Study Identifies Ocean Processes That Drive Surface Material Clustering

The spatial distribution of Lagrangian divergence energy in the Gulf of Mexico is represented in this 3 km model simulation for the period of July 20, 2012 to August 30, 2012. See Figure 8 in the publication for more detailed comparisons that show local peaks.  Image provided by Gregg Jacobs.

The spatial distribution of Lagrangian divergence energy in the Gulf of Mexico is represented in this 3 km model simulation for the period of July 20, 2012 to August 30, 2012. See Figure 8 in the publication for more detailed comparisons that show local peaks. Image provided by Gregg Jacobs.

Scientists analyzed Gulf of Mexico model simulations to understand the flow processes that drive clustering of buoyant material such as Sargassum, oil from seeps and spills, and debris on the ocean surface. They observed similar clustering patterns from the deep ocean and continental shelf, though the processes driving clustering differed between areas. Smaller-scale ocean features prompted stronger surface divergence and were the dominate driver of initial material clustering. As the effect of small-scale features on clustering diminished over time, larger-scale processes drove continued clustering. Understanding how different ocean processes determine the way materials accumulate on the surface can improve the effectiveness of oil spill cleanup efforts. The researchers published their findings in Journal of Geophysical Research: Oceans: Ocean processes underlying surface clustering.

Lagrangian divergence is the major force that contributes to clustering of material at the ocean surface. This study examined the effects of various surface ocean processes on Lagrangian divergence using data from the Grand Lagrangian Deployment or GLAD (deep ocean surface water) and the Surfzone Coastal Oil Pathways Experiment or SCOPE (continental shelf surface water). The team focused on surface clustering influenced by submesoscale to mesoscale ocean features (500 m to 500 km horizontal scales).  These small- and large-scale processes control cluster formation, deformation, and dispersal. The scientists conducted a series of numerical ocean model simulations with increasing resolutions – each of which captured a different spectrum of phenomena – to systematically investigate ocean processes.

Study author Denny Kirwan stated, “This work along with the companion paper of Huntley et al. (2015) have begun to unravel a perplexing mystery: in an ocean that is known to disperse material over great distances, how is it that stuff at the surface tends to cluster? It is only in the last few years that computing technology along with high-resolution data acquired by CARTHE with GoMRI support has it been possible to coalesce the fundamental technologies and begin to address this problem.”

Study author Gregg Jacobs noted the progress in oil spill response that this research contributed to, “Addressing hazardous spills has previously taken into account ocean forecasts that predict where currents will transport ocean material. Now, we have an initial understanding of clustering and have simulated how to address a hazardous spill taking into account the additional clustering forecasts, which shows that cleanup efficiency can be increased by a factor of 20 over a few days.”

Technologies of ocean forecast systems and Lagrangian dynamical understanding from different institutes working together have resulted in synergistic capabilities that enable scientists to make advancements for future applications.  This study’s team has made fundamental science advances, resulting in their submission of a patent application based on the new algorithms and insights. Jacobs noted, “There remain many difficult problems, and the CARTHE consortium continues to resolve many intertwined problems that affect our natural resources.”

Data from model experiments is available through the Gulf of Mexico Research Initiative Information and Data Cooperative under DOI numbers: 10.7266/N7FQ9TJ6, 10.7266/N76Q1V5G, and 10.7266/N72Z13F4, or by contacting author Gregg Jacobs.

The study’s researchers are Gregg A. Jacobs, Helga S. Huntley, A. D. Kirwan, Jr., Bruce L. Lipphardt Jr., Timothy Campbell, Travis Smith, Kacey Edwards, and Brent Bartels.

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This research was made possible in part by a grant 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/.

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