Friday, December 2, 2011

Persistent warming has caused dramatic changes in the Arctic Ocean and the ecosystem it supports

NOAA: The Arctic Report Card ... considers a wide range of environmental observations throughout the Arctic, and is updated annually. A major conclusion of the 2011 Report is that there are now a sufficient number of years of data to indicate a shift in the Arctic Ocean system since 2006. This shifted is characterized by the persistent decline in the thickness and summer extent of the sea ice cover, and a warmer, fresher upper ocean. As a result of increased open water area, biological productivity at the base of the marine food chain has increased and sea ice-dependent marine mammals continue to lose habitat. ....The 2011 Report Card shows that record-setting changes are occurring throughout the Arctic environmental system. Given the projection of continued global warming, it is very likely that major Arctic changes will continue in years to come, with increasing climatic, biological and social impacts.

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.

Observations of the Arctic marine ecosystems provide a glimpse of what can only be described as profound and continuing changes. For example, primary production by phytoplankton in the Arctic Ocean increased ~20% between 1998 and 2009, mainly as a result of increasing open water extent and duration of the open water season. 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....

NOAA photo from one of its ships

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