8/8/96 

Cruise Plan for R/V Melville - 3/26/97-4/26/97

Project: U.S.-Australia Cooperative Study of the Northern Branch of the
         Antarctic Circumpolar Current

Chief Scientist, Doug Luther, Univ. of Hawaii
Co-P.I.'s
   Jim Richman, OSU
   Randy Watts, URI
   Alan Chave, WHOI
   Jean Filloux, SIO

Science Party - Not determined at this time.

     The principal task of this cruise is to recover 9 full-depth current-meter  
moorings, and 40 small self-contained seafloor instruments deployed in  
March-April, 1995, in an elongated array extending from approximately 47S to  
54.5S, 141E to 145E, SSW of Tasmania. The array spans the northern (strongest)  
current jet associated with the Antarctic Circumpolar Current (ACC). The  
experiment was designed to evaluate the important momentum and energy balances  
in the ACC. The experiment also has goals relating to the intensity and  
dynamics of the total transport of water and heat through the array, which are  
relevant to WOCE objectives.
     All the deployed instrumentation will be recalled acoustically. The  
horizontal electrometers (18), bottom pressure recorders (4), and inverted echo  
sounders (18) all are very small packages (usually a single 17" glass sphere in  
a plastic hard hat), requiring reasonably good weather for radio and visual  
detection when at the surface, and requiring precision ship maneuvering for  
pickup.
     Depending on the availability of a CTD from our Australian collaborators,  
we will collect full-depth CTD profiles over at least the 18 inverted echo  
sounders before they are recovered. Time permitting, we will also attempt to  
complete a high-resolution CTD section from 54.5S to Tasmania (approximately 25  
full-depth CTD profiles), all the while collecting direct measurements of  
near-surface currents with the ship's 150 kHz ADCP, using the Ashtech 3DF GPS  
receiver for position and heading. The focus of this CTD/ADCP section is to  
provide additional information on the strength of the westward currents just  
north of our array relative to the eastward currents that exist in the ACC.
     Dr. Antony White of Flinders University of South Australia deployed 4  
magnetometers within our electrometer array in April, 1996, and has requested  
time on this cruise to recover those instruments. White's request will be  
accommodated on a time permitting basis. [While the sub-diurnal electric fields  
are oceanically induced, the super-diurnal fields are dominated by  
ionospherically generated EM waves and can be combined with the magnetometer  
data to provide information on the conductivity of the crust and upper mantle.]