CGRG Bibliography of Canadian Geomorphology
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Author : Cooke, C.; Hobbs, W.; and Wolfe, A.
Date : 2005.
Title : Are current rates of atmospheric nitrogen deposition inducing biogeochemical shifts in lakes of the Eastern Canadian Arctic?
Publication : 35th Annual International Arctic Workshop. March 9-12, 2005. Timms Centre for the Arts, University of Alberta, Edmonton, Alberta, Canada.
Issue :
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Abstract
Although arctic lakes rank among the most pristine ecosystems remaining on Earth, widespread paleoecological analyses have revealed rapid recent changes in lake ecology that surpass Holocene natural variability, and are generally attributed to climate warming since the end of the Little Ice Age. However, the possibility that climate is only one dimension of these ecological shifts has not yet been explored, even though current warming is unlikely to exceed maximum naturallymediated postglacial warmth. Here, we assess whether increased anthropogenic nitrogen deposition from distant sources is contributing to directional changes in the biogeochemistry and ecology of two remote lakes on Baffin Island in the eastern Canadian Arctic. Paleolimnological analyses, including diatom assemblages and a suite of biogeochemical proxies (total organic matter, biogenic silica, organic nitrogen and carbon content and stable N and C isotopic ratios) reveal a complex suite of progressive changes that are coherently expressed in both lakes. Diatom assemblages began to change as early as the mid-19th century, but major inflections in the biogeochemical proxies occurred significantly later, being most pronounced after 1950. Among these changes are increases in sediment organic matter, C and N concentrations, and depletions of 2‰ in sediment d15N. It seems likely that climate warming, subsequently coupled to anthropogenic N deposition, are synergistically driving these ecosystems towards states for which no prior natural analogues exist.
Bibliography of Canadian Geomorphology