An empirical eigenfunction analysis of sea surface temperatures in the North Atlantic

R.M. Everson, P. Cornillon, L. Sirovich and A. Webber

Abstract

The Empirical Orthogonal Function (EOF) decomposition is used to analyze time records of AVHRR sea surface temperature observations of the Western North Atlantic from 32.9 to 43.6 degrees N and from 62.7 to 76.3 degrees W. A manually declouded dataset covering the spring of 1985 is analyzed. The majority (80 percent) of the variance about the mean is accounted for by an empirical eigenfunction which is identified with seasonal warming. This eigenfunction shows that the shelf water, excluding Georges Bank, warms the most rapidly; the surface water of the Gulf of Maine warms a little less rapidly and the Gulf Stream and Sargasso Sea surface water warm the least rapidly. The SST of the Gulf Stream is also shown to behave more like that at 30 degrees N than like Sargasso Sea water immediately to its south (approximaltely 35 degrees N). The second EOF is found to be a small correction to the general warming rate described by the first EOF. The third and fourth EOF's are determined primarily by meander propagation. Observations with partial cloud cover from the period 1985 to 1991 are also analyzed. Again, the dominant effect is identified as seasonal warming.

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