Compare this picture with the one accompanying my last post on this season’s record-breaking sea-ice melt in the Arctic Ocean. More ice has gone, and although the end of the melt season is fast approaching, this year’s low is already about one million square kilometres less than the previous minimum, set in 2005. The NSIDC’s most recent report (Sept 10) also demonstrates that an area of ocean about the size of California is ice-free for the first time since satellite observations began in 1979. As the ocean cools, it will give up heat to the atmosphere. This could delay the onset of the northern hemisphere winter – and perhaps mean a repeat of last year’s mild NH autumn and the late arrival of winter. In turn, this sets up the Arctic for another year of record low ice in 2008, leading to suggestions that the Arctic could be ice-free in summer long before the IPCC expected. From The Guardian [UK]:
Tag: Arctic
Arctic ice sets new record
I follow the Arctic sea ice extent at Cryosphere Today. The site publishes pictures, maps and graphs of sea ice in the Arctic and Antarctic, derived from NASA satellite data. They’ve just announced a worrying new record:
Today (August 9th), the Northern Hemisphere sea ice area broke the record for the lowest recorded ice area in recorded history. The new record came a full month before the historic summer minimum typically occurs. There is still a month or more of melt likely this year. It is therefore almost certain that the previous 2005 record will be annihilated by the final 2007 annual minima closer to the end of this summer. In previous record sea ice minima years, ice area anomalies were confined to certain sectors (N. Atlantic, Beaufort/Bering Sea, etc). The character of 2007’s sea ice melt is unique in that it is dramatic and covers the entire Arctic sector. Atlantic, Pacific and even the central Arctic sectors are showing large negative sea ice area anomalies.
I find this news disturbing for two reasons. First, the fact that the new record should be set so early in the season. That suggests that there is a lot more melting to go. The second is the language: normally cautious scientists seldom use words like “annihilate
On thin ice
Glaciers on the Antarctic Peninsula are thinning and speeding up, according to new research by the British Antarctic Survey. They tracked 300 glaciers using aerial and satellite imagery, and report that 87% are retreating. Ice flow has speeded up by 12% from 1993 to 2003. From the BAS press release:
These observations – that echo recent findings from coastal Greenland – indicate that the cause is melting of the lower glaciers, which flow directly into the sea. As they thin, the buoyancy of the ice can lift the glaciers off their rock beds, allowing them to slide faster.
BBC coverage here.
At the other end of the planet, Reuters has been blogging (here and here) the activities of Koni Steffen of the University of Colorado and Jay Zwally from NASA as they make their annual visit to the Swiss Camp research post high on the Greenland ice sheet. Asked if he thought the IPPC’s fourth report underestimated future sea level increase, Steffen did not pull any punches:
I think it definitely underestimated. We complained heavily before it was released and that’s why they added a few lines that if there is a dynamic response of ice sheets the upper uncertainty might be higher. That tells you that the current IPCC report only takes into account the current understanding. We can model melt but we cannot model the dynamics.
And that’s why I keep covering this stuff…
Meanwhile, two Belgian explorers have been walking across the Arctic from Siberia to Greenland, taking snow measurements to help calibrate a new ESA satellite. ESA were able to help them to avoid early sea ice break-up to the northwest of Greenland in the Lincoln Sea. Story here, with some very cool animated pix of sea ice. For a look at the ice today, go to the NSIDC’s sea ice snapshot. Considerable thinning north of Alaska, where last year there was an unusual polynya. Cryospshere Today shows the same thing.
Melting at both ends
Arctic sea ice is melting. The Greenland ice sheet is losing mass, and the Antarctic Peninsula is one of the fastest warming parts of the planet. But the main part of Antarctica has often been assumed to be pretty safe from extensive surface melting. It’s very cold, and very high. NASA now reports that in January 2005, large parts of the surface of West Antarctica experienced a week long melt, the first time this has been seen.
“The observed melting occurred in multiple distinct regions, including far inland, at high latitudes and at high elevations, where melt had been considered unlikely. Evidence of melting was found up to 900 kilometers (560 miles) inland from the open ocean, farther than 85 degrees south (about 500 kilometers, or 310 miles, from the South Pole) and higher than 2,000 meters (6,600 feet) above sea level. Maximum air temperatures at the time of the melting were unusually high, reaching more than five degrees Celsius (41 degrees Fahrenheit) in one of the affected areas. They remained above melting for approximately a week.”
The picture accompanying the NASA story clearly shows large melt areas – the size of California (how many Belgiums is that?) – over the West Antarctic ice sheet. There hasn’t been a repeat of the event in the last two years, and the period studied only began in 1999, so it’s not clear how unusual the melt was, or if there is any trend. Given the concerns about the stability of the West Antarctic ice sheet in a warming world, this news will add urgency to this year’s International Polar Year effort (which is getting a bit of help from the International Space Station).
Arctic sea ice melting faster than expected
Arctic sea ice is melting faster than modelling (and the IPCC) predicts, the US National Snow and Ice Data Centre (NSIDC) reports.
The shrinking of summertime ice is about thirty years ahead of the climate model projections,