Abstract:

At the mouth of Mobile Bay (Main Pass), a CTD survey was conducted using Seabird SBE 25 Sealogger CTD on 2016-04-19. It measured depth, conductivity, temperature, salinity, oxygen, pH, beam attenuation, beam transmission, and density.

Suggested Citation:

Brian Dzwonkowski, Steven Dykstra and Grant Lockridge. 2017. CTD data at Main Pass, Mobile Bay, April 19, 2016. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N75X279Z

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.

Data Parameters and Units:

FILENAME convention: FILENAME convention: surveyname_ddMonthYYYY_ CTDnamecastnumber_stationlocation e.g. DZ_19April2016_mini010_M01 Each CTD cast file is organized as: Column 1 = Depth [salt water, m]; Column 2= Conductivity [uS/cm]; Column 3 = Temperature [ITS-90, deg C]; Column 4 = Salinity, Practical [PSU]; Column 5= Oxygen, SBE 43 [mg/l]; Column 6 = Oxygen, SBE 43 [% saturation]; Column 7= ph: pH; Column 8 = Scan Count; Column 9 = Beam Attenuation, Chelsea/Seatech [1/m]; Column 10 = Beam Transmission, Chelsea/Seatech [%]; Column 10 = Density [sigma-t, Kg/m^3 ]

Methods:

CTD was allowed to soak for approximately one minute at shallow depth than raised to the near-surface before beginning the descent to the bottom. Bottom was determined when casting line went slack, at which point the CTD was raised to the surface. Field work: Survey of Main Pass with subsequent drifter release then moved offshore where surveyed an upper arch inside the C smile line (including moorings sites M1-M3) and finishing with transect down the channel. Drifters were released at site sw (DZ1) at 13:01 CDT, site se (DZ3) at 13:09 CDT, site cw (DZ5) at 13:14 CDT and site ce (DZ7) at 13:19 CDT. Stations locations/Cast Time(CDT) in Main Pass, Mobile Bay: Shoal west (sw): 30 14.617 -88 04.161 Time: 12:11 CDT Shoal center (sc): 30 14.367 -88 03.646 Time: 12:20 CDT Shoal east (se): 30 14.138 -88 03.1365 Time: 12:29 CDT Channel west (cw): 30 13.780 -88 02.397 Time: 12:39 CDT Channel center (cc): 30 13.668 -88 02.132 Time: 12:47 CDT Channel east (ce): 30 13.547 -88 01.883 Time: 12:55 CDT NOTE: Two extra casts in the channel center as well as channel west to make sure good data was collected there. In addition, another two casts were collected following the drifter that was released in Channel West Channel center (006_cc): 30 13.668 -88 02.132 Time: 13:23 CDT Channel west (007_cw): 30 13.780 -88 02.397 Time: 13:28 CDT Tracking drifter (T01) 30 13.505 -88 02.615 Time 13:33 CDT Tracking drifter (T02) 30 13.206 -88 02.913 Time 12:53 CDT Stations locations offshore field work: Mooring array and inner arch. M1: 30 10.479 -88 01.157 Time: 14:37 CDT GC9: 30 10.3657 -88 02.9915 Time: 15:07 CDT M2: 30 10.950 -88 04.675 Time: 15:22 CDT SI1: 30 11.367 -88 06.298 Time: 15:36 CDT M3: 30 12.058 -88 07.369 Time: 15:48 CDT SI2: 30 13.060 -88 08.589 Time: 16:05 CDT SI3: 30 14.036 -88 09.243 Time: 16:17 CDT SI4: 30 14.704 -88 09.514 Time: 16:33 CDT NOTE: Lots of Bird and Dolphin activity in this area, but front wasn’t clearly delineated. NOTE: Two additional cast were conducted at the location of the drifter pick-ups. dp3: 30 12.209 -88 08.490 Time: 17:06 CDT dp5: 30 10.475 -88 06.584 Time: 17:27 CDT Start of along channel transect AL07 (Farewell Buoy): 30 07.5181 -88 04.128 Time: 17:52 CDT GC1 (Green Can 3): 30 08.482 -88 03.736 Time: 18:01 CDT GC5 (Green Can 5): 30 09.441 -88 03.336 Time: 18:07 CDT AL05 (Green Can 7): 30 09.9097 -88 03.2919 Time: 18:17 CDT AL04 (Green Can 11): 30 10.9800 -88 02.9824 Time: 18:23 CDT AL03 (Green Can 13): 30 12.0156 -88 02.6829 Time: 18:31 CDT AL02 (Green Can 15): 30 12.8353 -88 02.5132 Time: 18:52 CDT Channel west (027_cw/DZ05): 30 13.7800 -88 02.3971 Time: 18:59 CDT Shoal center (028_sc): 30 14.367 -88 03.646 Time: 19:06 CDT NOTE: Drifter was picked up between AL04 and AL03. NOTE: Additional cast was conducted in Main Pass on the shoal center site (sc/DZ2) for comparison to the earlier cast as well as the spatial difference with the channel west site (cw/DZ5).

Instruments:

SeaBird SBE25 CTD, SeaBird SBE43, Chelsea/Seatech transmissometer

Individual Files: