Journal Article

Bringing physics to life at the submesoscale

Lévy, Marina, Franks, Peter J. S., Rivière, Pascal, Ferrari, Raffaele, Martin, Adrian P.

2012

Overview

A common dynamical paradigm is that turbulence in the upper ocean is dominated by three classes of motion: mesoscale geostrophic eddies, internal waves and microscale three‐dimensional turbulence. Close to the ocean surface, however, a fourth class of turbulent motion is important: submesoscale frontal dynamics. These have a horizontal scale of O(1–10) km, a vertical scale of O(100) m, and a time scale of O(1) day. Here we review the physical‐chemical‐biological dynamics of submesoscale features, and discuss strategies for sampling them. Submesoscale fronts arise dynamically through nonlinear instabilities of the mesoscale currents. They are ephemeral, lasting only a few days after they are formed. Strong submesoscale vertical velocities can drive episodic nutrient pulses to the euphotic zone, and subduct organic carbon into the ocean's interior. The reduction of vertical mixing at submesoscale fronts can locally increase the mean time that photosynthetic organisms spend in the well‐lit euphotic layer and promote primary production. Horizontal stirring can create intense patchiness in planktonic species. Submesoscale dynamics therefore can change not only primary and export production, but also the structure and the functioning of the planktonic ecosystem. Because of their short time and space scales, sampling of submesoscale features requires new technologies and approaches. This paper presents a critical overview of current knowledge to focus attention and hopefully interest on the pressing scientific questions concerning these dynamics. Key Points Submesoscale physics control ecology locally, but also feedback to basin scales Strong gradients in community structure are created at the submesoscale Despite recent innovations, sampling the submesoscale remains a major challenge

• Publisher: Blackwell Publishing Ltd,American Geophysical Union,John Wiley & Sons, Inc
• Subject: Earth Sciences / Earth, ocean, space / ecosystems / Eddies / Environmental Sciences / Euphotic zone / Exact sciences and technology / Fluid dynamics / Fluid flow / fronts / Horizontal / Internal waves / Marine / Nonlinear dynamics / Oceanic turbulence / Oceanography / Oceans / Organic carbon / phytoplankton / Primary production / Sampling / Sciences of the Universe / submesoscale / Turbulence / Turbulent flow / Upper ocean