[1] Dalhousie Univ, Dept Engn Math, Halifax, NS B3J 2X4, Canada
[2] Fisheries & Oceans Canada, Bedford Inst Oceanog, Dartmouth, NS B2Y 4A2, Canada
[3] Fisheries & Oceans Canada, Inst Ocean Sci, Sidney, BC V8L 4B2, Canada
[4] Univ Victoria, Sch Earth & Ocean Sci, Victoria, BC, Canada