Transport and Modification of Near-Surface and Intermediate Waters by the Gulf Stream along the US East Coast

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The Gulf Stream is a major part of the global climate system transporting warm waters from the tropics toward mid-latitudes. Despite decades of study, understanding of the quantity and types of water carried by the Gulf Stream as it flows along the US East Coast remains incomplete, in part due to historically sparse subsurface data. Recent observations from autonomous underwater gliders as well as long-term observations from other platforms such as buoys, will be used to examine Gulf Stream transport along the entire US East Coast. The research will examine how the Gulf Stream varies along its flow path, identify changes in its water characteristics, and evaluate future needs for observing this important ocean current. The results of the analysis should also be valuable for comparing with numerical models of the ocean circulation. This project will support a Ph.D. student who will be actively involved in all aspects of the project, including data processing, analysis, and publication of results. Results will be incorporated in educational efforts for the MIT-WHOI Joint Program and summer undergraduate programs such as the WHOI Summer Student Fellow program and the Woods Hole Partnership Education Program. The PI and student will continue to participate in media and public events that showcase the research.This work relies heavily on an unprecedented set of over 150 high-resolution glider-based transects across the Gulf Stream that have been collected over the past several years. Building on previous work with subsets of the glider observations, the analyses will make use of the full, multi-year set of observations, complemented by measurements from other platforms, to comprehensively examine spatial variability in the time-mean volume and temperature transport of the Gulf Stream along the US East Coast. No such examination of a western boundary current has previously been possible from observations, so these results will serve as key benchmarks. With over 20,000 hydrographic profiles from gliders alone, the available data set also offers a unique opportunity to examine the distribution and modification of subsurface water masses along the continental margin, which will lead to better understanding of the role of those water masses in the climate system. Products of the analyses, such as time-mean transports as a function of along-stream distance, can be used for the validation of numerical models and for guiding boundary current observational efforts globally. Analyses carried out as part of this project will guide the development of comprehensive and fit-for-purpose observing systems for the Gulf Stream and other western boundary currents and will be disseminated to the communities engaged in the planning and developing a global boundary current observing network.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.