ABSTRACT

The Arctic is changing rapidly. Onset of seasonal ice melt is occurring earlier in the year with a later date of fall freeze up. There has been a dramatic reduction in the lateral extent, thickness and age of the sea ice cover. Significant freshening of surface waters has been observed along with warming in several subsurface layers. Additional ocean heat contributes to additional sea ice melting. All of these changes have consequences for the polar ecosystem, earth's climate state and the resilience of near-shore native communities, as well as impact on human use of the high northern latitudes including commercial shipping, natural resource extraction, ecotourism and the accompanying search, rescue and defense activities. Historically, the ice-covered Arctic Ocean has been poorly observed, particularly in winter. The Ice-Tethered Profiler instrument (ITP), developed at the Woods Hole Oceanographic Institution in 2003-4, is designed to sample the upper Arctic Ocean water properties and sea ice motion in all seasons and transmit those data to shore-side users in real time. The system consists of a surface buoy typically deployed on an ice floe that supports a wire rope tether extending through the ice down to around 800 m depth, and an underwater vehicle that repeatedly crawls up and down the tether carrying sensors that sample sea water properties such as temperature and salinity. To date, approximately 100 ITP systems have been deployed in the Arctic (each operating for 1-3 years) that have collectively returned more than 70,000 observations of Arctic Ocean water properties as well as nearly 150 cumulative years of ice drift data, all contributing to the National Science Foundation's Arctic Observing Network program. These data have been used by researchers and students (so far resulting in approximately 150 published peer-reviewed papers that have directly utilized ITP data, cited research based on ITP observations or otherwise referenced the ITP program) as well as operational agencies the world over. The present research project will continue this activity for a 5-year period as sustained observations are considered vital to documenting and understanding the rapid changes now underway in the Arctic and predicting its future evolution. A three-pronged effort is planned that consists of 1) annual deployment of conventional ITPs, 2) development, testing and then operational deployments of a new instrument, the Tethered Ocean Profiler (TOP) that focuses on the upper 100 200 m of the water column, and 3) scientific analysis of the resulting ITP and TOP data. Initial focus of the latter will be the Arctic surface waters and their interaction with the sea ice. As in the past, data from these autonomous instruments will be publicly distributed via the project website, the Global Telecommunications System network, the Arctic Data Center and the National Center for Environmental Information. Beyond science and engineering, the new project will enhance the ITP website and develop a display for the WHOI Exhibition Center to provide the public with a broader understanding of the research and the exciting engineering now underway, along with the reasons to gather Arctic information during this time of dramatic change.

Technically, the new award will support continuation of the WHOI Ice-Tethered Profiler project with similar scope and activity as in recent years. Four standard ITP systems will be built and fielded in each of the first 4 years of the project with real time data recovery, automated processing and distribution. The real-time data from each ITP system will consist of daily (or more frequent) vertical profiles of ocean temperature and salinity at 2-m resolution (as well as the raw data) and hourly or better buoy position fixes from which ice velocity may be derived. Also, as in the past, the recovered data will be edited, calibrated and gridded, with these science-quality products being made publicly available as soon as they are completed. The new Tethered Ocean Profiler development activity will contribute 2 operational TOP systems annually. TOP data handling and distribution will parallel the ITP protocol. Deployments of ITP and TOP buoys will be decided annually in light of available expeditions with the goal (in collaboration with other buoy programs) of sustaining broad spatial coverage of the deep Arctic. Beyond continuing the present data handling, the new project will create and maintain a data base of individual ITP profiles archived by position and time, and develop and support a utilities toolbox to facilitate exploration and analysis of these observations by students/postdocs, fellow scientists, and computer-savvy members of the general public. The envisioned data base will hold individual profile data in netCDF format together with functions written in both Matlab and Python to extract and present data subsets to the user as specified. The archive will be accessible from the ITP program website as well as offered to the national data centers for archival. The initial science topic that will be investigated will focus on the Arctic Ocean surface mixed layer, using a combined dataset from ITPs and manned stations to document mixed layer thickness (using a variety of criteria), temperature and salinity in Arctic geographic subdomains versus time. In turn, these characteristics (and any trends with time) will be assessed relative to surface forcing (air-sea exchange of heat and momentum, sea ice growth and melt) through direct correlation and simple models. Focus will be the period from 2000 to present. Analysis of these new observations by the project Principal Investigators and others will contribute to a better understanding of the extreme changes taking place in the Arctic Ocean and their impacts on earth's climate, the polar ecosystem and human activities in the far north.

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.

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