Understanding dramatic warming and altered fisheries on the US Continental Shelf through observations and multi-scale models

Statement of the Problem: The warming trend observed in the NEUS Continental Shelf Large Marine Ecosystem during recent decades is one of the strongest in the global ocean and has impacted regional fisheries. This warming pattern was accompanied by significant changes in the distribution, productivity, and trophic interactions of many commercially important species. Yet, the oceanographic drivers of these temperature changes have not been identified. The proposed work aims to advance our understanding of these physical processes and their connection with fisheries, ultimately leading to better predictions and preparations for future change.
Methods and Summary of Work to be Completed: Our guiding hypothesis is that the increased presence of the Gulf Stream at the Tail of the Grand Banks (TGB) restricts the southwestward transport of the Labrador Current along the NEUS slope, thereby increasing the fraction of subtropical waters on the continental shelf. Because these subtropical waters substantially warm and deoxygenate the shelf, such circulation changes would strongly impact the marine ecosystem. If this hypothesis is correct, then knowing the conditions at the TGB could translate to substantial predictability for temperature-linked fisheries impacts, given that anomalies likely propagate along the slope at relatively slow advective time scales. Despite substantial preliminary evidence, a robust test of the hypothesized connection between circulation at the TGB and anomalous properties on the NEUS slope and shelf has been lacking. Thus, our proposed work will characterize the fluctuations of the Gulf Stream position relative to the TGB and the connection with shelf property and fisheries fluctuations through the following 3 objectives:
1. Reconstruct and compare historical variability in water masses, ecosystem characteristics, and fisheries at the TGB and along the NEUS slope and shelf through the coordinated analysis of satellite, hydrographic, isotopic, and fisheries data.
2. Use the observational record, alongside a numerical model, to expose the mechanisms that lead to co-variability between TGB and slope anomalies, as well as quantify the alongslope propagation time scales for these anomalies. This goal is timely given that models are only recently capable of faithfully simulating dynamics in this complex region.
3. Run a regional ocean model to explore how anomalies propagating along the slope are exchanged across the shelf. This step is necessary to understand when and how alongslope anomalies come to influence the shelf, potentially providing lead time to anticipate changes in the shelf physical environment that are crucial to ecosystems and fisheries.
Relevance to the competition: The proposed work directly responds to CVP’s priority to combine observational data analysis with ocean model process studies to better quantify and understand physical changes on the NEUS continental shelf. It also evaluates the impacts of these physical changes on the distribution and migration phenology of the economically important fish and invertebrate species that are part of the Large Marine Ecosystem.