Research Document - 1999/048

Oceanographic conditions in NAFO Divisions 2J 3KLMNO during 1998 with comparisons to the long-term (1961-1990) average.

By E. Colbourne

Abstract

Oceanographic observations from Hamilton Bank on the Southern Labrador Shelf to the Southern Grand Bank during 1998 are presented and referenced to their long-term (1961-1990) means. Temperatures at Station 27 ranged from 0.3 to 0.5 ^oC above normal during winter and spring over most of the water column and into early summer near the surface. By mid-summer, however, a negative temperature anomaly developed in the upper water column with temperatures reaching 1 to 2° C below normal by late summer. These colder than normal temperatures propagated deeper into the water column reaching below 100 m depth by November. Bottom temperatures throughout the year at Station 27 were slightly above normal and upper layer salinities were below normal during the first half of the year, particularly during the summer months. The 1998 summer CIL area off Bonavista and Hamilton Bank increased over 1997 values but was still below normal, continuing a trend established in 1995. Along the Flemish Cap transect across the Grand Bank the CIL area was normal during 1998, a decrease from 1997 and identical to the 1996 value. The total volume of sub-zero ^oC water on the Newfoundland Shelf during both summer and fall is below normal continuing the trend established in 1995. Bottom temperatures on the Grand Bank during the spring were up to 1° C above the long-term average. During the fall of 1998 bottom temperatures were still above normal over many areas, particularly on the offshore portion of the Northeast Newfoundland. An analysis of the areal extent of bottom water in different temperature bins revealed a significant decrease in the areal extent of sub-zero ^oC water and a corresponding increase of about 70% in the extent of water above 1^oC during the spring of 1998 compared to 1997. In general, the below normal oceanographic trends in temperature and salinity, established in the late 1980s reached a peak in 1991, started to moderate during 1994 and were above normal by 1996. During 1997 and 1998 temperatures continued above normal over many areas, particularly on the Grand Bank during spring and over the deeper portions of the Northeast Newfoundland Shelf. The main exception being the near shore coastal regions in the upper to mid water column where temperatures were colder than normal during summer and early fall.

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