An Empirical Eigenfunction Analysis of Sea Surface Temperatures in the Western North Atlantic

The empirical orthogonal function decomposition is used to analyze time records of AVHRR sea surfacetemperature observations of the western North Atlantic from 32.9° to 43.6°N, 62.7° to 76.3°W. A manuallydeclouded dataset covering the spring of 1985 is analyzed. The majority (80%) of the variance about the meanis accounted for by an empirical eigenfunction, which is identified with seasonal warming. This eigenfunctionshows that the shelf water, excluding Georges Bank, warms the most rapidly; the surface water of the Gulf ofMaine 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°N than like Sargasso Sea waterimmediately to its south (∼35°N). The second EOF is found to be a small correction to the general warmingrate described by the first EOF. The third and fourth EOFs are determined primarily by meander propagation.Observations with partial cloud cover from the period 1985 to 1991 are also analyzed. Again, the dominanteffect is identified as seasonal warming.