|Title||Submesoscale processes at shallow salinity fronts in the Bay of Bengal: Observations during the winter monsoon|
|Publication Type||Journal Article|
|Year of Publication||2018|
|Authors||Ramachandran S., Tandon A., MacKinnon J., Lucas A.J, Pinkel R, Waterhouse A.F, Nash J., Shroyer E., Mahadevan A., Weller RA, Farrar J.T|
|Journal||Journal of Physical Oceanography|
|Type of Article||Article|
|Keywords||baroclinic instability; indian-ocean; ocean mixed-layer; oceanography; parameterization; part i; potential; restratification; summer monsoon; surface-layer; turbulence; vorticity|
Lateral submesoscale processes and their influence on vertical stratification at shallow salinity fronts in the central Bay of Bengal during the winter monsoon are explored using high-resolution data from a cruise in November 2013. The observations are from a radiator survey centered at a salinity-controlled density front, embedded in a zone of moderate mesoscale strain (0.15 times the Coriolis parameter) and forced by winds with a downfront orientation. Below a thin mixed layer, often <= 10 m, the analysis shows several dynamical signatures indicative of submesoscale processes: (i) negative Ertel potential vorticity (PV); (ii) low-PV anomalies with O(1-10) km lateral extent, where the vorticity estimated on isopycnals and the isopycnal thickness are tightly coupled, varying in lockstep to yield low PV; (iii) flow conditions susceptible to forced symmetric instability (FSI) or bearing the imprint of earlier FSI events; (iv) negative lateral gradients in the absolute momentum field (inertial instability); and (v) strong contribution from differential sheared advection at O(1) km scales to the growth rate of the depth-averaged stratification. The findings here show one-dimensional vertical processes alone cannot explain the vertical stratification and its lateral variability over O(1-10) km scales at the radiator survey.