Ocean Gateways and Choke Points: Progress and Challenges

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The global ocean circulation affects our climate in myriad ways and plays a central role in mediating the planet's response to climate change. A key aspect of this circulation is the importance of specific localized gateways (or choke points) which control the strength, structure and basin connectivity of the circulation. Examples of such gateways are the Indonesian Throughflow, the Agulhas retroflection, and outflows from the Ross and Weddell Seas to name a few. These systems often consist of multiple strong jets that vary over a range of space and time scales and so remain extremely challenging to observe, model and predict. Professor Arnold Gordon's singular research career, spanning over 50 years, has transformed our understanding of ocean gateways and their role in climate, biogeochemistry and ecosystems. Given the rapid development of new observing technologies, and the emergence of a new class of high-resolution global ocean models that are critical for understanding the accelerating rate of climate change, the time is ripe to assess the state of knowledge in the field of ocean gateways and define key challenges for future research. This two-day workshop to bring together distinguished and early-career researchers from across the world, including observationalists, theoreticians and modellers to address these topics. The workshop, to be held at Scripps Institution of Oceanography in San Diego in February 2020, will coincide with Arnold Gordon's 80th birthday and occur in the week prior to the 2020 Ocean Science meeting to minimize time and money spent on travel. This grant will support the participation of 15 early career researchers, who will gain exposure to the opportunities and challenges in the field of ocean gateways. Extensive web-based outreach will be used to ensure a broad, diverse pool of participants in addition to those present at the symposium. Results will be shared via an article in EOS and incorporated in the various national and international science agendas. Contemporary global ocean observing programs like Argo do not sample ocean gateways with sufficient spatial and temporal detail to uncover their physics. Monitoring these gateways requires specialized, dedicated observational campaigns and sustained moored observatories. Many fundamental questions about the pathways, structure and variability of these gateways on climate time scales remain unanswered. It is crucial that the knowledge garnered from the past of how to successfully collect these observations is passed on to the next generation of oceanographers, to maintain the impetus from earlier studies and to advance new observing technology. Numerical models have traditionally struggled to realistically represent ocean gateways, but advances in computational power and numerical techniques have recently led to major improvements. Bringing together the observational and modeling communities at a single workshop will catalyze rapid progress and provide a unique forum for identifying knowledge gaps in the system so as to build a better integrated strategy for a gateway observing system of the future.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.