Study Provides Insights into How Floating Material Moves on the Ocean

View from the RV Walton Smith where the Gulf of Mexico and Mississippi River freshwater meet. Photo by Tamay Ozgokmen.

View from the RV Walton Smith where the Gulf of Mexico and Mississippi River freshwater meet. Photo by Tamay Ozgokmen.

Scientist John Taylor with the University of Cambridge analyzed simulations of small-scale fronts (<10 kilometers across) to better understand how they influence buoyant material transport across the ocean. The ocean circulation can cause the front to sharpen, leading to long and narrow features with an abrupt change in temperature or salinity. Taylor observed that small-scale fronts can be associated with strong surface convergence and downwelling, which causes buoyant material to accumulate and then be pulled beneath the surface by strong downwelling currents. These results have implications for oil spill response and for monitoring microplastics in the ocean by helping forecast where floating material may be accumulating, either on or beneath the ocean’s surface.

The author published his results in the Journal of Physical Oceanography: Accumulation and subduction of buoyant material at submesoscale fronts.

Buoyant material are particles that move upward relative to the surrounding water, such as bubbles, some types of phytoplankton, oil droplets, and microplastics. These floating particles play an important role in air–sea gas exchange, biogeochemical cycles, fisheries, and pollutant transport; and how the particles move depends upon what is happening just above, on, or just below the ocean’s surface.

During Deepwater Horizon, ocean models tracked how the oil spill was moving; but the spill’s location, magnitude, and depth revealed a need for improved transport modeling, including incorporating parameters for chaotic short-lived and small-scale surface flows or currents. Since then, research on small-scale ocean processes are helping to improve ocean transport predictions (for example, research on surface currents, how oil moves toward shore, and how riverine fronts influence oil transport).

This study focused on examining small-scale processes under controlled conditions to contribute to future work conducted under more realistic conditions. Study author John Taylor explained, “Fronts are ubiquitous features of the ocean surface, so this process is probably very common. I used very high-resolution numerical simulations to resolve features down to 2m in size. This was important to capturing the sharpness of the front and the strong downwelling along it. Because these processes happen on relatively small scales, ocean models may not capture this activity.”

Taylor observed that the downwelling of high concentrations of buoyant material enhances the vertical flux and can significantly modify the vertical distribution of the buoyant material. “Buoyant material can become concentrated in thin ribbons along fronts and a significant fraction of that might be beneath the surface at a given time. This work could help forecast where buoyant material will accumulate, with implications for oil spill remediation efforts.”

Data for this study are publicly available through the Gulf of Mexico Research Initiative Information & Data Cooperative (GRIIDC) at DOI:10.7266/N7T1520X and also at https://www.repository.cam.ac.uk/handle/1810/276133.

By Nilde Maggie Dannreuther. Contact maggied@ngi.msstate.edu with questions or comments.

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This research was made possible in part by grants from the Gulf of Mexico Research Initiative (GoMRI) to the Consortium for Advanced Research on Transport of Hydrocarbon in the Environment II (CARTHE II).

The Gulf of Mexico Research Initiative (GoMRI) is a 10-year independent research program established to study the effect, and the potential associated impact, of hydrocarbon releases on the environment and public health, as well as to develop improved spill mitigation, oil detection, characterization and remediation technologies. An independent and academic 20-member Research Board makes the funding and research direction decisions to ensure the intellectual quality, effectiveness and academic independence of the GoMRI research. All research data, findings and publications will be made publicly available. The program was established through a $500 million financial commitment from BP. For more information, visit http://gulfresearchinitiative.org/.

© Copyright 2010-2019 Gulf of Mexico Research Initiative (GoMRI) – All Rights Reserved. Redistribution is encouraged with acknowledgement to the Gulf of Mexico Research Initiative (GoMRI). Please credit images and/or videos as done in each article. Questions? Contact web-content editor Nilde “Maggie” Dannreuther, Northern Gulf Institute, Mississippi State University (maggied@ngi.msstate.edu).