We’re underway! After a long day of traveling and one day in San Juan running errands and savoring land, we are officially at sea! Spirits are high, the crew is wonderful, and the science party is about 100x more laid back than my last cruise (more on why that is in a newsletter to come).
For no specific purpose at all I’m going to wave to the camera #3 (or whichever live feed is projecting to the control center) on the ship at 1:30pm EST (11:30pm PST I think?) on Wednesday the 6th if nothing too intense is going on! If you see me take a screenshot!
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Sonar has been the primary tool for the past 100+ years of ocean seafloor exploration. Sonar is a pretty simple concept, but one that may be unfamiliar to some of the readers of this newsletter. I thought it would be prudent to get us all, generally, on the same page.
You may recall from physics in high school that sound and light have specific speeds at which they travel. Dig deep into that lodged memory and you also may remember that sound travels at different speeds depending on what medium its in, including water.
Sonar sends very specific frequencies of sound out from below a ship. This sound then travels down, eventually hits the seafloor, and is reflected back to the surface. The ship is also fitted with specific receivers to capture this sound. Depending on the time it takes the sound to go down and back up you can estimate the length the sound traveled, and therefore the depth of the water (thanks Snell’s Law!)
Sonar has obviously gotten more advanced in the past 100 years. We now use multiple beams of sound (multibeam). Our ship has one of the best multibeams out there, an EM 304, which sends out about 500 beams and covers a swath (section of seafloor) of about 140 degrees.
Theres a lot of things that can interfere with soar. If this was the cold war, for example, a Soviet submarine could interfere (this is why submarines “hide” btw. They’re not escaping visual detection, rather sonar and other wave detection). Fish can also get in the way. The gas in their bladders are a different medium than the ambient water, and as a result can distort the speed of sound traveling through them.
Theres other components to sonar as well. A muddy sea bottom may distort and absorb the sound more than a metal anchor, for example. Another component is the actual temperature of water. Temperature changes density, and the density of water will be higher at the bottom of the ocean compared to closer to the surface, therefore the speed of the sound beam will increase going down and decrease going up.
My job on this ship is to ensure that the data coming back from the multibeam sonar and other seafloor imaging products looks good, and if there is interference or error it is my job to locate those anomalies and ‘clean’ the data.
We’ve visually seen very little of our seafloor, but sound allows us to visualize it. Wild right?
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4-5-22
There are few stranger feelings than waking up in the middle of the night on a ship. Last night we were traveling perpendicular to the swell, making the boat roll like nobody’s business. Nothing beats those 2 seconds of confusion before your brain turns on, when everything in your bed, including yourself, moves up and down in your pitch black little compartment bunk because of a large swell. This was all fine and well until I had to stand up and stare at a computer screen for eight hours. I am proud to say I didn’t loose my breakfast (I also never even got the courage to eat breakfast but that’s besides the point…).
I love being out here. I love the sea. I love checking out of society and social media. I knew I needed this and I was right. In fact I think everyone could gain a lot from an experience like this, even if you don’t love the ocean.
Lots more to come :). - XOXO Paige
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