North Atlantic thermal persistence and coherent evolution

Abstract

North Atlantic thermal persistence and coherent evolution are examined. A region near Cape Cod and the Gulf of Maine is identified as the North Atlantic (NA)'s most thermally persistent, with a unique combination of high‐amplitude, long‐lasting sea surface temperature (SST) anomalies. A mechanism is advanced, whereby that region's surface ocean reflects deep upper ocean dynamics, with thermal evolution that tracks heat advection by the slowly evolving upper ocean. This is consistent with the subtropical gyre playing an active and central role in NA climate variability. The proposed interpretation is supported by broad, high lag correlations between the Bermuda potential vorticity time series (representing the subtropical gyre state) and surface anomalies. Using the Bermuda potential vorticity time series as a “dynamical filter”, successive lag correlation patterns reveal surface oscillations that are not apparent in the raw surface data.