#TEMPORARY ACCESSION NUMBER: #ACCESSION NUMBER: #CONTRIBUTOR: Dr. Roger Lukas #CONTRIBUTOR INSTITUTION: University of Hawaii Dept. of Oceanography 1000 Pope Road Honolulu, HI 96822 #ORIGINATOR: same #ORIGINATOR INSTITUTION: same #TITLE: CTD Data of the Hawaii Ocean Time-series (HOT) program in the North Pacific 100 Miles North of Oahu, Hawaii for Cruises HOT189-198 during 2007 #PROJECT: Hawaii Ocean Time-series (HOT) HOT was initiated and funded through grants from the National Science Foundation under the auspices of the Joint Global Ocean Flux Study (JGOFS) and the World Ocean Circulation Experiment (WOCE). The field phase of these programs has ended, but support from the Ocean Sciences Division of NSF has enabled continuation of our basic HOT measurement program. The physical oceanographic component contributes to the objectives of the World Climate Research Programme (WCRP) Climate Variability and Predictability (CLIVAR) Programme by providing information on interannual to decadal variability of the North Pacific Ocean. The US CLIVAR Office funded the physical oceanographic data during 2007. #ABSTRACT: The HOT program makes repeated observations of the physics, biology and chemistry at a site approximately 100 km north of Oahu, Hawaii. Two stations are visited about once a month: Kahe Point (Station 1: 21.34N, 158.27W) and Station ALOHA (Station 2: 22.75N, 158W). Various other stations are made intermittently in support of similar research objectives or mooring deployments. HOT CTD data are collected using a SeaBird CTD 9-11 Plus with dual sensors at the maximum sampling rate of 24 samples per second (24 Hz). They are screened for errors and processed to 2-dbar averages. Starting in 2006, the percent transmission field was replaced with a nitrate in the dataset. In separate NODC Accessions, Niskin bottle and thermosalinograph data from these same cruises are available. #PURPOSE: The objective of the physical component of HOT is to describe and understand the ocean climate and variability at a deep-water site in the North Pacific subtropical gyre near Hawaii. This requires a long time series of physical oceanographic variables, including water mass properties and currents, supporting and complementing the objectives of the biogeochemical component of HOT. #LOCATION EXTREMES: SOUTHERNMOST LATITUDE: 21.34 SOUTHERNMOST LATITUDE HEMISPHERE: N NORTHERNMOST LATITUDE: 22.75 NORTHERNMOST LATITUDE HEMISPHERE: N WESTERNMOST LONGITUDE: 158.27 WESTERNMOST LONGITUDE HEMISPHERE: W EASTERNMOST LONGITUDE: 158.00 EASTERNMOST LONGITUDE HEMISPHERE: W #LOCATION KEYWORDS: Hawaii, North Pacific Ocean #SAMPLING STATIONS: Station Coordinates Approximate Comments Depth (m) 1 (Kahe) 21 20.6'N, 158 1,500 HOT Program coastal station 16.4'W 2 (ALOHA) 22 45.0'N, 158 4,800 HOT Program open ocean station 00.0'W 3 23 25.0'N, 158 4,800 Established and ended in 1993 00.0'W 4 21 57.8'N, 158 4,000 Established and ended in 1993 00.0'W 5 21 46.6'N, 158 450 Established and ended in 1993 00.0'W 6 Kaena 21.85N,158.36W 2,500 Not taken on every cruise Point 7 (Kauai 22 30.8'N, 158 Basin) 10.0'W 4,800 Established in 1996 8 (HALE 22 27.5'N, 158 ALOHA) 7.9'W 4,800 Established in 1997 Casts have been obtained at station HALE-ALOHA during cruises conducted for retrieval and/or re-deployment of the bottom-moored buoy. #BEGIN AND END DATES: January 2007 - December 2007 #SAMPLING PERIODS: Year Crs# Start & End Dates Ship Chief Scientist ------------------------------------------------------------------------ 189 5 Feb - 9 Feb 07 R/V K-O-K Grabowski 190 19 Mar - 23 Mar 07 R/V K-O-K Mandujano 191 3 May - 7 May 07 R/V Kilo-Moana Sadler 192 8 Jun - 11 Jun 07 R/V Kilo-Moana Curless 193/ST-13A 6 Jul - 10 Jul 07 R/V Kilo-Moana Mandujano 194 2 Aug - 6 Aug 07 R/V Kilo-Moana Curless 195 1 Sep - 5 Sep 07 R/V Kilo-Moana Lethaby 196 1 Oct - 5 Oct 07 R/V K-O-K Lethaby 197 30 Nov - 4 Dec 07 R/V Kilo-Moana Mandujano 198 19 Dec - 23 Dec 07 R/V Kilo-Moana Curless ------------------------------------------------------------------------ K-O-K denotes Ka`imikai-O-Kanaloa #PARAMETERS: CTD: Pressure (Decibars) Temperature (Degrees Celsius, International Temperature Scale of 1990) Salinity (1978 International Practical Salinity Scale) Oxygen (micromoles per kilogram) Chloraphyll, Pigment (uG/L) Nitrate (uMOL/KG) #METHODOLOGY: Generalities are given below. Please see REFERENCES for additional information. Each of the (approximately monthly) HOT cruises follows the same basic pattern with some flexibility for ancillary projects to be done after the core sampling has been completed. During transit from Honolulu to the time-series station ALOHA (A Long-term Oligotrophic Habitat Assessment) one weight test is done to between 700 and 1000 m at station 1 off Kahe Point (16 km offshore from the western tip of Oahu, 21 20.6' N, 158 16.4' W, 1500 m water depth). Following the successful winch test, a CTD/rosette cast to 1000 m is conducted. This cast serves as a "shakedown" for the remainder of the cruise, and the functioning of the components of the CTD/rosette system as well as coordination between winch, deck and console operators can be tested. The training of new personnel in activities such as taking meteorological observations, and sampling salinities is also done in this station. The data taken at Kahe Point (station 1) represent an additional time-series of water properties at a near-shore site. Upon arrival at ALOHA (station 2), operations commence with a deep cast (maximum depth approximately 4750 m), 36-hour burst sampling3 of the upper 1000 m at the same location, plus CTD casts to support ancillary JGOFS work of about an extra 12 hours duration. Time permitting, the last CTD cast of the cruise will be a deep cast. On occasion, one cast will be done at station 3 (40 miles north of ALOHA at 23 25' N, 158 W). The second and following casts at station ALOHA are sampled to at least 1000 m depth. Cast 2 is called a "density cast" because water samples are taken at a number of specified density values ranging from [sigma-theta]= 27.37 to the surface with the intent to resolve the profiles of salinity, dissolved oxygen, and nutrients in potential density coordinates Depths sampled during the following casts within the 36-hour burst sampling period are chosen both by the science teams, who have to ensure that at least one water sample each is taken within the mixed layer, the shallow salinity maximum, the intermediate salinity minimum and the deepest position of the rosette for calibration of the CTD conductivity sensor. If oxygen bottles will be taken from the cast, then the sampling should include at least the mixed layer, oxygen maximum, oxygen minimum and the deepest rosette position for calibration of the CTD oxygen sensor. The second deep cast of the cruise (if there is one) should include sampling of oxygen bottles in at least seven levels appropriate for calibration of the CTD oxygen sensor, i.e. in the oxycline and two more levels below the oxygen minimum, in addition to the four levels mentioned before. The primary objective of the HOT program is to assess variability in the central Pacific Ocean on annual and interannual time scales. One of our most important concerns, therefore, is to ensure that the highest possible precision and accuracy is consistently maintained for all water column chemical measurements. In order to achieve the highest possible data quality, we have instituted a quality-assurance/quality-control program, and have attempted to collect all ancillary information necessary to ensure that our data are not biased by sampling artifacts. Because sampling is over 36 hours, one can average out the effects short-term changes of the depth of density surfaces and the magnitude of hydrographic and nutrient variables (inertial, tidal, and shorter periods). CTD data were acquired at a rate of 24 samples per second. Digital data were stored on a laptop personal computer and, for redundancy, the analog signal was recorded on VHS videotapes. Backups of CTD data were made onto Zip disks and later onto compact disks. The raw CTD data were quality controlled and screened for spikes as described in Winn et al. (1993). Data alignment, averaging, correction and reporting were done as described in Tupas et al. (1993). Salinity spike rejection parameters were modified for some cruises in 2004 because of rough sea conditions. Spikes occur when the CTD samples the disturbed water of its wake; therefore, samples from the downcast are rejected when the CTD is moving upward or when its acceleration exceeds 0.5 m s-2 in magnitude. Cruises 155, 156, and 157 were conducted under 19 relatively rough conditions. The CTD acceleration cutoff value had to be increased to between 0.55 and 0.65 m s-2 for some of the casts to relax the data rejection criteria and avoid eliminating an excessive number of points. The data were additionally screened by comparing the temperature and conductivity sensor pairs. These differences permitted identification of problems in the sensors. Only the data from one set of T-C sensors and one oxygen sensor, whichever was deemed most reliable, is reported here. #INSTRUMENT TYPES: Sea-Bird CTD SBE-9/llPlus Continuous measurements of temperature, salinity, oxygen and fluorescence are made with a Sea-Bird SBE-9/11Plus CTD package with dual temperature, salinity and oxygen sensors and fluorometer described in Fujieki (2004). CTD underwater unit No.91361 was used during 2006. Starting HOT-177 (2006), the Transmissometer (XMISS) data that was once included in the CTD files have been replaced by continuous Nitrate measured using Satlantic's InSitu Underwater Spectrometer (ISUS V2). Satlantic's ISUS V2 is a chemical free sensor that uses UV absorption technology to provide accurate nitrate concentration measurements in real-time. Temperature is reported in the ITS-90 scale. Salinity and all derived units were calculated using the UNESCO (1981) routines; salinity is reported in the practical salinity scale (PSS-78). Oxygen is reported in µmol kg-1 and Chloropigment (Fluorescence) in µg/l. #REFERENCES 1990 Chiswell, S., E. Firing, D. Karl, R. Lukas and C. Winn. Hawaii Ocean Time-series Program Data Report 1, 1988-1989. SOEST Tech. Rept. 1, School of Ocean and Earth Science and Technology, Univ. of Hawaii, Honolulu, HI, 269 pp. 2006 Fujieki, L.A., F. Santiago-Mandujano, P. Lethaby, R. Lukas, and D. Karl. Hawaii Ocean Time-series Program Data Report 18, 2006. School of Ocean and Earth Science and Technology, Univ. of Hawaii, Honolulu, HI, 475 pp. #SUBMITTING MEDIUM: FTP #FILE FORMATS: Directories and files: /data root data directory /0-data Files as received by NODC from the originator /woce_sum WOCE-type sum file which gives details on position and parameters taken of each cast and station of each cruise. Filenaming convention: hotccc.sum where ccc is cruise number /ctd CTD data. Filenaming convention: hcccasstt.ctd where ccc is cruise number a is constant ss is station number tt is cast number CTD Data Format Document, January 13, 1992 CTD data are distributed in a format specified by the international WOCE Hydrographic Programme Office (WHPO). This document describes that format. Each station/cast is stored in a separate file. A file's name can be determined by the concatenation of 'h', 2 digit cruise number, 'a', a 2 digit station number, a 2 digit cast number and a file extension of ctd. For ex- ample, HOT-1, station 2, cast 3, would be found in h01a0203.ctd. The cruise and position information for each cast is in the cruise summary file (*.sum). The EXPOCODE, station number and cast number can be used to cross-reference the CTD data files with the cruise summary file. This code allows for the identification of the cruise. It consists of a 4 character NODC country-ship code, a maximum of 8 character cruise number followed by a "/" and leg number. For example, the EXPOCODE for HOT-13 on the R/V Moana Wave would be 31MW013/1. The CTD data file has a fixed record length of 65 characters / record. The first six records of a CTD file contain header information: Record 1: Column Format Item 9-22 a14 EXPOCODE (KA=Kaimalino,WE=Wecoma,MW=Moana Wave) 31-34 a4 WHP station identification 41-42 i2 Month 43-44 i2 Day 45-46 i2 Year FORTRAN FORMAT (8x,a14,8x,a4,6x,3i2) C "%*s %s %*s %s %*s %2d%2d%2d" Record 2: 7-12 a6 Station number 20-22 i3 Cast number 36-40 i5 Number of data records in the file FORTRAN FORMAT (6x,a6,7x,i3,13x,i5) C "%*s %d %*s %d %*s %d" Record 3: 16-21 i6 Instrument number 37-41 f5.2 Sampling rate (hz) FORTRAN FORMAT (15x,i6,15x,f5.2) C "%*s %d %*s %f" Record 4: Headers for data columns (variable labels). Record 5: Unit header for data columns. Record 6: Quality byte designators. All columns requiring a quality byte are underscored by seven asterisks. The remaining records contain CTD data. The order of variables in a record are as follows: pressure, temperature, salinity, oxygen, nitrate, fluorescence and quality. Missing values are flagged with -99.0. Data Record Format: Column Format Item 1-8 f8.1 Pressure (Decibars) 9-16 f8.4 Temperature (Degrees Celsius, International Temperature Scale of 1990) 17-25 f9.4 Salinity (1978 International Practical Salinity Scale) 26-33 f8.1 Oxygen (micromoles per kilogram) 34-41 f8.3 Nitrate (micro Moles per Kilogram) 42-49 f8.3 CHLPIG (uG/L) 50-57 i8 Number of observations averaged at this pressure level 58-65 i8 Quality (defined by investigator) ** FORTRAN FORMAT (f8.1, f8.4, f9.4, f8.1, 2f8.3, i8, i8) C "%f %f %f %f %f %f %d %d" ** The quality word is the left-to-right concatenation of required qualityi bytes for the variables measured. They are defined as follows: byte value Definition 1 Not calibrated with water samples. 2 Acceptable measurement. 3 Questionable measurement. 4 Bad measurement. 5 Not reported. 6 Interpolated value. 7 Not assigned for CTD data 8 Not assigned for CTD data 9 Not sampled #DATASET SIZE: 8101 kbytes; 200 files #NUMBER OF DATA UNITS: 10 unique cruises #MISCELLANEOUS: Previous HOTs Bottle submissions to NODC: NODC Accession Contents 9900208 HOTs 1988-1998 0000639 HOTs 1999-2000 0001707 HOTs 2001-2003 0010624 HOTs 2004-2005 0041594 HOTs 2006 Previous HOTs CTD submissions to NODC: NODC Accession Contents 9900206 HOTs 1988-1998 0000640 HOTs 1999-2000 0001704 HOTs 2001-2003 0010740 HOTs 2004-2005 0042029 HOTs 2006 Previous HOTs thermosalinograph submissions to NODC: NODC Accession Contents 9900213 HOTs 1988-1998 0000641 HOTs 1999-2000 0001710 HOTs 2001-2003 0011142 HOTs 2004-2005 0041849 HOTs 2006