Sea Level Variations in the North Atlantic

Variations in mean sea level are considered as an indicator for global as well as regional environmental change. The spatial distribution of sea level variations can be observed by satellite altimeters with a high precision. The sea level variations in the North Atlantic are studied in this paper by using eight years of sea level data derived from the TOPEX/Poseidon altimeter mission. The mean sea level change for this time period shows regionally remarkable differences and does agree only partly with the mean sea surface temperature change. The annual oscillation has a dominant contribution to the total sea level variability, but within the central Gulf Stream, eddy activity contributes even more strongly to the overall variability. After removing the annual and semi-annual oscillation and an alias period of the altimeter with the M2 tide, the residuals are smoothed by a moving 90 day mean filter and examined by Principal Component Analysis. A low frequency variation with an approximate period of 6-7 years as well as an anomalous sea level change at the end of 1995 have been detected. The analysis of sea surface temperature data also shows a similar long periodic and anomalous behaviour.