Inverse solution for pentadal variability in the North Atlantic
Seven pentads (1960-1964 to 1990-1994) of the North Atlantic climatology by Lozier et al. (1995) are analyzed with the help of an inverse finite-element ocean circulation model. The model solves for temperature and salinity fields that are close to observations and respect stationary dynamical balances, and produces estimates of the circulation. The first two EOF's of transport streamfunction variability (39% and 26% of the explained variance) are found to have a high correlation with the North Atlantic Oscillation (NAO) index averaged over pentads and lagged negatively by three years (first EOF) and between zero and one years (second EOF). The spatial pattern of the first EOF corresponds to an anticyclonic anomaly (in the positive NAO phase) located between 20 and 45°N with the largest variability between 30 and 45°N, and much weaker cyclonic anomalies in the subpolar gyre. The second EOF shows a sharp anticyclonic anomaly along the Gulf Stream and its extension and a wide cyclonic cell over most of subtropical gyre. The anomaly in the meridional overturning streamfunction is characterized by a single positive cell which poorly correlates with the NAO index. Copyright 2008 by the American Geophysical Union.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > German community ocean model