| Summary: | Recent studies indicate that the Arctic may be both a sensitive indicator and an active agent of climate variability and change. While progress has been made in building understanding the Arctic's coupled atmosphere-ice-ocean system, full comprehension of its evolution has been hindered by a lack of data, particularly of the ocean below sea ice. This observational gap represents a critical shortcoming of the 'global' ocean observing system. Addressing this gap, a new instrument, the 'Ice-Tethered Profiler' (ITP) was conceived to repeatedly sample the properties of the ice-covered Arctic Ocean at high vertical and temporal resolution over time periods of up to three years. Analogous to the international Argo float program that is employing autonomous profiling floats to return real-time seawater property data from the temperate and tropical oceans, under funding provided from the U.S. National Science Foundation's Arctic Observing Network (AON) program, we worked together with fellow North American, European and Asian investigators to maintain an array of ITPs and other similar instruments throughout the ice-covered Arctic. We hope that the analysis of data from these instruments will lead to better appreciation of the Arctic Ocean's response to, and role in, global climate change. The ITP system consists of a small surface capsule that sits atop an ice floe and supports a plastic-jacketed wire rope tether that extends through the ice and down into the ocean, terminated with a weight (designed to keep the wire vertical). A cylindrical underwater instrument (in shape and size much like an Argo float) mounts on this tether and cycles vertically along it, carrying oceanographic sensors through the water column. The nominal sampling schedule for the ITPs sees two one-way vertical profiles collected daily between approximately 7 and 750 m depth. (The profiling schedule of the ITP is very flexible and may be varied based on time of year or upon command from shore during a deployment.) Water property data are telemetered from the ITP to shore via satellite, automatically subjected to preliminary processing, and made available in near-real-time from our project web site: www.whoi.edu/itp and over the Global Telecommunication System (GTS). At a later point in time once the data are edited, calibrated and processed, the final version of the data are made available, again from our web site and also from national archives. The goal of the present grant was to build and deploy 6 ITP systems per year in the Arctic (a total of 24 systems - locations dictated by available deployment platforms), recover and make available in near-real-time the telemetered data, to edit, calibrate and grid the observations, and to submit these final data to national centers for archival and general distribution. Data found here are the results of collaborative projects funded by multiple NSF awards and other sources. The project funded by NSF award 0631951 works in conjunction with multiple national and international International Polar Year (IPY) projects to include: the Russian Central Arctic Ocean Complex Study (CAOCS), the Canadian Ocean Monitoring Experiment (COME) and the Canadian Arctic Margin Experiment (CAME) projects; the European Union Developing Arctic Modeling and Observing Capabilities of Long-term Environmental Studies (DAMOCLES) project; uses the facilities at the North Pole Environmental Observatory (NPEO), and is a part of the International Arctic Buoy Program (IABP). The research expands ongoing efforts to develop, test and field a set of Woods Hole Oceanographic Institution (WHOI) Ice-Tethered Profilers (ITPs): autonomous instruments that return high-vertical-resolution measurements of upper ~800 m ocean temperature, salinity, and dissolved oxygen beneath sea ice during all seasons at better than daily temporal resolution over a projected three year lifetime. The WHOI ITP repeatedly samples the upper ocean water properties beneath the permanently ice-covered Arctic for up to a 3-year period (expected lifetime of an average multi-year ice floe) and telemeter those data to shore in near-real time. Data returned from these instruments supports studies of ocean processes, facilitates numerical model initialization and validation, and stimulates general interest in Arctic science issues. Research and understanding that builds on these observations will lead to better appreciation of the Arctic's role in the earth's climate system. NSF award 0519899 continues development and deployment in the Arctic Ocean of new ITP buoys that are an automated profiling conductivity, temperature, and depth (CTD) instrument capable of returning daily high-vertical-resolution measurements of the upper 800 m ocean underneath sea-ice during all seasons over an approximately 3-year life time. The project is collaborative on an international scale and the plan is to eventually extend the scope of this work to involve up to 17 ITPs. Ideally, they would be deployed in conjunction with a suite of other automated instruments. This new source of high-vertical-resolution CTD data from all seasons and from multiple years will increase knowledge of the state and variability of the Arctic Ocean by an unprecedented amount. The publicly available data from the proposed ITPs will provide the basis for both process studies and model validation/assimilation research, work that will ultimately lead to better understanding of the Arctic Ocean's role in global climate change. In addition, the project will, in consultation with the polar research community, use this information to develop a plan for establishing and maintaining ITPs within a full array of Ice-Based Observatories (IBO)s contributing to a sustained Arctic Ocean observing system, as was discussed and recommended by participants of the international workshop Arctic Observing Based on Ice-Tethered Platforms.
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