North Pole Environmental Observatory 2005 Aerial CTD Survey NSF Grants OPP-9910305 and OPP-0352754 CTD Station/Location Position Latitude _ Longitude Cast Date _ Time Cast 1 Borneo 89 deg 21.5 min North _ 147 deg 26.9 min East 4/25/2005 _ 1928 UTC Cast 2 86N_90E 86 deg 06.9 min North _ 090 deg 03.1 min East 4/27/2005 _ 0004 UTC Cast 3 87N_90E 87 deg 00.0 min North _ 089 deg 51.8 min East 4/27/2005 _ 0307 UTC Cast 4 88N_90E 88 deg 04.3 min North _ 091 deg 46.1 min East 4/27/2005 _ 1600 UTC Cast 5 89N_90W 89 deg 01.9 min North _ 088 deg 33.8 min West 4/27/2005 _ 2138 UTC Cast 6 90N North Pole 89 deg 47.2 min North _ 151 deg 31.0 min East 4/28/2005 _ 0100 UTC Cast 7 87.5N_90W 87 deg 27.0 min North _ 089 deg 08.9 min West 4/28/2005 _ 1343 UTC Each cast is an ASCII file of seven numerical columns with a short header- _ Depth (m) _ Pressure (dbar) _ Temperature in situ (deg C) _ Potential Temperature (deg C) _ Conductivity (S/m) _ Salinity (psu) _ Density (sigma-theta) These measurements were made with a Seabird SBE-19 Seacat following a Twin Otter landing at these positions on the Arctic sea ice, as part of the observational program of the North Pole Environmental Observatory. These stations had to be recorded using the backup CTD instrument, as the conductivity cell in the primary instrument was unfortunately found to be actually broken when opened at Mooring Camp. Since the primary CTD included the SBE-43 Oxygen Sensor, we are unable to report profiles of dissolved oxygen. These stations included water sampling with Niskin Bottles for chemistry, and are an attempt to assemble a cross-Pole section north along 90¡ East across the Pole along 90¡ West, and, when combined with stations from the Switchyard project, toward Alert on the Canadian side. Processing followed the recently-modified (June 2003) SEASOFT recipe with certain constants determined by empirical trial. Conductivity and temperature were low pass filtered with a time constant of 0.5 seconds, pressure filtered with a time constant of 2.0 seconds, and temperature was advanced relative to pressure by 0.5 seconds. Varying the temperature advance showed the nominal 0.5 seconds did the best job of minimizing salinity spiking. Except where noted below, the reported profile is the down trace which minimizes instrument wake effects. In spring Arctic conditions with cold air temperatures, a frequent problem has been seawater freezing in the plumbing the instant it enters the water and not dissipating until at a substantial depth or even on the way back up, despite efforts to keep the instrument warm and even after a long period with the instrument soaking in the Mixed Layer. The downcasts generally show the best resolution and were selected whenever such problems with the top of a downcast were not evident. Four casts required using all or part of the upcast: Cast 1 at Ice Station Borneo uses the upcast above 101 meters depth and the downcast below. Cast 2 at 86 North and 90 East showed a reversal of the problem described above, as the downcast looks OK down to 287 meters, below which the conductivity goes low to a small but recognizable degree. Perhaps aggravated by the stops to install Niskin bottles on the line, biology seems the most likely explanation. Since the upcast is unaffected, it is used below 287 meters, and the downcast is retained above. Cast 4 at 88 North and 90 East showed an odd, unstable band in the downcast between 272 and 290 meters, just above a bottle stop. On consideration, the upcast was felt to better represent the the water column there, and it has been patched into the record with the downcast both above and below. Cast 7 at 87.5 North and 90 West uses the upcast above 50 meters depth and the downcast below. Profile plots and other analysis using these data may be viewed at the NPEO website (http://psc.apl.washington.edu/northpole/CTDSurvey2005.html). For further information, please contact Dr. James Morison morison@apl.washington.edu (206) 543-1394 Dr. Michael Steele mas@apl.washington.edu (206) 543-6586 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