Research Document 2019/051

Physical Oceanographic Conditions on the Newfoundland and Labrador Shelf during 2017

By Cyr, F., Colbourne, E., Holden, J., Snook, S., Han, G., Chen, N., Bailey, W., Higdon, J., Lewis, S., Pye, B. and D. Senciall

Abstract

An overview of physical oceanographic conditions in the Newfoundland and Labrador Region during 2017 is presented as part of the Atlantic Zone Monitoring Program (AZMP). The North Atlantic Oscillation (NAO) Index, a key indicator of the direction and intensity of the winter wind field patterns over the Northwest Atlantic was weakly positive during 2017. The associated atmospheric pressure fields resulted in a reduced arctic air outflow in the northwest Atlantic during the winter months resulting in near-normal winter air temperatures, however air temperatures were below normal during the spring. Sea ice extent across the Newfoundland and Labrador Shelf between 45-55°N, although above normal during late spring, was below the long-term mean in 2017. In the inshore regions along the east and northeast coast of Newfoundland sea ice duration was up to 15-60 days longer than normal. Sea ice in these regions disappeared by mid-June, which is 15-45 days later than normal depending on the area. 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 2017, driven largely by very cold spring conditions. In 2017, the annual bottom (176 m) temperature/salinity at the inshore monitoring site (Station 27) was below normal by -0.6/-1.5 standard deviations (SD), respectively. Observations from the summer AZMP oceanographic survey indicated that the area of cold-intermediate-layer (CIL <0°C) water overlying the northeast Newfoundland and southern Labrador shelf increased over 2016 to about 1 SD above normal, implying more extensive cold winter chilled water throughout the region. Labrador Current transport through the Flemish Section remained high during the spring (13.5 Sv) but decreased to lower than normal during the summer (4.6 Sv). Summer transport through the Seal Island section was higher than normal in 2017 at 12 Sv. The spatially averaged bottom temperature during the spring in NAFO Division 3Ps remained slightly above normal, a significant decrease over the 37-year record high in 2016. In Divs. 3LNO spring bottom temperatures were about normal. The spatially averaged bottom temperature during the fall in 2J and 3K show an increasing trend since the early 1990s of about 1°C, reaching a peak of >1.8 SD above normal in 2011 before returning to near normal values, including in 2017. Oceanographic data from the fall 2017 3LNO indicate that bottom temperatures were about 1 SD below normal. In Divisions 2J and 3K fall bottom temperatures continued to decrease from the record high in 2011 to about normal conditions in 2017. A standardized composite climate index for the Northwest Atlantic derived from 28 time series of meteorological, ice, water mass areas and ocean temperature and salinity conditions since 1950 reached a record low (cold) value in 1991. Since then it shows a warming trend that reached a peak in 2010 and thereafter decreased to mostly below normal conditions (cold/fresh) during the past 4 years. The 2015 value was the 7th lowest in 68 years of observations and the lowest value since 1993, while the 2017 value was the 15^th lowest.

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