Observed 80-Years of Climate Change in Baffin Bay: Facts, Fiction, and the NAO

Climate change often appears dramatic when one averages the oscillatory system under investigation over short periods of its most extreme positive and negative stages and calls the difference change. While formally correct, the suggested change is often mistaken for a trend especially by the public and those not trained in the delicacies of statistics. Hence we reject this methodology and settle for a careful regression analysis of Baffin Bay and Davis Strait hydrographic data from 1916 through 2003. We estimate the degrees of freedom in the sampled temperature and salinity fields conservatively after discarding all data that do not fit within a few standard deviations from an iteratively calculated mean profile for suitably defined regions. Strong and significant subsurface warming emerges at locations where the water is deeper than 2000-m. We find weak and barely significant freshening of waters in the upper 300-m of the water column along the western, but not the eastern rim of Baffin Bay. Formal correlations of temperature and salinity anomalies with the often used North-Atlantic Oscillation (NAO) index are weak and generally not significant. Averaging hydrographic conditions along isobaths selectivly during positive and negative stages of the NAO, however, we find a fresher and cooler water column along the western rim of Baffin Bay during positive NAO as compared to the negative NAO phase. This contrasts with our finding along the eastern rim. Along Greenland during the positive NAO phase near bottom waters are both saltier and warmer than during the negative phase of the NAO. These finding are consistent with enhanced (positive NAO phase) and diminished (negative NAO) inflows of warm and salty waters from the North-Atlantic advecting heat and salt northward along the eastern rim of Baffin Bay and enhanced inflow of cold and fresh from the Arctic advecting ice and freshwater southward along the western rim of Baffin Bay. The effect on density results in lighter, more vertically and horizontally stratified waters during the positive NAO. Geostrophically, this implies a more intense circulation.