Entry 12 ======== .. image:: entry12.png :width: 684 :download:`Video <2008-07-15T00.mp4>` Authors ------- - Kristen Thyng - Rob Hetland The circulation of the waters on the Texas and Louisiana continental shelf is complex and dynamic. Many of the applications of understanding the circulation are related to how material in a region, like spilled oil or a harmful algal bloom, is transported by the currents. This transport can be investigated using drifters, which are passively moved by the ocean currents. This animation shows simulated drifters (with short tails showing a time history) at the sea surface of a numerical model of the currents on the Texas and Louisiana shelf. The drifters are started uniformly throughout the model domain. The released drifters immediately demonstrate the complexity of the underlying flow fields: drifters offshore near the outer model edge generally move together while drifters nearer the mouths of the Mississippi and Atchafalaya rivers form filaments due to convergence and divergence associated with eddies along the edge of the river plume. These eddies are seen within the river plume, the extent of which is marked by a solid black line. The drifters are colored by the water column depth of their starting location. As the drifters evolve in time, they sometimes move on- or off-shore, as seen by greener drifters found farther from, and bluer drifters nearer to, the coast. This represents cross-shelf movement and is a means by which off-shore oil spills can move toward the shore, or by which river-borne materials can leave the shelf toward deeper waters. The regular circular "jiggling" of the drifters is not due to tides, but rather inertial oscillations in the flow field: the regular land/sea breeze due to heating and cooling of the land during the day and at night aligns with the approximately 24-hour period of particle motion due to the Coriolis effect near 30˚ latitude. Visualizations of drifter motion in time allows for better understanding of important transport processes in this region. Products -------- - :download:`Video <2008-07-15T00.mp4>` Source ------ .. literalinclude:: plot_drifters.py - :download:`grid.nc `