September 23, 2016
At 12:45 PM after dinner (Canadian lunch), the continuous ringing of the General Alarm bells means to go to our Emergency Station. For most of us that’s the helicopter hanger aft. When we hear 7 shorter blasts followed by one long blast on the General Alarm or Ship’s Whistle we go to our Boat Station because it would mean we were abandoning ship.
When the alarm goes off I put on cold-weather clothes, parka, hat, gloves, and grab the life jacket in the closet, and head to the hanger where we stand about waiting for the next drill -- to the lifeboats.
There’s a science meeting every day at 11 a.m. in the outer boardroom. We gather at a long table and sit around the edges of the room in comfortable couches and computer workstations. Chief scientist Sarah Zimmerman from DFO-IOS British Columbia leads the meeting with a slide show that begins with two slides of newborns, the reason some scientists have not been able to join us this season. Then Sarah shows a map of where we’re headed and where the stations are for Buoys, Moorings and CTDs. CTD measures Conductivity, Temperature, and Depth.
(from the Methods link on the BG website)
The CTD itself is a set of small probes attached to a large metal rosette wheel. The rosette is lowered on a cable down to the seafloor, and scientists observe the water properties in real time via a conducting cable connecting the CTD to a computer on the ship. The water temperature and salt content, or salinity is important to oceanographers because it tells us about the types of water masses present, and how they are moving in the ocean. There can also be a host of other accessories and instruments attached to the CTD package. These include Niskin bottles which collect water samples at discrete depths for measuring chemical properties, Acoustic Doppler Current Profilers that measure the horizontal velocity, and oxygen sensors that measure the dissolved oxygen content of the water.
At these “stations,” prefigured locations all along our journey, the captain will bring the ship to a halt while the rosette is lowered into the water. The rosette is lowered and raised through the water column at a rate of 1 meter per meter so depending on the depth of the bottom, this process, from start to finish, can take up to 2 hours. The rosette conglomeration weighs more than 800 lbs. so when it is moved out of the nearby lab on a dolly into the open, safety measures are taken so no one gets hurt. Those working at the edge of the boat have extra harness straps and manipulate the rosette either away from or back onto the deck. Mike Dempsey and Glenn Cooper are leaders on the CTD crews who have either a day shift of 6 PM to 6 AM or the night shift, also 12 hours, sometimes working under the Northern Lights which entertained the night crew last night.
Sarah points north of our intended course on the map, to show where this year we will likely head in order to find solid ice for the buoys.
To learn more about Peter Lourie click here.