============================= Originally posted 2008-8-20 ================================== North Pole Environmental Observatory 2008 Aerial CTD Survey NSF Grants OPP-9910305, OPP-0352754, and ARC-0634226 CTD Station/Location Position Latitude _ Longitude Cast Date _ Time Cast 1 Sta73_140W 73 deg 00.0 min North _ 140 deg 00.0 min West 3/21/2008 _ 2157 UTC Cast 2 Sta72_140W 72 deg 03.0 min North _ 140 deg 06.7 min West 3/22/2008 _ 2145 UTC Cast 3 Sta7240_145W 72 deg 41.2 min North _ 144 deg 50.4 min West 3/23/2008 _ 0136 UTC Cast 4 Sta7340_135W 73 deg 35.2 min North _ 136 deg 32.4 min West 3/23/2008 _ 2055 UTC Cast 5 Sta74_140W 74 deg 02.4 min North _ 140 deg 18.7 min West 3/24/2008 _ 0045 UTC Cast 6 Sta7440_146W 74 deg 38.1 min North _ 146 deg 40.3 min West 3/24/2008 _ 2050 UTC Cast 7 Sta7420_143W 74 deg 18.1 min North _ 143 deg 17.0 min West 3/24/2008 _ 2350 UTC Cast 8 Sta75_150W 74 deg 58.7 min North _ 150 deg 08.7 min West 3/26/2008 _ 2033 UTC Cast 9 Sta74_150W 74 deg 03.4 min North _ 149 deg 48.6 min West 3/27/2008 _ 0020 UTC Cast 10 Sta73_150W 72 deg 58.3 min North _ 149 deg 51.9 min West 3/27/2008 _ 1948 UTC Cast 11 Sta72_150W 72 deg 03.7 min North _ 150 deg 05.3 min West 3/27/2008 _ 2300 UTC Cast 12 Sta7540_158W 75 deg 41.9 min North _ 157 deg 42.9 min West 3/29/2008 _ 2046 UTC Cast 13 Sta7520_154W 75 deg 21.6 min North _ 154 deg 18.3 min West 3/29/2008 _ 2350 UTC Cast 14 Sta7620_164W 76 deg 19.3 min North _ 163 deg 41.8 min West 3/30/2008 _ 2021 UTC Cast 15 Sta76_161W 75 deg 56.5 min North _ 160 deg 37.1 min West 3/30/2008 _ 2318 UTC Cast 16 Sta86_173W 85 deg 59.7 min North _ 173 deg 23.2 min West 4/06/2008 _ 2110 UTC Cast 17 Sta87_180 87 deg 00.7 min North _ 178 deg 21.7 min East 4/07/2008 _ 0013 UTC Cast 18 Sta86_136W 86 deg 19.6 min North _ 135 deg 59.5 min West 4/08/2008 _ 1451 UTC Cast 19 Sta87_137W 86 deg 54.4 min North _ 136 deg 46.9 min West 4/08/2008 _ 1806 UTC Cast 20 Sta85_90E 85 deg 03.5 min North _ 089 deg 31.1 min East 4/10/2008 _ 1348 UTC Cast 21 Sta86_90E 85 deg 59.3 min North _ 090 deg 40.6 min East 4/10/2008 _ 1705 UTC Cast 22 Sta8548_135E 85 deg 49.0 min North _ 134 deg 18.0 min East 4/11/2008 _ 1425 UTC Cast 23 Sta87_135E 87 deg 11.4 min North _ 135 deg 19.8 min East 4/11/2008 _ 1813 UTC Cast 24 Sta87_90E 86 deg 53.2 min North _ 089 deg 34.2 min East 4/12/2008 _ 1252 UTC Cast 25 Sta88_90E 88 deg 04.1 min North _ 085 deg 54.8 min East 4/12/2008 _ 1601 UTC Cast 26 Sta89_90E 89 deg 00.8 min North _ 092 deg 51.5 min East 4/12/2008 _ 1922 UTC Cast 27 Borneo_88_000 88 deg 21.8 min North _ 015 deg 06.6 min East 4/13/2008 _ 2200 UTC Cast 28 Sta88_180 88 deg 00.5 min North _ 179 deg 38.0 min West 4/18/2008 _ 1216 UTC Cast 29 Sta8835_135E 88 deg 38.6 min North _ 135 deg 25.1 min East 4/18/2008 _ 1528 UTC Cast 30 Sta89_180 88 deg 59.6 min North _ 178 deg 49.7 min East 4/18/2008 _ 1827 UTC Cast 31 Sta89_135W 88 deg 32.1 min North _ 135 deg 07.1 min West 4/19/2008 _ 1141 UTC Cast 32 Sta90_NP 89 deg 54.5 min North _ 054 deg 16.3 min East 4/19/2008 _ 1514 UTC Cast 33 Sta89_000 89 deg 02.6 min North _ 000 deg 34.6 min West 4/19/2008 _ 1806 UTC Cast 34 Sta86_000 86 deg 08.1 min North _ 000 deg 16.8 min East 4/20/2008 _ 1115 UTC Cast 35 Sta87_000 86 deg 57.9 min North _ 000 deg 29.6 min West 4/20/2008 _ 1406 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 Dissolved Oxygen Sensor (s/n 229). Profiles of dissolved oxygen were successfully recorded and will be provided in a later submission, together with chemical data from water sampling with Niskin Bottles at each station. Falling during the International Polar Year (IPY), the 2008 Aerial Survey was augmented to extend the survey to the Beaufort Sea directly north of Alaska. The more southerly latitude there allowed an earlier start to the campaign, and flying out of Deadhorse and Barrow, Alaska beginning on March 21, the project Twin Otter recorded Stations 1 through 15 in a sampling pattern of surface stations across the southern Beaufort, before staging to the Russian Ice Station Borneo near the North Pole via Inuvik, Resolute, and Alert. As in the Beaufort, the survey in the North Pole area benefited from vast areas of relatively smooth first year ice for landing sites and much better weather than during spring 2007. Flying out of Borneo, stations 16 through 35 form ocean sections from the Pole along 90 degrees East, 135 East, 180 degrees, 135 West and the Greenwich meridian, each at least as far south as 86 degrees North. 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. However, this problem was largely compensated for during the 2008 survey, allowing the downcasts all to be reported here, since they show the best resolution and are freer of instrument wake effects. In addition to this archive, measurements by the Switchyard Project (http://psc.apl.washington.edu/switchyard/index.html) taken during early May form another section along 90 degrees West toward Alert. Additionally, the Beaufort Sea effort was extended northward in mid-April by dropping Airborne eXpendable Conductivity, Temperature, and Depth probes (AXCTD) into open leads from a second Twin Otter on wheels flying from Deadhorse with two long-range ferry tanks. Eight CTD profiles were obtained from the northern Beaufort, and will be submitted as a separate archive. Profile plots and other analysis using these data may be viewed at the NPEO website (http://psc.apl.washington.edu/northpole/CTDSurvey2008.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