Abstract
Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability.
Highlights
In this paper, we build on previous investigations of Arctic Ocean wind-driven circulation regimes [1,2,3,4,5,6] and2015 The Authors
The Arctic Ocean Oscillation (AOO) index was used in several studies to explain decadal-scale regime shifts in northwest Atlantic shelf ecosystems [61] and understand climatic regulations of growth rates of bivalve shells around Svalbard and in the northwestern Barents
Timeseries of the AOO index from 1948 to 1996 indicate that anticyclonic circulation regime (ACCR) and circulation regime (CCR) alternate at approximately 5- to 7-year intervals with a period of quasi-oscillation of about 10–15 years
Summary
We build on previous investigations of Arctic Ocean wind-driven circulation regimes [1,2,3,4,5,6] and. We apply a 30-year running mean to all of the annual data (black lines in figure 1) to examine general trends in these parameters with the understanding that ‘climate’ is defined as weather averaged over a 30-year period (thick black lines in figure 1) following World Meteorological Organization and IPCC [17] recommendations This averaging provides information on climate changes from approximately 1963 to 1998, and demonstrates that the Arctic climatological annual values of: (a) sea ice extent reduced by about 14%, (b) air temperature increased by 10% (from −12.55◦C in 1963 to −11.30◦C in 1998), (c) SLP reduced by approximately 0.7 hPa; (d) sea level rose by approximately 0.06 m; (e) geostrophic wind speed over the Arctic Ocean increased by about 15%; (f) Eurasian river runoff increased by 14%; (g) freshwater flux from Greenland has increased rapidly since the 1980s with acceleration after 1997 (present values are around 60% of the magnitude of Eurasian river discharge); and (h) areal ice flux via Fram Strait increased by 15% which must have had a significant influence on the total ice volume in the Arctic Ocean and on the minimum of ice extent in September [18]. We use this index to identify and explain mechanisms regulating changes in Arctic circulation regimes and environmental
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