The Atlantic Meridional Overturning Circulation forcing the mean sea level in the Mediterranean Sea through the Gibraltar transport

Understanding the causes of the variability of the North Atlantic and Mediterranean overturning circulations, and the possible correlation between them is important to disentangle the processes which link the two ocean basins. In this study, we hypothesize that the Gibraltar inflow transport is the main driver of the basin-mean sea surface height variability in the Mediterranean Sea and that they are both anti-correlated to the Atlantic Meridional Overturning Circulation (AMOC) in the North Atlantic.

We analyze here the AMOC and the Mediterranean mean sea surface height (SSH) in an ensemble of eddy-permitting global ocean reanalyses and the Gibraltar inflow transport using an eddy-resolving Mediterranean Reanalysis over the period 1993-2019. In this contribution, firstly we extend the results obtained in past literature with observations (2004-2017 period) and confirm the anti-correlation between the Mediterranean mean sea level and the upper branch of the AMOC at 26.5°N over the 1993-2019 period. Secondly, for the first time, we examine the correlation of the different components of the AMOC and the Gibraltar inflow transport and find significant anti-correlations at interannual time scales.

We show that during years of weaker/stronger AMOC and higher/lower SSH in the Mediterranean Sea, a stronger/weaker Azores Current results in stronger/weaker Gibraltar inflow transport. We argue that the anticorrelation between AMOC and the mean sea level of the Mediterranean Sea is explained by the anticorrelation between AMOC and the Gibraltar inflow transport which in turn is changed by the wind driven Azores current strength.