“Anomalies for each day are calculated relative to the average over the 1979 -2009 period for that day to remove the annual cycle.” [And yes, “anomaly” is a poor word choice for a long-term trend driven by human emissions.]
Back in mid-May, I argued the Arctic is poised to see record low sea ice volume this year. Since then, volume has plummeted some 3000 km3 (relative to its recent historical average) to “19,000 km3, the lowest May volume over the 1979–2010 period, 42% below the 1979 maximum and 32% below the 1979–2009 May average,” according to the Polar Science Center, which has the best Arctic ice volume model around.
If I’m reading their historical average right, we’re probably below 10,000 km3 now. The September minimum record was set 9 months ago, at 5,800 km3.
Most attention gets focused on the more visible but less important metric of sea ice extent, which collapsed last month faster than any May in the satellite record. As a result, at least one group in the highly touted suite of forecasts is looking to sharply lower their September sea ice extent estimate.
Here is where we are now on extent, via the National Snow and Ice Data Center:
NSIDC notes: “In May, Arctic air temperatures remained above average, and sea ice extent declined at a rapid pace. At the end of the month, extent fell near the level recorded in 2006, the lowest in the satellite record for the end of May.”
And here’s the Japan Aerospace Exploration Agency (JAXA, click to enlarge):
So will we hit a record low extent, which is what the media will focus on?
I asked NSIDC’s Julienne Stroeve, and she emailed me:
The thing to look for right now is persistence of the Arctic Dipole we’ve seen this June. If that continues all summer like it did in 2007 then I think we’ll be close to 2007 values by September. There are strong meridional winds pushing ice away from the coast of Siberia at the moment (like what happened in 2007). Also Nares Strait is open like it was in 2007 which can help to remove more of the old ice in that location.
It seems clear that the band of old ice that was advected into the Beaufort/Chukchi seas this winter will be key to what we see in September. If that old ice survives the melt season then I don’t think we’ll see a new record low, but if that ice melts out given it’s southerly location, then I do think we’ll be close to 2007.
The NSIDC says of ice volume and the PSC’s PIOMAS model:
Ice extent measurements provide a long-term view of the state of Arctic sea ice, but they only show the ice surface. Total ice volume is critical to the complete picture of sea ice decline. Numerous studies indicate that sea ice thickness and volume have declined along with ice extent; unfortunately, there are no continuous, Arctic-wide measurements of sea ice volume. To fill that gap, scientists at the University of Washington have developed regularly updated estimates of ice volume, using a model called the Pan Arctic Ice Ocean Modeling and Assimilation System (PIOMAS)….
PIOMAS blends satellite-observed sea ice concentrations into model calculations to estimate sea ice thickness and volume. Comparison with submarine, mooring, and satellite observations help increase the confidence of the model results. More information on the validation methods and results is available on the PIOMAS ice volume Web site.
If PIOMAS is right, then we are almost certainly headed toward record low ice volume this September.
The ice is simply getting thinner and more rotten. Climate Central has a nice figure:
As Andrew Freedman wrote recently:
A NASA study published last year found that Arctic sea ice thinned about 0.17 meters (seven inches) per year between 2004 and 2008, for a total of 0.68 meters (2.2 feet) over four winters. Also, the total area covered by thicker “multi-year” ice shrank by 42 percent. Other studies have documented longer-term declines in sea ice thickness, due to warming temperatures as well as winds and ocean currents that have transported thicker ice out of the Arctic and into the North Atlantic.
As I discussed May 24 — As Arctic sea ice shrinks faster than 2007, NSIDC director Serreze says, “I think it’s quite possible” we could “break another record this year” — “one of Canada’s top sea-ice experts suggests things might even be worse than Dr. Serreze thinks” (see The Arctic Ocean is full of rotten ice: New study by Barber et al. supports finding that “the amount of [multi-year] sea ice in the northern hemisphere was the lowest on record in 2009”³).
“What we think is thick multiyear ice late in the summer is in fact not,” he said. “It’s heavily decayed first-year ice. When that stuff starts to reform in the fall, we think it’s multiyear ice, but it’s not.”
… He pointed out the Arctic continued to lose multiyear ice even in 2008 and 2009, when total ice coverage rebounded somewhat.
“What really matters is the condition and thickness of the multiyear ice.”
“Last summer we studied sea ice recovery in the Southern Beaufort Sea aboard the research vessel Amundsen. We expected to be stopped at some point by thick multiyear ice, but the Amundsen, only ice classed to break ice 1.2 metres thick, was able to continue at full speed. We realised that the ice was rotten.”
Dr Barber and his team saw swells penetrating far into the Beaufort Gyre and breaking up huge ice sheets. Normally, the ice should be too strong for this to happen.
“We also observed that melt pond formation on the multiyear ice had continued all the way through the ice, leaving separate chunks of multiyear ice. When the freeze started, a thin layer — only about 5 cm — of first-year ice formed across the surface, and the combination was mistaken by the radar for multiyear ice.” This means that some of the data on the extent of multiyear ice are misleading.
On a streetcar named denial, aka WattsUpWithThat, two people scour the world for databases that they can misinterpret and mislead their readers with (see Arctic death spiral: Naval Postgrad School’s Maslowski “projects ice-free* fall by 2016 (+/- 3 yrs)”). In the last month they’ve written:
“The death spiral continues, with Arctic ice extent and thickness nearly identical to what it was 10 years ago.” (5/31)
“Over the last three years, Arctic Ice has gained significantly in thickness…. Conclusion : Should we expect a nice recovery this summer due to the thicker ice? You bet ya.” (6/2)
“Arctic Basin ice generally looks healthier than 20 years ago.” (6/23)
Arctic Basin ice generally looks healthier than 20 years ago the same way that my hair generally looks healthier than 20 years ago, what’s left of it, that is.
To paraphrase Tennessee Williams, WattsUpWithThat has always relied on the blindness of strangers.