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The Pacific Gateway to the Arctic – Quantifying and Understanding Bering Strait Oceanic Fluxes
Intellectual Merit: The Bering Strait, a narrow (~ 85 km wide), shallow (~ 50 m deep) strait at the northern end of the Pacific, is the only ocean gateway between the Pacific and the Arctic. Although the flow through the strait is small in volume (~ 0.8 Sv northward in the annual mean), due to its remarkable properties (high heat and freshwater content, low density, high nutrients) it has a startling strong influence, not only on the Chukchi Sea and the Arctic Ocean, but also on the North Atlantic overturning circulation and possibly world climate. Draining the Bering Sea shelf to the south, the Bering Strait throughflow is an integrated measure of Bering Sea change. The comparatively warm, fresh throughflow contributes ~ 1/3rd of the freshwater input and possibly ~ 1/5th of the oceanic heat input to the Arctic, and provides the most nutrient-rich waters entering the Arctic Ocean. Furthermore, the low density of these waters keeps them high in the Arctic water column, giving them a key role in upper ocean ecosystems and physical processes including ice-ocean interactions. At the time when dramatic change, especially the retreat of sea ice, s observed in the Bering and Chukchi seas and the Arctic, we have measured significant increases of Bering Strait fluxes of volume, freshwater and heat, the heat flux in 2004 being the maximum recorded in the last 15 years.
Yet, our understanding of what sets the properties and variability of the Bering Strait throughflow is still rudimentary. Indeed, our ability to measure these fluxes accurately has, in the past, been constrained by lack of data, both from the most nutrient-rich western half of the strait (which lies in Russian waters), and from the upper water column (due to potential ice-keel damage to instrumentation), where stratification and coastal boundary currents (especially the Alaskan Coastal Current in the eastern channel) contribute significantly to freshwater and heat fluxes.
To address these deficiencies at a time of dramatic system change, we propose (in collaboration with Russian, Canadian and Japanese colleagues), an observationally focused study of the entire Bering Strait region, consisting of a high resolution mooring array, deployed from 2007-2011, covering the two channels of the strait and one “climate” site to the north of the strait, supported by annual CTD surveys and mooring servicing, satellite data and theoretical and modeling results. The project is urgent since present year-round measurements in the strait (now constituting a 16-year climate time-series) end in summer 2007. Our science objectives are:
1) to measure the velocities and water properties of the Bering Strait throughflow;
2) to understand the physical processes influencing the properties of the Bering Strait throughflow, with
special focus on mechanisms driving change, and impacts on the Arctic Ocean;
3) to quantify oceanic fluxes of volume, freshwater, heat, nutrients and chlorophyll biomass through the
strait;
4) to design an optimum monitoring system for oceanic fluxes through the Bering Strait.
Our hypotheses are that Bering Strait throughflow properties are set by global and regional oceanic and atmospheric processes, which are vulnerable to climate change; and that understanding the physical processes and scalings in the strait are key to quantifying current conditions, assessing future change scenarios, and designing an efficient observational scheme for this oceanic gateway.
Relevance to IPY: The Bering Strait is recognized as a key ocean gateway by the Arctic Observing Network plans of SEARCH (Study of Environmental Arctic Change), the National Academies report, and international IPY projects. Our proposed work is the lead of an international (US-Russian-Canadian-Japanese) IPY project, built on our ICSU endorsed IPY proposal for the Bering Strait. The work is also a key element of the IPY projects COME (Canada Ocean Monitoring Experiment - studying linkages among the subarctic and arctic waters around Canada), “66N” (Ocean transports across 66ºN from satellite altimetry, numerical models and in situ observations), and iAOOS (international Arctic Ocean Observing System). Our approach includes a pulse of activity in the IPY years,a legacy of data and infrastructure, training the next generation of scientists, and outreach to the public.
Broader Impacts: We will provide an opportunity for the science community to incorporate other instrumentation into the Bering Strait moorings. We will create an electronic “Friends of the Bering Strait” science forum. A “one-stop” website will disseminate the (annually-updated) status of Bering Strait fluxes and Bering Strait data products for observational and modeling studies. Oceanography and marine science technology students will be trained by this proposal. We will bring the excitement of international polar research and global ocean circulation to K-12 and college students and the general public via a Washington and Alaskan teacher-at-sea program aimed at middle schools; classroom visits to schools and community colleges; and an established Polar Science Weekend at the Pacific Science Center (Seattle’s major science museum). Quantifying Bering Strait fluxes is a key component of the international ASOF (Arctic Subarctic Ocean Fluxes) project, NSF’s FWI (Freshwater Initiative) and CHAMP (Community-wide Hydrologic Analysis and Monitoring Program), and connects the BEST (Bering Ecosystem Study) program to the Arctic.
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