Dispatch 5: "Ice Blink" and Water Sky"     Print

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Fred Marin

September 16, 2019

Location: 76° 17’ N 137° 43’ W

Sea Conditions: 3679m water depth; open water transitioned to thin floes of ice sea ice.

Monday as we continued to travel north across the Arctic deep water in open seas, an “ice blink” came into view.  I learned today that “ice blink” is a sea term for locating ice foes on the horizon.  If the opposite situation occurred where we would be traveling through ice and saw open water on the horizon, the term would instead be “water sky”.  Traveling through sheets of ice rather than open water has an effect on the ride of the ship.  Ice damps wind and wave energy so the water is calm and flat.  As the ship crushes through the ice, you can hear it slide and push against the sides of the ship as the ship’s hull passes through.

I find one of the most fascinating and unique features of the heavy icebreaker (CCGS Louis S. St-Laurent) to be the design of its bow.  The bow rides just above the waterline where a blunt ridge forms the “ice knife” which utilizes the weight of the ship to apply a downward force splitting the ice.  Below the water line the bow is at a steeper angle forming the “horn”, a heavy concrete filled mass designed to prevent the ship from riding too high on heavy ice.  The sides of the ship are protected by a 50mm belt of steel plating.  The bow is slightly thicker at 54mm of plate steel.

Another interesting feature onboard is the “air bubbler system”.  This is a system where large air compressors force air out openings on either side of the ships bow below the water line.  The rising air helps to displace ice, reduce fiction of ice against the hull, and also acts as a bow thruster to help the ship with delicate maneuvers and positioning. 

Our routine of sampling stations along our cruise track continued as we moved north to higher latitudes.  Stations CB-18, CB-17 were located over deep water (3607m and 3679m depth respectively).  Then a jog to the east brought us closer to the edge of the Canadian basin where station PP7 was sampled in deep water as well (3555m depth).  These stations were sampled using the CTD-rosette, “bongo” net, and “NORPAC” closing net.  XCTDs were launched between stations to fill in hydrographic data between stations.

Observing the sunset, I noticed how long twilight seemed to linger.  We are so far north the sun takes a longer time to rise and set than it does at more southern latitudes.  The sun also doesn’t rise as high in the sky during the day as it follows a low sweeping arc across the sky.  The constant low cloud cover gives a hazy appearance and gives the illusion that the sky is low, like we are in the Earth’s attic!

Thank you for taking the time to join us and learn about our day aboard the heavy icebreaker CCGS Louis S St-Laurent!