Does Pacific Variability Influence the Northwest Atlantic Shelf Temperature?

Abstract

The relationship between North Pacific variability and sea surface temperature (SST) of the Northwest Atlantic continental shelf is examined over interannual time scale in 1982–2014. Statistically significant negative correlations exist between Pacific Decadal Oscillation (PDO) index and SST in the Gulf of Maine (GoM) in spring and summer. Cross-correlation analysis further suggests significant negative lead-lag correlations, with the spring PDO leading the GoM SST by 0–3 months while the summer PDO lags by 1–3 months. These correlations are dominated by the interannual component of the PDO. Statistical relationships are placed in context by further investigating the physical processes controlling the upper ocean mixed layer temperature budget in the GoM. The results reveal contrasting roles between the atmosphere and the ocean in spring and summer, respectively. Local atmospheric forcings, in particular the radiative air-sea fluxes, are the dominant driver for the interannual variability of springtime SST over the Northwest Atlantic shelf. In contrast, oceanic terms are important in controlling the interannual variability of summertime SST. As a result, reconstructed SST using atmospheric forcings successfully reproduces the statistical relationship with PDO in spring, but not in summer. Furthermore, it is shown that the SST anomalies in the central and eastern North Pacific play a key role in these relationships.