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The long-term goal is to understand and quantify processes mixing the ocean. In November 2011 we participated in NRL's Mixing Over Rough Topography (MORT) program focused on East Flower Garden Bank, on the outer continental shelf southeast of Galveston, Texas (Fig. 1). Our objectives are to: 1) understand the three-dimensional velocity and scalar fields around the bank and how they respond to wind forcing over the bank and to low-frequency flows impinging on the bank, and 2) identify hydraulic controls, and 3) quantify mixing rates and relate them to the processes generating them. Most measurements were made with SWIMS3, a depth-cycling towed body carrying up and down 300 kHz acoustic Doppler current profilers (ADCPs). When weather permitted, SWIMS3 was run along a grid pattern centered on the bank, rerunning the same pattern multiple times to observe changes during a tidal cycle. Figure 2 shows one pattern, grid1, which executed four times in succession early in the cruise and again several days later. Some later patterns used individual legs from this grid to concentrate on specific features in the water tied to the bathymetry. In addition, several lines were run using Modular Microstructure Profilers (MMPs) to measure mixing more directly.

The primary objective was to assess mixing levels over a coastal regime, Monterey Bay, extending the scope of previous measurements that have been restricted to single lines or small domains. Secondarily, we sought to obtain enough data to compare mixing intensity, known to be high, with measurements on the New England shelf, which were low.

Objectives of this research were 1) to compare internal waves and mixing at shallow (100 m) and intermediate (500 m) depths, 2) to relate internal wave variability to changes in local winds, and 3) to observe how internal waves and mixing evolve between the basin and plateau, meaning the deep Cretan Sea and the Cyclidic Plateau. To obtain moored internal wave records of several months we deployed four moorings, three McLane Moored Profilers (MPs) and two ADCPs. Results observed included 1) shallow depths were mostly in the pycnocline and consequently have much larger dissipation rates than weakly stratified deep water, 2) mixing increased with increases in wind stress accompanying the rapid transition from summer to autumnal weather, and 3) internal waves were dominated by the internal tide, apparently generated along the upper part of the slope. Closely confined near the bathymetry, detectable mixing was very weak and intermittent in deeper water.

LONG-TERM GOALS: To identify the major processes producing mixing in the upper ocean and to understand their dynamics sufficiently well to permit accurate parameterization of mixing for use in numerical models. OBJECTIVES: This was the first attempt we know of to survey a coastal domain with sufficient coverage to assess how mixing levels vary across the domain. Previous measurements have been concentrated in subregions, often revealing particular mixing processes, but insufficient to guide modelers in how to represent mixing over the whole domain.

Our goal is to understand mixing in shallow water, i.e., the upper 500 to 1000 m, by observing it in relation to the larger-scale processes producing it. Regimes of interest include open-ocean fronts, continental slopes and shelves, ridges and canyons. This project will add a chiometer to SWIMS3, our depth-cycling towed body, to observe scalar microstructure in addition to the larger-scale variables currently measured. It will also replace the winch used to cycle SWIMS3 in depth.

Funds from this ONR grant were used to fabricate and assemble a nearly identical replacement for a Modular Microstructure Profiler (MMP) lost during ONR-funded AESOP work in Monterey Bay in August 2006. Funds were available to us in September 2007, fabrication began in December 2007, and the MMP was finished in January 2009. The new MMP was successfully tested in Puget Sound and taken on a research cruise in Monterey Bay in April 2009.

LONG-TERM GOALS. Our goal is to understand mixing in shallow water, i.e., the upper 500m, by observing it in relation to the larger-scale processes producing it. Regimes of interest include open-ocean fronts, continental slopes and shelves, ridges and canyons. OBJECTIVES. This project will add a chiometer to SWIMS3, our depth-cycling towed body, to observe scalar microstructure in addition to the larger-scale variables currently measured. It will also replace the winch used to cycle SWIMS3 in depth. APPROACH. Owing to its faster speed and tighter profiles, SWIMS3 can sample mixing processes much more intensively than can microstructure profilers. We have been estimating dissipation rates using Ozmidov scaling of density overturns. Adding the Chiometer will provide a more direct measure by adding the variance of small-scale scalar gradients to the data suite. The new winch is needed simply to replace the present one, which we have used since 1993. Because it will carry longer and thicker tow line, it will let us profiler deeper and reduce the chance of losing SWIM3 by cable failure. WORK COMPLETED. Electronic and mechanical design of the chiometer is nearing completion, as is the analysis to choose the optimum cable size for the winch.

This study contributes to long-term efforts toward understanding: * Dynamics of coastal circulation. * Strongly forced mesoscale and submesoscale dynamics. * Processes that communicate atmospheric forcing to the ocean interior.

The long term goals are to identify the major processes producing mixing in the upper ocean and to understand their dynamics sufficiently well to permit accurate parameterization of mixing for use in numerical models. These measurements during August 2006 were the first attempt we know of to survey a coastal domain with sufficient coverage to assess how mixing levels vary across the domain. Previous measurements have been concentrated in sub-regions, often revealing particular mixing processes, but insufficient to represent mixing throughout a regional model. We ran lines of microstructure profiles 5-10 km long (Fig. 1), balancing needs for rapid temporal sampling against spatial windows containing at least some structure. Staying with each line for 12.5 hours resolved changes produced by the M2 twice-daily tide, and some lines were rerun at different phases of the monthly tide. As we began to understand patterns of tidal currents and mixing, the original set of lines was modified to reveal pulsing of water in and out of the large canyon splitting the bay down its middle. Powerful Doppler sonars installed on R/V Revelle by Rob Pinkel at Scripps, provided excellent velocity records, supplemented by a 300 kHz ADCP we installed on the bottom the bay?s southern half.

LONG-TERM GOALS. This grant is to replace the Modular Microstructure Profiler (MMP) that was lost in Monterey Bay in August 2006 during AESOP, apparently due to an attack by a large shark. OBJECTIVES. Our objective is to complete the work as soon as possible. APPROACH. The new instrument, MMP4, will be made as similar to the one lost, MMP2, as possible. WORK COMPLETED. Because the money was received only a few weeks ago, fabrication has not begun. Because some electronic components in MMP2 are no longer made, it was built in 1993, new ones have been selected. Also, because MMP2 mechanical components were designed using an old CAD system, some of the drawings are being updated.

The long-term goal of this work is to develop a physical understanding of oceanic flow along irregular, sloping, coastal topography and to quantify and parameterize, if possible, the mixing these flows produce. To model the coastal ocean effectively, it is essential that we understand how flow over rough topography affects boundary drag. By understanding the basic processes of internal wave generation and flow separation we will be able to predict the effects of unresolved bathymetric roughness in numerical simulations.

The long-term goal is to identify the major processes producing mixing in the upper ocean and to understand their dynamics sufficiently well to permit developing accurate parameterizations of mixing for use in numerical models. The objective is to understand mixing over continental shelves and slopes and in straits.

The long-term goal is to understand the physics of flows generated by currents passing over small topographic features and to quantify, and parameterize if possible, the mixing these flows produce.

The semi-annual report reflects the technical status of internal/ surface wave interaction and microstructure projects conducted within the Advanced Ocean Engineering Laboratory at the Scripps Institution of Oceanography. These projects are: (1) Thermal Microstructure - to examine in detail the structure and dynamics of temperature and salinity and (2) Atmospheric Boundary Layer - to provide an understanding of the interaction between atmospheric boundary effects and surface waves.