Johnny Rook's Climaticide Chronicles

Nearly a month ago the National Snow and Ice Data Center announced that although 2008 Arctic sea ice extent did not quite reach the minimums of 2007, sea ice volume had probably set a record.

NSIDC Research Scientist Walt Meier said, “Warm ocean waters helped contribute to ice losses this year, pushing the already thin ice pack over the edge. In fact, preliminary data indicates that 2008 probably represents the lowest volume of Arctic sea ice on record, partly because less multiyear ice is surviving now, and the remaining ice is so thin.”[emphasis–JR]

Envisat ASAR image of the McClure Strait in the Canadian Arctic Archipelago, acquired on 31 August 2007. The McClure Strait is the most direct route of the Northwest Passage and has been fully open since early August 2007.

Credits: ESA

Figure 4. A comparison of ice age in September 2007 (left) and September 2008 (right) shows the increase in thin first-year ice (red) and the decline in thick multi-year ice (orange and yellow). White indicates areas of ice below ~50 percent, for which ice age cannot be determined. AVHRR, SMMR SSM/I, and IABP buoy data.

—From National Snow and Ice Data Center courtesy C. Fowler, J. Maslanik, and S. Drobot, University of Colorado at Boulder

Meier’s judgement was confirmed today when the European Space Agency (ESA) issued a press release declaring that in 2008, Arctic sea ice had declined by 19% compared with the previous five winters.

The research, reported in Geophysical Research Letters, showed that last winter the average thickness of sea ice over the whole Arctic fell by 26 cm (10%) compared with the average thickness of the previous five winters, but sea ice in the western Arctic lost around 49 cm of thickness.

Circumpolar average winter season (October to March) ice thickness anomalies (from Katharine A. Giles, Seymour W. Laxon and Andy L. Ridout, Circumpolar thinning of Arctic sea ice following the 2007 record ice extent minimum, Geophysical Research Letters).

Credits: Giles – Laxon – Ridout

Dr Katharine Giles of UCL, who led the study, said: “This summer’s low ice extent doesn’t seem to have been driven by warm weather, so the question is, was last winter’s thinning behind it?”
…

“As the Arctic ice pack is constantly moving, conventional methods can only provide sparse and intermittent measurements of ice thickness from which it is difficult to tell whether the changes are local or across the whole Arctic,” Giles said.

“Satellites provide the only means to determine trends and a consistent and wide area basis. Envisat altimeter data have provided the critical third dimension to the satellite images which have already revealed a dramatic decrease in the area of ice covered in the Arctic.”

it will be very interesting to see how low the ice goes in 2009. With volumes dropping so radically and the ice thin because so much of it is new, if temperatures next year (a recent report from NOAA states that fall temperatures in the Arctic are at a record high, 5 degrees Celsius above average ) are closer to those of 2007 than those of 2008, expect to see another big step toward an ice free Arctic summer.