Record Sea-Ice Loss Amplifies Need to Stop Global Warming Now

Posted: 28-Sep-2005; Updated: 28-Feb-2007

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Less sea ice in summer means a shorter hunting season for polar bears. (PHOTO: Scott Schliebe/U.S. Fish & Wildlife Service)

Will Arctic summers soon be completely free of sea ice? It's possible. Last year the Arctic lost a record amount of sea ice, and some scientists are wondering whether we are approaching a dangerous "tipping point." Today, the National Snow and Ice Data Center (NSIDC), NASA and the University of Washington released a joint report detailing "a stunning reduction in arctic sea ice" for the fourth consecutive summer. (Read more on today's announcement.)

The latest findings support earlier studies (reported in both the Journal of Climate and EOS, a publication of the American Geophysical Union) revealing a disturbing trend for a world increasingly feeling the heat of a warming planet. They also provide compelling, on-the-ground evidence that action on global warming is urgently needed now.

A dramatic change

Fluctuations in Arctic sea ice levels naturally occur throughout the year. Sea ice melts during the summer months, and reforms during the winter. However, the years 2002-2005 have seen record or near-record low-ice coverage. The loss of sea ice last summer was especially severe and, as a result, the winter recovery was much weaker than normal. And less sea ice during the winter means even less ice at the beginning of the summer melting season. This trend spells trouble for an ecosystem dependent on ice -- and for the world beyond. "This latest evidence of a downward trend seems to be accelerating, an indication that we should start cutting heat-trapping emissions immediately," says Environmental Defense climate scientist Dr. James Wang.

Sea ice loss means accelerated warming

Sea ice forms from ice chunks that have accumulated into pancake-shaped ice floes when they knock into each other during the ocean's natural buffeting. As temperatures drop further, the ice grows thicker and the pancake ice becomes more of a solid sheet that floats on the ocean's surface. For generations, sea ice during summer months in the Arctic region covered an area about the size of Australia, but that cover has dwindled over the past decades with dramatic losses in the past four years.

Such a loss creates a self-perpetuating scenario called a positive feedback loop, which hastens more loss of sea ice and more global warming. Less ice cover means less sunlight is reflected into space and the oceans are less protected from heat. As a result, heat from sunlight penetrates the ocean's surface and gets absorbed by its dark waters, creating an even warmer surface temperature. In short, a loss of sea ice could hasten global warming.

On-the-ground evidence

Already in Canada's Hudson Bay, the sea-ice season has shortened by three weeks.  This is a problem for polar bears whose diet relies on ice-dwelling seals. The reduced time the bay's polar bears have for hunting this main food source seriously damages their health and is contributing to a 15% decline in polar bear cubs. At present rates of shrinkage, Arctic sea ice could disappear completely each summer by the end of this century and push polar bears to the brink of extinction. Shrinking and thinning ice has also made hunting more challenging and even life-threatening for humans. Continued warming could destroy traditional societies.

But it would be a mistake to think that only people and wildlife in the Arctic will feel the brunt of this warming. The Arctic is like an air conditioner for the planet, so the effects of this melting Arctic sea ice will be felt around the world.

"If we want to ensure the survival of wildlife and human communities around the world, we need to think ahead and act now when these warning signs are flashing in our faces," says Dr. Wang.

What you can do

Join the hundreds of thousands of Americans calling for passage of a bill designed to dramatically reduce the nation's heat-trapping pollution