Current Data from ADCP on SHEBA IOEB A 150-kHz narrowband RD Instruments Acoustic Doppler Current Profiler (ADCP) internally recorded 34,805 current ensembles in 362 days from an Ice-Ocean Environmental Buoy (IOEB) deployed during the SHEBA Experiment . The IOEB was initially deployed about 50 km from the main camp and drifted from 75.1— N, 141— W, to 80.6— N, 160— W, between October 1, 1997 and September 30, 1998. The ADCP was located at a depth of 14 m below the ice surface, and was configured to record data at 15 minute intervals from 40, 8-m wide bins, extending downward 320 m below the instrument. The retrieved 24 Mbyte raw data are processed to remove noise, correct for platform drift and geomagnetic declination, remove bottom hits, and output interpolated 2-hr average Earth-referenced current profiles along with ancillary data. Random errors in the 2 hr averaged ADCP measurements are estimated to be about 0.6 cm/s, while platform drift and Argos location uncertainty (~200 m) may introduces another 1-2 cm/s of error in the absolute currents. Processing consists of five major steps: 1. Raw binary ADCP files are unpacked to provide header, beam velocity profiles, echo amplitudes, and percent good data. 2. Beam data are analyzed to remove bottom hits, low percent good, and other discrete bad points in individual beams. This removed less than 1% of the input data. 3. Earth-referenced Janus velocities are computed from the filtered beam data, and smoothed interpolated Argos locations. Simultaneously, geomagnetic declination is determined from the National Geophysical Data Center (NGDC) IGRF model and applied at each time step. 4. A first difference filter is used on the computed velocities to remove spurious points above selected thresholds. This eliminates less than 0.5% of the data. 5. Gaps in the velocity data are linearly interpolated. The velocity and ancillary data are averaged over 2 hours and output in ASCII text. The processing results in 4345 records at 2 hr interval at 38 depths (bins 39 and 40 removed) beginning on yearday 274 and ending on 636, 1997. Individual text files are provided for each velocity component (u, v, and w), one for error, another for selected header data (temperature, pitch, roll, etc.), and one of ancillary data (location, drift u and v, declination, bathymetry, ice concentration, air temperature, etc.). The raw Argos locations are de-spiked, linearly interpolated, and smoothed with a 6 hour triangular filter. The bathymetry data is determined from the ETOPO5 grid, while the ice concentration was obtained from the National Snow and Ice Data Center (NSIDC) and determined from SSMI satellite data using the Boostrap algorithm. In addition, air temperature and seawater temperatures, salinities, and densities at 3 depths (65, 105, and 165 m) from the same IOEB are included. The air temperatures measurements were made at a nominal depth of 2 m above the ice with a RM Young wind monitor. The CTD measurements were made by Sea-Bird SBE-16 SeaCats, which were calibrated before and after the deployment, indicating sensor drift within manufacturer specifications. Bottom hits and other missing data are nulled using "NaN". S97ADCP ASCII DATA FILES drif_2hr.s97 (828k): yearday, date, time, lon, lat, drift u, v (cm/s), declination, bath (m), ice conc. (%), air T (C), temperature, salinity, density @ 65 m, temperature, salinity, density @ 105 m, temperature, salinity, density @ 165 m je_2hr.s97 (1074k): yearday, date, time, jerr bins 2-39 (cm/s) ju_2hr.s97 (1074k): yearday, date, time, ju bins 2-39 (cm/s) jv_2hr.s97 (1074k): yearday, date, time, jv bins 2-39 (cm/s) jw_2hr.s97 (1074k): yearday, date, time, jw bins 2-39 (cm/s) prht_2hr.s97 (404k): yearday, date, time, pitch, roll, heading, temp (C), std pitch, std roll, std heading DEPTH OF BINS bin depth (m) bin depth (m) bin depth (m) 2 29.6 15 131.0 28 232.4 3 37.4 16 138.8 29 240.2 4 45.2 17 146.6 30 248.0 5 53.0 18 154.4 31 255.8 6 60.8 19 162.2 32 263.6 7 68.6 20 170.0 33 271.4 8 76.4 21 177.8 34 279.2 9 84.2 22 185.6 35 287.0 10 92.0 23 193.4 36 294.8 11 99.8 24 201.2 37 302.6 12 107.6 25 209.0 38 310.4 13 115.4 26 216.8 39 318.2 14 123.2 27 224.6 MORE INFORMATION The SHEBA IOEB was funded by the Japan Marine Science and Technology Center (JAMSTEC), and supported by IOEB program partner Woods Hole Oceanographic Institution (WHOI). Data processing was in part supported by the National Science Foundation and Office of Naval Research - High Latitude Program. More information on the IOEB program is available online at , or in WHOI and JAMSTEC technical reports. Honjo, S., T. Takizawa, R. Krishfield, J. Kemp, and K. Hatakeyama, 1995, Drifting Buoys Make Discoveries About Interactive Processes in the Arctic Ocean, EOS, 76 (21) 209 & 215. Krishfield, R., K. Doherty, and S. Honjo, Ice-Ocean Environmental Buoys (IOEB); Technology and Deployment in 1991 - 1992, WHOI Tech. Rep., WHOI-93-45, 1993. Krishfield, R., S. Honjo, T. Takizawa, and K. Hatakeyama, IOEB Archived Data Processing and Graphical Results from April 1992 through November 1998, WHOI Tech. Rep. WHOI-99-12, 1999. Takizawa, T., K. Hatakeyama, T. Nakamura, S. Honjo, R. Krishfield, and N. Koyama, Report of Arctic Observational Data by Ice-Ocean Environmental Buoys (IOEB) 1 and 2 (April 1992 to July 1995), JAMSTEC Technical Report, August 1995 (in Japanese). ADDRESSES The authors should be informed of the intended use of the data and consulted as to potential scientific collaboration. Dr. Albert Plueddmann Department of Physical Oceanography Woods Hole Oceanographic Institution Woods Hole, MA 02540 Phone: (508) 289-2789 aplueddmann@whoi.edu Dr. Takatoshi Takizawa Japan Marine Science and Technology Center 2-15 Natsushima-cho Yokosuka Kanagawa 237 JAPAN takizawat@jamstec.go.jp Richard Krishfield Department of Geology & Geophysics Woods Hole, MA 02540 Woods Hole Oceanographic Institution rkrishfield@whoi.edu