Drivers of Low-Frequency Variability of Ocean Heat Content on the U.S. North East Shelf

Abstract The drivers of low-frequency (i.e., interannual to multidecadal) variability and change in the ocean heat content (OHC) on the U.S. North East shelf (USNES) are investigated through heat budget analysis and Regional Ocean Modeling System experiments. Surface heat flux on the USNES has been responsible for warming since 1977, and it dominates the interannual-to-decadal OHC variability in the shallow shelf near the coast. In contrast, remote forcing from the open Atlantic has a weak impact on the warming trend due to contrasting effects from the northern and eastern parts of the Atlantic. Still, it plays a more significant role in interannual-to-decadal OHC variability in the deep shelf near the continental break. Both regional and remote forcings are important for the interannual-to-decadal variability of OHC integrated over the entire USNES. Regionally and remotely forced sea surface temperature (SST) anomalies alter surface heat flux over the USNES, inducing OHC variability. The remotely forced OHC anomalies result primarily from the advection of remotely forced temperature anomalies from the Scotian Shelf and along the shelf break by the currents driven by both regional and remote forcings. Furthermore, the interannual variability of shelfbreak jet significantly contributes to OHC advection through the northern boundary of the USNES. In contrast, the influence of the Gulf Stream on OHC advection across the USNES boundaries is relatively weak.