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Thursday, August 14, 2008

The Barents and Bering Seas


It seems that each time I see an SST anomaly map there’s a hot spot north of Scandinavia in the Barents Sea. Refer to Figure 1.

Figure 1

Figure 2 illustrates the Barents Sea SST anomalies from January 1854 to May 2008, smoothed with an 85-month filter. With the possible exception of ENSO, the amplitude and frequency of the SST modulations are greater than any other SST data set I’ve downloaded and graphed so far, especially with what is essentially a 7-year filter. Is the decrease in amplitude before 1930 a function of the smoothing they apply in periods of reduced samples? Or does the increase in amplitude after 1930 result from a reduction in Arctic sea ice?
Figure 2

Figures 3 and 4 show a decrease in summer, spring, and annual Arctic ice extent since the 1950s. For the winter and autumn sea ice extent, the declines began in the 1970s and 80s. (For those concerned about the “hockey stick” appearance of these graphs, sea ice extent is limited my North Atlantic and North Pacific Ocean currents. These graphs do not illustrate ice thickness.) Assuming that some of the sea ice loss was in and around the Barents Sea, would less sea ice there have allowed larger variations in SSTs?
Figure 3

Figure 4

Is this confirmed by the fact that in recent years, the Arctic Oscillation (AO) appears to have had more of an impact? Refer to Figures 5 and 6. Like the Barents Sea SST anomalies, the AO has changed its amplitude after 1950 as well. And it appears as though, as time progresses, Barents Sea SST responds more to a change in the AO. Is this also a function of continued sea ice loss, or did other influences, such as ENSO and the AMO, cause the difference? (I will not be comparing ENSO and AMO in this post.)
Figure 5

Figure 6


On the Pacific Ocean side of the Bering Strait lies the Bering Sea. Figure 7 illustrates its SST anomalies smoothed with an 85-month filter. The amplitude of the oscillation is remarkable.
Figure 7

As shown in Figure 8, the Bering Sea SST anomalies follow the general trends of the North Pacific.
Figure 8

But they also contain a varying portion of ENSO. Refer to Figure 9.
Figure 9


AMO Data (1899 to 2002)

AMO (1950 to 2007)


Data is Smith and Reynolds Extended Reconstructed SST (ERSST.v2) available through the NOAA National Operational Model Archive & Distribution System (NOMADS).

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