Monday, April 2, 2012

A good day

It's a bit over three days since we started 'production', i.e., collecting seismic reflection data. It's been quite rough in the past three days, with 6 meters of waves and over 40 knots of winds. The ship was constantly rolling and pitching, and the sky was gray, which was a bit depressing. Sea currents were also against us. We were supposed to cruise at the speed of 4.5 knots (=8.3 km/h), but because of strong currents, we were only able to move at a crawling rate of 2 knots (=3.7 km/h). By the way, the ship itself can of course move at much faster speed (say 10 knots) even with this much of currents, but we're towing a 6-km-long streamer behind us, which records seismic data. In this case, we cannot move faster than 5 knots relative to water; otherwise the streamer would break off from the ship owing to extreme tension.

This slow speed is a big headache for our science, because our time at sea is limited. The Langseth need to get back to Honolulu by April 16th to prepare for the next cruise, and it takes 10 days to go from Shatsky Rise to Honolulu. This means that we need to start packing by April 7th (note: as we'll cross the International Date Line, we'll gain one day during our transit).

Fortunately, however, the weather seems to be improving. Maybe just for now, but I still feel great today. Also, we just changed our direction and turned into a new seismic line, and currents are now helping us; we're moving at 5.5 knots (yeah!).

I'd like to take this opportunity to explain a bit more about our seismic survey (see figure). Yellow lines show where we collected reflection data in the summer of 2010. Pink lines are where we plan to collect data this time. Thin red lines are our actual path, with yellow star denoting our current location. We travelled from Guam (far south) and started shooting at waypoint #1. We just turned waypoint #3 and are heading eastward, crossing Ori Massif, which is the second largest feature in Shatsky Rise.

The largest feature is, as you see in the figure, called Tamu Massif. This figure actually shows only the southern half of the entire Shatsky Rise, and there is another massif called Shirshov Massif to the northeast. Tamu, Ori, and Shirshov are all based on the names of institutions, the scientists from which contributed to the mapping of Shatsky Rise: Texas A&M University (TAMU), Ocean Research Institute (ORI) of University of Tokyo in Japan, and Shirshov Institute of Oceanography in Russia. By the way, Shatsky Rise itself is named after a Soviet geologist, Nikolay Shatsky.

The scientist from Texas A&M in this case is our Will Sager (who is unfortunately not here). When I was a masters student in Japan many years ago, I studied at ORI, and some scientists there collaborated with Will (though I never met him then). When I chose to investigate Shatsky Rise, I did so for purely scientific reasons, but it was interesting to find out that the degree of separation between Will and myself was just two. And it's exciting to shooting over the place named after my former institution!

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