North Pole Environmental Observatory 2006 Aerial CTD Survey NSF Grants OPP-9910305 and OPP-0352754 CTD Station/Location Position Latitude _ Longitude Cast Date _ Time Cast 1 89N_168E 88 deg 51.3 min North _ 168 deg 40.0 min East 4/24/2006 _ 0700 UTC Cast 2 88N_180 87 deg 59.4 min North _ 179 deg 52.9 min West 4/24/2006 _ 1300 UTC Cast 3 87N_180 86 deg 55.8 min North _ 179 deg 44.2 min West 4/24/2006 _ 1650 UTC Cast 4 86N_170W 85 deg 57.9 min North _ 169 deg 56.6 min West 4/25/2006 _ 1250 UTC Cast 5 85N_170W 84 deg 58.8 min North _ 169 deg 45.5 min West 4/25/2006 _ 1620 UTC Cast 6 90N 89 deg 58.6 min North _ 170 deg 09.4 min West 4/26/2006 _ 1020 UTC Cast 7 89N_90W 89 deg 00.5 min North _ 088 deg 24.3 min West 4/26/2006 _ 1420 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 (s/n 2373) 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. Mounted on and plumbed together with the SBE-19 CTD was an SBE-43 Disolved Oxygen Sensor. Profiles of dissolved oxygen were successfully recorded and will be provided in a later submission, once data processing issues associated with operating this sensor in a very cold environment are resolved. These stations included water sampling with Niskin Bottles for chemistry, and are an attempt to assemble an ocean section from the North Pole toward Alaska as far south as 85N and toward Alert far enough to interface with measurements by the Switchyard Project. Processing followed a modified SEASOFT recipe with certain constants determined by empirical trial. Conductivity was 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 0.7 seconds, a value determined by varying the temperature advance to select the value that did the best job of minimizing salinity spiking. Finally a cell thermal mass correction was applied, choosing parameters Alpha = 0.025 and Tau = 9.0 from the theoretical equations offered in Morison, et al (1994) based upon a flow rate of approximately 29.4 mL/sec measured in the laboratory. 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 before reaching a substantial depth, 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, are freer of instrument wake effects, and were selected whenever such problems with the top of a downcast were not evident. Only one cast required using part of the upcast; Cast 7 at approximately 89N and 90W uses the upcast above 52.5 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/CTDSurvey2006.html). Reference: Morison, J., R. Andersen, N. Larson, E. D'Asaro, and T. Boyd, 1994: The Correction for Thermal-Lag Effects in Sea-Bird CTD Data. J. Atmos. Oceanic Technol., 11, 1151-1164. 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