| 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.
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