======================== Originally posted 2011-8-30 ============================= Freshwater Switchyard of the Arctic Ocean 2011 Expendable Current Profiles NSF Grants ARC-0633885 and OPP-0230427 Circulation in the Freshwater Switchyard of the Arctic Ocean and ARC-0909408 Sensitivity of Arctic Ocean Change to Background Mixing Switchyard 2011 XCP Drops Dropped at Switchyard 2011 CTD Station UW 3 XCP Drop 1 2011-04-30/1600 UTC 84deg 45.3min North 057deg 22.8min West Dropped at Switchyard 2011 CTD Station UW 4 XCP Drop 2 2011-05-01/1245 UTC 85deg 50.6min North 027deg 36.8min West Dropped at Switchyard 2011 CTD Station UW 6 XCP Drop 4 2011-05-01/1700 UTC 84deg 09.4min North 045deg 18.5min West Dropped at Switchyard 2011 CTD Station UW 7 XCP Drop 5 2011-05-02/1635 UTC 86deg 56.5min North 056deg 26.5min West Dropped at Switchyard 2011 CTD Station UW 8 XCP Drop 6 2011-05-02/1843 UTC 86deg 01.9min North 060deg 37.6min West Dropped at Switchyard 2011 CTD Station UW 11 XCP Drop 7 2011-05-03/1200 UTC 84deg 56.3min North 085deg 08.1min West Dropped at Switchyard 2011 CTD Station UW 12 XCP Drop 8 2011-05-03/1345 UTC 84deg 56.5min North 074deg 59.8min West These measurements were made with a Sippican Expendable Current Profiler following a Twin Otter landing at these positions on the Arctic sea ice, as part of the observational program of the Switchyard project. A brief description of XCPs may be found at http://www.sippican.com/contentmgr/showdetails.php/id/312 . Switchyard 2011 XCP Drops 3 and 9 failed to record. CTD profiles recorded during the same stations are included in the Project - A Modular Approach to Building an Arctic Observing System for the IPY and Beyond in the Switchyard Region of the Arctic Ocean => Dataset - Switchyard UW CTD data archive at CADIS ( http://aoncadis.ucar.edu/home.htm ), and are a source of buoyancy data for further XCP analysis. The XCP measures velocity by sensing the voltage generated by the movement of conductive seawater through the earth's magnetic field. The voltage difference is measured between two electrodes on the surface of the XCP, which rotates about once every meter of fall. We use a MATLAB program written by John Dunlap of the UW Applied Physics Lab to process the raw data. This program is available at http://ohm.apl.washington.edu/~dunlap/xcpdsp/ In processing, the components of a harmonic fit to the oscillating potential that are in phase and in quadrature with the oscillating output of a flux gate compass are taken as the magnetic north and magnetic east components of velocity. In order to maximize the potential vertical resolution of the resulting profiles, we chose to do the fits over 2-m, half overlapping "chunks". This gives a vertical wavenumber cutoff of 0.5 cycle m-1 that for the Arctic data is well into the noise floor of the instrument. Users may then filter these basic data in ways appropriate to their applications. Further analysis using these data may be viewed at (http://psc.apl.washington.edu/northpole/Mixing.html). For further information, please contact Dr. Michael Steele mas@apl.washington.edu (206) 543-6586 Dr. James Morison morison@apl.washington.edu (206) 543-1394 Roger Andersen roger@apl.washington.edu (206) 543-1258 at Polar Science Center, Applied Physics Lab, University of Washington 1013 NE 40th, Seattle, WA 98105-6698 USA FAX (206) 616-3142 2011 XCPs 3 and 9 failed