Paleolimnology of thermokarst lakes: a window into permafrost landscape evolution

Abstract

Widespread across northern permafrost landscapes, thermokarst ponds and lakes provide vital wildlife habitat and play a key role in biogeochemical processes. Stored in the sediments of these typically shallow and dynamic waterbodies are rich sources of paleoenvironmental information whose potential has not yet been fully exploited, likely because of concerns over stratigraphic preservation and challenges to develop reliable sediment core chronologies. Here, we present an overview of recently derived informative paleolimnological reconstructions based on multiparameter analysis of sediment archives from permafrost aquatic basins. We include examples from across the Canadian North, Alaska, and Siberia that illustrate their value for providing insights into temporal patterns of lake inception, catchment erosion, aquatic productivity, hydrological evolution, and landscape disturbances. Although not captured in our survey, emerging research directions focused on carbon accumulation, storage, and balance hold much promise for contributing to global climate change science.Key words: thermokarst lakes, permafrost, paleolimnology, lake sediments.Résumé : Répandus d'un paysage de pergélisol septentrional à l'autre, les étangs et les lacs thermokarstiques fournissent un habitat essentiel à la faune et jouent un rôle clé dans les processus biogéochimiques. Accumulées dans les sédiments de ces plans d'eau typiquement peu profonds et dynamiques se trouvent des sources riches en informations paléoenvironne-mentales dont le potentiel n'a pas encore été entièrement exploité, probablement à cause des préoccupations concernant la conservation stratigraphique et les défis de développer des chronologies fiables à partir des carottes sédimentaires. Ici, nous présentons une vue d'ensemble des reconstitutions paléolimnologiques informatives récemment dérivées d'après l'analyse multi paramétrée d'archives de sédiments des bassins aquatiques du pergé-lisol. Nous incluons des exemples provenant du Nord canadien, de l'Alaska et de la Sibérie qui For personal use only.illustrent que ceux-ci peuvent offrir des perspectives sur les tendances temporelles de création de lacs, de l'érosion de bassins versants, de la productivité aquatique, de l'évolution hydrologique et des perturbations du paysage. Bien que non mises en lumière dans notre enquête, les directions de recherche émergentes centrées sur l'accumulation, le stockage et le bilan carbone s'annoncent bien quant à leur contribution à la science du changement climatique mondial.

Limnological evolution of Zelma Lake, a recently drained thermokarst lake in Old Crow Flats (Yukon, Canada)

“…Few studies have targeted thermokarst lakes over concerns that sediment mixing due to shallow depth and thermokarst processes obscures their sediment profiles. However, recent research suggests that informative paleoenvironmental records are preserved in these lake basins (Bouchard et al 2017). Even fewer studies have reported limnological or paleolimnological data for thermokarst lakes prior to and after drainage.…”

Organic Carbon and Nitrogen Stocks Along a Thermokarst Lake Sequence in Arctic Alaska

“…In general, thermokarst lakes in these regions primarily evolved throughout the Holocene with initiation peaks during the Pleistocene‐Holocene transition and the Holocene Thermal Maximum (Grosse et al, ; Romanovskii et al, ; Walter et al, ). They grow and coalesce but also drain partially or completely as a consequence of lake tapping, headward gully erosion, bank overtopping, coastal erosion, and anthropogenic disturbance (Bouchard et al, ; Grosse et al, ; Hinkel et al, ; Jones et al, ; Lenz, Grosse, et al, ; Marsh et al, ; Weller & Derksen, ). These partially or fully dewatered former lake depressions are called drained thermokarst lake basins (DTLBs; Hinkel et al, ).…”

Periphytic diatom community structure in thermokarst ecosystems of Nunavik (Québec, Canada)

“…Thermokarst lakes show distinct limnological and environmental properties depending on their ecoclimatic setting Roiha et al 2015;Deshpande et al 2016;Bouchard et al 2017). They are generally surrounded by peat deposits with sitespecific shoreline vegetation.…”

“…They strongly influence primary production dynamics, nutrient cycling, carbon transport and processing, and oxygen concentrations (Smol and Stoermer 2010;Majewska et al 2012 and references therein). Diatom assemblages are used around the world as accurate bioindicators of environmental conditions (e.g., Lowe 1974;Smol and Stoermer 2010) and have been used successfully in numerous shallow-lake studies to evaluate climate-driven changes in aquatic environments (Bennion et al 2010;Lotter et al 2010;Bouchard et al 2017). Diatom-based paleoenvironmental reconstructions have been conducted in numerous sites across the circumpolar regions (Douglas et al 2004), from subarctic (Ponader et al 2002;Bouchard et al 2013;Rühland et al 2014) to high-Arctic Canada (Antoniades et al 2005;Ellis et al 2008;Douglas and Smol 2010) as well as in Siberia (Pestryakova et al 2012;Biskaborn et al 2013).…”