Research Document - 2009/032
An assessment of the physical oceanographic environment on the Newfoundland and Labrador Shelf during 2008
By E. Colbourne, J. Craig, C. Fitzpatrick, D. Senciall, P. Stead, and W. Bailey
Abstract
The North Atlantic Oscillation (NAO) index, a key indicator of climate conditions in the Northwest Atlantic, for both 2007 and 2008 was slightly above normal (<0.5 standard deviations) and as a consequence, outflow of arctic air masses to the Northwest Atlantic was stronger than in 2006. This resulted in a broad-scale cooling of air temperatures throughout the Northwest Atlantic from West Greenland to Baffin Island to Labrador and Newfoundland relative to 2006. Sea-ice extent and duration on the Newfoundland and Labrador Shelf increased in 2008 but remained below average for the 14th consecutive year. As a result of these factors, water temperatures on the Newfoundland and Labrador Shelf generally cooled compared to 2006 but remained above normal in most areas in 2008, continuing the warmer than normal conditions experienced since the mid-to-late 1990s. Salinities in general on the NL Shelf, which were lower than normal throughout most of the 1990s, increased to the highest observed since the early 1990s during 2002 and have remained mostly above normal during the past 7 years. In particular, at Station 27 off St. John’s, the depth-averaged annual water temperature decreased from the record high observed in 2006 to about normal in 2007 and to about 1 SD above normal in 2008. Annual surface temperatures at Station 27 also decreased from the 61-year record of 1.7 ºC (3 SD) above normal in 2006 to about normal in 2007 and to 1 SD (1 ºC) above normal in 2008. Bottom temperatures at Station 27 remained above normal for the 13th consecutive year. From 2004-06, they were >2.5 SD above normal but decreased to about 1 SD above normal during 2007-08. Upper-layer salinities at Station 27 were above normal for the 7th consecutive year. Annual surface temperatures on Hamilton Bank were 1.8 SD above normal, 1.3 SD above normal on the Flemish Cap and near normal on St. Pierre Bank. Bottom temperatures on Hamilton Bank were normal, ~2 SD above normal on the Flemish Cap and ~1 SD below normal on St. Pierre Bank. The area of the Cold-Intermediate-Layer (CIL) water mass on the eastern Newfoundland Shelf during 2008 was below normal for the 14th consecutive year and the 5th lowest since 1948. The average temperature and salinity during the summer of 2008 along the Bonavista section has remained significantly above normal by 2.4 and 3.3 SD, respectively. Bottom temperatures during the spring of 2008 remained slightly above normal on the Grand Banks (3LNO) but were below normal on St. Pierre Bank (3Ps). During the fall they were above normal in NAFO Div. 2J and 3K and slightly below normal in 3LNO. The area of the bottom on the Grand Banks covered by <0 ºC water during the spring decreased from near 60% in 1991 to <5% in 2004 but increased to near-normal at about 30% in 2007-08. A composite climate index derived from several meteorological, ice and oceanographic time series indicate a continuation of warm-salty conditions with 2008 ranking 6th warmest in 59 years of observations.
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