LONG-TERM GOALS To determine whether lateral mixing at O(1-10 km) scales is due to a balanced or unbalanced downscale cascade from the mesoscale, or due to local vertical mixing by internal waves and surface forcing. OBJECTIVES Our work is testing hypothesis 3 of the white paper "Scalable Lateral Mixing and Coherent Turbulence": Non-QG, submesoscale instabilities feed a forward cascade of energy, scalar and Ertel PV variance, which enhances both isopycnal and diapycnal mixing. Related

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... are that submesoscale variability is associated with coherent structures and anisotropic mixing. Further, submesoscale processes are inherently vertical, as well as horizontal, and that submesoscale processes facilitate cross-front exchange. APPROACH Our approach is to run a number of process studies using a three-dimensional non-hydrostatic model written by Amala Mahadevan (PI from Boston University e.g. Mahadevan and Tandon 2006). The typical model resolution for resolving submesoscales is about 1 km in the horizontal. We examined processes in a domain approximately 100 km x 200 km, but recently, we have improved the model to run on much larger domains (approximately 500 km x 1000 km) at the same horizontal resolution. Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.