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Research Document - 2005/020

An Overview of Meteorological, Sea Ice and Sea-Surface Temperature Conditions off Eastern Canada during 2004

By Petrie, B., R.G. Pettipas, W.M. Petrie

Abstract

A review of meteorological, sea ice and sea surface temperature conditions in the Northwest Atlantic in 2004 is presented. During 2004, the winter NAO index was below normal (~9 mb) for the fourth consecutive year and close to the 2001 value. A negative NAO index implies weakened winds, higher air temperatures and reduced heat loss from the ocean during winter over the Labrador Sea and partly over the Labrador and Newfoundland Shelf. Because of the important role that southward advection plays on the Canadian Atlantic seaboard, the effects of a negative (positive as well) NAO index, particularly four successive years of negative values, are eventually felt throughout the region. Annual average air temperatures were above normal by ~1.2°C over the Labrador Sea and Shelf, the Newfoundland Shelf and the Gulf of St. Lawrence; Scotian Shelf and Gulf of Maine air temperatures were about 0.4°C below normal. The winter wind anomalies over the Labrador Sea were generally towards the northwest at about 1-2 m/s, consistent with the negative NAO index and implying reduced heat flux from the ocean to the atmosphere. The Newfoundland ice coverage was the 2nd lowest in 42 years and its duration was generally less than average; the Gulf of St. Lawrence coverage was also less than normal ranking 11th of 42 years and its duration was typically less than average; on the other hand, the Scotian Shelf, where most of the ice is the result of export form the Gulf, featured unexceptional coverage (rank 19th of 43 years) with ice duration slightly longer than normal. The 262 icebergs that reached the Grand Bank was considerably less than the 927 in 2003 and the 5th lowest since 1985, when more accurate counts became available. The analysis of satellite data indicates a north-south gradient of sea surface temperatures similar to the air temperature distribution. The Labrador Sea and Shelf, the northern Newfoundland Shelf and northern Grand Bank, featured sea surface temperature anomalies that were 0.2-0.5°C above normal. Southeast Shoal and St. Pierre-Green Bank temperatures were slightly below normal. Above normal sea surface temperatures were seen in the northeastern Gulf of St. Lawrence but the rest of the Gulf had values slightly below normal. Sea surface temperatures on the Scotian Shelf and in the Gulf of Maine were 0.3-1.1°C below normal.

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