Research Document 2020/018

Physical Oceanographic Conditions on the Newfoundland and Labrador Shelf during 2018

By Cyr, F., Colbourne, E., Galbraith, P.S., Gibb, O., Snook, S., Bishop, C., Chen, N., Han, G., and D. Senciall

Abstract

An overview of physical oceanographic conditions in the Newfoundland and Labrador (NL) Region during 2018 is presented as part of the Atlantic Zone Monitoring Program (AZMP). The winter North Atlantic Oscillation (NAO) index, a key indicator of the direction and intensity of the winter wind field patterns over the Northwest Atlantic was strongly positive during 2018. However, the spatial patterns of the associated atmospheric sea level pressure fields resulted in normal air temperatures, characterized by a warm month of March, a cold spring and a warm summer. The sea ice volume across the Newfoundland and Labrador Shelf, although close to the long-term mean, exhibited a strong negative anomaly in March as a consequence of warm air temperature over the Arctic during this month. Annual sea surface temperature (SST, based on infrared satellite imagery) trends on the Newfoundland and Labrador Shelf, while showing an increase of about 1°C since the early 1980s, were mostly below normal during 2018, e.g., up to -1.6 standard deviation (SD), and -1.9 SD for Hamilton Bank and Hudson Strait, respectively. In 2018, vertically averaged salinity at Station 27 was at its freshest (negative anomaly) since 1970. Observations from the summer AZMP oceanographic survey indicate that after a predominance of colder than average conditions since 2012, the volume of the cold intermediate layer (CIL, <0°C) reduced in 2018, especially in the northern part of the region where it was -1.6 SD below normal along the Seal Island section (second smallest volume since 1980). The spatially averaged bottom temperature during the spring in 3LNOPs remained slightly above normal at +1.0 SD in 2018. For the fall, bottom temperature in 2J3KLNO was also above normal at +0.8 SD, a return to positive anomaly after the cold anomaly of 2017 (the first one since 1995). The Labrador Current transport index along the Labrador and northern Newfoundland slope in 2018 was a record high since the beginning of the time series in 1993 (equal with 1994 at +1.7 SD) while it was lower than average on the Scotian slope. A new NL climate index was introduced. It was near normal in 2018, characterized by approximately an equal number of sub-indices above and below normal.

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