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Cruise Info
| Cruise ID | MV1202 |
| Vessel | R/V MELVILLE |
| Title | Seismic Oceanography of Agulhas Mixing |
| Abstract | Seismic Oceanography of Agulhas Mixing: The Agulhas Return Current is a particularly good study region for this topic because it is characterized by very large horizontal temperature gradients (Lutjeharms and Valentine, 1984) and has considerable eddy activity (Lutjeharms, 1981). Thus the signal to noise will be maximized for seismic methods and there is considerable energy for intrusion and instability processes to mix sub-tropical waters with surrounding waters. In particular, the region identified in this current that would maximize these factors extends from just east of the Retroflection towards the east (roughly from 38-40°S and 20-28°E) and includes the first meander over the Agulhas Plateau. The exact positioning of the study area should be relatively compact to allow for adequate coverage with seismic tows taken at ship speeds of 4 knots and therefore will likely be limited to spatial coverage of an area on the order of 300 km by 300 km (approximately the eddy and meander scale of the system). The approach will be to first use high-resolution tow-yo CTD (Scanfish) measurements to initially locate the Agulhas Front and any associated eddies. Then 6-8 long-line moorings will be deployed across and in the Agulhas Return Current with 500-1000 m range Acoustic Doppler Current Profilers (ADCPs) and temperature/salinity sensors to measure the barotropic and baroclinic streamfunction during the study period. High-resolution seismic measurements will then be taken simultaneously with additional Scanfish measurements if possible or with some switching between methods if required. The seismic measurements will provide full water-column images of temperature gradients at order of 10 m horizontal resolution and the Scanfish will provide 0-400 m casts of temperature, salinity, and other data at 500 m resolution and thus the two can be combined to invert and estimate isopycnal structure at very high resolution. XBTs will additionally be used during seismic tows for ground-truth temperature profiles. Finally at identified points of interest, dedicated full water column CTDs and micro-structure turbulence casts will be made to further quantify mixing parameters. Additionally, ship board ADCP and meteorological measurements would be useful for interpreting results. We will also be collaborating with other projects in the Oceanography Division and thus gain access to the extensive remote sensing and numerical modeling products that are produced daily. For the cruise period we should be able to obtain, at a minimum, MODIS sea-surface-temperature and chlorophyll-a images, and high-resolution COAMPS meteorological and HYCOM ocean nowcast/forecast products. |
| Starting Port | Cape Town, South Africa |
| Ending Port | Cape Town, South Africa |
| Starting Date | 2012-01-23 |
| Ending Date | 2012-02-08 |
| Principal Investigator | Wood, Warren T. |