================= Re-posted with revised processing recipe 2007-12-12 ==================== North Pole Environmental Observatory 2007 Aerial CTD Survey NSF Grants OPP-9910305 and OPP-0352754 CTD Station/Location Position Latitude _ Longitude Cast Date _ Time Cast 1 Borneo_89_0 89 deg 10.7 min North _ 0 deg 12.3 min West 4-21/2007 _ 1820 UTC Cast 2 Sta85N_90E 84 deg 58.7 min North _ 90 deg 20.7 min East 4-22/2007 _ 0128 UTC Cast 3 Sta86N_90E 86 deg 01.5 min North _ 90 deg 05.9 min East 4-23/2007 _ 1639 UTC Cast 4 Sta88N_90E 88 deg 03.4 min North _ 92 deg 40.6 min East 4-23/2007 _ 2228 UTC Cast 5 Sta84N_135W 84 deg 28.7 min North _ 134 deg 42.9 min West 4-24/2007 _ 2057 UTC Cast 6 Sta86N_135W 85 deg 44.5 min North _ 134 deg 08.8 min West 4-25/2007 _ 0123 UTC Cast 7 Sta90N 89 deg 57.3 min North _ 168 deg 38.7 min East 4-25/2007 _ 2015 UTC Cast 8 Sta87N_135W 87 deg 10.4 min North _ 136 deg 09.8 min West 4-28/2007 _ 1618 UTC Cast 9 Sta89N_135W 88 deg 35.0 min North _ 136 deg 02.4 min West 4-28/2007 _ 2015 UTC Cast10 Sta89N_90E 89 deg 03.9 min North _ 84 deg 30.4 min East 4-29/2007 _ 0039 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-19plus Seacat (s/n 5076) 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 together form ocean sections from the North Pole along 90E and 135W nearly as far south as 84N. Measurements by the Switchyard Project taken during the succeeding few weeks form another section from the North Pole toward Alert. Processing followed a modified SEASOFT recipe with certain constants determined by empirical trial. Temperature and conductivity were low-pass filtered with a time constant of 0.5 seconds, pressure filtered with a time constant of 1.0 seconds, and temperature was advanced relative to pressure by 0.55 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). 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. During the 2007 survey, the all downcasts were selected, showing the best resolution and being freer of instrument wake effects. Profile plots and other analysis using these data may be viewed at the NPEO website (http://psc.apl.washington.edu/northpole/CTDSurvey2007.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