A synthesis of thermokarst lake water balance in high-latitude regions of North America from isotope tracers

Abstract

Numerous studies utilizing remote sensing imagery and other methods have documented that thermokarst lakes are undergoing varied hydrological transitions in response to recent climate changes, from surface area expansion to drainage and evaporative desiccation. Here, we provide a synthesis of hydrological conditions for 376 lakes of mainly thermokarst origin across high-latitude North America. We assemble surface water isotope compositions measured during the past decade at five lake-rich landscapes including Arctic Coastal Plain (Alaska), Yukon Flats (Alaska), Old Crow Flats (Yukon), northwestern Hudson Bay Lowlands (Manitoba), and Nunavik (Quebec). These landscapes represent the broad range of thermokarst environments by spanning gradients in meteorological, permafrost, and vegetation conditions. An isotope framework was established based on flux-weighted long-term averages of meteorological conditions for each lake to quantify water balance metrics. The isotope composition of source water and evaporation-to-inflow ratio for each lake were determined, and the results demonstrated a substantial array of regional and subregional diversity of lake hydrological conditions. Controls on lake water balance and how these vary among the five landscapes and with differing environmental drivers are assessed. Findings reveal that lakes in the Hudson Bay Lowlands are most vulnerable to evaporative desiccation, whereas those in Nunavik are most resilient. However, we also identify the complexity in predicting hydrological responses of these thermokarst landscapes to future climate change.

Inconsequential effects of flooding in 2014 on lakes in the Peace‐Athabasca Delta (Canada) due to long‐term drying

“…by the strong influence of evaporation. This agrees with model predictions that lakes in the Mackenzie Delta, downstream of the PAD, will become increasingly sensitive to local climate conditions as frequency and magnitude of flooding decreases (Marsh and Lesack 1996). We suspect that cumulative effects of long-term and ongoing decline in frequency and magnitude of river flooding, and arid conditions, are the dominant influence on the hydrological and limnological trajectory of lakes in the PAD, which, apparently is now unlikely to be altered by a single and isolated large flood event.…”

“…The 2000–2015 PAD isotope framework was then used to calculate evaporation to inflow ( E/I ) ratios, an index of lake‐water balance described by Gibson and Edwards () and others. As in many regional studies that have used this approach (e.g., Brooks et al ; Gibson et al ; MacDonald et al ), we compare E/I ratios across a large number of lakes to differentiate regions of the delta. E/I ratios were calculated as: where δ E is the isotope composition of evaporative flux (Craig and Gordon 1965), δ L is the lake water isotope composition, and δ I is the isotope composition of input waters to the lake ( see Supporting Information).…”

Using stable isotopes to illuminate thermokarst lake hydrology in permafrost regions on the Qinghai‐Tibet plateau, China

“…Continued climate warming and permafrost thawing will alter regional hydrologic systems and the spatial distribution of surface water resources, creating subsurface flow pathways . Previous studies have shown that permafrost degradation has significantly changed the water balance of thermokarst lakes, meltwater of ground ice contributes about one‐third of the input water to thermokarst lakes, and permafrost thaw controls changes of thermokarst lake status (number, size) and related hydrological variabilities …”

“…Due to the spatial heterogeneity of permafrost, vegetation cover and climate controls, the hydrological processes of thermokarst lakes were found to vary at each site . The distribution of permafrost also revealed different impacts on the initial source water . However, large‐scale investigations of the hydrology of thermokarst lakes on the QTP are rare.…”

Use of principal component analysis to extract environmental information from lake water isotopic compositions

“…Once the water reaches the lake, however, evaporation from the lake surface causes enrichments of both deuterium and 18 O and displaces the lake isotopic compositions below the MWL (e.g., Craig 1961;Dinçer 1968;Gat et al 1994;Teranes and McKenzie 2001;Brock et al 2009;Turner et al 2010). Multiple lakes within a region characteristically define a line in dD vs. d 18 O space, which is referred to as the "local evaporation line" (e.g., Gibson 2001;Gibson and Edwards 2002;Gibson et al 2005;Henderson and Shuman 2009;Kebede et al 2009;MacDonald et al 2017). Figure 1 shows a typical local evaporation line (LEL), which intercepts with the LMWL at the depleted end, and extends upward with a positive dD-d 18 O slope less than 8.…”