Canada and U.S. Coast Guard Monitoring Conditions
OBSERVATION
While visiting the east coast of the island portion of Newfoundland and Labrador in February 2016, I observed an iceberg near the community of Elliston. - S. Mouland
BACKGROUND
Icebergs are usually first observed in late April through June, they are prominent in an area known as iceberg alley – an area stretching from the coast of Labrador to the north-east coast of the island of Newfoundland) thus seeing them in February is unseasonably early.
The majority of the icebergs in the North Atlantic come from about 100 iceberg-producing glaciers along the Greenland coast while a few originate in the eastern Canadian Arctic Islands. The icebergs observed off Newfoundland are carried south in the cold Labrador current. Originating at around 75º north latitude in Baffin Bay, an iceberg may travel up to 4000 km south to around 40º north latitude (800 km south of St. John’s).
CONSULT:
Norm Catto
Department Head, Geography Memorial University of Newfoundland
Icebergs are present throughout the year in the open Labrador Sea, and drift southward along the coast (depending on the fluctuations of the Labrador Current) during the summer. Between 1990 and 2015, approximately 2000 icebergs reached Cape Chidley (north tip of Labrador) annually. All of the icebergs are produced by calving along the margins of Baffin Bay and Davis Strait, predominantly from Greenland. The icebergs begin to ablate rapidly once they move southward from Hudson Strait. During the peak iceberg transit season (typically mid- July), the sea surface temperature off Hopedale is 6C, and off southern Labrador it can reach 10C. Under these conditions, the icebergs ablate rapidly. An iceberg 40 m high above the water line and 100 m long (approximate volume 2,000,000 m3 and mass approximately 10 million tonnes) will completely ablate in 24 days in 2C water, and requires only 15 days in 4C water. Such large icebergs make up approximately 20 % of the iceberg population off Cape Chidley, about 10 % off Makkovik, and about 5-6 % at the mouth of the Strait of Belle Isle. Smaller fragments (’growlers’) increase in proportion southwards as the larger icebergs disintegrate, but an average ‘growler’ will endure for less than 5 days in 4C water. Less than 10 % of the icebergs which enter Labrador waters offshore of Cape Chidley succeed in running the gauntlet to 52 N.
The icebergs which reach the northeast Newfoundland coastline thus are rare survivors. The major factor controlling the number is the initial supply of calved ice from the glaciers in Greenland. Because a single calved chunk can break up into thousands of icebergs, increases or decreases in iceberg numbers off Elliston, Twillingate, or Bonavista are not directly related to changes in climate or glacial activity in Greenland.
Credit: Dr. Norm Catto , Head Department of Geography, Memorial University of Newfoundland
