Fig. 1: Western North Atlantic sea surface temperature anomalies (SSTA) for Feb. 16, 2021.
Discussion: Likely the warmest water surface temperatures for February east of New England on record are observed during past week or so (Fig. 1). A sea surface temperature of 55-60F due east of New England and due south of Nova Scotia is indicated which is in the 11-13F range above normal. Frequently waters in this zone cool to near or below normal due to the established cold winter chill flowing off the North America continent across this region or the cold Labrador Current flowing south toward the Gulf Stream.
The explanation is likely the combination of three factors. A persistent and apparently strengthening warm phase of the Atlantic Meridional Oceanic Current (AMOC), the warm surface water blocked by the North Atlantic Warm Hole (NAWH) which is southeast of Greenland and possibly a suppressed (cold) Labrador ocean current into this region (caused by the AMOC and NAWH regimes).
Regional strong warm (or cool) ocean anomalies modify climate. In this case, if a strong arctic air mass flows offshore an explosive storm will form in the vicinity of the warm waters. If a sustained east develops coastal areas are modified warmer, low atmospheric moisture (for storms) increases and the warmer waters which and their attendant sea level rise can more easily flood coastal areas.