WHOI PO

The processes regulating heat flux in the Gulf of Maine (GOM) have receivedconsiderable attention from the research community due, at least in part, tothe rapid rates of warming observed over the last several decades.  While our understanding of these dynamics hasimproved significantly, a comprehensive long-term analysis that closes the heatbudget for the GOM has not been performed to my knowledge.  In this seminar, I will present the resultsfrom a 15-year simulation with a high-resolution (x ~ 1km) numerical circulation model forced on the oceanicboundaries by the output from a larger scale model that includes extension dataassimilation.  The simulations capture observedinter-annual variability with high skill and conserve heat, which assimilativemodels do not, allowing a closed heat budget analysis.  The model indicates that the GOM receives anexcess of surface heat flux (1.55 TW), much of which is exported advectively tooffshore waters (-1.42 TW).  Over the15-year period of these simulations, this imbalance resulted in long-termwarming (0.13 TW), consistent with observations.  To provide more insight into the physicaltransport mechanisms, the advective heat flux is decomposed into a barotropic,baroclinic and internal tide component, each of which exhibit variability atseasonal and inter-annual time scales.  Baroclinicprocesses export significant heat from the interior GOM (-2.4 TW) in a mannerconsistent with wind-driven Ekman transport, while the internal tide generatedon the inshore side of Georges Bank imports nearly 0.8 TW.  Barotropic processes result in a relativelyweak import (0.2 TW, on average), but exhibit significant inter-annualvariability, which is the dominant mechanism controlling whether the interiorwaters of the GOM warm or cool at inter-annual time scales.  Model results suggest that the key advectivepathway that controls heat content at inter-annual time scales is the exchangethrough Great South Channel and around the southwest corner of Georges Bank,particularly during late summer and early fall. Preliminary analysis suggests that this transport pathway is linked tothe strength of the along slope transport of cold water that originates in theLabrador Sea.