Spatio-temporal variation in the spring freshet of major circumpolar Arctic river systems

• Main Author: Ahmed, Roxanne
• Other Authors: Prowse, Terry Donald
• Format: Thesis
• Language: English
• Published: 2015
• Subjects: Arctic; spring freshet; hydrology; hydro-climatology; Arctic Ocean; Canada; Mackenzie River; Mackenzie river
• Online Access: http://hdl.handle.net/1828/5955

The spring freshet is the dominant annual hydrologic event occurring on largely nival Arctic river systems. It provides the greatest proportion of freshwater influx to the Arctic Ocean, amongst all other atmospheric input sources. To assess whether any shift in the seasonality of spring freshets has occurred, and how climatic drivers and flow regulation govern trends in sub-basin freshets and their contribution to outlet flow, a temporal and spatial analysis of 106 hydrometric stations located across four major Arctic-draining river systems is performed to extract information regarding the timing, magnitude and volume of the spring freshet of the four largest Arctic-draining rivers; namely, the Mackenzie River in Canada, and the Ob, Yenisei and Lena rivers in Eurasia. Total annual freshwater influx to the Arctic Ocean from these basins increased by 14% during 1980-2009. Despite freshet volume displaying a net increase, its proportional contribution to annual flow has decreased. In fact, rising winter, spring and fall discharge proportions, combined with lower peak freshet magnitudes, potentially increased freshet durations, and lower summer proportions indicate a shift towards flatter, more gradual annual hydrographs with earlier pulse onsets. Discharge assessed on a sub-basin level during 1962-2000 and 1980-2000 reveals regional differences in trends, with higher-relief drainage areas displaying the strongest trends. Sub-basin trends generally agree with those at the outlets, particularly in sub-basins without upstream flow regulation. Flow regulation has had a greater impact on observed trends in freshet volume compared to peak freshet magnitude. Timing measures are found to be strongly linked to spring temperatures. Volume relationships are also apparent with winter precipitation, however, these are less distinct. Moreover, flow regulation appears to suppress climatic drivers of freshet volume but has a lesser effect on timing measures. Significant relationships are found with several major atmospheric and ...