Reference
Déry, S.J. and Wood, E.F. 2005. Decreasing river discharge in northern Canada. Geophysical Research Letters 32: doi:10.1029/2005GL022845.
What was done
About three quarters of Canada is drained by rivers discharging into the Arctic and North Atlantic Oceans, which discharge affects atmospheric, oceanic, cryospheric and biologic processes in these high-latitudes. In the present study, Déry and Wood attempt to gain a better understanding of the variability of this river runoff over the past four decades. In doing so, they analyze hydrometric data from 64 rivers in northern Canada covering more than half of the Canadian landmass for the period 1964-2003. Then, after assessing variability and trends, they explore the influence of several large-scale teleconnections as drivers of the trends.
What was learned
A statistically significant mean decline of 10% in the discharge rates of the 64 Canadian rivers was found over the four decades of study, which was nearly identical to the observed decline in precipitation falling over northern Canada between 1964 and 2000, leading the authors to conclude that changes in river discharge in this region are driven "primarily by precipitation rather than evapotranspiration." As to what might be causing the precipitation/river discharge decline, statistically significant links were found between the Arctic Oscillation, El Niño/Southern Oscillation, Pacific Decadal Oscillation and the total annual freshwater discharge of the 64 northern Canadian rivers at interannual-to-decadal timescales.
What it means
The results of this study indicate there is nothing unusual about the four-decade trends in northern Canada river discharge rates, which is exactly the point: there is nothing in these trends that would suggest a fingerprint of global warming. If anything, the results of this study argue against the worrisome climate-alarmist notion, for state-of-the-art climate models predict global warming will enhance river discharge rates due to an enhanced hydrologic cycle. The trends observed here, however, are just the opposite; and it is clear that they are merely the products of natural variations in various natural phenomena.