Monitoring 13 years of drastic catchment change and the hydroecological responses of a drained thermokarst lake

Abstract

Catastrophic drainage of thermokarst lakes transform portions of former lakebed to terrestrial settings, which have largely unknown consequences for the remaining aquatic habitat. Old Crow Flats, northern Yukon (Canada), is a lake-rich area that has recently experienced a climate-driven increase in lake drainage frequency. A notable example occurred during June 2007 when Zelma Lake (originally 12 km2) lost over 80% of its volume. Here we integrate remote sensing techniques with in-situ hydrological and limnological measurements over 13 years following drainage to 1) monitor water surface area and terrestrial land cover change and 2) identify associated effects on aquatic conditions. An airborne drone system was used to provide training data for land cover classification of AVIRIS-NG data, which indicated that tall willow shrubs covered 30.8% of the former lake area by 2017. Lake water isotope-derived deuterium-excess increased during the 13-year record indicating that hydrological input increased with greater snowpack accumulation within encroaching vegetation. Limnological conditions were highly variable and eutrophic during the first few years following drainage but became more stable as vegetation colonized the former lakebed. This long-term study provides insight of aquatic responses to thermokarst lake drainage and shrub vegetation proliferation, which are increasing in Arctic and subarctic regions.

Ecosystem responses of shallow thermokarst lakes to climate-driven hydrological change: Insights from long-term monitoring of periphytic diatom community composition at Old Crow Flats (Yukon, Canada)

“…18,19,21 Measurements of water chemistry at the LTM lakes since 2009 have occurred sporadically. 36 The use of artificial-substrate periphyton samplers began in 2008, which were deployed in early June shortly after ice-off and retrieved in September/October shortly before ice-on. In 2015, inclement weather prevented the retrieval of periphyton samplers; thus, diatom data are missing for that year.…”

“…Since 2007, partnerships among Parks Canada, VGG, and university researchers have advanced methods for LTM of the shallow, mainly thermokarst, lakes in OCF to track hydrological and limnological changes. 16,18,19,21,33,[35][36][37][38][39][40] Recently, increased input of rainfall runoff and, possibly, meltwater from degrading permafrost to lakes, have been identified based on water isotope monitoring of 14 lakes in OCF during 2007-2019, 39 which increases the vulnerability of lakes to catastrophic drainage via outlet erosion. 16,36 In this study, we use the analysis of periphytic diatom community composition in biofilms accrued on artificial-substrate samplers to track physicochemical and biological responses at the 14 LTM lakes in OCF during a 12-year period (2008-2019) associated with a rise in rainfall runoff and increasingly positive lake water balances.…”

“…16,18,19,21,33,[35][36][37][38][39][40] Recently, increased input of rainfall runoff and, possibly, meltwater from degrading permafrost to lakes, have been identified based on water isotope monitoring of 14 lakes in OCF during 2007-2019, 39 which increases the vulnerability of lakes to catastrophic drainage via outlet erosion. 16,36 In this study, we use the analysis of periphytic diatom community composition in biofilms accrued on artificial-substrate samplers to track physicochemical and biological responses at the 14 LTM lakes in OCF during a 12-year period (2008-2019) associated with a rise in rainfall runoff and increasingly positive lake water balances. 39 The findings improve knowledge of ecosystem responses of shallow thermokarst lakes to hydrolimnological changes and their vulnerability to climate change.…”

“…Since 2007, partnerships among Parks Canada, VGG, and university researchers have advanced methods for LTM of the shallow, mainly thermokarst, lakes in OCF to track hydrological and limnological changes. 16 , 18 , 19 , 21 , 33 , 35 – 40 Recently, increased input of rainfall runoff and, possibly, meltwater from degrading permafrost to lakes, have been identified based on water isotope monitoring of 14 lakes in OCF during 2007–2019, 39 which increases the vulnerability of lakes to catastrophic drainage via outlet erosion. 16 , 36 …”

“… 16 , 18 , 19 , 21 , 33 , 35 – 40 Recently, increased input of rainfall runoff and, possibly, meltwater from degrading permafrost to lakes, have been identified based on water isotope monitoring of 14 lakes in OCF during 2007–2019, 39 which increases the vulnerability of lakes to catastrophic drainage via outlet erosion. 16 , 36 …”