Winter–to–winter recurrence of the tripole pattern of the sea surface temperature anomalies in the North Atlantic ocean and its interaction with the NAO

The evolution of temperature anomalies in the North Atlantic (15° N – 70° N 80° W – 8° W) is analyzed. The results are based on the decomposition of the GECCO3 (1948–2018), ORA-S5 (1979–2018) and SODA3.12.2 (1980–2017) oceanic reanalyses data using extended empirical orthogonal functions. The leading pattern during the entire 16–month period (January–April of the next year) in the 0–300 m layer is a tripole, with temperature anomalies of the same sign in the tropical and high latitudes and the opposite sign in the subtropical gyre. The evolution of the leading pattern shows the deepening of temperature anomalies in winter, their preservation with a maximum in the summer seasonal thermocline (~ 65–90 m) and partial weakening in the subsurface layer in summer, and their emergence on the ocean surface in the subsequent autumn–winter season. The temporal evolution of the reemergence of the tripole pattern of the sea surface temperature anomalies (SSTAs), explained by the first extended principal component (EPC1), is in good agreement with the variability of the main atmospheric circulation mode over the North Atlantic on interannual scales – the North Atlantic Oscillation (NAO), especially after 1979. The recurrence of SSTAs is found in all three centers of action of the tripole pattern. In the subpolar and midlatitude centers of action, the reemerging signal maximum appears in the subsurface layer in late summer and early autumn and in the subsequent autumn–winter season ~ 2/3 of this signal occurs at the surface. In the subtropical center of action, the reemerging signal maximum appears in the mixed layer in winter–spring and in the subsequent autumn–winter season ~ 1/2 of this signal occurs at the surface. For the subtropical center of action, a moderate correlation was found between the regional EPC1 and the mixed layer depth and the wind stress modulus over a 16–month period. Recurrence of temperature anomalies in all centers of action of the tripole structure from January 2014 to April 2015 associated with the repeated positive NAO phase is shown.