Secretary of the Navy Professor of Oceanography
Abstract
Measurements by P. Wadhams from a British submarine have indicated a more rapid thinning of the Arctic ice cover than previous estimates, leading possibly to an ice-free summer by 2016 (The Economist estimated by the end of the century, Special Report on the Arctic in the 16 June 2012 issue). Disappearance of the ice cover and the attendant drop in polar albedo has first order consequences that should be monitored during the transition decade. We will study various schemes of polar tomography, possibly involving a polar source and peripheral receivers, with the acoustic sources doing double duty for navigating gliders and AUV s. The ongoing Philippine Sea experiment has led to developments that will be useful in the more difficult polar environment. An attractive feature is the continued collaboration with the Nansen Institute in Bergen. I have worked on the acoustic properties of the ocean wedge between the sea floor and a floating ice sheet, stretching from the continental grounding line to the ice front (for several hundred kilometers in the Ross Sea). These are the only ocean volumes not yet visited by men. Work is being done to lower instruments through holes drilled through the ice sheets, and by launching AUV s from the ice edge into the interior cavern. Navigation is difficult; GPS is not available under the ice cover. I have been working on a scheme for augmenting these efforts with an application of ocean acoustic tomography to the ocean caverns. Acoustic transponder arrays would be deployed just seaward of the ice edge radiating into the cavern. It is a known (but not well known) property of wedge-like caverns that acoustic rays are refracted away from the wedge apex back to the wedge opening (just as they are refracted away from the deep waters of the polar ocean back towards the surface). The broad Ross Sea ice shelf has the ideal geometry for such an experiment.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 2012
- Accession Number
- ADA574984
Entities
People
- Walter Munk
Organizations
- University of California Regents