The massive data sets in the Gulf (close to 20 million velocity points) were made possible through the development of a new type of drifter, which is biodegradable, compact, cost-effective, and scalable to hundreds of deployments over a few hours (patent for \"Ozg\"okmen and co-inventors). GPS-tracked drifters naturally provide circulation data without any interruptions and far longer than the ship time used in ocean expeditions. Drifters are the only instruments that can locate and track these features in real-time accurately. Yet these convergence zones are very narrow and very rapidly evolving.
One of the primary findings of these expeditions is that the ocean's surface is covered by convergence zones and fronts containing high vertical velocities. The proposer spent the past 5 years advancing drifter-based ocean sampling to a massive scale by releasing some 2500 drifters in the Gulf of Mexico under four major expeditions. Identification and Real-Time Tracking of Fronts and Subduction Zones Through Deployments of Massive Arrays of Biodegradable Drifters The whole suite of observations (mesoscale survey, float array, and submesoscale survey) will be relocated and repeated. Along each section, temperature and salinity profiles will be obtained at a horizontal resolution of about 250 m every 4 minutes. Cross-front sections of about 20-km length will be completed every 6 hours. The submesoscale UCTD survey will follow the float array at the front. Each float profiles to 200 m every 100 minutes and obtains about 400 profiles over a 30-day cruise. The float array will be deployed in a submesoscale streamer in a box pattern and recovered after several days. A feature will be identified in an initial mesoscale UCTD or SeaSoar survey, a forecast model, and near-realtime satellite products, e.g., sea surface temperature and chlorophyll. Repeated meso- and submesoscale-resolving surveys in the upper 200 m with Underway CTD (UCTD) and/or SeaSoar will follow an array of up to 8 SOLO-II floats at a mesoscale front and submesoscale streamers on its flanks during 3 cruises. This project will use a combination of rapid spatial surveys from a ship and a rapidly-profiling float array to assess w at an intense front across a range of scales: (a) at mesoscale from the spatial surveys using quasigeostrophic approximations, such as the omega equation, (b) in submesoscale streamers by tracking tracers (such as chlorophyll, salinity, spice, and potential vorticity) with finer spatial surveys and a float array, and (c) in submesoscale streamers by acoustically tracking isopycnal-following floats, and (d) due to internal waves from each float's displacement fluctuations. Vertical velocity in submesoscale streamers from spatial surveys following a profiling float array What dynamics shapes these pathways? What are the Lagrangian trajectories, what are the time and space scales of subduction and where does the water end up?.What coherent pathways act as conduits for exchange?.How are water and properties from the surface boundary layer exported to depth?.This proposal will use modeling and observationally motivated process studies to address the following questions: But, vertical velocities are very weak (about a thousand times smaller than horizontal velocities) and difficult to detect. The vertical movement of water from the surface to depth across the base of the mixed layer has implications for the transport of properties, gases, biogeochemistry, and the fate of drifting particles and objects. The goals of Calypso are to unravel the three-dimensional coherent pathways by which water carrying tracers and drifting objects is transported from the surface ocean to depths below the mixed layer.
Frontogenesis and Subduction at the Alboran FrontsĪmala Mahadevan, Mara Freilich, Mathieu Dever
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