First posted April 24, 2009 - ULS data is not currently available but will be added soon. --------------------------------------------------------------------------------- North Pole Environmental Observatory 2006-2008 Bottom Moored Oceanographic Data NSF Grants OPP-9910305 and OPP-0352754 As part of the North Pole Environmental Observatory, an oceanographic mooring is anchored to the ocean floor beneath the drifting ice. Vertically distributed instruments measure ocean properties at fixed depths, recording internally since satellite telemetry cannot reach beneath the ice. Typically, the data have been retrieved annually when the mooring was recovered and a new mooring deployed. The first NPEO mooring was deployed in April 2001 by Twin Otter skiplane. Subsequent recoveries and redeployments were carried out by helicopters and airplanes flying from the Russian seasonal ice station Barneo. However, in April 2007, the weather in the central Arctic proved too horrible for any aircraft to reach the site and so the the sixth NPEO mooring, deployed in April 2006, had to remain in place for a second year, It was recovered in April 2008. Most of the instruments had sufficient data storage capacity and battery life to record a full second year, adding to a remarkably long Arctic Ocean time series. The NPEO mooring is located on the Pole Abyssal Plain about 50 kilometers from the North Pole. The location of the initial mooring in 2001 was chosen because it provided a suitable landing site for the supporting aircraft. Since the sea ice from which the mooring operations are conducted drifts between the recovery of a mooring and the deployment of its replacement a day or so later, sequential mooring sites are typically a few kilometers apart each year. The flatness of the abyssal plain suggests that small variations in location are not critical to the usefulness of the observational time series. The ocean depth at the site is approximately 4300 m. The top instrument, nominally near 50 m, is an APL/UW Upward Looking Sonar (ULS) to record ice draft. Deeper instruments include an RDI Workhorse Acoustic Doppler Current Profiler (ADCP), Aanderaa RCM-7 and RCM-11 current meters, and Sea-Bird temperature and conductivity recorders, either SBE-16 or SBE-37. In addition, collaborating investigator John Christensen of Bigelow Laboratory mounted two bio-optical packages carrying sensors for nitrate concentration, pigment biomass, and spectral irradiance, along with temperaure and conductivity, at nominal depths of 53m and 120m under NSF Grant OPP 0352641. To enable mooring location and recovery, three Edgetech 8242 acoustic releases, two Edgetech XT-7500 transponders, and a Pieps avalanche beacon are mounted on the mooring line. Included with the data archive is a PDF image file showing the mooring configuration. The 2006-2008 instruments and their design depths are listed below. NPEO 2006-2008 Bottom-Anchored Mooring Position = 89 degrees 20.810 minutes North, 077 degrees 07.208 minutes East Sounded ocean depth = 4315 meters Year/day/time at depth = 2006/114/0805 UTC Year/day/time of release = 2008/102/0155 UTC Design_depth Instrument (s/n) Principal_measurements 50 m Upward Looking Sonar (s/n 60) Ice draft 53 m Bio-optical package (See text above) 55 m Sea-Bird SBE-16 (s/n 04) Temperature, Conductivity, Pressure 80 m RDI Workhorse ADCP (s/n 2277) Current profile 84 m Aanderaa RCM-7 (s/n 6919) Speed, Direction, T, C, P 110 m Sea-Bird SBE-16 (s/n 1224) Temperature, Conductivity, Pressure 120 m Bio-optical package (See text above) 210 m Sea-Bird SBE-16 (s/n 2262) Temperature, Conductivity, Pressure 235 m Aanderaa RCM-7 (s/n 2243) Speed, Direction, Temperature 260 m Sea-Bird SBE-16 (s/n 2264) Temperature, Conductivity, Pressure 600 m Aanderaa RCM-7 (s/n 6547) Speed, Direction, Temperature 601 m Sea-Bird SBE-37 (s/n 2310) Temperature, Conductivity, Pressure 1000 m Aanderaa RCM-7 (s/n 11456) Speed, Direction, Temperature 1001 m Sea-Bird SBE-37 (s/n 2311) Temperature, Conductivity, Pressure 1700 m Aanderaa RCM-7 (s/n 1926) Speed, Direction, Temperature 1701 m Sea-Bird SBE-37 (s/n 2312) Temperature, Conductivity, Pressure 2500 m Aanderaa RCM-11 (s/n 365) Speed, Direction, Temperature 2501 m Sea-Bird SBE-37 (s/n 2315) Temperature, Conductivity, Pressure 4284 m Aanderaa RCM-11 (s/n 536) Speed, Direction, Temperature The data provided in this archive are organized by instrument type, with separate directories for the ULS, ADCP, RCMs, and Sea-Birds. Calibration and processing of each data type is documented in a separate ReadMe file. Wherever possible, measurements have been checked for consistency against other instruments on the line. Pressure has been checked for consistency between different instruments, noting that precise ocean depth is difficult to determine and that line length errors are possible. An echo sounding at deployment yielded a corrected ocean depth of 4315m, 23m deeper than the design assumption. The numerous pressure sensors of good quality distributed along the mooring provide an internally consistent view of the mooring geometry. In particular, the discrepancy between the actual static depth of the individual sensors and their design depths, a discrepancy that decreases linearly with depth, suggests that the actual stretch of the mooring under the deployed loading (~0.3%) is significantly less than the design had assumed. Furthermore, extrapolating the discrepancy to zero at the sea floor, which is physically realistic, suggests that the actual water depth was 11m less than the sounding, i.e., the correct water depth may well have been 4304m, only 11m more than the design depth of 4293m. We raise this as a strong possibility, but for data archiving purposes have reported the sounded depth as observed, viz., 4315m. General information about the North Pole Environmental Observatory, the NPEO mooring, and various data extracts and summaries may be viewed at the NPEO website (http://psc.apl.washington.edu/northpole/Mooring.html). In reports and publications that use these data, please acknowledge their source: K. Aagaard, North Pole Environmental Observatory NSF Grants OPP-9910305 and OPP-0352754. For further information, please contact Dr. Knut Aagaard aagaard@apl.washington.edu (206) 543-8942 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