The record-breaking loss of Arctic sea ice during 2007 continues to stun scientists as they try to sort out what the meltdown portends for the future.
Only a few weeks ago, the ice extent in the Far North’s inland sea declined to the lowest level observed since satellite coverage began 29 years ago. The Northwest Passage opened for the first time in memory. Data from earlier decades, when ice extent was calculated largely by ship observations, suggests that ice has never shrank this far during the age of shipping.
Vast expanses of the Arctic Ocean remain ice free for the first time in human history.
It could mean no summer ice by 2030, say scientists at the National Snow and Ice Data Center. It’s an outcome that will drive polar bears to the edge of extinction and force devastating changes to hunting ability of Alaska’s coastal Natives.
“The sea ice cover is in a downward spiral and may have passed the point of no return,” said NSIDC senior scientist Mark Serreze in this online story. “As the years go by, we are losing more and more ice in summer, and growing back less and less ice in winter. We may well see an ice-free Arctic Ocean in summer within our lifetimes.
“The implications for global climate, as well as Arctic animals and people, are disturbing.”
So how bad was it?
Ice extent — the area with at least 15 percent ice floes — has been tracked by satellite since 1979. During that era, the average ice extent for September usually covered about 2.30 million square miles. But this September, the extent averaged about 39 percent less, about 1.65 million square miles.
The low point hit about Sept. 16, with ice extent reaching over an estimated 1.59 million square miles. That’s about 22 percent below the previous all-time record set in 2005.
Consider ship and aircraft records for Arctic ice in the decades before satellite coverage, and scientists say Arctic sea ice of 2007 may be 50 percent smaller than the extent observed in the 1950s.
The ice in the Arctic in September has been declining at least 10 percent per decade, or about 28,000 square miles per year — slightly larger than Massachusetts, Vermont and New Hampshire combined. In the end, the Arctic has lost about 650,000 square miles of ice covered for September — an area just about as large as Greenland.
Here’s more from the NSIDC’s online analysis, Arctic Ice Shatters All Previous Record Lows:
“Computer projections have consistently shown that as global temperatures rise, the sea ice cover will begin to shrink,” Serreze said. “While a number of natural factors have certainly contributed to the overall decline in sea ice, the effects of greenhouse warming are now coming through loud and clear.”
One factor that contributed to this fall’s extreme decline was that the ice was entering the melt season in an already weakened state.
NSIDC Research Scientist Julienne Stroeve said, “The spring of 2007 started out with less ice than normal, as well as thinner ice. Thinner ice takes less energy to melt than thicker ice, so the stage was set for low levels of sea ice this summer.”
Another factor that conspired to accelerate the ice loss this summer was an unusual atmospheric pattern, with persistent high atmospheric pressures over the central Arctic Ocean and lower pressures over Siberia.
The scientists noted that skies were fairly clear under the high-pressure cell, promoting strong melt. At the same time, the pattern of winds pumped warm air into the region. While the warm winds fostered further melt, they also helped push ice away from the Siberian shore.
NSIDC Research Scientists Walt Meier said, “While the decline of the ice started out fairly slowly in spring and early summer, it accelerated rapidly in July. By mid-August, we had already shattered all previous records for ice extent.”
Arctic sea ice receded so much that the fabled Northwest Passage completely opened for the first time in human memory. Explorers and other seafarers had long recognized that this passage, through the straits of the Canadian Arctic Archipelago, represented a potential shortcut from the Pacific to the Atlantic.
Roald Amundsen began the first successful navigation of the route starting in 1903. It took his group two-and-a-half years to leapfrog through narrow passages of open water, with their ship locked in the frozen ice through two cold, dark winters.
More recently, icebreakers and ice-strengthened ships have on occasion traversed the normally ice-choked route. However, by the end of the 2007 melt season, a standard ocean-going vessel could have sailed smoothly through.
On the other hand, the Northern Sea Route, a shortcut along the Eurasian coast that is often at least partially open, was completely blocked by a band of ice this year.
In addition to the record-breaking retreat of sea ice, NSIDC scientists also noted that the date of the lowest sea ice extent, or the absolute minimum, has shifted to later in the year.
This year, the five-day running minimum occurred on September 16, 2007; from 1979 to 2000, the minimum usually occurred on September 12.
NSIDC Senior Scientist Ted Scambos said, “What we’ve seen this year fits the profile of lengthening melt seasons, which is no surprise. As the system warms up, spring melt will tend to come earlier and autumn freezing will begin later.”
Changes in sea ice extent, timing, ice thickness, and seasonal fluctuations are already having an impact on the people, plants, and animals that live in the Arctic.
NSIDC Research Scientist and Arctic resident Shari Gearheard said, “Local people who live in the region are noticing the changes in sea ice. The earlier break up and later freeze up affect when and where people can go hunting, as well as safety for travel.”
NSIDC scientists monitor and study Arctic sea ice year round, analyzing satellite data and seeking to understand the regional changes and complex feedbacks that we are seeing.
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