Research Summaries

Back Origin, Dynamics, and Maintenance Mechanisms of Super Long-Lived Eddies

Fiscal Year 2019
Division Graduate School of Engineering & Applied Science
Department Oceanography
Investigator(s) Radko, Timour
Sponsor National Science Foundation (NSF)
Summary Coherent mesoscale eddies with traceable pressure extrema are able to survive in the turbulent oceanic environment for several months or even years according to numerous observations and eddy-resolving general circulation models. Many vortices propagate thousands of kilometers from their point of origin, transporting water-masses with distinct properties trapped in their cores. Despite decades of investigation, the remarkable longevity of such structures has not been fully explained. The transport characteristics of coherent vortices and their impact on general circulation are also yet to be fully quantified. Nevertheless, it is apparent that coherent mesoscale vortices can influence the variability of the Atlantic Meridional Overturning Circulation, control the pattern and transport of the Antarctic Circumpolar Current, and tangibly impact regional and global ecosystems. The proposed study is focused on the dynamics of Super Long-Lived Eddies (SLLE hereafter), defined here as coherent vortices with lifespans exceeding two years. The project will greatly enhance our understanding of fundamental physical processes, which is vitally needed to adequately represent mesoscale eddies in numerical and theoretical models. This knowledge becomes particularly urgent in light of the ongoing efforts by the geophysical community to improve the accuracy of future climate projections.
The proposed research program represents a synthesis of numerical modeling, theory, and data analysis, aimed at the identification of key features of SLLE responsible for their longevity. Our preliminary results and some observational evidence suggest that the interaction of SLLE with more irregular and time-dependent sub-mesoscale structures frequently causes the intensification, rather than decay, of their dynamic signatures. To unravel the interplay between coherent vortices and background variability, both internally and externally induced, we propose a hierarchy of numerical simulations with an increasing degree of realism. This interaction will be conceptualized using multiscale asymptotic models, which are ideally suited for the task due to their transparency and ability to represent interactions between phenomena operating on distinct spatial and temporal scales. The analysis of altimetry-based observations will serve as an ultimate benchmark for the evaluation of analytical and numerical models. The combination of all approaches will make it possible to establish the phenomenology of SLLE, concurrently producing an objective and comprehensive view of various maintenance mechanisms of coherent long-lived vortices in the ocean.
Keywords eddies ocean dynamics
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Data Publications, theses (not shown) and data repositories will be added to the portal record when information is available in FAIRS and brought back to the portal