As we cruise south in international water, a few instruments have been turned on. We are currently mapping the seafloor bathymetry and sub-bottom using multi-beam SWATH and CHIRP. These two devices generate an acoustic signal from beneath the ship hull and then listen to the echo that is reflected from the ocean’s bottom. The resolution we image the ocean bottom is relatively lower to the resolution of the topography on land, however this is the state-of-the-art. The limit on the resolution is mainly because the ocean bottom is very deep, about 5 km. The exciting part is that while we sail to our target destination we are seeing never-seen-before maps of the ocean bottom: seamounts, canyons and cliffs.
In today’s photos you can see a series of images that relate to the imaging process. First, the temperature with respect to the ocean depth is measured using an Expendable Bathythermograph (XBT) probe. As it sinks into the ocean (also known as the water column) it sends information about the depth and temperature. The temperature is very important in order to estimate the velocity of sound in water, and in turn, estimate the depth from the time it takes for the acoustic echo is recorded back.
The exciting part is that while we sail to our target destination we are seeing never-seen-before maps of the ocean bottom: seamounts, canyons and cliffs.
CHIRP maps the depth right under the ship, and penetrates through a couple of metres into the sediments of the sub-bottom. On the other hand, SWATH maps a wider distance on the order of a few kilometers beneath the ship as it sails through.
For more information about the various equipment available on board the R/V Marcus G.Langseth visit this page.