Water temperatures over the inner-half of continental shelves are typically cold in winter and warm in summer, consistent with the annual cycle of surface heat fluxes from the atmosphere. However, preliminary analysis of historical data and synthesis of previous regional studies indicate there are large regional differences in the amplitude of the annual cycle. For example, the average temperature difference between August and February is less than 5 C along much of the U.S. West Coast, but is between 15 and 20 C along the East Coast. While there are also large regional differences in the annual cycle of surface heat, the surface heat fluxes do not generally account for the observed amplitude of the annual cycle or the regional differences. Both these results and previous studies indicate that advective heat fluxes are important over the inner shelf and that they tend to buffer the response to surface heat fluxes and lead to important biological and societal implications. Thermal stresses play a key role in both organism function and community ecology, and small increases in inner shelf temperatures or alterations in the processes that control them can lead to dramatic shifts in community structure and/or mass mortality events. Thus, a clear understanding of how buffering by advection functions would allow some predictive capacity for the potential changes in both ecologically and commercially important coastal marine species in future climate scenarios. This research project aims to understand the processes controlling water temperature variations over the inner shelf on annual and interannual timescales. The project involves training of a graduate student.
This study will provide the first comprehensive look at the heat budget of the inner continental shelf, including its seasonal cycle and inter-annual variability. Available temperature and velocity data sets will be used to examine how the heat balance can be maintained by a number of possible sources of cooling including: across-shelf exchange due to depth-dependent upwelling, the along-shelf advection of an along-shelf temperature gradient, and the across-shelf exchange due to eddies. The results will be synthesized to determine the relative contributions of heat flux components and their associated processes for the different shelf regions of the continental US. The analysis will enable an assessment of the role of shelf environment (e.g. width) versus external forcing (e.g. surface heat flux, wind stress) in driving the regional temperature patterns observed. The results will yield new information about inner-shelf circulation, the role of advection in controlling or moderating inner-shelf heating, as well as give broader context to previous studies of across-shelf exchange in the coastal ocean.
