Mixed Layer Salt Balance and the Role of Eddies in a Global Ocean Simulation
[12-Nov-2014] Carton, J., Grodsky, S., Johnson, B., and Bryan, F.
Presented at the 2014 Aquarius/SAC-D Science Team Meeting
Here we examine the detailed salt balance of the mixed layer in a 0.1 degree resolution multi-decadal simulation of the global ocean/ice system forced by observed historical surface fluxes (1979-2010), with the flux calculations carried out on the original grid every time step. Initial conditions were provided by a simulation forced by Normal Year forcing. The simulation is generally realistic with a slight negative bias in salinity. Here we focus on a comparison of the salt balance as it varies with latitude from the rainy tropics through the dry subtropics and into the humid midlatitudes. To separate the contribution of eddies to the salt balance from those associated with the seasonal cycle we define the eddy flux contribution, e.g. , to be associated with timescales of two months or less.
The results show a complex set of balances that vary with latitude and timescale. One striking result is that the net surface salt flux does not dominate the salt balance. Horizontal advection and vertical diffusion of salt across the base of the mixed layer are generally large as well. The contribution of eddy transports is smaller than recently reported and generally not a dominant term, although eddies may be dominant in certain regions. We include comparison of the balances in the dry SPURS1 and rainy SPURS2 regions as well as a discussion of the changes associated with the phase of ENSO.