Dominant modes of variability of the sea surface height from altimetry data in the North Atlantic Subtropical gyre

• Main Author: Alba Rivas, Isabel Maria
• Other Authors: Hernández Guerra, Alonso, Laiz Alonso, Irene, Departamento de Física, BU-BAS, Máster Universitario en Oceanografía por la Universidad de Cádiz, la Universidad de Las Palmas de Gran Canaria y la Universidad de Vigo
• Format: Master Thesis
• Language: English
• Published: 2016
• Subjects: 251007 Oceanografía física; Western Basin; North Atlantic
• Online Access: http://hdl.handle.net/10553/91853

A temporal Empirical Orthogonal Function (EOF) analysis has been performed on monthly maximum sea surface height (SSH) satellite data over twenty-two years (January 1993-December 2014) to examine the SSH patterns of variability of the North Atlantic Subtropical Gyre (NASG). Data was downloaded from the Archiving, Validation, and Interpretation of Satellite Oceanographic data (AVISO) remote sensing service (http://www.aviso.oceanobs.com/). EOFs separate the gridded data into distinct orthogonal modes which concentrate the variance into a set of orthogonal spatial maps and time series. The EOF method allows us to observe where and when the sea level variations occur in each mode. The subtropical gyre in the North Atlantic includes a recirculation regime toward the equator in the eastern basin and an intense transport in the western basin. EOF mode 1 represents 21.81% of the total SSH variance and suggests the steric contribution as the main forcing agent. EOF mode 2 accounts for 4.33 % of the total SSH variance, being associated with the north-south shifts of the Gulf Stream (GS). These have been previously reported to be highly correlated with changes in the SST. In this sense, during the months of mode 2 positive temporal amplitude the European climate was warmer than average. EOF mode 3 explains 2.62 % of the total SSH variance. This mode is related to the formation of warm anticyclonic and cold cyclonic core rings that are generated when meanders of the GS pinch off to the north and south, respectively.