Down the Slope

Unique among the sites, Saglek Bank and Hatton Sill are deep-water habitats with very powerful currents out on the continental slope. Driven by the tides on the distant shore of the Labrador coast, the currents swing 180 degrees every six hours. Right in the middle of these tides is a lull, where the current is slow enough that a remotely operated vehicle can successfully navigate the ocean floor. Miss the window, and the currents will come back, strong enough to blow the ROV right off of the sea floor.

Drop camera footage of the benthos (Basket Star) Photo by: Dave Cote

The site had been scheduled for previous cruises; however, after having to retrieve an ROV that could make no headway against the powerful currents, it was clear that there needed to be more data on the strength and direction of the flow before it could be dove again.

In order to gather the data required, instruments need to be left at the site for months at a time to log as many parameters of the site as possible. This is done through moorings - an anchored series of floats and instruments that can span up to hundreds of meters or more vertically in the water to measure any number of things; ice contours, water parameters, zooplankton movement or, most importantly for this site, ocean currents. Two stations with moorings are near the Saglek Bank dive location, named HiBioA and HiBioC, so the ship tracked between the stations and the dive sites for the three days it was in the area, retrieving previous moorings and deploying new ones to collect the next batch of data.

The benthos using a drop camera; Photo by: Dave Cote

Using the information retrieved from 2019 and analyzed by one of the students to predict the tidal currents, the ROV was able to successfully dive at the Saglek Bank site four times within the 4-hour windows of time that corresponded to slack tide, and once at the more distant Hatton Sill. Collecting sediment, coral, and video data until the last possible moment, the dives started as soon as the ROV was able to reach the sea floor and ended only when it was physically forced off of the bottom by the currents.

Photo by: Kathryn Murray

The Amundsen cruises are multidisciplinary by necessity and by design - all sites require the confluence of skillsets and experience brought in by having researchers and experts in many disparate fields. In Saglek Bank and Hatton Sill, the successes of this trip to the site were thanks to everyone on board the ship - researchers, students, coast guard crew, Amundsen Science staff, and ROV pilots - working together.

Written By: Sophie Wolvin