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Gulf of Mexico Hydrographic and Marine Mammal Data On CD-ROM

CTD, XBT, & Bottle Data, 1987-1995

GulfCet Program:

CTD, XBT, & Marine Mammals Database, 1992-1994

The files on this CD-ROM are divided into two data groups:

• TAMU-GULFCET and
• TAMU-OCEANOGRAPHY

Data are reported from 256 CTD and 580 XBT stations in the TAMU-GULFCET section and from 695 CTD and 707 XBT stations in the TAMU-OCEANOGRAPHY section.

TAMU-GULFCET

The "TAMU-GULFCET" hydrographic data were collected by researchers from the Texas Institute of Oceanography and from Texas A&M University at Galveston during the course of a 2-year field program to study the "Distribution and Abundance of Marine Mammals in the North-Central and Western Gulf of Mexico" in 1992 and 1993. The GulfCet program was sponsored by the United States Minerals Management Service (MMS), under contract number14-35-0001-30619, with Dr. R.W. Davis as Program Manager (Department of Marine Biology, TAMU Galveston). Dr. G.S. Fargion (also Department of Marine Biology, TAMU Galveston) was PI for TAMU-GULFCET hydrographic data collection, was Technical Editor for hydrographic data reports, and headed the GulfCet Data Management Office. Hydrographic data were collected over the continental slope of Texas and Louisiana on seven TAMU sponsored cruises, one cruise per season, from April 1992 through December 1993. The first GulfCet cruise was fielded aboard the University of Texas research vessel Longhorn; the subsequent six GulfCet cruises were aboard the Louisiana Universities Marine Consortium (LUMCON) ship, R/V Pelican.

TAMU-OCEANOGRAPHY

The "TAMU-OCEANOGRAPHY" hydrographic data were collected over a broader geographic area of the Gulf of Mexico, prior to and subsequent to as well as concurrent with the GulfCet project. The data archived here have been drawn together from 46 cruises over a 9-year period that were staffed by seagoing Marine and Electronics Technicians of the Department of Oceanography, Texas A&M University (a.k.a. TAMU Technical Support Services Group) on the research vessels Gyre (AGOR-21, operated by the Department of Oceanography, Texas A&M University), J.W. Powell (operated by the Geochemical and Environmental Research Group, Texas A&M University), and Antares (formerly USNS S.P. Lee; this vessel was transferred 1994 by the US Navy to the Direccion General de Oceanografia Naval of the Mexican Navy).

The TAMU-OCEANOGRAPHY hydrographic data encompass the 9-year period March 1987 through June 1995. The 45 cruises of Gyre and Powell were sponsored by NSF, DOE, and Navy grants and contracts, as well as by the State of Texas for graduate student training and research, and by oil and gas industry contracts for piston coring and other MG&G exploration; the cruise on Antares was sponsored by the Mexican Navy. Starting in October 1989 and continuing through June 1995, a Cooperative Agreement 14-35-0001-30501 between MMS and TAMU for the collection of Ship Of Opportunity Program hydrographic data (a.k.a. TAMU-SOOP) helped support the at-sea participation of TAMU technicians on most of the TAMU-OCEANOGRAPHY cruises 1990-1995, as well as the preparation of technical reports to archive and share the hydrographic data with NOAA's National Oceanographic Data Center (NODC) and with GulfCet and other MMS-sponsored field programs. Dr. D.C. Biggs (Department of Oceanography, TAMU College Station) was Program Manager for the TAMU-SOOP hydrographic data collection and Technical Editor for the data reporting.

Shiptime Sponsors

• TAMU - Department of Oceanography, Texas A&M University (College Station, TX)
• UT - Institute for Geophysics, University of Texas (Austin, TX)
• TIO - Texas Institute for Oceanography (Galveston, TX)
• GERG - Geochemical & Environmental Research Group, Texas A&M University
• NSF - National Science Foundation
• DOE - Department of Energy (Ocean Margins Program)
• ONR - Office of Naval Research, Naval Research Lab (Stennis MS); Naval Air Warfare Center (Warminster,PA)
• MMS/LATEX - Minerals Mgmt Service (LATEX Shelf Circulation Study: CM Recovery)
• DGON - Mexican Navy (Direccion General de Oceanografia Naval)

The TAMU-OCEANOGRAPHY data are partitioned in 46 subdirectories, each named with a 5 character code which identifies the year-vessel-cruise. For example, subdirectory 89G15 is cruise 15 of R/V Gyre for the year 1989; 91P03 is cruise 3 of R/V J.W. Powell for 1991; 95ANT is a 1995 cruise on Antares. When sorted by vessel, the data archive contains 43 cruises of Gyre, 2 cruises of Powell, and 1 cruise of Antares.

Within each of these 46 subdirectories, the hydrographic data are partitioned by type: Raw Data (CTD; XBT; Bottle) and Processed Data (Splined XBT; Dynamic Height; Transport).

Raw Data

CTD Data: in subdirectories CTD

The CTD data are downcast files. During this 9-year period, a succession of various Conductivity-Temperature-Depth (CTD) instruments were used to profile temperature and salinity. From 1988 on, most cruises were supported with either a SeaBird SBE-09 "Deep Ocean" CTD or a SeaBird SBE-19 "SeaCat" CTD. In 1987, however, two other types of CTDs were used:

On the first two cruises (87G-03, 87G-04), a so-called "Aggie" CTD was used. This had SeaBird temperature and conductivity sensors mounted on a rebuilt Grundy/Plessy series 9404 fish, to which was mated a SeaTech 25-cm pathlength transmissometer. This package scanned conductivity + temperature + pressure + 8-bit transmissometer voltage every 1.7 seconds. The 87G-03 data are raw data, while data reported for 87G-04 have been 5 m averaged (generally, about 3 scans per 5 m bin). For 87G-10, 87G-11, and 87G-12, a Neil Brown Mark-III CTD was used instead of the experimental "Aggie" CTD which had supported 87G-03 and 87G-04. The Mark-III CTD was mated to a 25-cm pathlength SeaTech transmissometer; the Mark-III scanned the conductivity + temperature + pressure + transmissometer voltage data faster (20 times per second) and also permitted the collection of 12-bit transmissometer voltage.

On cruise 88G-05 (Oct 88) and most subsequent cruises 1989-1995, a SBE-09 CTD outfitted with dual temperature and dual pumped conductivity sensors was used. This was generally mated with a SeaTech 25-cm pathlength transmissometer (12-bit voltage data) and/or a Chelsea Instruments 'Aquatrakka' submersible fluorometer (12-bit voltage data). This SeaBird system scans each of the data channels about 20 times per second; 1 m averaged data is the standard data product. On cruises aboard R/Vs Powell and Antares, a SeaBird SBE-19 was used. The conductivity sensor of the "SeaCat" was unpumped for the first of these cruises (91P-03) but a pump was subsequently added prior to cruises 94P-12 and 95ANT.

Exceptions: Neil Brown CTDs were used on two cruises subsequent to 1987: 89G-03 and 94G-03. For R/V Gyre cruise 89G-03, Dr. Denis Wiesenburg outfitted the Neil Brown Mark-III CTD with a conductivity sensor of non-standard (wide) range, to allow T,S data to be collected within the high salinity brine of the Orca Basin. Previous experience had shown that in this high salinity brine pool, standard conductivity sensors of most CTDs read offscale high. Please see the file "readme.1st" in the /89G03/CTD subdirectory for additional details. For R/V Gyre cruise 94G-03, an EG&G/NBIS CTD provided by the University of Rhode Island was used. Data from a test cast made in the central Gulf of Mexico, while Gyre was enroute to the Caribbean, are reported with the kind permission of Mr. Jan Szelag, URI.

Bottle Data: in subdirectories BOTTLE

Bottle samples were collected with 5-, 10-, or 30-L Niskin bottles on most of the upcasts. For each cruise, the CTD salinity data were compared with bottle salinity samples collected with a 12-place or 24-place rosette multisampler package. For this process, the CTD data were first averaged into 5 m bins (87G-03 and 87G-04) or into 1 m bins (87G-10 and subsequent cruises) and then corrected station by station to minimize any offset between CTD salinity and bottle salinity determined at sea on a Guildline conductive laboratory salinometer. For any individual CTD cast, adjusted CTD salinities generally agreed within 0.005 with bottle salinity. Details can be found in each of the TAMU Technical Reports 88-01-T through 95-09-T that have been produced in conjunction with each cruise (D.C. Biggs, Technical Editor). Bottle samples were also analyzed for nutrients and dissolved oxygen, and sometimes for chlorophyll and phaeopigment content. Nutrient analyses were carried out on board with a Technicon autoanalyzer (on board for all cruises except 87G-03, on which samples were frozen and analyzed 2-3 weeks later, post-cruise); dissolved oxygen was determined on board by manual titration with a Manostat ultra-micropipetter. Pigments were calculated from fluorescence of 1 liter samples filtered on to GF/F filters and then extracted in 90% acetone. The accuracy and resolution of these procedures was as follows:

Guildline model 8400 series "AutoSal" Salinometers (8400, 8400A, 8400B):

Manufacturers specifications are as follows: Range: 0.005-42 psu (practical salinity units) Accuracy: Better than +/-0.002psu over 24hrs without restandardization; technicians generally standardized at least once a day. Resolution: Better than +/-0.0002psu @ 35 psu.

Nutrients: Technicon AA-ll, adapted for 6 channels of simultaneous analyses:

Analytical procedures followed protocols developed for the WOCE Hydrographic Program, under the scientific guidance of Professor L.I. Gordon (Oregon State University).

6 channels of simultaneous analyses

	Range	Accuracy	Resolution
Silicate	0-30 uM/L	0.5 uM/L	0.1 uM/l
Phosphate	0-3	0.02	0.01
Nitrate	0-35	0.5	0.1
Nitrite	0-2	0.01	0.01
Ammonia	0-5	0.05	0.01
Urea	0-5	0.1	0.05

Dissolved oxygen: Carpenter/Carritt modification of Winkler manual/visual titration procedure:

Range: 0.02-10 ml/L
Accuracy: +/-0.5%
Resolution: +/-0.1%

Pigments: Measured at sea on a Turner Designs model 10 fluorometer:

Range: 0.01 - 10 ug/L Accuracy, Resolution: +/- 0.01 ug/L Agreement with High-Performance Liquid Chromatography (HPLC) analytical methods: see Bianchi et al. (1995) in Bull. Mar. Sci. 56: 25-32.

XBT Data: in subdirectories XBT

Data from the 1987 cruises were digitized by hand and are reported in standard, condensed NODC format. Data from 88G-05 and subsequent cruises were digitized by Sippican Mark-9 (and later Mark-12) systems; raw data are reported as (Z, T) data pairs computed by the Sippican software.

With the exception of one cruise (91G-02), the Expendable Bathythermographs (XBTs) used were probe type T7 (data to 760 m), manufactured by the Sippican Corporation (Maynard, MA) or by Sparton of Canada, Ltd (Ontario). On cruise 91G-02, the Sippican "Deep Blue" probe type T5 were used (data to 1500 m).

XBTs were provided by a variety of sponsors: the US Minerals Management Service (via subcontract to Science Applications International Corporation, Raleigh NC, for Ship Of Opportunity Program fieldwork); the Office of Naval Research (via Naval Research Laboratory, Stennis Space Center, MS); the Eddy Joint Industry Project (Houston, TX); and for test purposes by the manufacturers (Sippican Corporation, Maynard MA; Sparton of Canada Ltd., Ontario).

Processed Data

XBT Data splined with salinity from adjacent CTD station(s): in subdirectories SPLNDXBT


On most cruises which transited the Loop Current and the various Eddies shed from the Loop Current 1989-1995, XBT data have been combined with CTD data to compute the local geostrophic circulation field. On most of these cruises, there were CTD stations located within 60-100 nautical miles of most XBT stations. This allowed very tight T-S control for the interpolation of salinity to XBT temperature, as well as the use of two or more different CTD stations to independently verify the resultant spline. In the XBT subdirectories within each cruise, the raw (Z, T) data pairs were not corrected for drop rate artifact. However, in the SPLNDXBT subdirectories, the depth (m) was first corrected by z = [1.047*z - 3] for probe type T7 and by z = [0.098*z + 1.8] for probe type T5, prior to splining salinity to each (Z,T) data pair. These two corrections reflect our empirical determination that T7 and T5 probes actually fall about 5% slower and 2% faster, respectively, than predicted by the manufacturers' software. Further explanation has been provided by Singer (1991) in J. Atmos. Oceanic Technol., 7: 603-611 and by Biggs (1992, in J. Geophys. Res. 97: 2143-2154.)


Geopotential Anomaly Calculations: in subdirectories DYNHGHT and TRANSPRT


Corrected XBT data were combined with corrected CTD data to compute dynamic heights. A micro VAX 3600 computer was used for the calculations of dynamic height and mass transport/geostrophic velocity between station pairs, as described by Biggs (1992, in J. Geophys. Res. 97: 2143-2154.) All of the geopotential computations were referenced to the 800 dbar (795 m) surface, since this geopotential surface is the deepest generally available from the T7 XBT probes.

Hofmann and Worley (1986, in J. Geophys. Res. 91: 14221-14236) have shown empirically that the optimum reference level of no motion in the central and western GOM is near the bottom boundary of the Antarctic Intermediate Water (AAIW) at a depth of 850 to 950 m. Their model is supported by transport calculations for anticyclonic eddies (Biggs 1992 JGR article cited in preceding paragraph).


Data Format Information (TAMU-OCNG):


Station information in the CTD and XBT subdirectories is given by data headers. These headers are of two types: a) 6-line header, or b) 1-line header. Both give cruise ID, Station number, Date, GMT, and Lat and Lon information, though the order of this information will differ.

For example, a 6-line header for Station 1 from Powell cruise 91P-03 is as follows:

Cruise:	91P-03 [Gyre, Powell, or Antares: 5-character code]
Date:	Mon Jun 10 1991, Julian day = 161
Time:	17:30:00 GMT
Lat:	26 53.00 N
Lon:	96 58.00 W
Stn.	01

This 6-line header is followed by a call to the raw data file:

[e.g. raw data file = sb003.dat] Since this station was a CTD cast, there are four or more columns of data:

[e.g., for SeaCat CTD data, this is generally of the form]

meters	temp	salinity	sigma-t
12.000	28.0465	33.6285	21.2755
13.000	etc	etc	etc

Additional columns of transmissometer and/or fluorometer data may follow. The 1-line headers compress the same information into a 58-character line:

Spaces 1-5 = 5 character cruise ID
Spaces 6-12 = repeat 5 character cruise ID prefaced by X (XBT) or C (CTD) or S (SeaBird), A (Aggie experimental CTD), or N (Neil Brown Mark III CTD)
Spaces 13-18 = station number
Spaces 19-20 = cast information [DD = downcast; T7 = XBT type]
Spaces 21-28 = date information [Day, Month]
Spaces 29-37 = time [Hours:Minutes GMT]
Spaces 38-45 = Latitude information [degrees, minutes.tenths]
Spaces 46-54 = Longitude information [degrees, minutes.tenths]
Spaces 55-58 = Initials of person who did the cast


For example, the header

95ANT C95ANT*0001*DD 14 JUN 16:24GMT 21 00.0 86 30.0 DCB

shows that this was cruise 95ANT, that this is a CTD data file, that this is station 01, that it is downcast (DD) data, that the date is 14 June, that the time was 16:24 GMT, and that the cast was done at 21 00.0 N and 86 30.0 W, by "DCB" (Douglas C. Biggs).

Header information for files in the SPLNDXBT and DYNHGHT subdirectories has been further condensed to include just: 1) 5-character cruise ID; 2) Latitude; 3) Longitude. There are three data columns in files in the SPLNDXBT subdirectories; these give (from left to right): Depth, Temperature, and Salinity.

The 12 data columns of "crunched" data in files in the DYNHGHT subdirectories give (left to right) not only Depth, Temperature, and Salinity, but they continue with computated Stability (Brunt-Vaisala frequency), Potential Temperature, Density (as five different modes: Sigma-0 thru Sigma-4), Dynamic Height (meters), and Transport Potential.

---

FORMAT INFO FOR SUBDIRECTORY [DYNHGHT] DATA FILES:

CRUISEID = Cruise identification.
STAID = Station identification.
IDD = Day.
IMM = Month.
IYY = Year.
ITTTT = Time.
ILAT = Latitude (degrees).
AMINLAT = Latitude (minutes and tenths).
ILON = Longitude (degrees).
AMINLON = Longitude (minutes and tenths).
IDDD = Depth.
NDATA = Number of lines of data in file.


Write and format statements for data file header.

WRITE (15,521) CRUISEID,STAID,IDD,IMM,IYY,ITTTT,
. ILAT,AMINLAT,ILON,AMINLON,IDDDD,NDATA
521 FORMAT (1X,5X,A5,1X,A3,1X,3(I2,1X),I4,1X,2(I2,1X,F4.1,1X),I4,X,I4)

Z = Depth (meters). Z(I)
TEMP = Temperature (degrees C). T(I)
SAL = Salinity (ppt). S(I)
STAB = Stability. E(I)
PT = Potential temperature (degrees C). PT(I)
SIG0 = Sigma t. SIG(I,1)
SIG1 = Sigma one. SIG(I,2)
SIG2 = Sigma two. SIG(I,3)
SIG3 = Sigma three. SIG(I,4)
SIG4 = Sigma four. SIG(I,5)
DYNHT = Dynamic height. DHT(I)
TRAN POT = Transport potential. IQ(I)


Write and format statements for data file.

WRITE(15,210) ! Output the data

210 FORMAT(3x,'Z',4X,'TEMP',3X,'SAL',6X,'STAB',5X,'PT',7X,'SIG0',

*5X,'SIG1',5X,'SIG2',5X,'SIG3',5X,'SIG4',3X,'DYNHT',3X,
*'TRAN POT')
WRITE(15,240)(Z(K),T(K),S(K),E(K),PT(K),
* (SIG(K,L),L=1,5),DHT(K),IQ(K),K=1,NEWN)

240 FORMAT(1x,F6.1,1x,F6.3,1x,f6.3,F9.1,6F9.3,F9.6,I9)

For more information about Ship of Opportunity Data, contact:

Technical Support Services Group
Department of Oceanography
Texas A&M University
College Station, TX 77843-3146

Phone: (409)845-7211
Fax: (409)845-6331
E-mail: dbiggs@ocean.tamu.edu
Internet: http://www-ocean.tamu.edu/ *

For more information about the GulfCet Program, contact:

GulfCet Data Management Office
Texas A&M University
5007 Avenue U
Galveston, TX 77551

Phone: (409)740-4729
Fax: (409)740-5003 or 5002
E-mail: lynns@tamug.tamu.edu
Internet: http://www.tamug.tamu.edu/gulfcet/ *

For technical questions about this CD-ROM, or for ordering other oceanographic data, contact:

National Oceanographic Data Center
NOAA/NESDIS E/OC1
User Services
SSMC3, 4th Floor
1315 East-West Highway
Silver Spring, MD 20910-3282

Phone: (301)713-3277
Fax : (301)713-3302
E-mail: NODC.Services@noaa.gov