Texas-Louisiana shelf connectivity and time variability using particle tracking

Poster presented at the Gulf of Mexico Research Institute (GOMRI) oil spill conference in Mobile, AL, in January 2014.

Transcript

1. Texas-Louisiana Shelf Connectivity and Time Variability using Particle Tracking Kristen M. Thyng and Robert D. Hetland Oceanography, Texas A&M University, kthyng@tamu.edu Goal Understand the factors affecting cross-shelf transport on the Texas-Louisiana shelf for application to oil spill transport to the coastline TX-LA shelf numerical grid with other GISR grids Starting locations of numerical drifters: 5km spacing [green dots] Example drifter tracks from two locations [green (red) circles: start (end) locations, cyan/purple lines: tracks] Where do drifters travel in the domain? Do they cross the shelf? Does this change seasonally? What does it depend on? ⇒ Address with summarizing histograms Numerical Model • Regional Ocean Modeling System (ROMS) circulation model of the Texas-Louisiana shelf • Includes wind and rivers, nested in HYCOM Gulf model • Validation: (Zhang et al., 2012a,b) Particle Tracker • TRACMASS, runs trajectories natively on staggered Arakawa C grid (D¨ o¨ os et al., 2013) • ...wrapped in Python: TracPy (https://github.com/kthyng/tracpy) Simulations • Started weekly sets of drifters seeded 5 km apart in x and y which ran for 30 days • 2004-2010 • Surface-limited • Included diffusion to the particle trajectories with AH = 5 m2s−1 References D¨ o¨ os, K., Kjellsson, J., and J¨ onsson, B. (2013). Tracmass - A La- grangian trajectory model. In Preventive Methods for Coastal Pro- tection, pages 225–249. Springer. Zhang, X., Hetland, R. D., Marta-Almeida, M., and DiMarco, S. F. (2012a). A numerical investigation of the Mississippi and Atchafalaya freshwater transport, filling and flushing times on the Texas-Louisiana Shelf. Journal of Geophysical Research, 117(C11):C11009. Zhang, X., Marta-Almeida, M., and Hetland, R. D. (2012b). A high-resolution pre-operational forecast model of circulation on the Texas-Louisiana continental shelf and slope. Journal of Opera- tional Oceanography, 5(1):19–34. 2014 Gulf of Mexico Oil Spill and Ecosystem Science Conference, January 26–29, 2014, Mobile, Alabama
2. Probability drifters leaving an area will cross the shelf at some point Conclusions • Seasonal winds and river water affect cross-shelf transport • Stronger coastal cross-shelf connection in summmer • Coast is more likely to be affect by off-shore spills in the summer than the winter Location of trans-shelf drifters after 30 days Probability of drifters reaching the Chenier plain Probability of drifters reaching the TX coastline Probability of drifters reaching the LA coastline Acknowledgments This research was made possible by a grant from BP/The Gulf of Mexico Research Initiative 2014 Gulf of Mexico Oil Spill and Ecosystem Science Conference, January 26–29, 2014, Mobile, Alabama