WHP Cruise Summary Information

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A. Cruise Narrative: A05 (Updated June, 2007) A.1. Highlights WHP Cruise Summary Information WOCE section designation A05 Expedition
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A. Cruise Narrative: A05 (Updated June, 2007) A.1. Highlights WHP Cruise Summary Information WOCE section designation A05 Expedition designation (EXPOCODE) 29HE06_1-3 Chief Scientists and their affiliation Gregorio Parrilla / IEO*, Harry Bryden / SOC** Ship B.I.O. Hespérides Dates Leg 1: July 14 to July 17, 1992 Leg 2: July 17 to July 18, 1992 Leg 3: July 19 to August 15, 1992 Ports of call Leg 1: Cádiz to Sta. Cruz de Tenerife. Leg 2: Sta. Cruz de Tfe. to Las Palmas de G.C. Leg 3: Las Palmas de G.C. to Miami Number of stations N Station geographic boundaries W W N Floats and drifters deployed none Moorings deployed or recovered none Contributing Authors E. Alvárez A. Cruzado J. Escánez M. Garcia M.J. Garcia J. García-Braun M.D. Gelado J.J. Hernández R. Millard F. Millero R. Molina A.F. Ríos G. Rosón W. Smethie Z.R. Velásquez *Dr. Gregorio Parrilla Instituto Espanol de Oceanografia Ministerio de Agricultura Pesca y Alimentacion Corazon de Maria 8 Madrid, SPAIN Tel: Fax: **Harry L. Bryden Southampton Oceanography Centre James Rennell Division Empress Dock Southampton SO14 3ZH UK Tel: Fax: Instructions: Click on headings below to locate primary reference or use navigation tools above. (Shaded headings were either not relevant to this cruise or not available when this report was assembled) Cruise Summary Information Hydrographic Measurements Description of scientific program Geographic boundaries of the survey Cruise track (figure) Description of stations Description of parameters sampled Bottle depth distributions (figure) Floats and drifters deployed Moorings deployed or recovered Principal Investigators for all measurements Cruise Participants Problems and goals not achieved Other incidents of note Underway Data Information CTD Data CTD - general CTD - pressure CTD - temperature CTD - conductivity/salinity CTD - dissolved oxygen Bottle Data Salinity Oxygen Nutrients CFCs Helium Tritium Radiocarbon CO2 system parameters Other parameters Navigation Bathymetry Acoustic Doppler Current Profiler (ADCP) Thermosalinograph and related measurements XBT and/or XCTD Meteorological observations Atmospheric chemistry data DQE Reports CTD S/O2/nutrients CFCs 14C Acknowledgment References Data Processing Notes CO2 Report CO2 Report Other BTL Data Other BTL Data 80 W 80 W 70 W 70 W 60 W 60 W 50 W 50 W 40 W 40 W 30 W 30 W 20 W 20 W 10 W 10 W E 10 E 10 S 10 S N 10 N 20 N 20 N 30 N 30 N 40 N 40 N 50 N 50 N 60 N 60 N Cruise summary Cruise track is shown in fig. 1. Situation and date of stations are given in table I. Sampling: Water sampling included measurements of salinity both by CTD and bottle samples, CTD and bottle sample Oxygen determination, CTD temperature, nutrients (silicate, nitrate, nitrite and phosphate), CFC, ph, alkalinity, CO 2, particulate matter, chlorophyll pigments, C14. Al. ACDP. Type and Number of stations: During the cruise 118 CTD/rosette stations were occupied using a 24 bottle rosette equipped with 10 or 12 liter in GO water sampling bottles; 6 test stations were made between Cadiz and Las Palmas de G.C., 101 on the A-5 section and 11 on the Strait of Florida Section. For navigation and placement of stations, GPS and dynamic positioning were used List of Principal Investigators Preliminary results Name Responsibility Affiliation G. Parilla CTD IEO H. Bryden CTD JRC R. Molina S IEO J. Escánez O 2 IEO A. Cruzado Nutrients CEAB W. Smethie CFC LDGO A. Ríos ph, Alk, CO 2 IIM F. Millero ph, Alk, CO 2 RSMAS G. Rosón Calcium IIM J. Garcia Braun Chlorophyll IEO Z. Velásquez Chlorophyll CEAB J. Hernández Al FCMLP W. Broecker C14 LDEO M. García ADCP UPC The ship departed from Cádiz on July 14, 1992 and 4 stations were made to test CTD and Rosette before arriving to Sta. Cruz de Tenerife on the 17th. After the ship left Tenerife on the 18th and before arriving to L. Palmas the same day two more test stations were performed and the ADCP was checked. During these stations several tests of a Falmouth Scientific Inst. CTD were also carried out. The ship departed from L. Palmas in the early hours of the 20th to arrive to the first station of the section A-5 the same day. This section was finished, after 101 stations were made, at the Bahamas on August 14 th. During the next day the Strait of Florida Section was completed and the cruise accomplished. We carried 3CTDs, 2 belonging to IEO and 1 to WHOI. They are EG&G NBIS MARK III instruments equipped with Sensor Medics dissolved oxygen sensors and titanium pressure sensor (Millard et al 1991). All were calibrated at the WHOI facilities before the cruise. Because the delays inflicted by the hurricane Andrew on the equipment shipment from Miami to Woods Hole the post-cruise calibration were not performed on the CTDs until December. The conductivity and oxygen sensors were also calibrated at sea using the analysis of the water samples collected at each station. The depths of the sampling were based on the classical standard ones although they were varied on a station by station basis according to participants need to sample a particular layer provided there was no impairment of the in situ calibration activities. Stn Latitude Longitude Depth Date Time N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W Stn Latitude Longitude Depth Date Time N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W N W Water samples were collected from 10 or 12 liters PVC Niskin GO bottles mounted on a GO Rosette Sampler. All the water sample conductivity and oxygen measurements were made in a constant temperature laboratory soon after each cast was completed. Descriptions of analytical techniques, precision and accuracy are given later in this report. Additional samples were also collected for the analysis of the other parameters listed above, description of which are presented in other sections of this report. According to the WOCE Implementation Plan this line was located at 24 N. As two oceanographic sections had been made previously in 1957 and 1981) around 24.5 N (Roemmich and Wunsch, 1985) we asked the WOCEIPO to move the WOCE section A5 to this latitude, which was agreed to. With respect to the station separations and because we were constrained by ship time, we decided to use the following judgment: the first 6 stations were located at the 50, 100, 150, 1500, 2000 and 2500 isobaths (about 18nm separation). From there to the 4000m depth (stl2) the separation was about 23nm. From station 12 to the eastern limits of the Mid Atlantic Ridge we separated the stations by 36nm. Across the Ridge the separation was 32nm. From its western limits to the 5000 isobath near the Bahamas, stations were separated again 36nm. Stations close to the Bahamas were separated by less than 30nm. The stations across the Straits of Florida were occupied every 5nm. Near to Bahamas we deviated the heading of the section slightly from the original plan in order to cross the continental slope perpendicular to the direction of the isobaths and to obtain a clear crossing of the Deep Western Boundary Current. The ADCP and a thermosalinograph recorded continuous during the whole cruise. Wind information was recorded every hour. At the end of the cruise the ship was checked for Tritium and C14 contamination by the Tritium laboratory of the University of Miami. Vertical profiles for T, S and O 2 together with a listing of this data for standard depths for each station are given in the Annex Incidents During the test stations, there were problems with the rosette: several of the bottles were not triggered. The trouble had to do, probably, with too much friction on the bolts since this rosette had never been used before. After some lubrication the problem disappeared. There were some problems, during the test stations and some of the first stations of the A-5 section, with the portside winch. The oil of the hydraulic circuit became too hot causing the winch to lose power. After station 11 we switched to the other winch that worked from the stern. On station 62, CTD # 1 stop sending conductivity data and it was replaced by CTD # 2 until station 74 when CTD# 1 was brought back, only for 7 stations since we started getting pressure spiking. From station 81 to 88 we used CTD #2 and from there on we used CTD# 1 after it was repaired on board. On station 83 the wire was reterminated after cutting off 10 m of wire because of a faulty electrical contact. It was also reterminated after station 110 (in the Florida Strait) because of two-blocking the CTD on recovery at this station. On station 61 the CTD hit the bottom because of a failure of the depth recorder. The portable hydrophone-recording system for use with the pinger failed from the beginning and we were not able to repair it. We tried to use the EA500 SIMRAD echo-sounder of the ship, but there was not the necessary documentation on board so we could not effectively use the pinger at all. We decided to keep the CTD package between 50 or 100 m above the bottom when the floor was too rough and less that 50 m when it was flat. The proposed Tritium and Helium survey by Dr. Z. Top could not be made since the equipment was lost during shipment from Miami and it never arrived to the ship. List of Participants Acronyms Name Responsibility Affiliation G. Parrilla Chief Scientist IEO H. Bryden Co-Chief Scientist WHOI J. Alonso CTD Watch IEO E. Alvarez CTD Watch/Thermosalingraph PCM B. Amengual S, O 2 IEO G. Bond CTD Watch/CTD Electronics WHOI J. Garcia-Braun O 2, Chlorophyll IEO J. Hernández Al FCMLP A. Cantos CTD Watch/ADCP Ainco I A. Cruzado Nutrients CEAB J. Escánez O 2 IEO S. Fiol CO 2 U. La Coruña M.J. García CTD Watch/Data Processing IEO D. Gelado Al FCMLP E. Gorman CFC LDGO A. Lavín CTD Watch/Data Processing IEO R. Millard CTD Watch/CTD Programming WHOI R. Molina CTD Watch/S IEO J. Molinero Electronics IEO A. Osiroff CTD Watch/ Data Processing SHMA A.F. Ríos CO 2 /M.O.P. IIM G. Rosón Calcium IIM P. Sánchez CTD Watch/Data Processing IEO W. Smethie CFC LDGO Z. Velasquez Chlorophyll CEAB A. Fougere Falmouth SI CTD WHOI C. Heuer Tritium/Helium RSMAS G. Mathieu CFC LDGO IEO IIM CEAB FCMLP PCM RSMAS WHOI LDGO SHMA UPC JRC Instituto Espanol de Oceanografia Instituto de Investigaciones Marinas Centro de Estudios Avanzados Blanes Facultad de C. del Mar Programa Clima Maritimo Rosenstiel School of Marine and Atmospheric Sciences Woods Hole Oceanographic Institution Lamont Doherty Geological Observatory Servicio de Hidrografía Naval Unversidad Politecnica de Cataluna James Rennell Centre 2. CTD MEASUREMENTS (R. Millard and M.J. Garcia) 2.1. Instrumentation, Calibrations and Standards Two EG&G/NBIS Mark IIIb CTD underwater units each equipped with pressure, temperature, conductivity and polographic oxygen sensors were used throughout the cruise. The CTD instrument numbers are 1100 and 2326 and they belong to the Instituto Espanol de Oceanografia (IEO). Each CTD is configured identically with the same data scan length, variables, and scanning rate of Hz. (A detailed description of the Mark IIIb CTD can be found in Brown and Morrison, 1978.) Both instruments were modified at Woods Hole Oceanographic Institution (WHOI) to add a titanium pressure sensor with a separately digitized resistive temperature device (RTD). A third EG&G/NBIS Mark IIIb CTD was provided by WHOI (WHOI instrument No. 8) but was not used during this expedition. A General Oceanics (GO) rosette fitted with liters Niskin bottles was used with the CTD for collecting water samples. The GO rosette bottles are mounted approximately 0.5 m above the CTD sensors. Titanium pressure sensors were manufactured by Paine Instrument and were installed with a separate pressure-temperature sensor in both CTDs prior to the cruise. The pressure data has a resolution of 0.1 decibars and an overall accuracy of decibars for CTD# 1100 and decibars for CTD # The pre-cruise pressure calibration was used for CTD # 1100 while a combination of pre and post cruise pressure calibration was used to process CTD # The Titanium pressure transducer processing methods follow Millard, et. al (1993). Pressure is calibrated across the pressure sensor's range in the laboratory before and after the cruise. These calibrations are carried out at both room temperature and at the ice point. The temperature sensor is Rosemount platinum # 171. The fast response temperature thermistor normally employed in the Mark IIIb has been removed. The temperature resolution is C and the accuracy is better than ± C (Millard & Yang (1993)) over the range 0 to 30.0 C. Temperature was calibrated in the laboratory before and after the cruise with the CTD instrument fully immersed as described by Millard & Yang (1993). A large (0.01 to C) shift of temperature in the same direction was observed to occur with both CTD's 1100 and This shift was traced to a faulty pre-cruise laboratory temperature standardization. The conductivity sensor is a 3 centimeter alumina cell manufactured by EG&G/NBIS. The resolution of conductivity is Ms/cm and the accuracy is directly tied to the water sample salinity accuracy discussed elsewhere in this report. The overall accuracy of the CTD conductivity calibrated to the rosette water bottle salinities is believed to be better than ± psu. The CTD oxygen is measured with a polographic sensor manufactured by Sensormedics. The CTD oxygens are calibrated to shipboard Winkler oxygens CTD data collection and processing The CTD data logging and processing was accomplished on two MSDOS PCs. The data logging was handled on an IBM compatible system with an math co-processor. The EG&G data logging program CTDACQ was used to record down and up profiles, separately on disk together with a rosette bottle file. The CTD data was edited to flag spurious data using the EG&G program CTDPOST. The remainder of the CTD post-processing was performed using the WHOI PC-based CTD processing system as described by Millard and Yang (1993). The post-processing was performed on an IBM compatible system with a 600 Mbyte optical disk (Sony SMO-C501) used for data archiving CTD calibration constants The standard Alumina conductivity cell materials expansion factors: Alpha = -6.5 E-6, Beta = 1.5 E-8 were applied to CTD #1100 and CTD #2326. When the pre-cruise pressure calibration was applied to CTD 2326 data, a Beta = -1.5 E- 8 was required to produce a salinity without a depth dependence; but a combination of pre/post-cruise pressure calibration allowed the use of the standard Beta value. The combined pressure calibration was used to process all CTD #2326 data because it produced CTD salinities free of depth dependence and yielded the pressure bias observed at sea. 2.4. Pre and post-cruise Laboratory calibrations polynomial coefficients Eng = E+Dr+Cr 2 (where r is the measured raw CTD data value and Eng is the standard engineering unit of the variable). The coefficients for each sensor are: A) Pressure: (Loading/unloading) CTD #1100 E= ; D= ; C= E-9 pre-cruise CTD #2326 E= 0.15; D= ; C= E-9 (pre-cruise) E= -12.5; D= ; C= E-9 (post-cruise) E= -6.3; D= ; C= E-9 (pre/post cruise combined) B) Temperature: (post-cruise) CTD #1100 (2 nd order fit, stand. dev. = ) E= ; D= E-3; C= E-11 : Lag= s CTD #2326 (1 st order fit, stand. dev. = ) E= ; D= E-3; Lag= s C) Conductivity: For CTD #2326 and CTD #1100 conductivity calibrations the post-cruise temperatures were used. For CTD #2326 the data was pressure averaged again after the cruise using the combined pre/post-cruise pressure calibrations while CTD 1100 used the pre-cruise pressure calibration. The conductivity (salinity) calibration was examined closely at the change of instruments during the cruise (i.e. instrument swap outs at stations 62 63, 73 74, 80 81, 88 89) and no shifts were found that were not arguably due to oceanic variability. CTD #1100 This CTD required some fine-tuning of conductivity slope calibrations. Bias, E= for all the stations Stations Slope D= E-2 74 (fit to itself) E E E E E E E E (fit to sta ) E-2 Stations 96, 97 and 98 salinities are low compared to the water samples, but we believe that water sample salinities are suspect for these stations. CTD #2326 For this CTD, there is significant down-up hysteresis in one of the salinity sensors (P, T, or C: mostly likely Conductivity). The up-profile salinity is fresher than the corresponding down-profile at a given potential temperature. Of course, at the bottom of the profile the salinity agrees but by 2.5 C (3500 dbars) on the 6000 dbar profiles a.005 psu discrepancy exists. A program was written to extract and create down-profile conductivity calibration data and we have to refit CTD #2326 conductivities below 2500 dbars. Stations 63 73, bias; E= Station Slope, D= 63 (Fit to down profile conductivity) E-2 64 (Fit to down profile conductivity) E E E E E E E E E E Bias, E= E-3 ( calibration) Final CTD data edit: Two mean profiles were created. One for the West African Basin and a second for the North American Basin, by averaging all deep BIO Hésperides stations on pressure surfaces. These mean profiles have been used to screen the individual casts of each basin for question able temperature, salinity and oxygen data, comparing individual profiles to respective mean profile. Two edit criteria were used to flag questionable data: Temperature, Salinity and Oxygen variations whose difference from the mean profile exceeding 5.5 standard deviations; Stability parameter exceeding 1.0E-5 per meter. A list of stations with bad or questionable data at the surface is given below: 1 2 W African B. 17, 26, 32, 35, 39, 41, 44, 47 2, 5, 10, 18, 19, 20, 22, 23, 27, 28, 29, 31, 33, 34, 36, 37, 38, 42, 43, 45, 46, 48, 50, 51, 52, 53 N American B. 57, 74, 76, 81 55, 56, 58, 59, 60, 61, 62, 68, 69, 70, 72, 77, 78, 79, 80, 82, 85, 86, Stations with bad or too low surface salinities. 2. Stations with questionable surface salinities. D) Oxygen The oxygen parameters were adjusted as shown on tables II and III. The header abbreviations denote the following: STA= First and last station numbers of the group used for calibration. BIAS, SLOPE, PCOR, TCOR, WT, LAG and Edit factor are parameters of the fit as described by Millard and Yang (1993). STD DEV= Standard deviation of the fit after some outlying water sample observations are discarded. OBS= Number of water sample observations used for the calibration. Table II Coefficients for Oxygen Calibrations STN BIAS SLOPE PCOR TCOR WT LAG e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e+02 Table III Statistics of Adjustments for Oxygen Calibrations STN STD DEV OBS STN STD DEV OBS e of e of e of e of e of e of e of e of e of e of e of e of e of e of e of e of e of e of e of e of e of e of e of 69 Notes to these tables Parameters obtained from stations 7 to 9 apply to stations Stations 15 to 19 were fit fixing parameters of except slope. Stations 32 to 39 calibrations applied to stations 32 to 40. Station 70 calibrated as group except slope Station 88 calibrated as except slope Station 89 to 101. Sta. 96 and 98 are excluded in setting calibration parameters. When they were included WT was negative. Figure 2 shows the histograms for salinity and oxygen differences between CTD and bottle samples deeper than 2500 db. The mean and standard error for the first one are 1.9 E-4 and 1.3 E-4 respectively. For oxygen, they are 1.1 E-4 and 2 E-3. Figure 2: The histograms for a) salinity and b) oxygen differences between CTD and bottle samples deeper than 2500 db. Figure 3: Nutrients diagrams. 3. BOTTLE DATA 3.1 Carbon System Parameters CARBON DIOXIDE, HYDROGRAPHIC, AN
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