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Samoan Passage: Field Work

We will accomplish these goals in three separate cruises. Don't forget to check out the videos we made in conjunction with APL and Wide Eye productions.

A "Mapping" cruise took place in fall 2011 to measure the seafloor more accurately with the multibeam system aboard the R/V Kilo Moana. We also conducted some test profiles with our new powered, real-time CTD system. Steve Emerson's student Kevin Tempest was also on board making chemical measurements.

A "pathways" cruise was just completed in summer 2012, attempting to determine the pathways the flow takes as it wends its way through the complicated bathymetry of the region. See Fig. 1 for a map with all the locations where we measured. Does all of the flow enter the narrow "main" passage, or does some leak through to the west? We also made the first direct measurements in the region with turbulence profilers, conducted detailed tow-yos near the sills, and took time series to determine the internal wave climate of the region. This should give us a sense of where lies the primary "hydraulic control" or location which sets the overall transport within the passage. Download the cruise report.
Figure 1: Station map of the "Pathways" cruise in summer 2012. White dots show CTD/LADCP stations where we measured temperature, salinity and velocity from the sea surface to the ocean floor from the ship. Triangles show mooring locations - pink for those that were deployed for the duration of our cruise, yellow triangles mark positions of the moorings that are measuring the flow until we go back in winter 2014.

A "Processes" cruise will then go to this location and intensively study the turbulence and wave environment there.

We deployed a "Monitoring" array at the entrance of the Passage at the same location as occupied during the World Ocean Circulation Experiment (WOCE) 20 years ago. In winter 2014, when we go on the "Processes" cruise, we will recover it. Will the transport have changed?

Both the two latter cruises will be severely challenged to conduct profiles fast enough in these extreme depths to avoid "aliasing" or confusing whether things are changing in time, space or a combination.  To mitigate these problems, we'll deploy arrays of moored profilers during each cruise as well as in between them.  Hence, each cruise will deploy the moorings, do a large amount of spatial surveying with the shipboard instruments, and then recover the moorings at the end. During the first cruise, they will be redeployed for the monitoring period. That's a lot of work!