Mixed Layer Restratification: Early Results from the AESOP Program
Abstract
As part of the Office of Naval Research-sponsored AESOP program, an observational effort employed acoustically-tracked Lagrangian floats and a towed, undulating profiler (Triaxus) to investigate the relative importance of vertical and horizontal mixing in governing boundary layer structure in the presence of O(1 km) scale horizontal variability. Remotely sensed sea surface temperature and ocean color directed sampling to regions characterized by strong lateral gradients. Lagrangian floats deployed near frontal interfaces defined a drifting reference frame and characterized vertical mixing, while the towed profiler executed synoptic, high-resolution surveys to map three-dimensional variability following the drifting float. Sampling encompassed a variety of conditions, including an illustration of mixed layer restratification in the presence of strong lateral density gradients. Sampling began during a period of 20 - 30 kt winds and 30-m deep mixed layers, focusing on a region of strong horizontal denstiy contrast associated with an upper ocean front. Winds weakened to 5 - 10 knots over a 12-hour period, during which observations captured a continuous sequence of sections around a drifting float. The mixed layer rapidly slumped as winds weakened, with lighter waters overriding waters from the front's dense side to produce a fully stratified boundary layer within a 20-hour inertial period. Strong intrusions, visible in temperature, salinity and chlorophyll fluorescence, also contributed to stratification changes, especially in the region beneath the 24.5 kg/m3 isopycnal that initially defined the mixed layer base.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFMOS51E..04L
- Keywords:
-
- 4504 Air/sea interactions (0312;
- 3339);
- 4528 Fronts and jets;
- 4572 Upper ocean and mixed layer processes