Abstract:

A chemical tracer was released at approximately 1100m depth east of the Mississippi Canyon. Later, CTD data and water samples were collected to measure tracer concentrations to determine initial transport and dispersion of the tracer. RAFOS floats were released to track the water movement.

Suggested Citation:

Ledwell, James. 2013. Tracer release and intitial sampling from the GISR: G02 Cruise southeast of the Mississippi River Delta in July-August 2012.. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N79P2ZK2

Publications:

Ledwell, J. R., He, R., Xue, Z., DiMarco, S. F., Spencer, L., & Chapman, P. (2016). Dispersion of a tracer in the deep Gulf of Mexico. Journal of Geophysical Research: Oceans, n/a–n/a. doi:10.1002/2015jc011405

Miron, P., Beron-Vera, F. J., Olascoaga, M. J., Froyland, G., Pérez-Brunius, P., & Sheinbaum, J. (2019). Lagrangian Geography of the Deep Gulf of Mexico. Journal of Physical Oceanography, 49(1), 269–290. doi:10.1175/jpo-d-18-0073.1

Purpose:

The tracer allows researchers to track the movement of water at depth. This simulates oil release at depth similar to that which occurred during the Deepwater Horizon event.

Data Parameters and Units:

Microcat netCDF files: 1. profile cf_role (profile id) [0] 2. time time (minutes since 1-Jan-4713 BC 12:00 noon GMT) 3. lat latitude (decimal degrees) 4. lon longitude (decimal degrees) 5. Prz sea water pressure (decibars) 6. Tmp sea water temperature (degrees Celsius) 7. Cod sea_water_electrical_conductivity (Siemens/meter) CTD SLED netCDF files: 2. time time (minutes since 1-Jan-4713 BC 12:00 noon GMT) 3. lat latitude (decimal degrees) 4. lon longitude (decimal degrees) 5. pressure sea water pressure (decibars) 7. sal salinity (PSU) 8. temp sea water temperature (degrees Celsius) 9. sigma tracer density (kg m^-3) RAFOS txt files: * Col 0 = qualify flag [0 : no interpolation, 1 : one point interpolation, 2 : more than one point interpolation.] * Col 1 = LineNum * Cal 2 = TimeStamp [UTC] * Cal 3 = Temp [ deg-C ] * Cal 4 = Pres [ 100hpa] * Cal 5 = Lat [ deg-N ] * Cal 6 = Lon [ deg-E ] * Cal 7 = Current Velocity, U [cm/s] * Cal 8 = Current Velocity, V [cm/s] * Cal 9 = Current Velocity, W [mm/s] TRACER txt files: Sampler Array Analysis * Col 0 = date * Col 1 = Cast * Cal 2 = Wire Out * Cal 3 = Height [ based on 1100 m depth level] * Cal 4 = Volume of water analyzed [ml] * Cal 5 = Total Volume * Cal 6 = Volume of gas get into the syringe to equilibrate with the water sample * Cal 7 = Gas Chromatograph loop * Cal 8 = Gas Chromatograph aera (peak) in microvolt-seconds * Cal 9 = Tracer concentration [pmol/l] * Cal10 = density surface * Bad/Missing Value = NaN

Methods:

A towed system with injection sled at depth was used to release a tracer. Later, another towed system with a sled at depth pulled a vertical array of integrating water samplers. A CTD feed-back system kept the sleds at a precise density surface.

Instruments:

SeaBird SBE9, SBE-37 Microcatl, RAFOS floats

Error Analysis:

Profiles were inspected by eye for irregularities.

Provenance and Historical References:

See the cruise report which is included in this data submission.

Individual Files: