Climate Fact: Baseflow Rise and Permafrost Melt
Average annual temperatures in Canada’s Northwest Territories (NWT) increased over the second half of the 20th century. Average winter minimum temperatures exhibited a particularly strong trend, with certain areas of the province showing 5.4 degree Fahrenheit increases. As this warming occurred, overall annual flow from NWT rivers has increased, particularly in the southern and central regions. Total annual discharge into the Beaufort Sea from NWT baseflow (baseflow is the portion of the river flow originating from groundwater) averages 74 cubic miles each year, and over the second half of the 20th century, almost all of the NWT rivers studied showed an increase in average winter baseflow. This trend is thought to be linked to melting of permafrost as a result of the temperature rise; the melting converts ice in the permafrost to groundwater. The amount of annual NWT streamflow is also controlled by the Northern Annular Mode (NAM), or the periodic shift in the pressure gradient between the North Pole and the mid-latitudes. Positive NAM phases are associated with a poleward displacement of storm tracks, and thus more precipitation falling over the high latitudes. Positive NAM phases result in greater NWT streamflow.
Seasons: Spring, Summer, Fall
Sources: St. Jacques, JM and Sauchyn, DJ. “Increasing winter baseflow and mean annual streamflow from possible permafrost thawing in the Northwest Territories, Canada.” Geophysical Research Letters 36 (2009): L01401 and McAfee, SA and Russell, JL. “Northern Annular Mode impact on spring climate in the western United States.” Geophysical Research Letters 35 (2008): L17701.