第66回 ESCセミナー
Submesoscale ocean dynamics: Eddy fluxes and the forward cascade
- 日時
- 2012年7月5日 (木) 14:00-15:00
- 場所
- 横浜研究所 シミュレータ研究棟1階 会議室
- 講演者
- Prof. Amit Tandon
(University of Massachusetts Dartmouth) - 使用言語
- 英語
要旨
Increased spatial resolution in recent observations and modeling has revealed a richness of structure and processes on lateral scales of a kilometer in the upper ocean. Processes at this scale, termed submesoscale, are distinguished by order-one (O(1)) Rossby and Richardson numbers; their dynamics are distinct from those of the largely quasi-geostrophic mesoscale as well as fully three-dimensional, small- scale processes. Submesoscale processes make an important contribution to the vertical flux of mass, buoyancy, and tracers in the upper ocean. They flux potential vorticity through the mixed layer, enhance communication between the pycnocline and surface, and play a crucial role in changing the upper-ocean stratification and mixed-layer structure on a timescale of days. In this talk, I present a synthesis of upper-ocean submesoscale processes that arise in the presence of lateral buoyancy gradients. Their generation through frontogenesis, unforced instabilities, and forced motions due to buoyancy loss or down-front winds will be covered. Using the semi-geostrophic (SG) framework, we present physical arguments to help interpret several key aspects of submesoscale flows. These include the development of narrow elongated regions with O(1) Rossby and Richardson numbers through frontogenesis, intense vertical velocities with a downward bias at these sites, and secondary circulations that redistribute buoyancy to stratify the mixed layer. We review some of the parameterizations for submesoscale processes that attempt to capture their contribution to, first, vertical buoyancy fluxes and restratification by mixed-layer instabilities and, second, the exchange of potential vorticity between the wind- and buoyancy-forced surface mixed layer, and pycnocline. We also examine the competition between destratifying wind forcing and restratifying submesoscale eddies.
Submesoscale processes are emerging as vital for the transport of biogeochemical properties, for generating spatial heterogeneity that is critical for biogeochemical processes and mixing, and for the transfer of energy from meso- to small scales. Many studies are in progress to model, measure, analyze, understand, and parameterize these motions.
問い合わせ先
地球シミュレータセンター佐々木 英治
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