Warming and freshening of Baffin Bay, 1916–2003

Abstract

Regression analysis of historical hydrographic data is used to determine changes in temperature and salinity in Baffin Bay for the time period from 1916 to 2003. We find two distinct sets of changes in the Baffin: First, areas affected by the Atlantic inflow to Baffin Bay show substantial and statistically significant warming trends. In the more than 2000 m deep basin the warming peaks at 0.11 ± 0.06°C/decade at 700 m depth below the 640 m sill depth of Davis Strait connecting Baffin Bay to the North Atlantic Ocean. A vertical heat flux divergence of 0.25 W/m2 is required to warm Baffin Bay below 900 m by the amount observed. The required heat appears to be advected from the shelf and slope regions of the eastern Labrador Sea via Davis Strait along the west Greenland shelf break and diffuses vertically and horizontally into the deep central basin. The North Atlantic Oscillation index accounts for about 30% of the interannual variance of temperature fluctuations below the Davis Strait sill depth. Second, areas affected by Arctic inflow to Baffin Bay show a marginally significant freshening of up to about 0.086 ± 0.039 psu/decade. This freshening trend extends along the western margin of Baffin Island to Davis Strait and into the Labrador Sea. The freshening in the northern reaches of Baffin Bay is similar in size to that at its southern reaches. Temporal variability of annual composites between these locations appears to be in phase, suggesting a swift transition of Arctic waters at 76°N to Labrador Sea waters at 62°N.