======================= Originally posted 2010-7-23 ============================ Aerial Hydrographic Surveys for IPY and Beyond: Tracking Change and Understanding Seasonal Variability May 2010 Expendable CTD Survey Arctic Ocean AXCTDs by USCG C-130 NSF Grants ARC-0634226, OPP-0352754 and ARC-0856330 AXCTD Position Latitude _ Longitude Drop Date _ Time AXCTD 1 73 deg 49.00 min North _ 140 deg 25.10 min West 2010-5-25/2237 UTC AXCTD 2 75 deg 06.60 min North _ 139 deg 48.90 min West 2010-5-25/2307 UTC AXCTD 3 75 deg 22.30 min North _ 150 deg 23.00 min West 2010-5-26/0009 UTC AXCTD 4 74 deg 30.70 min North _ 150 deg 18.20 min West 2010-5-26/0039 UTC Probes manufactured by The Tsurumi-Seiki Co., LTD. http://www.tsk-jp.com Drop T.S.K. AXCTD serial number 1 10026984 2 10026981 3 10026982 4 10026980 Each profile is an ASCII file of six numerical columns with a short header- _ Depth (m) _ Pressure (dbar) _ Temperature in situ (deg C) _ Conductivity (S/m) _ Salinity (psu) _ Density (sigma-theta) Calculation of Salinity uses Conductivity of Standard Seawater C(35,15,0) = 42.914. Depth is obtained from probe fall rate, and pressure is derived from depth also as a function of latitude. The trailing wire limits the profile depths to about 1100m. The National Science Foundation's North Pole Environmental Observatory carries out Arctic Ocean CTD-chemistry stations from Twin Otter skiplane landings in the North Pole region during April. In 2008, this related project, Aerial Hydrographic Surveys for IPY and Beyond, extended that to include a survey of the Beaufort Sea, and the digital Airborne eXpendable Conductivity, Temperature, and Depth probes (AXCTD) manufactured by the Tsurumi-Seiki Co., LTD. (http://www.tsk-jp.com/tska/PDF_Files/AXCTD.pdf) were successfully used to obtain accurate hydrographic profiles beyond the range of a Twin Otter loaded with a heavy winch and other equipment needed for the surface stations. Planning for subsequent seasons, it was realized that, as long as sufficient open water could be found, these air-dropped probes could extend the sample season and geographic area, a particular goal of this project. Logistically, the burden is small enough to allow such a survey to "piggy-back" on flights over the Arctic Ocean scheduled for other purposes. The United States Coast Guard C-130s based in Kodiak, Alaska schedule Arctic Domain Awareness flights approximately twice monthly. This dataset consists of the ocean profiles obtained by AXCTDs dropped from the ADA flight over the Arctic Ocean north of Barrow, Alaska on 25 May 2010 local time. Finding open leads took some searching, but the Coast Guard crew's skill in flying low and slow enabled them to find a lead large enough for them to hit within reasonable proximity of each target. The first three AXCTD probes dropped during this flight were not successfully recorded. Troubleshooting pointed to an antenna problem that could be remedied in flight, and the four profiles included in this archive represent the final four AXCTD drops that were successful. For further information, please contact 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