The ocean mixed layer is a near-surface region of the ocean that is kept well-mixed by the effects of winds and surface waves. Water in the mixed layer remains in direct contact with the atmosphere and thus the seasonal cycle of mixed layer depths are critical for the exchange of heat and gases between the atmosphere and the ocean. Traditional, one-dimensional models of mixed layers are now recognized to have limitations in reproducing observed changes in mixed layer depth, especially at sub-seasonal time scales. Three-dimensional processes, typically occurring at ocean submesoscales (roughly from 1 to 10 kilometers) are least partially responsible for this dynamical variability. Submesoscale motions are also associated with strong vertical velocities that have large impact on ecosystem dynamics through nutrient delivery and plankton transport.
Insight into submesoscale processes has, to date, largely been achieved through careful numerical simulations. Observations of submesoscale processes have been limited due to the constraint of capturing intermittent events that evolve rapidly, on the order of 1 to 10 days. Our group has worked to characterize submesoscale dynamics in different environments through the dedicated use of autonomous vehicles. The OSMOSIS field program used a pair of ocean gliders to observe mixed layer variability in the North Atlantic over a full seasonal cycle. This provided the first year-long continuous observational record of submesoscale processes. The study was also carried out in region removed from strong boundary currents representative of much of the world ocean. Previous and on-going field programs (GENTOO and ChinStrAP) are probing the behavior of the ocean submesoscale in the Southern Ocean.
Erickson, Z.K., A.F. Thompson, N. Cassar & J. Sprintall, 2016. Advective generation of deep chlorophyll maxima (DCMs) in southern Drake Passage. Geophys. Res. Lett., in press.
Ruan, X. & A.F. Thompson, 2016. Bottom boundary potential vorticity injection from an oscillating flow: a PV pump. J. Phys. Oceanogr., in press.
Thompson, A.F., A. Lazar, C.E. Buckingham, A.C. Naveira Garabato, G.M. Damerell & K.J. Heywood, 2016. Open-ocean submesoscale motions: A full seasonal cycle of mixed layer instabilities from gliders. J. Phys. Oceanogr., 46, 1285-1307.
Buckingham, C.E., A.C. Naveira Garabato, A.F. Thompson, L. Brannigan, A. Lazar, D.P. Marshall, A.J.G. Nurser, G. Damerell, K.J. Heywood & S.E. Belcher, 2016. Seasonality of submesoscale flows in the ocean surface boundary layer. Geophys. Res. Lett., 43, 2118-2126.