Tropical Teleconnection to the Seesaw in Winter Temperatures between Greenland and Northern Europe
INSTAAR Occasional Paper 28
1979, 110 pp. (cost: $5)
A prominent feature of inter-annual variability in middle and high latitudes is the so-called “Greenland Seesaw,” the well-known tendency for winter temperatures to be low over northern Europe when they are high over Greenland (GA), and vice versa (GB). Well-defined mean pressure anomalies over the North Pacific, America, North Atlantic, and Europe are associated with these temperature patterns. In this study tropical teleconnections associated with the seesaw are discussed. It has been found that the strength of mean sea-level westerlies in the central North Atlantic Ocean during seesaw winters is highly correlated with that of the northeast and southeast trades in the Atlantic, with the trades being stronger (weaker) during GB (GA) winters. Similar associations exist with the trade winds in the North Pacific. There is a statistically significant correlation between the strength of the northeast and southeast trades in the Atlantic during the seesaw winters, but not in other winters. The position of the subtropical jet at 300 mb in the Northern Hemisphere appears to move north (south) in the GB (GA) winters with the exception of a shift in the opposite sense over Africa. A southward (northward) shift in the position of the ITCZ in Africa, as defined by the belt of heaviest precipitation, is seen during the winters when Greenland temperatures are well below (above) those in northern Europe.
Relative sea levels taken across the Gulf Stream indicate that geostrophic velocity of the current decreases (increases) in the GB (GA) winters. Significantly lower (higher) sea surface temperatures exist across the tropical North Atlantic, North Pacific, and Indian Oceans during GB (GA) winters. Atmospheric-related patterns appear strongly only during seesaw winters, although small magnitude pressure anomaly patterns of the type seen during seesaw winters are present in autumns preceding those seesaw winters. Trade wind anomalies seem to persist through all seasons prior to and following seesaw winters south of 20°N, with the northern fringes of the trade wind belt reacting mainly during seesaw winters. In contrast, ocean-related features associated with the seesaw occur at all latitudes in summers and autumns preceding, and springs following, seesaw winters.PDF (8 MB)