The recent shrink of the Arctic ice cap has stunned scientists and swamped previous projections. After melting back at a rate never seen before, the 2007 minimum ice extent fell 1 million square miles below the 29-year average for September — the loss of a habitat as large as Argentina.
The decline occurred much faster than scientists thought possible, consuming as much ice in one season as one might expect to lose over three consecutive summers, according to a story published online by NASA.
Here’s the latest from the Arctic slush bowl. And the news is not reassuring.
As of Sept. 25, the ice cover in the Arctic Ocean hovered at about 1.61 million square miles — a scant 1 percent increase over the all-time minimum extent observed about 10 days earlier. The Northwest Passage, more ice free than at any time in decades, had slowly begun to clog up. But open water extended hundred of miles north and west of Alaska, exposing coastal villages to enormous fetches for storms and forcing marine mammals to deal with the smallest and most seaward ice habitat of their lives.
As the Bush Administration spends time chatting with other major carbon-producing nations about making soft, ineffectual (and almost certainly symbolic) reductions in greenhouse gas emissions, the Arctic has gone soggy, appearing as ice-free as some climate researchers once predicted for 2050. (See the UN meeting on clmate change earlier in week.)
In fact, given the accelerated rate of melt, several scientists now say the ocean could become ice free in summer as early as 2030. That’s only 23 years — less than a generation for coastal residents, ice seals and bears.
“The amount of ice loss this year absolutely stunned us,” ice scientist Mark Serreze of the National Snow and Ice Data Center, told the Boulder Daily Camera in this story. “It didn’t just beat all previous records — it completely shattered them.”
“Going, going, gone,” Deborah Williams of Alaska Conservation Solutions, told the House Select Committee on Energy Independence and Global Warming, in a story published in the Anchorage Daily News. “We must take action now; it is urgent. We want to be part of the solution, not just the poster child of the problem.”
And though the season of dark and cold has begun, the process of reforming ice seems almost stalled, much slower than usual. The NSIDC explains further in their online update:
Source: NSIDC
Now that freeze-up has begun, ice extent will continue to increase until it reaches its maximum sometime during March of next year. However, because the Arctic lost so much ice this summer, exposed open-water areas have absorbed a lot of solar energy; freeze-up will begin slowly, as you can see in Figure 2 (to the left side.)
Once the ocean waters cool to the freezing temperature, the rate of ice growth will accelerate. Nonetheless, the extreme loss of this summer’s sea ice cover and the slow onset of freeze-up portends lower than normal ice extent throughout autumn and winter, and the ice that grows back is likely to be fairly thin.
While the NSIDC works mostly with satellite records since 1979, other records reach further in the past. An analysis from the United Kingdom’s Hadley Centre for Climate Prediction used ship reports and aircraft observations to push the ice records back to the early 1900s.
“Although the data quality prior to the early 1950s is debatable, no year in this century-long record comes close to matching what we have seen in 2007,” says the NSIDC. “September 2007 sea ice extent is nearly 50% lower than during the 1950s and 1960s.”
NASA argues that getting a fix on why the ice has retracted so fast, and then tracking its fate in the coming years, depends on keeping and upgrading its fleet of satellites. In ‘Remarkable’ Drop in Arctic Sea Ice Raises Questions’, NASA scientists discuss satellite priorities and their questions about what’s driving the meltdown in the Far North:
Source: NSIDC
“The decline in the amount of thick ice that survives the summer melt season this year is quite remarkable,” said Josefino C. Comiso, senior scientist at NASA’s Goddard Space Flight Center, Greenbelt, Md. “The extent of this ‘perennial’ sea ice and the area it covers are both nearly 38 percent lower than average. Compared to the record low in 2005, the extent and area are 24 percent and nearly 26 percent lower this year, respectively.”
“From what we know of how Arctic sea ice behaves after nearly 30 years of continuous satellite observations, this kind of drop in sea ice usually takes more than three years to happen. The rapid trend of the perennial ice previously reported in 2002 appears now to be in an accelerated mode,” Comiso observed.
“Because Arctic ice cover varies so much year to year, it can be dangerous to look at any one year and draw too much of a conclusion from it,” said Waleed Abdalati, head of Goddard’s Cryospheric Sciences Branch. “But this year, the amount of ice is so far below that of previous years that it really is cause for concern. The trend in decreasing ice cover seems to be getting stronger and stronger as time goes on.”
NASA developed the original capability to observe the extent and concentration of sea ice from space using passive microwave sensors.
More recently, NASA launched an advanced microwave instrument in 2002 — the Advanced Microwave Scanning Radiometer (AMSR-E) on the Aqua satellite — that provides a view of sea ice dynamics in greater detail than has ever been seen before. Researchers use this information to study polar bear habitats and the unique movements of sea ice from season to season…
The accelerating decline in sea ice may be due to changes in climate brought on by the lack of sea ice itself, Comiso believes.
“When there is less sea ice in the summer, the Arctic Ocean receives more heat. The warmer water makes it harder for the ice to recover in the winter, and, therefore, there is a higher likelihood that sea ice will retreat farther during the summer. This process repeats itself year after year,” Comiso said.
“The longer this process continues, the less likely recovery becomes,” Abdalati believes. “The implications on global climate are not well known, but they have the potential to be quite large, since the Arctic ice cover exhibits a tremendous influence on our climate. It really is imperative that we try to understand the interactions between the ice, ocean and atmosphere. And satellites hold the key to developing this understanding.”
[...] ‘Going, going, gone:’ Scientists try to explain ice loss [...]
Nice article, but the link to NASA is broken (there’s a spurious break tag in the url).
“And though the season of dark and cold has begun, the process of reforming ice seems almost stalled, much slower than usual.”
Looking at the end of the “Tale of the tape” at The Cryosphere today seems to me to illustrate this well. Previous anomaly lows have been transient, this year we seem to have been stuck at -2m for several weeks now.
Oh dear, my link is also broken …
I meant NASA.
Apologies.