Paleolimnological Reconstruction of Hydrologic Change in the Slave River and Great Slave Lake During the Past Millennium

• Main Author: Ennis, Matthew
• Format: Text
• Language: unknown
• Published: Scholars Commons @ Laurier 2010
• Subjects: Hydrology; Great Slave Lake; Peace-Athabasca Delta; Mackenzie Basin; Slave River
• Online Access: https://scholars.wlu.ca/etd/1013; https://scholars.wlu.ca/context/etd/article/2012/viewcontent/MR75370.PDF

The Slave River Delta (SRD), NWT, represents a pivotal node in the upper Mackenzie Basin watershed and is a productive northern wetland landscape with a rich natural and cultural heritage. Concerns over environmental consequences of natural and anthropogenic-driven decline in river discharge as well as climate variability have prompted hydroecological sstudies to improve understanding of how this ecosystem functions over time and space. However, long-term natural hydrological variability of the Slave River system is not well documented and needs to be further developed. In order to provide a temperal context for understanding and evaluating the impacts of climate variability and change and other stressors on Slave River discharge, multi-proxy paleolimnological analyses have been conducted to reconstruct a long-term record of hydrologic variability in the Slave River system. Study sites include two small closed-drainage lakes (GSLI1, SD34) located near a former elevated strandline of Great Slave Lake and another lake (SR1) located upstream on an island in the Slave River. Multi-proxy analysis of lake sediment cores collected from SD34, GSL1, and SR1 provided a ∼1200-year record of water level variation for the Slave River and Great Slave Lake. Sediment composition and elemental and stable isotope geochemistry proved to be sensitive indicators of hydrologic change within the study basins. Interpretation of C/N ratios and δ18Olw, high δ13Corg and inorganic sediment indicated open-drainage conditions caused by riverine inundation of both study lakes. River inundation of SD34 and GSL1 was attributed to Slave River discharge dominated by a large flashy spring freshet and high ice-jam flood frequency. The percent organic carbon, organic nitrogen, δ15N, C/N ratios, δ18Olw values and δ13Corg values appear to indicate isolation of SD34 and GSL1 from the Slave River at ∼1000 AD and ∼1150 AD, respectively. However, reduced ice-jam flood frequency in the SRD precedes a similar change in the upstream Peace-Athabasca Delta ...