HR: 17:30h
AN: GC44A-07    [Abstracts]
TI: Long Term Decline in River Discharge in the Canadian Middle Arctic Recorded in Laminated Lake Sediments: a Hydrological Response to Global Warming?
AU: * Lamoureux, S F
EM: lamoureux@lake.geog.queensu.ca
AF: Department of Geography, Queen's University, Kingston, ON K7L 3N6 Canada
AU: Stewart, K A
EM: kailey@lake.geog.queensu.ca
AF: Department of Geography, Queen's University, Kingston, ON K7L 3N6 Canada
AU: Forbes, A C
EM: forbes@lake.geog.queensu.ca
AF: Department of Geography, Queen's University, Kingston, ON K7L 3N6 Canada
AB: Detailed sedimentological and diatom investigations were used to develop an understanding of the long term hydrological behaviour in the Lord Lindsay River on the central Boothia Peninsula, Nunavut, Canada (71dN, 95dW). This location was chosen to avoid geomorphic controls that could influence long term sediment availability and limit the interpretation of the sedimentary record. Additionally, two years of sediment delivery observations in the Lord Lindsay River and two major tributaries were carried out to support analysis of the sediments. Results indicate that sediment transport occurs dominantly during short period of peak discharge during the spring snowmelt period. Our monitoring indicates a broad proportional control over total sediment delivery by integrated catchment snow water equivalence. Summer rainfall events did not result in substantial additional sediment delivery. Analysis of the long varve record from Sanagak Lake indicates declining sedimentation since the 17th century, with the lowest levels in the 20th century. The decline since c. 1850 AD is coincident with a decrease in lotic (riverine) diatoms in the sedimentary record. Both records suggest that peak and overall discharge in the Lord Lindsay River have substantially declined. Comparison with long arctic proxy temperature records suggest a linkage between increased warmth and declining discharge intensity, potentially through increased snow sublimation and melt infiltration, or, a reduction in snow pack. While the mechanisms for the observed changes remain uncertain, our data are consistent with a hydrological response rather than a geomorphic change in sediment availability. Contrary to many glacierized catchments, the large rivers in this region appear to have been affected by a shift towards shorter or less intense nival discharge peaks.
DE: 9315 Arctic region
DE: 1655 Water cycles (1836)
DE: 1815 Erosion and sedimentation
DE: 1860 Runoff and streamflow
SC: Global Climate Change [GC]
MN: 2004 AGU Fall Meeting