BEST Bering Shelf Project (Bering Ecosystem Study) NSF Grant ARC-0732428 2008-2009 University of Washington Oceanographic Mooring C55-08 Part of Bering Ecosystem Study is the BEST Bering Shelf Project, a joint effort of the University of Alaska Fairbanks (UAF) and the University of Washington (UW). During 2008-2010, nine ocean moorings have been deployed on the eastern shelf of the Bering Sea. Vertically distributed instruments measure ocean properties at fixed depths, recording internally. These are located along three lines (N = North, C = Central, S = South) perpendicular to the isobaths, roughly centered on Nunivak Island, at approximate depths 55m, 40m, and 25m. (PDF map provided.) This archive contains the data from the UW instruments on the deepest mooring of the C-line deployed in 2008, labeled C55-08. Data from the UAF instruments are posted in a separate archive. This mooring was deployed from USCGC Healy in July 2008 and recovered from RV Point Sur in July 2009. Like the other 55m moorings, C55-08 had an ice-avoiding modem-linked temperature/conductivity recorder (ISCAT) at 10m, another temperature/conductivity recorder with a fluorometer at 22 m, below that a chain of 15 temperature recorders (HOBO), an Acoustic Doppler Current Profiler at 47m, and finally another temperature/conductivity recorder at 52m, just 3m above the bottom. The ISCAT consists of a Sea-Bird SBE-37 contained in a housing designed not to be entrapped in drifting ice. A backup data recording system has a modem connecting the SBE-37 with a data logger attached to the steel float located at about 20m depth. In the event that the SBE-37 is damaged or lost through drifting ice, the data are rerieved from the backup data logger. To enable recovery, two Oceano model RT121 acoustic releases rigged in parallel connected the mooring to the anchor. Data from the Wet Labs Fluorometer (UW) and the HOBO temperature recorders (UAF) will be submitted separately. A PDF diagram is included with this archive. The C55-08 instruments and their design depths are listed below: BEST 2008-2009 Bottom-Anchored Mooring C55-08 Position = 60 degrees 10.376 minutes North, 170 degrees 05.374 minutes West Sounded ocean depth = 55 meters Year/day/time initial at depth = 2008/192/1923 UTC Recovery/re-deployment to remove ADCP cover Year/day/time final in water = 2008/193/1951 UTC Year/day/time of release = 2009/193/0427 UTC Design_depth Instrument (s/n) Principal_measurements 10 m ISCAT SBE-37 (s/n 5592) Temperature, Conductivity 22 m Sea-Bird SBE-16 (s/n 1225) Temp., Cond., Pressure 22 m Wet Labs FLNTUSB (s/n 932) Fluorescence 23.6 m HOBO (s/n 182) Temperature 25.2 m HOBO (s/n 193) Temperature 26.8 m HOBO (s/n 197) Temperature 28.4 m HOBO (s/n 198) Temperature 30.0 m HOBO (s/n 626) Temperature 31.6 m HOBO (s/n 627) Temperature 33.2 m HOBO (s/n 628) Temperature 34.8 m HOBO (s/n 629) Temperature 36.4 m HOBO (s/n 630) Temperature 38.0 m HOBO (s/n 631) Temperature 39.6 m HOBO (s/n 632) Temperature 41.2 m HOBO (s/n 633) Temperature 42.8 m HOBO (s/n 636) Temperature 44.4 m HOBO (s/n 637) Temperature 46.0 m HOBO (s/n 638) Temperature 47 m RDI Workhorse ADCP (s/n 1495) Current profile (upward looking) 52 m Sea-Bird SBE-37 (s/n 5410) Temperature, Conductivity 55 m Anchor The data provided in this archive are organized by instrument type, with separate directories for the Sea-Birds and ADCP. 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 mooring line. The record for the ISCAT, nominally at 10 m, was only recovered via the separate data logger, but shows good qualitative agreement with the 22 m Sea-Bird. However, there are a significant number of data gaps when the logger apparently failed to capture a sample, and these affect the usual time comparisons that we apply between the two instruments. When working with the two records, precedence should be given to the time from the 22 m Sea-Bird and consideration given to adjusting the ISCAT time by a few samples if necessary to get time agreement for discrete events some 12 m apart. Comparison of the temperature and conductivity records from the instruments at nominally 22 m and 52 m suggests a drift of the conductivity sensor on the deeper instrument toward increasingly lower values over the entire deployment. Additionally, there are episodic events with sharply reduced conductivity, at least some of which are associated with large currents. Both the trend and the short-term perturbations give rise to apparent static instabilities when compared with the 22 m record. Comparison of the 22 m and 52 m registrations during a CTD cast at the time of the mooring recovery suggests that the 52 m calculated salinity was low by ~0.3 psu, while the 22 m salinity was accurate to within the limits of the cast comparison, which are perhaps +/- 0.01 psu. We have also compared the pre- and post-deployment calibration constants provided by Sea-Bird, and we find that perhaps half the drift can be accounted for by the calibration change. We conclude that the large suspended sediment concentration near the sea floor coated the electrodes, increasingly reducing the sensed conductivity. Episodic changes in the suspended sediment led to shorter-term variations superimposed on the drift. When the instrument was cleaned and re-calibrated by Sea-Bird, the electrodes were partially restored to their earlier state. In this data file we report the sensed conductivity as recorded, recognizing that these values will be increasingly low over the duration of the deployment, with a characteristic value of ~0.15 psu. General information about BEST (Bering Ecosystem Study) can be found at http://bsierp.nprb.org/index.html and BEST data is permanently archived at http://www.eol.ucar.edu/projects/best/ In reports and publications that use these data, please acknowledge their source: K. Aagaard, BEST Bering Shelf NSF Grant ARC-0732428. 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