The National Snow and Ice Data Center (NSIDC) announced October 1 that the summer melting of the sea ice at the North Pole hit a new record this year, shrinking to its lowest extent since satellite records started being kept in 1979. The big melt left 23 percent less ice than in 2005, the previous record year, and 39 percent less than the long-term average. This was a significant year.
Scientists say climate change is one of the factors causing the massive melting. According to NASA, however, the primary cause was a large loss of old, thick year-round sea ice during the last two winters.
Other factors included unusually sunny weather in June and July, clouds and water vapor trapping heat near the surface, and also warm winds from Siberia.
Back to that old, thick ice that normally stays frozen year-round. In a NASA press release, scientist Son Nghiem said that “Unusual atmospheric conditions set up wind patterns that compressed the sea ice, loaded it into the Transpolar Drift Stream and then sped its flow out of the Arctic.” When the ice reached more southerly latitudes, it melted in the warmer water.
NASA found a 23-percent loss of the perennial sea-ice cover during the last two years. The Arctic is shifting to more seasonal ice cover. The seasonal ice does not grow as thick and thus melts more quickly. NASA said this shift is “preconditioning the sea ice cover there for more efficient melting and further ice reductions each summer.” The shrinking ice cap also decreases the reflectivity of Earth’s surface and thus allows more solar energy into the ocean-ice system.
Scientists predict the entire ice cap could melt during summer as soon as 2030. One even says 2013!
NSIDC noted the summer melting season lasted four days longer this year, with the five-day running minimum occurring on September 16. The sea ice is also melting earlier in the spring.
Experts cannot find records from Russia, Alaska or anywhere of such a widespread melt in recent times.
The big melt has already affected people and animals. The changing ice affects when people can travel and hunt. Thousands of walruses came ashore in Alaska this summer, because the ice had melted way past their feeding grounds. They used to live on the ice and dive on to the outer continental shelf, to feed on clams and snails. This became impossible this year.
The U.S. government is considering putting polar bears on the endangered species list, because
the melting sea ice affects their ability to hunt and feed themselves year-round.
As NSIDC senior scientist Mark Serreze said, “The implications for global climate, as well as Arctic animals and people, are disturbing.”
(Also see the New York Times article, ‘Arctic Melting Unnerves Experts,’ Oct. 2, 2007. http://www.nytimes.com/2007/10/02/science/earth/02arct.html?_r=3&ref=science&oref=slogin&oref=slogin&oref=slogin)
Caption for map graphic: The image below shows the average sea ice extent in September 2007 (in white), compared to the long-term median sea ice extent from 1979-2000 (in magenta) for the end of the melt season.
Please note the corresponding record maximum extent in the Southern Hemisphere sea ice as noted on the UIUC cryosphere today website
In 1905 and again in the 1940’s, the Arctic sea ice had receded enough so that the fabled Northwest Passage was navigable. It was navigated both times and not by icebreaker.
In Antarctica, the ice is reaching record levels and the temps have dropped by over a degree F.
This earth is constantly changing. We have not been observing things long enough to know what is going on. We especially have no idea what trends may exist, for how long and what “normal” would have been sans human effects. It can be colder on one end of the earth and warmer on the other. THis does not global warming make.
Here’s the link to The Cryosphere Today that JR mentioned, http://arctic.atmos.uiuc.edu/cryosphere/. The site is maintained by the University of Illinois at Urbana-Champaign’s Polar Research Group.
Scroll down to the October 1 entry, where it does mention how the Southern Hemisphere sea ice “narrowly surpassed” the historic maximum — by 0.87 percent, if I read it correctly.
This page from the NSIDC, ‘All About Sea Ice,’ http://nsidc.org/seaice/characteristics/difference.html, notes that the Arctic and Antarctic have very different geographies, which creates differences in the sea ice in each place. Here the NSIDC says that the trend in Antarctic sea ice gain is not significant. I’d like to know if this year’s gain was more significant than usual.
In any case, the Arctic sea ice loss was huge, at 39 percent below the long-term average. If I understand correctly, the trend for Arctic sea ice since 1979 had been down, but this year it made a sharp plunge.
As I noted in my post, scientists cited climate change as one factor involved in the Arctic melt, not the only factor.
As for climate change itself, the Intergovernmental Panel on Climate Change said in its Feb. 7, 2007 report that “warming of the climate system is unequivocal,” and that the planet has warmed 1.3 degrees Fahrenheit since 1850. The report also said that scientists are 90 percent certain that human activities are causing that warming. See the IPCC Web site, http://www.ipcc.ch/, and the summary of the Physical Science Basis, http://ipcc-wg1.ucar.edu/wg1/wg1-report.html
The IPCC was formed in 1988 and issued its First Assessment Report in 1990. This year it has issued sections of its Fourth Assessment Report. It will release a Synthesis Report in November.
The casual reader may miss the fact that the quoted percentages, in the following two statements from Dan Kulpinski’s post, are not a comparison of apples with apples. The first is a deviation from a maximum; the second, a deviation from an average–a rather HUGE difference!
1)Scroll down to the October 1 entry, where it does mention how the Southern Hemisphere sea ice “narrowly surpassed” the historic maximum — by 0.87 percent, if I read it correctly.
2)In any case, the Arctic sea ice loss was huge, at 39 percent below the long-term average
I don’t really understand the math exactly, but the graphic showing the Greenland-sized open ocean where there’s usually ice north of Russia was easy to understand. I’m glad I’m not a polar bear swimming across it, hoping to find an icy spot so I can eat something…
How much more open will the northwest passage have to be for shipping to resume there now?
According to scientists who model climate change at the poles, a warming Earth would cause more open sea at the North Pole (as Dan’s article indicates is happening). But that same warming might cause more precipitation and thus more ice in Antarctica.
Here’s a brief Earth & Sky radio program about whether global warming will make Antarctica icier. And Here’s Earth & Sky’s complete interview with NASA’s Thorsten Marcus, on how global warming might make some places colder.
Best to all,
Deborah