Prelimnary Data report may 15, 1995 A. Cruise Narrative A.1 Highlights A.1.a WOCE designation: PR6 A.1.b Expedition designation: 18999105/1 A.1.c Chief Scientist: Ron Bellegay A.1.d Ship: Endeavor A.1.e Ports of Call: Esquimalt, B.C., Canada A.1.f Cruise Dates: Oct. 17 to Nov. 1, 1991 A.2 Cruise Summary A.2.a Geographic boundaries A.2.b Total number of stations Table 1: Stations by type ------------------------------------------------------ Sample type No. stations Max. depth (m) ------------------------------------------------------ CTD casts 36 1500 Bottle casts 7 4200 Bucket samples 36 surface Sed. Trap Moorings 2 4200 ------------------------------------------------------ A.2.c Floats and drifters deployed No floats or drifters deployed A.2.d Moorings deployed or recovered At station AG, sediment trap moorings were recovered and redeployed. At St. P, a trap mooring was lost and a new mooring deployed. Near MP20, two current meter moorings were recovered. A.3 List of Principal Investigators for All Measurements A.4 Scientific Programme and Methods This was the first WOCE designated cruise along Line RP5, although this section has been covered for over 30 years. After delaying for the time necessary to repair the desalinization system on the ship, the cruise set sail from Esquimalt harbor on Thursday, October 17, 1991 on board the Canadian Naval Auxiliary Vessel ENDEAVOR. Participating organizations were the Institute of Ocean Sciences(Pat Bay) and the University of British Columbia. In order to meet the objective of recovering two sediment trap moorings before any infelicity could occur, the ship sailed directly to Station P, 50 N, 145 W, without taking any measurements. Mooring recovery and redeployment were completed at Station P. The ship then immediately sailed north to Station AG, 55 N, 145 W to recover and redeploy the second sediment trap mooring. Bottle casts were done at Station AG together with a CTD comparison. CTD casts were completed on 46 stations along the return track to Station P and along Line P. Bottle reversing thermometer casts were done at Stations P (MP26), MP20, MP18, MP16, MP06, and MP04. Near station MP20, two current meter moorings were recovered for the Quiet Eddy Program. The ship docked in Esquimalt harbor on the morning of Nov 1. The cruise began in moderate seas following a fall storm and enjoyed good weather and low sea state for the balance of the time. Most post-cruise effort has gone into inspection of T/S data quality. Routines have been revised for correcting CTD profiles, eliminating most of the error from instrument drift. Comparisons of bottle cast and CTD data show a slight but significant temperature offset between the two sampling procedures that demands closer inspection. Inspection of oxygen data show that we must use larger Niskin samplers to increase the flushing time of sample bottles, as an initial step in improving this data. We will also be checking flask calibrations to see if these are changing with time. A.5 Major Problems and Goals not Achieved The cruise was delayed to allow temporary repairs to the freshwater generating system which had been damaged by corrosion and continued to threaten to limit the endurance of the cruise. Under the limitations imposed by this problem, the cruise did well to achieve the major objectives of the program. On Oct. 21, a sediment trap mooring was released and partially recovered when a kevlar splice parted and the instruments and acoustic release sank to the bottom. A further recovery attempt using a ROV is under consideration. Nutrient samples were frozen because analytical instrumentation did not return to Victoria soon enough to be put aboard the ship. Consequently, data quality will be reduced. The calibration thermistor case attached to the CTD started leaking during the first cast sending one thermistor off scale and affecting the second thermistor at about 1000 m. As a result there was only a partial check on in-situ temperatures which indicated a temperature .002 higher than the final calibrated temperature for that cast. The thermistors were removed and the connector was insulated from the seawater. Subsequent inspection showed a micro-hole in a solder joint. Since the case was being flooded at the time this information was not deemed reliable enough to be used except as a rough indication of agreement between the CTD and the thermistors. In future, this sensor unit, which had never been under pressure before, will be pressure tested before a cruise. Goals achieved Line PR6 was completed. Not achieved Line PR5 was not occupied . A.6 Other Incidents of Note A.7 List of Cruise Participants Table 2: List of Cruise Participants ----------------------------------------------------- Name Responsibility Affiliation* ----------------------------------------------------- R.D. Bellegay Moorings/sampling IOS R.G. Perkin CTD IOS B.G. Minkley T/S/O IOS L.A.F. Spearing Moorings/CTD casts IOS T.J. Soutar Electronics IOS J. Wu C & N isotopes DOUBC R. Mugo Trace metals DOUBC H. McLean Trace metals DOUBC M. Dempsey Moorings Oceanetics ---------------------------------------------------- *See Table 3 for list of Institutions Table 3: List of Institutions ---------------------------------------------------------------------- Abbreviations Address ---------------------------------------------------------------------- IOS Institute of Ocean Sciences 9860 West Saanich Road, Sidney, B.C. Canada, V8L 4B2 DOUBC Department of Oceanography University of B.C., Vancouver, B.C. Oceanetics Oceanetics Measurements Inc. Sidney, B.C. ---------------------------------------------------------------------- B. Underway Measurements B.1 Navigation and bathymetry B.2 Acoustic Doppler Current Profiler (ADCP) B.3 Thermosalinograph and underway dissolved oxygen, fluorometer, etc. B.4 XBT and XCTD B.5 Meteorological observations B.6 Atmospheric chemistry C. Hydrographic Measurements Water sampling Niskin samplers (1.7 L) were used for all hydro casts. Water samples were collected in the order O2, TCO2 (not on every cast), nutrients and salinity. Oxygen samples were immediately pickled with standard reagents (Carpenter, 1966) and the temperature of the sample recorded using a Guildline Model 2175A digital thermometer. TCO2 samples were pickled with HgCl2, and cool stored for future analysis. Nutrients were only sampled to 500 m and were frozen for future analysis, since our Autoanalyzer had not returned from a joint program with USSR. Salinity samples were drawn into borosilicate bottles for analysis onboard ship. Rinses for gas samples are likely insufficient, due to the limited amount of water available in 1.7 L Niskins. Future cruises will employ 10 L Niskins. Hydro cast temperature and depth Reversing thermometers were used to record temperature and provide correct depths on all hydro casts. Protected thermometers were used in pairs, and an average value recorded, unless there was a discrepancy greater than 0.04o C. Then thermometers were cross checked with those that were known to be consistent. This ongoing process removed thermometers that were not properly working or were in need of recalibration. Unprotected thermometers were used to estimate the bottle depths. Oxygen The micro-Winkler procedure of Carpenter (1966) with a starch end-point titration was used. After the first 3 hydro casts, the sulfuric acid concentration was increased from 280 mL/L acid, to 420 mL/L to improve the dissolution of the precipitate. Duplicate samples drawn from the same bottle did not show good agreement. Depth Range(m) Conc. Range (uM/kg) Sp of pairs (k = no. of pairs) 500 to 1500 10 to 35 0.53 (k=6) 2000 to 4000 55 to 130 1.00 (k=12) The major source of error is likely in sample drawing. Also flask calibrations need to be verified. Standards were prepared as outlined in WOCE Report 73/91. Nutrients Since frozen samples provide poor results at high concentrations (especially for silicate, see Macdonald and McLaughlin, 198 ), samples were only collected to 500m and frozen. Analyses will be done by standard Technicon procedures, for NO3 & NO2, PO4 and dissolved Si. Salinity A Guildline Model 2400 Autosal (SN 40.364) was used onboard ship to analyze all samples except for those from the last hydro cast. Because the instrument became unstable near the end of the trip, samples from station MP04 were analyzed at IOS using a Guildline Model 2410 Salinometer (SN 58879). IAPSO Standard Seawater batch P115 was used for daily calibrations. Duplicate samples from 2000 to 3800 m, run in sequence, had a standard deviation Sp = 0.001 (k=9), confirming that sampling and analyses are precise, and that Niskin bottles were not leaking (since a salinity gradient is evident in leaking bottles). CTD CTD casts were done using one of two Guildline instruments with intercomparisons at stations with bottle casts. CTD-5 (an Arctic version of Guildline Model 8705) was equipped with a 3-bottle Rosette triggered electronically from the surface without interrupting the cast; It also had a pair of narrow range thermistors to verify the main temperature sensor. Calibration samples from the rosette were transferred into borosilicate bottles provided by the Standard Seawater Service and analyzed for salinity using an Autosal salinometer either aboard the ship or shortly after landing at Esquimalt. A summary of the bottle calibrations is given in Table 4,5,6. Both CTD's were recalibrated in a lab shortly after returning to IOS. Calibrations and Standards The digital CTD(Model 8706 and 8715) probes used during this cruise are made by Guildline Instruments of Smiths Falls, Ontario, Canada. Their resolution and accuracy are given in the following table. Table 4. Oxygen: standard deviation of pairs Sp = {(sum d2)/2k}1/2, d is difference between pairs, and k is the number of pairs. ------------------------------------------------------------------- Variable Accuracy Resolution Stability ------------------------------------------------------------------- Conductivity .005 psu .001 psu .002 psu/6 months Temperature .005 .001 .002/30 days Pressure .15% FS .01% FS FS = 1500 dbar ------------------------------------------------------------------- Pre-cruise calibrations for CTD-5 were as follows Table 5 Guildline CTD specifications. ------------------------------------------------------------------------------- Sensor #Slope Offset Date Standards ------------------------------------------------------------------------------ Conductivity 1.00032 -.00021 June 19,1991 Batch No.P106 Temperature .999762 .0055 Oct. 15, 1991 NRC of Canada* Pressure(@15oC) 1.001566 .55 Oct. 15,1991 Ashcroft 1305B F.S.=1500 dbars deadweight Tester: .1% of F.S. Pressure(@8oC) 1.003943 -.93 Oct. 15,1991 Ashcroft 1305B deadweight Tester: .1% of F.S. Thermistor #810 1.0000 0.000 Oct. 15, 1991 NRC of Canada* Thermistor #811 1.0000 0.000 Oct. 15, 1991 NRC of Canada* ------------------------------------------------------------------------------ * Temperature calibrations traceable to the Temperature Standards Lab. of the National Research Council of Canada: accuracy = .002 C and are maintained with triple point cells. Corrected variable = Measured variable*Slope+Offset Post-cruise calibrations for CTD-5 were as follows: Table 6 Pre-cruise calibrations. ------------------------------------------------------------------ Sensor Slope Offset Date Standards ------------------------------------------------------------------ Conductivity 1.00009 -.00021 Nov. 12,1991 Batch N0. P106, Temperature .999762 .0072 Nov. 12, 1991 NRC of Canada* ------------------------------------------------------------------ The temperature correction was averaged between the pre and post cast values. The difference of .00170 in the calibrations is at the estimated limit of accuracy of the calibration bath system. The pressure sensor was not recalibrated. The conductivity sensor was calibrated using the salinities from the rosette samples. Table 7 gives a summary of the computed cell constants normalized to the pre-cruise value. These are plotted in Fig. 3 and show a systematic change over the first 4 casts amounting to .014 in salinity equivalent. The cell constant remained constant for the remaining casts and rebounded marginally for the post-cruise calibration. Additional checks with the hydro-casts and comparisons with the other CTD remain to be done. Near the end of the cruise the Autosal showed signs of increasing drift at the .001 level of salinity equivalent. Post-cruise checks could find no problem with the electronics or mechanical parts however, a thorough cleaning of the cell returned the Autosal to its previous stability. Fig. 2 shows the CTD/rosette with a bumper attached to the bottom of the pressure case for added weight and protection. The performance of this system was tested by triggering three bottles through strong salinity/temperature gradients in the presence of moderate wave action. The bottles could be made to agree with the CTD only after applying a 5.5 m long running mean to the CTD data. This suggests that the bumper was causing a significant wake which interfered with the flushing of the bottles. Because of the low gradients in the deeper water, this effect was significant at only one of the calibration bottles and the filter was applied bringing this salinity into line. Modifications are under consideration to eliminate this wake effect. Some samples were lost because of the dislodging of O-rings when the rosette bottles were triggered. O-rings with greater stretch are being installed for future cruises. Carpenter, J.H. 1965. The Chesapeake Bay Institute technique for the Winkler dissolved oxygen method. Limnol. Oceanogr., 10: 141-143. Macdonald, R.W. and McLaughlin, F.A. 1982. The effect of storage by freezing on dissolved inorganic phosphate, nitrate and reactive silicate for samples from coastal and estuarine waters. Water Res. 1: 95-104. Table 7. IOS (Pat Bay) Cruise 91-15: Summary of CTD calibration bottle data ------------------------------------------------------------------------------ 1503 270.00 O-ring rolled 1503 505.60 3.606 0.739864 34.1828 0.739790 0.999901 0.999909 34.1832 -0.0003 1503 706.50 3.235 0.736276 34.2821 0.736211 0.999912 0.999909 34.2819 0.0001 1503 706.50 3.235 0.736276 34.2821 0.736211 0.999912 0.999909 34.2819 0.0001 1504 253.40 3.762 0.736357 33.9677 0.736157 0.999728 0.999827 33.9678 0.0001 1504 253.40 3.762 0.736357 33.9675 0.736153 0.999723 0.999827 33.9678 -0.0003 1504 1007.20 2.741 0.731674 34.4039 0.731538 0.999815 0.999827 34.4044 -0.0005 1504 1007.20 2.741 0.731674 34.4043 0.731546 0.999825 0.999827 34.4044 -0.0001 1504 1494.30 2.220 0.728098 34.5205 0.727980 0.999838 0.999827 34.5201 0.0004 1504 1494.30 2.220 0.728098 34.5203 0.727976 0.999833 0.999827 34.5201 0.0002 1516 649.80 3.673 0.743084 34.1973 0.742908 0.999763 0.999778 34.1979 -0.0006 1516 649.80 3.673 0.743084 34.1971 0.742904 0.999758 0.999778 34.1979 -0.0008 1516 1000.00 O-ring rolled 1516 1519.00 2.342 0.730424 34.4976 0.730258 0.999773 0.999778 34.4977 -0.0002 1516 1519.00 2.342 0.730424 34.4993 0.730292 0.999819 0.999778 34.4977 0.0016 1526 597.60 3.768 0.743252 34.1313 0.743028 0.999698 0.999648 34.1294 0.0019 1526 597.60 3.768 0.743252 34.1309 0.743020 0.999688 0.999648 34.1294 0.0015 1526 997.60 3.001 0.735975 34.3539 0.735768 0.999719 0.999648 34.3512 0.0027 1526 997.60 3.001 0.735975 34.3535 0.735761 0.999709 0.999648 34.3512 0.0023 1526 1500.00 O-ring rolled 1531 500.00 O-ring rolled 1531 1000.64 3.038 0.736826 34.3543 0.736553 0.99963 0.999648 34.3550 -0.0007 1531 1000.64 3.038 0.736826 34.3539 0.736545 0.999619 0.999648 34.3550 -0.0011 1531 1500.48 2.358 0.730580 34.4911 0.730275 0.999583 0.999648 34.4936 -0.0025 1531 1500.48 2.358 0.730580 34.4936 0.730324 0.99965 0.999648 34.4936 0.0001 1538 1000.98 3.257 0.741252 34.3511 0.740956 0.9996 0.999648 34.3530 -0.0018 1538 1000.98 3.257 0.741252 34.3513 0.740960 0.999605 0.999648 34.3530 -0.0016 1538 1492.65 2.404 0.731586 34.4987 0.731278 0.999579 0.999648 34.5014 -0.0027 1538 1492.65 2.404 0.731586 34.4999 0.731301 0.99961 0.999648 34.5014 -0.0015 Nov. 1, 1991 1538 499.51 4.606 0.758158 34.0653 0.757869 0.99962 0.999648 34.0664 -0.0011 1544 498.49 5.010 0.766610 34.0753 0.766367 0.999683 0.999648 34.0739 0.0013 1544 998.78 3.503 0.746260 34.3556 0.746044 0.999711 0.999648 34.3533 0.0024 1544 998.78 3.503 0.746260 34.3580 0.746090 0.999772 0.999648 34.3533 0.0047 1544 1497.48 2.444 0.732624 34.5097 0.732346 0.999619 0.999648 34.5108 -0.0011 1544 1497.48 2.444 0.732624 34.5115 0.732379 0.999665 0.999648 34.5108 0.0007 1546 533.67 4.849 0.764445 34.1138 0.764189 0.999666 0.999648 34.1131 0.0007 1546 533.67 4.849 0.764445 34.1117 0.764146 0.999609 0.999648 34.1131 -0.0015 1546 798.32 4.042 0.754001 34.2885 0.753752 0.99967 0.999648 34.2876 0.0008 1546 798.32 4.042 0.754001 34.2886 0.753756 0.999675 0.999648 34.2876 0.0010 1546 997.61 3.524 0.747389 34.3872 0.747088 0.999598 0.999648 34.3891 -0.0019 1546 997.61 3.524 0.747389 34.3866 0.747077 0.999582 0.999648 34.3891 -0.0025 RMS 0.0016 BOTTLES TRIGGERED IN UPPER 50 M IN A STRONG GRADIENT(not used for calibration) 1548 39.71 9.294 0.815481 32.4259 0.814533 0.998838 0.999648 32.2750 0.1509 1548 39.71 9.294 0.815481 32.4244 0.814498 0.998795 0.999648 32.2750 0.1494 1548 46.29 8.429 0.798776 32.4758 0.798004 0.999035 0.999648 32.4782 -0.0024 1548 46.29 8.429 0.798776 32.4778 0.798047 0.999088 0.999648 32.4782 -0.0004 1548 50.29 8.130 0.793064 32.5046 0.792587 0.999399 0.999648 32.5050 -0.0004 1548 50.29 8.130 0.793064 32.5055 0.792609 0.999426 0.999648 32.5050 0.0005 ------------------------------------------------------------------------------ Comments: Cast No 1504,1548 were filtered, Cast No. 1526 triggers missing for cast D. Acknowledgments E. References Unesco, 1983. International Oceanographic tables. Unesco Technical Papers in Marine Science, No. 44. Unesco, 1991. Processing of Oceanographic Station Data, 1991. By JPOTS editorial panel. F. WHPO Summary Several data files are associated with this report. They are the en9105.sum, en9105.hyd, en9105.csl and *.wct files. The en9105.sum file contains a summary of the location, time, type of parameters sampled, and other pertient information regarding each hydrographic station. The en9105.hyd file contains the bottle data. The *.wct files are the ctd data for each station. The *.wct files are zipped into one file called en9105.wct.zip. The en9105.csl file is a listing of ctd and calculated values at standard levels. The following is a description of how the standard levels and calculated values were derived for the en9105.csl file: Salinity, Temperature and Pressure: These three values were smoothed from the individual CTD files over the N uniformly increasing pressure levels using the following binomial filter- t(j) = 0.25ti(j-1) + 0.5ti(j) + 0.25ti(j+1) j=2....N-1 When a pressure level is represented in the *.csl file that is not contained within the ctd values, the value was linearly interpolated to the desired level after applying the binomial filtering. Sigma-theta(SIG-TH:KG/M3), Sigma-2 (SIG-2: KG/M3), and Sigma-4(SIG-4: KG/M3): These values are calculated using the practical salinity scale (PSS-78) and the international equation of state for seawater (EOS-80) as described in the Unesco publication 44 at reference pressures of the surface for SIG-TH; 2000 dbars for Sigma-2; and 4000 dbars for Sigma-4. Gradient Potential Temperature (GRD-PT: C/DB 10-3) is calculated as the least squares slope between two levels, where the standard level is the center of the interval. The interval being the smallest of the two differences between the standard level and the two closest values. The slope is first determined using CTD temperature and then the adiabatic lapse rate is subtracted to obtain the gradient potential temperature. Equations and Fortran routines are described in Unesco publication 44. Gradient Salinity (GRD-S: 1/DB 10-3) is calculated as the least squares slope between two levels, where the standard level is the center of the standard level and the two closes values. Equations and Fortran routines are described in Unesco publication 44. Potential Vorticity (POT-V: 1/ms 10-11) is calculated as the vertical component ignoring contributions due to relative vorticity, i.e. pv=fN2/g, where f is the coriolius parameter, N is the bouyancy frequency (data expressed as radius/sec), and g is the local acceleration of gravity. Bouyancy Frequency (B-V: cph) is calculated using the adiabatic leveling method, Fofonoff (1985) and Millard, Owens and Fofonoff (1990). Equations and Fortran routines are described in Unesco publication 44. Potential Energy (PE: J/M2: 10-5) and Dynamic Height (DYN-HT: M) are calculated by integrating from 0 to the level of interest. Equations and Fortran routines are described in Unesco publication, Processing of Oceanographic station data. Neutral Density (GAMMA-N: KG/M3) is calculated with the program GAMMA-N (Jackett and McDougall) version 1.3 Nov. 94. G. Data Quality Evaulations