers
180,000
.45
Total
32,328,300
80.32

The big one is the East Antarctic ice sheet — almost 65 meters worth of water — but there plenty in Greenland and the rest of  West Australia as well. I’m not sure this takes into account the fact that water expands at higher temperatures as well. But more on that at another time.

How soon will the seas start rising?

The article goes on to say that most sea rise is “several centuries off” — but don’t get comfortable. I’m getting up to speed on the rate of sea level rise, and every prediction is wrong to the small side. For example, from the article:

The two studies between them suggest sea-level rise will be far greater than envisaged by the United Nations’ IPCC report earlier this year. The IPCC forecast on sea-level rise did not factor in the melting of the western Antarctica ice sheet.

And:

Rignot said he was taken aback at how fast change was occurring.

“This system, whether Greenland or Antarctica, is changing on a faster time scale than we anticipated. We are discovering that every day,” Rignot said.

Yet the article still sees the timescale of major sea level changes as taking centuries, not decades. But again, everyone is wrong to the slow side. Remember this, from 2009?

Arctic sea ice — projected vs. observed as of 2009, Fig. 12 from the Copenhagen Diagnosis

Arctic sea ice — projected vs. observed as of 2009 (Fig. 12 from the Copenhagen Diagnosis)

The red line above is reality. The blue, IPCC best guesses. How does it help us to be so conservative?

I’m looking into the rate of projected sea level rise closely, and will try to summarize the best estimates later. But for scale of sea rise, however, much is known. Just keep the above in mind. There somewhere between 65 and 80 meters sea rise if we don’t … well, stop spewing carbon.

It gets worse. According to James Hansen, in a non-ice-free world, a change of 1°C in mean surface temperature means a change in sea level of about 20 meters. We’ve already seen +1°C change (with an equal amount in the pipeline) since pre-industrial time. We’re due for that 20 meters, even if we stop here and stick with the CO2 we’ve already emitted. (Hansen has a way to pull the emissions back, but again, that’s for later.)

I wonder — what kind of crisis will it take before people even try to make meaningful change? Do you wonder that too? What are your thoughts about what it will take?

GP

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Gaius Publius is a professional writer living on the West Coast of the United States.

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