Isopycnal Intrusions in Doubly Diffusive Fluids

Florida State University, Tallahassee FL

Investigators

Abstract

0236304 Stern Two dimensional doubly diffusive intrusions will be investigated analytically and numerically in a frontal model. For the case of finger favorable vertical temperature and salinity gradients (salinity increasing upward) the small scale fluxes will be parameterized by previously obtained (numerical) calibrations. Application to the finite lateral width model will give a minimum critical value of the lateral salinity variation for the onset of a two-dimensional intrusive instability. For supercritical lateral salinity variation the eigenfunctions will initialize a numerical integration which will give the modification of the mean lateral gradients and the condition for isopycnal overturns. The case of a stable salt gradient heated from below will also be examined in a laterally bounded frontal model, and the vertical scale of the intrusive instability will be related to the smallest thermocline steps observed in the Weddell Sea. The upward heat flux in these steps may help to maintain the large gaps (polynyas) observed in the Antarctic ice which could affect the atmospheric climate. This project will contribute to our understanding of the horizontal mixing of water masses by using a very elaborate and precise salt finger parameterization to model the intrusions occurring on a density-compensated thermohaline front and answer questions such as preferred intrusion scales and magnitudes. This research will be made available to the climate modeling community with presentations and publications so that the results can be incorporated into the general ocean circulation models. In addition, the post doc and Ph.D. student will gain invaluable experience in using state-of-the art scientific computational equipment and techniques to solve fluid dynamical problems of significant practical interest. The PI will also participate in the Summer Program in Geophysical Fluid Dynamics (GFD) at Woods Hole Oceanographic Institution..