Abstract:

A CTD survey was conducted on the inner Alabama shelf using Seabird SBE 25 Sealogger CTD on 2016-04-04. It measured depth, conductivity, temperature, pressure, salinity, beam attenuation, beam transmission, sound velocity, and density.

Suggested Citation:

Brian Dzwonkowski, Grant Lockridge, and Steven Dykstra.. 2017. CTD data on Alabama shelf, April 2016. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7SQ8XS9

Purpose:

The objective of this ongoing research is to identify the influence of fluvial water and its suspended particulate matter on coastal regions including the ecosystem and its susceptibility to oil. This particular study aims to understand the nature of buoyant freshwater plumes in shallow micro-tidal environments. Hydrographic surveys were conducted with a CTD. The survey was focused on taking CTD cast around locations where drifters were picked-up. Only two drifters were picked up – STATION DP1 and DP4. The other locations are around the drifter pick-ups. Note that an along channel survey was done on the ebb tide, but it started from the east (on the 35 isobath) and went in, which is slightly different from the normal ship channel survey.

Data Parameters and Units:

FILENAME convention: Surveyname_ddMMMMMYYYY_CTDnamecastnumber_stationlocation e.g. DZ_04April2016_Mini000_dp1 Stations locations/Cast Time (CDT) on the Alabama Shelf. Each CTD cast file is organized as: Column 1 = Temperature [ITS-90, deg C] Column 2 = Conductivity [uS/cm] Column 3 = Pressure [db] Column 4 = Salinity, Practical [PSU] Column 5 = Sound Velocity [Chen-Millero, m/s] Column 6 = Salinity, Practical [PSU] Column 7 = Density [sigma-t, kg/m^3] Column 8 = Depth [salt water, m] Column 9 = Specific Conductance [uS/cm] Column 11 = flag

Methods:

CTD was allowed to soak for approximately 1 minute at shallow depth than raised to the near-surface before beginning the descent to the bottom. Bottom was determine when casting line went slack, at which point the CTD was raised to the surface. dp01 (Drifter #8 pick-up): 29 58.837 -87 47.308 Time: 12:41 CDT dp02 (visible front): Estimated 30 01.656 -87 45.804 Time: 12:59 CDT dp03 (inshore cast): 30 04.472 -87 44.296 Time: 13:20 CDT dp04 (Drifter # 5 pick-up): 30 07.XXX -88 07.XXX Time: 14:16 CDT dp05 (inshore waiting for text-17 m): 29 59.020 -87 59.123 Time: 14:50 CDT dp06 (offshore start of channel transect): 29 47.812 -88 01.604 Time: 16:17 CDT dp07: 29 54.034 -88 01.627 Time: 16:48 CDT dp08: 29 59.832 -88 01.693 Time: 17:07 CDT dp09: 30 05.841 -88 02.353 Time: 17:27 CDT AL06 (Green Can 03): 30 08.908 -88 03.711 Time: 17:42 CDT AL05 (Green Can 07): 30 09.910 -88 03.292 Time: 17:48 CDT AL04 (Green Can 11): 30 10.980 -88 02.982 Time: 17:55 CDT AL03 (Green Can 13): 30 12.016 -88 02.683 Time: 18:03 CDT AL02 (Green Can 15): 30 12.835 -88 02.513 Time: 18:09 CDT Channel west (cw/DZ5): 30 13.780 -88 02.397 Time: 18:15 CDT AL00 (Green Can 21) : 30 14.825 -88 02.44 Time: 18:22 CDT Shoal Center (sc/DZ2): 30 14.367 -88 03.646 Time: 18:30 CDT

Instruments:

SeaBird SBE 25 Sealogger CTD

Individual Files: