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Santiago-Mandujano, F. ., University of Hawaii, Honolulu, USA, santiago@soest.hawaii.edu
Nosse, C. T., University of Hawaii, Honolulu, USA, nosse@soest.hawaii.edu
Weller, R. A., Woods Hole Oceanographic Institute, Woods Hole, USA, rweller@whoi.edu
Plueddemann, A. J., Woods Hole Oceanographic Institute, Woods Hole, USA, aplueddemann@whoi.edu
Lukas, R. B., University of Hawaii, Honolulu, USA, rlukas@hawaii.edu

OBSERVATIONS AND MODELING OF THE MIXED LAYER AT STATION ALOHA

Mixed layer depth variations at Station ALOHA were estimated from Hawaii Ocean Time-series CTD profiles (1988-2011) and from the WHOTS mooring (2004-2011) using a density criterion. An improved version of the Price-Weller-Pinkel (PWP) 1-dimensional mixed layer model was forced with wind stress, heat and freshwater fluxes observed from the WHOTS buoy. The model captures the seasonal variation of mixing, but the mean MLD from PWP is shallower (28 m) than WHOTS (53 m). The model bias seems to arise from fewer deep mixing events in winter (though maximum depth is well captured) and from a generally shallower ML during summer. This bias may be attributed to daytime shoaling in the model that is more frequent and intense than observed. Strong, intermittent shears due to baroclinic tides and eddies are observed at ALOHA and are probably an important source of entrainment that is not modeled. 3-dimensional advection is important to close the ML heat and salt budget. Experiments with externally imposed Ekman pumping and large-scale horizontal advection are described.

Session #:048
Date: 2/20/2012
Time: 08:00
Location: Ballroom C

Presentation is given by student: No