|Title||Adrift upon a salinity-stratified sea: A view of upper-ocean processes in the Bay of Bengal during the southwest monsoon|
|Publication Type||Journal Article|
|Year of Publication||2016|
|Authors||Lucas A.J, Nash J.D, Pinkel R, MacKinnon JA, Tandon A., Mahadevan A., Omand M.M, Freilich M., Sengupta D., Ravichandran M., Le Boyer A.|
|Type of Article||Article|
|Keywords||chlorophyll maximum; equatorial; growth-rate; model; pacific; ratio; summer monsoon; Surface temperature; wirewalker|
The structure and variability of upper-ocean properties in the Bay of Bengal (BoB) modulate air-sea interactions, which profoundly influence the pattern and intensity of monsoonal precipitation across the Indian subcontinent. In turn, the bay receives a massive amount of freshwater through river input at its boundaries and from heavy local rainfall, leading to a salinity-stratified surface ocean and shallow mixed layers. Small-scale oceanographic processes that drive variability in near-surface BoB waters complicate the tight coupling between ocean and atmosphere implicit in this seasonal feedback. Unraveling these ocean dynamics and their impact on air-sea interactions is critical to improving the forecasting of intraseasonal variability in the southwest monsoon. To that end, we deployed a wave-powered, rapidly profiling system capable of measuring the structure and variability of the upper 100 m of the BoB. The evolution of upper-ocean structure along the trajectory of the instrument's roughly two-week drift, along with direct estimates of vertical fluxes of salt and heat, permit assessment of the contributions of various phenomena to temporal and spatial variability in the surface mixed layer depth. Further, these observations suggest that the particular "barrier-layer" stratification found in the BoB may decrease the influence of the wind on mixing processes in the interior, thus isolating the upper ocean from the interior below, and tightening its coupling to the atmosphere above.
Co-located time series of temperature, salinity, velocity, optical properties, and turbulent microstructure measurements collected on board a drifting wave-powered profiler elucidated the patterns of upper-ocean variability and vertical heat and salt fluxes in the Bay of Bengal....We expect that the quantitative assessment of these mechanisms will ultimately provide better prediction of sea surface temperature and the associated air-sea coupling over the Bay of Bengal, yielding increased fidelity in monsoon weather forecasting for South Asia.