In evaluating last year’s changes in the Arctic, the National Oceanic and Atmospheric Administration (NOAA) rated three categories as undergoing significant change (atmosphere, sea ice and ocean, and hydrology and terrestrial cryosphere) and the remaining two as experiencing some change (terrestrial ecosystems and marine ecosystems).
Water temperatures in summer 2011 were well above the 1982-2006 temperature average. In a self-perpetuating cycle, sea ice melted and converted to open water. Compared to ice, open water reflects less heat back into the atmosphere and absorbs more. The warming waters abet the melting of sea ice and the thawing of permafrost on adjacent coastlines. Globally, changes in sea ice affect atmospheric wind patterns and the Earth’s heat balance.
More open water leads to more biological activity at the base of the food chain, while adversely affecting habitat of larger animals dependent on ice, such as polar bears and walruses. Melting glaciers and ice sheets freshen the top layers of the ocean and increase sea level.
The increased expanse of open water absorbs more carbon dioxide from the atmosphere, raising the acidity level of sea water. Suppressing calcium carbonate, more acidic sea water will affect the ability of some organisms to form shells, a consequence that will work its way through the food chain and add stress to the Arctic ecosystem.
In 2011 ice coverage was 15 to 20 percent below the 1979-2000 average. Loss of old, slow-melting ice has increased, leaving new, thin ice that allows solar radiation to penetrate into the upper ocean more easily, warming water both at the surface and at depth.