Leg One, Open Ocean to Inner Sea

Researchers once thought of low-oxygen water intrusions inland as fairly uniform, but more recent research suggests that the water instead follows disjointed paths dictated by the topography of the seafloor. Specifically, rocky seafloor channels may effectively form submerged rivers or creeks of lower-oxygen water.  The team focused their water measurements on the most likely pathways for these flows.

The data collected created a baseline against which future studies can compare to answer questions about the normal movements of low-oxygen water, and whether these intrusions are increasing, changing, or decreasing in coming years. This growing understanding will aid Canadians in better understanding their coastal waters, but should also offer insights about waters in other regions such as Washington and Oregon in the U.S. In keeping with the Schmidt Ocean Institute mission, all the data collected was made publicly available to aid other scientists in their related research efforts, and to provide the public with clear information about the region.

One of the most critical tools for the first leg was the Moving Vessel Profiler, an instrument equipped with oxygen and other sensors that the team will deploy behind Falkor. The MVP sends a constant stream of data back to the ship while it is moving, and researchers can raise and lower it in the water column like a yo-yo to characterize different depths.

The team used the traditional method of stopping and lowering sampling bottles and sensors at single spots, for instance to test water samples for oxygen levels in Falkor’s lab to make sure equipment is properly calibrated, but the MVP allows for much more efficient studies of large areas than would be possible otherwise.

To augment this basic chemical data collection, the team also used Falkor’s sonar system to map the bottom topography that controls water movement, quantify the plankton and fish present in areas studied, and measured currents in the regions. “What we really appreciate about Falkor is that it comes with this very advanced suite of acoustic sampling capabilities,” says Dewey.

Finally, the team collected a number of moored sensors they deployed about six months previous in preparation for the Falkor expedition. These sensors collected some of the same oxygen and other data gathered at the observatories, but they are not wired to land. That means that researchers had to retrieve them in order to get data from them, but this offered a multi-month record of water movements and conditions that added to the baseline picture the team created of what is happening between the observatories.

by Mark Schrope