Abstract:

This dataset contains CTD data collected from the R/V Point Sur during the June 2018 GoMix Cruise III (PS18_28). The experimental site is on the continental slope of the northern Gulf of Mexico, next to the Deepwater Horizon Spill site. During the cruise nine sections of CTD tow-yo's and three CTD casts were conducted. For each tow-yo, multiple vertical profiles were collected in the water column about 300 m above the bottom to map the water properties near the bottom. CTD casts are regular CTD stations covering the entire water column. The CTD used was a SEA-BIRD 911plus/917plus double sensor. The high-resolution data are available both in ASCII format and Matlab format. 1-m bin averaged profiles were generated separately to map the data in the depth and along-section dimensions; the data were saved as Matlab files.

Suggested Citation:

Kurt Polzin, Zhankun Wang and Steven F. DiMarco. 2020. Oceanographic profiles from CTD casts and tow-yos collected from the R/V Point Sur during GoMix Cruise III (PS18_28) in the northern Gulf of Mexico from 2018-06-22 to 2018-06-28. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/M8B3B9QN

Purpose:

Data was collected in support of studies of GoMix project with the goal of understanding the mechanisms, spatial inhomogeneity, and temporal intermittency of boundary mixing along the Northern Deepwater Gulf.

Data Parameters and Units:

CTD files: altM: Altimeter [m], Beam Attenuation (WET Labs C-Star [1/m]), Beam Transmission (WET Labs C-Star [%]), Conductivity [uS/cm], Conductivity, 2 [uS/cm], Fluorescence (WET Labs CDOM [mg/m^3]), Fluorescence (WET Labs ECO-AFL/FL [mg/m^3]), Nitrogen saturation [ml/l], Dissolved oxygen (SBE 43 [umol/l]), Dissolved Oxygen (SBE 43, 2 [umol/l]), Pressure (Digiquartz [db]), Temperature [ITS-90, deg C], Temperature 2 [ITS-90, deg C], Elapsed Time [seconds], Salinity (Practical [PSU]), Salinity 2 (Practical, 2 [PSU]), Density [sigma-t, kg/m^3 ], Density 2 [sigma-t, kg/m^3 ], Depth (salt water, lat = 28.80 [ m]), Descent Rate [m/s], Thermosteric Anomaly [10^-8 * m^3/kg], Potential Temperature [ITS-90, deg C], Potential Temperature 2 [ITS-90, deg C], Salinity (Practical [PSU]), Salinity 2 (Practical [PSU]), Density (sigma-t, [kg/m^3 ]), Density 2 (sigma-t [kg/m^3 ]), Depth (salt water, lat = 28.80 [m]), Descent Rate (WS = 2 [m/s]), Geopotential Anomaly [J/kg], Potential Temperature [ITS-90, deg C], Potential Temperature, 2 [ITS-90, deg C], Absolute Salinity [g/kg], Absolute Salinity, 2 [g/kg], Density, TEOS-10 [density, kg/m^3], Density, TEOS-10, 2 [density, kg/m^3], Potential temperature [ITS-90, deg C], Potential temperature 2 [ITS-90, deg C], flag. 1-m binned .mat files: A Matlab file for each cast containing 1-m binned data for each variable, interpolated along-section. High resolution .mat files: A single Matlab file with cell arrays for each variable containing data aggregated from all thirteen casts. alt_all (altitude, [m]), beam_all (beam attenuation [1/m], beam_tran_all (beam transmission [%]), cdom_all [mg/m^3], con2_all [uS/cm],con_all [uS/cm], depth_all [m], descent_rate_all [m/s], doxy2_all (dissolved oxygen, [umol/l]), doxy_all (dissolved oxygen, [umol/l]), fluor_all [mg/m^3], fnames_all [file list], lat_all [degrees], lon_all [degrees], mdate_all (date and time, Mon DD YYYY HH:MM:SS]), mlat_all (start position for casts 8-13), mlon_all (start position for casts 8-13), nbin_all, pre-all (pressure [dbar]), sal_a2_all (salinity [PSU]), sal_a_all (salinity [PSU]), salt2_all (absolute salinity [g/kg]), salt_all (absolute salinity [g/kg]), seat2_all (temperature [degrees Celsius]), seat_all (temperature [degrees Celsius]), sigmat2_all [kg/m^3 ], sigmat_all [kg/m^3 ], temp_p2_all (potential temperature [degrees Celsius]), tem_p_all (potential temperature [degrees Celsius]), times_all (elasped time [s]).

Methods:

Data from the CTD were acquired at 24 Hz. The CTD data were acquired by an SBE Model 11 plus CTD Deck Unit providing demodulated data to a computer in the engineering room running SeaBird software. After the cruise, the raw CTD data were run through the SeaBird data conversion software (SeaBird, Version 7.25.0.151). Data Conversion performs the first step in data processing, converting the raw CTD and auxiliary sensor data (typically frequencies and voltages) to engineering units. Data Conversion uses the instrument configuration file, which defines sensors, sensor channels, and calibration coefficients, to convert raw data to engineering units. The conductivity was advanced approximately 0.073 seconds relative to pressure for CTD alignment. No low pass filter was applied to the data to reserve the high-resolution signals. The practical salinity was calculated using DERIVE sal.cfg and the absolute salinity, density and potential temperature were calculated using DERIVE EOS80.

Instruments:

SBE Model 11 plus CTD Deck Unit

Individual Files: