The Samoan Passage, 5500 m beneath the sea surface, is one of the "choke points" in the abyssal circulation. A veritable river of Antarctic Bottom water flows through it on its way into the North Pacific. As it enters the constriction, substantial turbulence, hydraulic processes and internal waves must occur - which modify the water.
Since climate models do not do a good job of resolving flows like these, we will take our stable of instruments - moored profilers, conventional current meter moorings, shipboard instruments - and measure the velocity, turbulence, and internal waves in the region. The overall goal is to understand these deep processes and the way they impact the flow, and to develop a strategy for eventually monitoring the flow through the Passage.
This work is in collaboration with Dr. James Girton (APL/UW), Dr. Glenn Carter (UH) and Dr. Jody Klymak (U. Vic).
Figure 1: Bottom topography from Smith & Sandwell. The red rectangle shows the Samoan Passage region.
Figure 2: Previous direct current measurements of the flow through Samoan Passage by Reid & Lonsdale (1974) and Rudnick (1997). The vectors show mean currents measured within the lower 300m above bottom. The Reid & Lonsdale mean currents are averaged over only up to a few days, the Rudnick array gives mean currents averaged over 500 days. The bottom topography is a combination of our newly measured multi-beam data and Smith & Sandwell database.