UPDATE: Two commenters pointed me to the Polar Science Center. They look to have the best Arctic ice volume model around — and it’s been validated (see below). Note: “Anomalies for each day are calculated relative to the average over the 1979 -2009 period for that day to remove the annual cycle.”
The big Arctic news remains the staggering decline in multiyear ice “” and hence ice volume. If we get near the Arctic’s sea ice area (or extent) seen in recent years this summer, then this may well mean record low ice volume — the fourth straight year of low volume. And the latest extent data from the National Snow and Ice Data Center suggests we will:
Of course, the anti-science crowd — and much of the media — remain stuck in two-dimensional thinking. So the headlines last month were mostly about how the Arctic ice was supposedly “recovering” to the 1979-2000 average. Now, it was reasonable to ignore the third dimension — ice thickness — when we didn’t have good data on it. But now we do, so it is unreasonable to continue focusing on just two dimensions in the Arctic.
Trends in multi-year ice “” ice volume “” are what matter most in terms of the long-term survivability of the Arctic ice in the summer (see New study supports finding that “the amount of [multi-year] sea ice in the northern hemisphere was the lowest on record in 2009″³). As we’ll see, even when the ice was supposedly recovering in area 2008 and 2009, it was still rapidly shedding the thickest ice — ice older than 2 years.
I noted in March that, contrary to much misreporting, no study has yet been published undermining our understanding that human emissions are the primary cause of the long-term decline in Arctic ice volume “” a decline that shows no sign of reversal (see Study: “It is clear “¦ that the precipitous decline in September sea ice extent in recent years is mainly due to the cumulative loss of multiyear ice,” Physicist: “If temperatures change just a few tenths of a degree then this oh-so-thin ice cap is doomed.”)
I asked NSIDC Research Scientist Walt Meier, “Do you have any indication that there has been a significant recovery of multiyear ice thickness? Do you have any indication that 2009 didn’t see a record low volume?” [see "The perennial pack ice in the southern Beaufort Sea was not as it appeared in the summer of 2009"]. He replied:
We’re doing some analysis on ice age now — we just received the latest data. So, we can’t too much now, but basically it looks like we’ve continued to lose the oldest (and thickest) ice, but we have gained some of the younger multiyear (2-3 years old) ice. There is still a whole lot of first-year ice though. As for volume, we can’t really quantify exact estimates and haven’t tried to do even rough qualitative estimates. I
don’t know if it would [be] the lowest volume, but it’s certainly far lower than it was in the 1980s and 1990s. This year and the two previous years have been the three lowest volume years, but what order they is harder to say.
So we’ve had record low ice volume for the past 3 years. And that’s why I say, if we get near the Arctic’s sea ice area (or extent) seen in recent years this summer, then this will likely yield the fourth straight year of record low ice volume.
Here is the ice age analysis that NSIDC published last month:
As you can see, even when the news stories were about the Arctic ice supposedly “recovering” (in area) in 2008 and 2009, it was still sharply shedding the thickest ice — ice older than 2 years. We’ve apparently had the tiniest of recoveries in multi-year ice the last few months. So while this may not exactly constitute a “death spiral,” the trend in ice thickness doesn’t look like a “loop the loop” either.
As a new study that “looked at the latest detailed atmospheric information, modelling and satellite measurements, including warming at different heights from the surface, for the period 1989 to 2008,” finds, “Melting ice makes the Arctic a vicious circle“:
The Nature study, “The central role of diminishing sea ice in recent Arctic temperature amplification” (subs. req’d), concludes:
Here we show that the Arctic warming is strongest at the surface during most of the year and is primarily consistent with reductions in sea ice cover. Changes in cloud cover, in contrast, have not contributed strongly to recent warming. Increases in atmospheric water vapour content, partly in response to reduced sea ice cover, may have enhanced warming in the lower part of the atmosphere during summer and early autumn. We conclude that diminishing sea ice has had a leading role in recent Arctic temperature amplification. The findings reinforce suggestions that strong positive ice-temperature feedbacks have emerged in the Arctic, increasing the chances of further rapid warming and sea ice loss, and will probably affect polar ecosystems, ice-sheet mass balance and human activities in the Arctic.
And that’s especially important since “Permafrost loss has been linked to Arctic sea ice loss.”
The news story explains: “Dr Screen said white ice reflects a lot of sunlight, but as it melts due to man-made warming from greenhouse gas emissions, the dark water that is exposed absorbs more heat, which in turn, melts more ice, and so on.” Actually, there are more amplifying feedbacks involved (see “What exactly is polar amplification and why does it matter?).
The story ends:
The amount of Arctic sea ice was at a record low in the summer of 2007, down about 40 per cent.
Although it has recovered slightly since, the long-term trend is down, he said. “We’re heading towards a situation where the Arctic Sea will be ice-free in summer.”
Yes, well, even the Sydney Morning Herald doesn’t quite get the story right, since “amount” would tend to suggest volume, not area.
As an aside, how hot has it been in the Arctic this spring? Reuters reported two weeks ago:
In what looks to be another sign the Arctic is heating up quickly, British explorers in Canada’s Far North reported on Tuesday that they had been hit by a three-minute rain shower over the weekend.
The rain fell on the team’s ice base off Ellef Rignes island, about 3,900 km (2,420 miles) north of the Canadian capital, Ottawa.
“It’s definitely a shocker … the general feeling within the polar community is that rainfall in the high Canadian Arctic in April is a freak event,” said Pen Hadow, the team’s expedition director.
Anecdotes aside, the ice cap is apparently doomed “” and the overwhelming majority of CP readers will probably live to see an ice free summer Arctic. Here is an earlier figure of mean monthly Ice Volume for the Arctic Ocean from a release by several scientific institutions:
You can compare it with the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) from the PSC at top. The PSC notes:
PIOMAS has been extensively validated through comparisons with observations from US-Navy submarines, moorings, and satellites. The example on the left [click here] shows a comparison of PIOMAS-derived ice volume anomalies with anomalies measured by the NASA ICEsat Satellite.
It looks like 2009 was below 2008 volume levels. The PSC model suggests 2010 is on track for the record. As the NSIDC reported last week:
An image from NASA’s Advanced Microwave Scanning Radiometer — Earth Observing System (AMSR-E) sensor from April 19 reveals numerous polynyas, or areas of open water in the pack ice in the Bering Sea, and broad areas of more scattered ice cover in the Sea of Okhotsk, Barents Sea, and Hudson Bay. Such conditions usually indicate that ice is about to retreat rapidly.
And guess what, that appears to be happening now, according to the NSIDC data reported in the top figure. Stay tuned.
I still like my odds on a 90% ice free Arctic by 2020 (see “Another big climate bet “” Of Ice and Men“).