Fig. 3

(a) Time series of the low-pass filtered (13 months) incoming velocity U_o (normal velocity component across the gray transect of Fig. 1) at the Sect. 33–34° N, 31° E averaged in the upper 1000 m of depth (black line); time series of the low-pass filtered (13 months) CE longitude center detected with the TOEddies algorithm (purple line); daily longitude values of the CE center detected with the TOEddies algorithm (gray dots); daily longitude center of the cyclonic eddy G2 (red crosses) and anticyclonic eddy G1 (blue crosses) detected with the TOEddies algorithm; CE longitude center calculated from in-situ glider data (green diamonds). (b) Time series of the low-pass filtered (13 months) spatially averaged current vorticity (green line) computed in the Northern Ionian Sea (blue box in Fig. 1, 37–39° N; 17–19.5° E); solid orange and blue arrows indicate the decreasing and the increasing of the NIG vorticity, respectively; cyclonic and anticyclonic phases of the NIG are highlighted by the pink and white shaded areas, respectively. (c) Time series of the low-pass filtered (13 months) CE longitude detected with the TOEddies algorithm (purple line); dashed orange and blue arrows correspond to the solid arrows of the upper panel, respectively (one dashed blue arrow is missing since it is not yet occurred).