Scientist at Work Blog: A Tide of Local Influences

Jim Thomson is principal oceanographer at the Applied Physics Lab at the University of Washington. He studies ocean surface waves and coastal processes and wrote about his expedition to the North Pacific in the fall. This is his last post from Chile.

Monday, Feb. 18

We?ve been loading up our gear and shuffling customs paperwork. In the evenings, I?ve been looking through the new data. They show some remarkable stuff. The turbulence we have recorded at the Canal de Chacao in Chile is similar to what we?ve seen at other sites, but stronger.

The similarities are in the structure and size of the motions. The energy in the turbulence starts at large scales and goes to small scales. The idea was famously described by Lewis Fry Richardson, who said that ?big whirls have little whirls, that feed on their velocity??.

Kolmogorov derived a mathematical form in 1941, and evidence, in the form of measurements, has been accumulating ever since. The turbulence in Chacao has these properties, but with enhancement from the shape of the channel. It is a combination of a process that is both general and local. The data we have generated will be used to decide whether the tidal currents are suitable for electricity-generating turbines.

In addition to the turbulence, our other measurement on the mooring was the ambient noise. These data look familiar as well and will become part of Chris Bassett?s Ph.D. dissertation on underwater sound. In looking, or listening, through the data, he hears the same things we hear in Admiralty Inlet in Washington: ships, sonars, waves breaking on the beach and the turbulence itself.

Chris says it is like listening to Chilean Spanish: on the surface, it is familiar Spanish. As you learn it, the differences reveal a rich language all its own. The fundamentals are the same, but the local influence is strong.

While we waited for customs paperwork, we took a day off and climbed the nearby volcano, Calbuco, which is similar in many ways to the volcanoes we climb at home in the Pacific Northwest. But it is different, too. We started in cow pastures, not a parking lot, and we saw no one else the whole day. We climbed through a temperate rain forest, up a scree slope, and onto snowfields. In the steady rhythm of placing my feet, I felt that I could have been anywhere, until I looked more closely.

This is the essence of learning and of exploration. We begin with something familiar, and we stretch ourselves to something new.

The climb up Calbuco was long and difficult; it took 11 hours, round trip. It was worth it. When we reached the edge of the crater at the top, the clouds cleared for moment. In the far distance, waiting patiently, we saw the ocean.

Source: http://scientistatwork.blogs.nytimes.com/2013/02/27/a-tide-of-local-influences/?partner=rss&emc=rss

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