Annual report card highlights ice loss, ecosystem changes
By Summit Voice
SUMMIT COUNTY — Arctic researchers say the persistent decline in the thickness and summer extent of sea ice and a warmer and fresher upper ocean are some of the key signs of profound and continuing changes in the Arctic Ocean system.
With more open water in the region, biological productivity at the base of the marine food chain has increased, while sea ice-dependent marine mammals like polar bears and walruses continue to lose habitat. Warmer land temperatures resulted in greener tundra vegetation in where adjacent sea ice has declined the most, according to the annual Arctic report card update for 2011.
The report suggests that the record-setting changes are likely to continue in the coming years, with, with increasing climatic, biological and social impacts. Find the report and all the background documents at this NOAA website.
Another sign of the long-term shifts is the repeated occurrence of 2010 Arctic winter wind patterns that mark a departure from the norm. These changes resulted in higher than normal temperatures in the Arctic, with record ice sheet mass loss, record low late spring snow cover in Eurasia, shorter lake ice duration, and unusually lower temperatures and snow storms in some low latitude regions. A potential indicator of recent atmospheric changes was record low ozone concentration in March 2011.
Highlights from the executive summary of the report:
Sea ice and ocean observations over the past decade (2001-2011) suggest that the Arctic Ocean climate has reached a new state, with characteristics different than those observed previously.
The new ocean climate has less sea ice (both thickness and summer extent) and, as a result, a warmer and fresher upper ocean. A clockwise ocean circulation regime has dominated the Arctic Ocean for at least 14 years (1997-2011), in contrast to the typical duration of a 5-8 year pattern of circulation shifts observed from 1948-1996. In the Bering Sea, aragonite undersaturation, i.e., ocean acidification, throughout the water column is causing seasonal calcium carbonate mineral suppression in some areas.
The September 2011 Arctic sea ice extent was the second lowest of the past 30 years. The five lowest September ice extents having occurred in the past five years, suggesting that a shift to a new sea ice state continues. The amount of older, thicker multiyear ice continues to decrease and both the Northern Sea Route and the Northwest Passage were ice-free in September.
Along with a 20 percent increase in phytoplankton production between 1998 and 2009, changes in Arctic Ocean bottom communities include shifts in composition, geographical ranges, and biomass. While polar bears and walrus are experiencing negative impacts due to loss of habitat, whales now have greater access to the Northwest Passage and other northern feeding areas.
Vegetation productivity ranged from a 26 percent increase adjacent to the Beaufort Sea to a small decline in several areas. On the North Slope of Alaska, immediately south of the Beaufort Sea, new record high temperatures at 20 m depth were recorded at all permafrost observatories, where measurements began in the late 1970s. River discharge into the Arctic Ocean during 2010 was close to the long-term mean. Despite changes in tundra biomass, migratory barren-ground caribou appear to be within known ranges of natural variation.
In 2011 there was continued widespread warming in the Arctic, where deviations from historical air temperatures are amplified by a factor of two or more relative to lower latitudes. This phenomenon, called Arctic amplification, is primarily a consequence of increased summer sea ice loss and northward transport of heat by the atmosphere and ocean.
December 2010 to January 2011, and summer 2011, repeated the shift in wind patterns observed in December 2009 and February 2010 that resulted in relatively warm Arctic temperatures and severe cold weather in eastern North America, northern Europe and eastern Asia.
Related to these shifts, the western slope of the Greenland ice sheet in particular experienced an increase in surface melting in summer 2011, amplified by albedo feedback and below-normal summer snowfall. Satellite gravity measurements show that the mass loss from the entire Greenland ice sheet during 2010-2011 was the largest annual loss in the satellite record of 2002-present. Lake ice cover duration, largely influenced by air temperature changes, was shorter by as much as 4-5 weeks in 2010-2011 compared to the 1997-2010 average in the eastern Canadian Arctic.