Temperature

The waters of the North Atlantic are temperate, as they get both cold and warm depending on the season. Surface water temperatures vary with air temperature. Deeper waters do not show much seasonal change but are instead influenced by currents. An important interaction is the mixing of cooler, fresher water from the Labrador Current and the warmer, saltier waters of the Gulf Stream.

Rising air temperatures driven by climate change and changes in currents are leading to warmer temperatures at both the seasurface and deep waters (Figures 3–4). Temperature is an important environmental factor. It influences everything from physical processes (such as sea ice formation and mixing of the water column) to the condition and behaviour of the species that live there.

Scientists measure water temperatures through the water column using automated sensors and direct measurements on research surveys. They also interpret satellite information. Sea-surface temperature from remote sensing is reported for ice-free periods of the year. These periods vary annually and regionally (from the north to south).

CCGS Teleost deploying equipment for oceanography measurements. Credit: Fisheries and Oceans Canada.

STATUS AND TRENDS

• Sea-surface temperature during ice-free months is related to air temperature. The rise in air temperature seen since the 1870s is about 1°C per century. As a result, sea surface waters are warming in Atlantic Canada. • For the region, two of the five warmest years since satellite records began were recorded in 2012 (warmest) and 2014 (4th). • In 2012, the Scotian Shelf, St. Pierre Bank, and the Grand Bank had their warmest sea-surface temperatures since 1985, when satellite records first became available. The St. Lawrence Estuary had its warmest sea-surface temperatures in 2016. • The influence of the Gulf Stream relative to the Labrador Current is increasing. This is leading to record high deep-water temperatures on the Scotian Shelf and in the deep channels of the

Gulf of St. Lawrence. A 100-year record high was observed in the northern Gulf of St. Lawrence in the 2012–2016 period. • Between 2012–2016, the

Newfoundland and Labrador

Shelves had overall aboveaverage bottom temperatures with some near-average temperatures in the latter half of the period. A 33-year record high was also observed off southern

Newfoundland. SEA-SURFACE TEMPERATURE

Figure 3 : Index of sea-surface temperature for the Atlantic bioregions measured during ice-free times of the year. These values are relative to the 1985-2010 average. The black trend line represents the combined anomalies for all areas (eGoM: eastern Gulf of Maine; BoF: Bay of Fundy; see Figure 1 for NAFO Divisions). Above average trends are warm conditions.