CGRG Bibliography of Canadian Geomorphology
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Author : Dugan, H.; Lamoureux, S.; Lafrenière, M.; and Lewis, T.
Date : 2010.
Title : The impact of permafrost disturbances and sediment loading on the seasonal mixing of two High Arctic lakes.
Publication : CMOS-CGU Ottawa 2010. 44th Annual CMOS Congress, 36th Annual Scientific Meeting of CGU, 3rd Joint CMOS-CGU Congress. May 31-June 4, 2010. Ottawa, Ontario.
Issue :
Page(s) :
Abstract
West and East lakes, Cape Bounty, Melville Island, Nunavut (74'N, 109'W) were studied over the melt seasons of 2003-2009. The lakes are morphometrically similar, with maximum depths of 30-34 m, and surface areas of 1.4-1.6 km2. Prior to the onset of nival melt, the lakes are isothermal, with slightly elevated conductivity, turbidity and low dissolved oxygen in a shallow layer in the lower 1-2 m. At the onset of melt, underflows generated from river inflow typically deliver fresh oxygenated water to the bottom of the lake and replace the lower water. By mid-June, both lakes have fully mixed, and temperature, conductivity, turbidity and oxygen are typically uniform throughout the water column. This seasonal mixing, observed in most Arctic freshwater lakes, is critical for benthic ecosystems in these environments. In 2007, record July air temperatures led to significant active layer thawing and subsequent active layer detachments in the West watershed. The disturbances immediately increased the sediment load in the river and overall sediment availability in the watershed. By comparison, disturbances in the East catchment were minimal. By the spring of 2009, the mid-column and bottom water turbidity of West Lake had increased to 15 and 400 NTU, respectively. Elevated levels of total organic carbon and total nitrogen were concomitant with the high turbidity. The elevated turbidity generated a density barrier in the hypolimnion, and unlike previous years, river inflow did not flush bottom water and replenish dissolved oxygen during the melt season. These results provide insights into the downstream impact of permafrost disturbance in a coupled river-lake system. In particular, the post-2007 sediment loading changed the lake from a seasonally mixed environment to one that is amictic and highly turbid.
Bibliography of Canadian Geomorphology