Science Advisory Report 2017/031

Oceanographic conditions in the Atlantic zone in 2016

Summary

• Winter sea surface temperatures (SSTs) were above normal from the Scotian Shelf to the Bay of Fundy, including many record levels (since 1985) in March and April. Temperatures were also at record levels in November from the southwest Grand Bank (Division 3O), through St. Pierre Bank (Div. 3P), Cabot Strait (Div. 4V), the Gulf of St. Lawrence and the St. Lawrence Estuary. Sea surface temperatures averaged over ice-free months were near normal on the Labrador and Eastern Newfoundland Shelf and above normal elsewhere in the zone. Temperatures averaged over 0 to 50 m water depth were above normal at all five Atlantic Zone Monitoring Program (AZMP) high-frequency stations, including a record high at Rimouski station.
• Winter average sea ice extent was near normal on the Newfoundland and Labrador (NL) Shelf but was 4th lowest since records began in 1969 in the Gulf of St. Lawrence. Consistent with this, summer cold intermediate layer (CIL) conditions were mostly near normal on the NL Shelf, or at least not strongly anomalous, but were much warmer than normal in the Gulf of St. Lawrence and the Scotian Shelf.
• Bottom temperatures were normal to above normal across the zone, including very high anomalies on the Scotian Shelf, a 33-year record high in 3Ps and a 100-year record high in the deeper waters of the northern Gulf of St. Lawrence. Rimouski station bottom temperatures were also at a series record high.
• Deep nutrient inventories demonstrated considerable spatial heterogeneity and were near normal throughout much of the Atlantic zone but strong negative anomalies occurred at Station 27, on the eastern Scotian Shelf and in the Bay of Fundy. The return to normal conditions represents a reversal of periods of persistent low inventories on the Newfoundland Shelf (seven years) and high inventories throughout much of the Gulf of St. Lawrence (four years).
• Annual chlorophyll a inventories were generally below normal throughout the zone, with the strongest negative anomalies occurring on the Newfoundland Shelf and in the northwest Gulf of St. Lawrence.
• The onset of the spring phytoplankton bloom was delayed on the Newfoundland Shelf and normal or early in the Gulf of St. Lawrence and the Scotian Shelf; the magnitude of the bloom was generally below normal with the exception of the Gulf of St. Lawrence where the bloom on the Magdalen Shallows was well above normal; bloom duration was highly variable, with short blooms on the Newfoundland Shelf, northern Gulf of St. Lawrence and Central Scotian Shelf, and longer than average blooms in the southern Gulf of St. Lawrence and eastern Scotian Shelf.
• The zooplankton community shift observed in recent years, characterized by lower abundance of the large energy-rich copepod Calanus finmarchicus, higher abundance of small and warm water copepods, and higher abundance of non-copepods, persisted in 2016; the lowest negative anomalies in C. finmarchicus occurred on the Scotian Shelf while strong positive anomalies in Pseudocalanus sp. and non-copepods occurred in the Gulf of St. Lawrence and the Newfoundland Shelf.
• In the winter of 2016 the Labrador Sea experienced the deepest convection since 1994. That was the fourth year of progressive intensification and deepening of convective mixing and production of Labrador Sea Water since 2012. Both upper, 0-200 m, and deeper, 200-2,000 m, layers have been cooling since 2010. The Labrador Current was intensified in 2016 relative to the previous four years. Although the spring phytoplankton bloom initiation and amplitude were only average, the longer duration and higher magnitude in the Labrador Shelf and Basin brought this year’s chlorophyll over the average typically recorded. Interannual to multi-decadal variability of temperature and salinity in the Labrador Sea is dominated by decadal-scale changes making any long-term trends less obvious.

This Science Advisory Report is from the Nineteenth Annual Meeting of the Atlantic Zone Monitoring Program (AZMP) held March 14-17, 2017. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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