Abstract:

This dataset contains conductivity, temperature and depth (CTD) data from the ship's CTD, deployed at each of the DEEPEND stations. The twenty-one CTD casts were made during the RV Point Sur cruise DP06 in the Gulf of Mexico from 2018-07-19 to 2018-08-01. Depth of cast is variable (usually ~1500m), but extends from near-surface waters to below the euphotic zone. Most of the CTD casts descended to approximately 1500 meters depth, but cast DP05_CTD-087 went to 1390 meters and cast DP05_CTD-090 descended to 200 meters. The CTD system included 2 temperature sensors, 2 conductivity sensors, 1 chlorophyll fluorometer, 1 dissolved oxygen sensor, and a WETLabs ECO-CDOM sensor. Specific information about the instrument configuration and calibrations for each cast can be found using the cast configuration file (.xmlcon). The binned CTD files' absorption of 400nm light (ag400) values were derived from the ECO-CDOM sensor voltage and the measured absorption from near-surface CTD water samples. The instrument data were processed from raw values to scientific units using Seabird’s “SBEDataProcessing” software version 7.26.6.28, which used the calibration data stored in the CTD data files from the cruise. Four files are available for each cast: a .hex file containing the binary cast data, a .xmlcon file with instrument configuration and calibrations, a .hdr file with information about the time and location of the cast, and a .bl file with information about the time individual sample bottles were closed during the cast. Along with the raw CTD files, 1-meter depth-binned files were also produced from the CTD downcast profiles to aid in inspection of the CTD results that are included in this dataset. The CTD raw-data and binned-data files are located in separate directories. This data is used in the assessment of the water column's vertical structure, and for comparison with physical models. The chlorophyll concentration and optical absorption spectra of particulate and dissolved material collected during this cruise can be found under GRIIDC Unique Dataset Identifier (UDI) R4.x257.000:0033 (DOI: 10.7266/n7-3t9h-8p38). The purpose of the R/V Point Sur DEEPEND cruise DP06 led by chief scientist Dr. Tracey Sutton was in situ samplings of water column properties and fauna.

Suggested Citation:

Sutton, Tracey; Hu, Chuanmin; English, David. 2019. Conductivity, temperature, and depth (CTD) data collected aboard the R/V Point Sur cruise DP06 in the Gulf of Mexico from 2018-07-19 to 2018-08-01. Distributed by: Gulf of Mexico Research Initiative Information and Data Cooperative (GRIIDC), Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-ceq1-5g82

Purpose:

To assess the water column's vertical structure during DEEPEND cruise DP06.

Data Parameters and Units:

Time[sec], latitude[degrees], longitude[degrees], cast number, depth bins, depth[m], temperature [deg C], temperature 2[degC], salinity[psu], salinity 2 [psu], oxygen[ml/l], saturated oxygen[%], CDOM (Colored Dissolved Organic Matter) absorption at 400nm[1/m], chlorophyll a concentration[mg/m^3], absolute salinity[gr/kg], absolute salinity 2[gr/kg], sigma t[kg/m^3], conservative temperature[degC], conservative temperature 2[degC]. Dataset also includes readme files and cruise data documentation. The time and location of all the twenty-one casts are also listed in the readme file. In the text version of the binned CTD files: the first 6 lines contain general information about the time and location of the cast, the 7th and 8th lines contain column headers and units for subsequent values, and lines 9 through the end of the file contains the 1 meter binned data separated into columns (tab deliminated).

Methods:

The information in the binned CTD files is only from the CTD’s downward casts, except for casts CTD-102 & CTD-104. There was no valid data in the upper 6 meters of CTD-102 and the upper 9 meters of CTD-104, so data for these upper depths were obtained from the upward CTD casts. The 1m binned data was binned (using medians) into 1 m depth intervals using custom Matlab scripts and functions, with only minimal application of alignment, filtering, and artefact removal. Fluorometric chlorophyll values have been scaled to approximate chlorophyll-a concentrations using selected water samples taken from multiple locations of this cruise. Values from the in situ ECO-CDOM sensor were scaled to the CDOM absorption of 400nm light from selected water samples. Only cautious interpretation of the ag400 values is suggested because of the limited number of samples and the low voltages produced by the sensor in these waters (many of the deeper values were at or below the CDOM sensor's output voltage detection limit).

Individual Files: