**2.3 Seasonal cycles and inter- and intra-annual anomalies**

The SLA and CHL variability in the Mediterranean are dominated by the seasonal cycle (Larnicol et al., 2002; Bosc et al., 2004). As a first step, it is necessary to remove these seasonal variations because otherwise they would dominate the resultant correlations. In our case, we calculate the seasonal cycles of SLA and CHL by averaging the value for each grid point and each 8-day window. We then subtract the seasonal cycles (8-day mean values) to the original time series for each grid point to create anomalies. Finally, we apply a low- and high-pass Lanczos filter with a cut-off period of 1 year at each grid point to compute the inter- and intraannual anomalies, respectively, of SLA and CHL.
