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Arctic Sea Ice Meltdown
The U.S. Coast Guard Cutter Healy just returned from two months in the frigid Arctic Sea waters measuring the amount of sea ice and mapping the seabed and continental shelf. Dr. Pablo Clemente-Colon, chief scientist at the National Ice Center and an expert in sea ice analysis, using satellite data, shares his insight and experiences on the Healy expedition. NOAA runs the NIC with the U.S. Navy and the U.S. Coast Guard.
How long were you on the Healy and where did you travel during this expedition?
My time on the Healy started on August 13. I was part of the NOAA-University of New Hampshire effort to measure the water depths and map the Chukchi and Beaufort Seas in the Arctic. Then, I participated in the joint U.S.-Canadian effort to measure and map the waters in the Canada Basin and Eastern Beaufort Sea until October 1.
What experiments or measurements did you take?
I recorded visual observations of sea ice conditions — ice type, stage of development, concentration, and thickness — to validate the satellite remote sensing observations used by NIC to chart sea ice conditions. I also deployed several buoys for the International Arctic Buoy Programme that we expect will help close the gap in data produced by the retreating ice pack. In addition, I gave two seminars on Arctic sea ice conditions. Along with a NIC analyst from NOAA, Kevin Berberich, we provided advice to the captain and chief scientists of the Healy cruises on sea ice conditions and routing.
The Arctic Sea ice extent is the second lowest on record, following last year's measure, which broke the record. Based on climate conditions you're seeing, is it possible this warming trend will continue?
The observations indicate both the planet, as a whole, and the Arctic region, even more rapidly, are warming up. The models are predicting this trend to continue in the foreseeable future. The ongoing decrease of sea ice in the Arctic is tied to this warming trend and is expected to continue. It should be noted that most of the thick, multiyear polar ice pack, composed in the 1980s of ice 10 years or more in age, has already been lost from the Arctic due to both drifting into the North Atlantic and melting. To get back to such a pack, we would need at least a 10-year cooling trend, which is not expected, nor forecasted, by any model.
What would you say are the most critical effects, both to humans and wildlife, of the shrinking Arctic Sea ice?
The decrease and eventual disappearance of a summer ice cover will noticeably change the Arctic polar albedo (or ability to reflect sunlight) and the planetary radiation balance. This can enhance the regional and global warming process. Less ice cover means more open water that can be directly heated by the sun. Large open ocean areas also can be influenced and affect weather with increased wave activity, storm surges, cloudiness, and fog conditions. Another important change will be increased human activity and, in particular, an increased number of vessels operating in the region.
As for wildlife, many animals, including polar bears and walrus, have been left ashore by the retreating ice pack and will need to change their fishing and hunting patterns. Sea ice retreat data from the Arctic buoy program, funded in part by NOAA and other federal agencies, were used this year by the Department of Interior to support listing the polar bear as a “threatened” species under the Endangered Species Act.
During a three-week mapping cruise last year, we saw well over 20 polar bears. This year, we’ve only seen five in more than five weeks. On the other hand, we have heard reports of nearly 20 polar bears roaming and posing safety issues back in the community of Barrow, Alaska. It should be expected that many other species will need to adapt, and some will even migrate north to a more seasonal Arctic sea ice pack in the future.
We know the extent of Arctic Sea ice is growing smaller. What's happening with sea ice around Antarctica?
Just to clarify, not only is the Arctic sea ice extent decreasing, but just as critical, the mean thickness of the Arctic sea ice pack also has precipitously decreased. In fact, although not quite an ice extent minimum record year, by February, this year was already a minimum record year for the amount of thick multiyear ice present in the pack.
We suspect that the increasing presence of icebergs broken off from ice shelves and glaciers within the Antarctic sea ice pack is a major contributor to a temporary but increasing trend in the Antarctic sea ice extent. Since the rapid disappearance of the Antarctic ice shelves and glaciers itself is seen as a response to global warming, the slight increase in sea ice extent that we are observing can be paradoxically linked to the same warming trend.
Is it possible there won't be any summertime Arctic Sea ice in the foreseeable future?
Yes, it is certain if the Arctic warming trend continues. Although variability in the ocean and atmosphere response and interaction makes it difficult to forecast when will this finally happen. For example, as we approach a new seasonal ice regime, it is foreseeable that there may be some years with essentially no summer ice followed by others with significantly more ice.
This variability also helps explain why, whereas there was significantly less total sea ice mass in the Arctic this summer compared to last year, the sea ice minimum extent record was not broken.
Interestingly, any single one of two processes that happened in 2007 could have easily diminished the extent past the record minimum but neither occurred in 2008. That is, 1) a fast trend of first-year ice melting or 2) the presence of anomalous pressure systems accelerating the flushing of sea ice through the Fram Strait. 