Divergent hydrological responses to 20th century climate change in shallow tundra ponds, western Hudson Bay Lowlands

Abstract

The hydrological fate of shallow tundra lakes and ponds under conditions of continued warming remains uncertain, but has important implications for wildlife habitat and biogeochemical cycling. Observations of unprecedented pond desiccation, in particular, signify catastrophic loss of aquatic habitat in some Arctic locations. Shallow tundra ponds are a ubiquitous feature in the western Hudson Bay Lowlands (HBL), a region that has undergone intense warming over the past ∼50 years. But it remains unknown how hydrological processes in these ponds have responded. Here, we use cellulose‐inferred pond water oxygen isotope records from sediment cores, informed by monitoring of modern pond water isotope compositions during the 2009 and 2010 ice‐free seasons, to reconstruct hydrological conditions of four shallow tundra ponds in the western HBL over the past three centuries. Following an interval of relative hydrological stability during the early part of the records, results reveal widely differing hydrological responses to 20th century climate change among the study sites, which is largely dependent on hydrological connectivity of the basins within their respective surrounding peatlands. These findings suggest the 20th century has been characterized by an increasingly dynamic landscape that has variably influenced surface water balance – a factor that is likely to play a key role in determining the future water balance of ponds in this region.

Landscape-gradient assessment of thermokarst lake hydrology using water isotope tracers

“…In the western Hudson Bay Lowlands, diverging hydrological responses of shallow thermokarst lakes to recent climate change has been largely attributed to the degree of hydrological connectivity (Wolfe et al, 2011;Bouchard et al, 2013). In Nunavik, permafrost thaw may induce greater subsurface hydrological connectivity, which would most likely serve to further enhance the dominance of lake inflow versus evaporation and lake persistence that is evident in our results.…”

“…The LEL for a given region generally represents the expected linear trajectory of evaporative isotopic enrichment of a lake fed by the weighted average annual isotope composition of local precipitation ( P ). Here we differentiate and utilize the 'predicted' LEL based on the linear resistance model of Craig and Gordon (1965) and used elsewhere (e.g., Wolfe et al, 2011;Turner et al, 2014), from the more commonly applied 'empirically-defined' LEL for a given region based on linear regression through a series of lake water isotope compositions. The advantage of the former is that it permits lake water isotope compositions to be interpreted independently.…”

“…Hydrological changes induced by climate change might have additional influence on limnological properties and biogeochemical cycling of these lakes, yet little is known about the hydrological processes that influence thermokarst lake water balance conditions in this region. Recent isotope-based studies from the western Hudson Bay Lowlands (Wolfe et al, 2011, Bouchard et al, 2013, Old Crow Flats (Tondu et al, 2013;Turner et al, 2010Turner et al, , 2014, Yukon Flats (Anderson et al, 2013) and northern Alberta (Gibson et al, 2015(Gibson et al, , 2016a concluded that shallow thermokarst lakes are hydrologically dynamic systems yielding a great diversity of lake water balance conditions, variably influenced by hydrological processes (snowmelt, rainfall, permafrost meltwater, evaporation) and catchment features (vegetation, topography; Table 1). The stable isotope mass balance approach has also been used to characterize the influence of hydrological processes on non-thermokarst northern lakes (Gibson and Reid, 2014;Gibson et al, 2015;Gibson et al, 2016b) and on lakes elsewhere (Steinman et al, 2013;Jones et al, 2016).…”

Spatial, Environmental, and Biotic Determinants of Zooplankton Community Composition in Subarctic Lakes and Ponds in Wapusk National Park, Canada

“…The concentration, extent, and duration of sea-ice cover on Hudson Bay have decreased significantly over the past three decades (Gough et al, 2004;Hochheim et al, 2011;Hochheim and Barber, 2014), resulting in a positive feedback cycle that has accelerated warming over land surfaces (Hochheim and Barber, 2010). While there is little evidence that warmer temperatures have thus far impacted permafrost extent in the HBL, likely because of thermal lags between changes in air temperature and ground ice conditions (Gough and Leung, 2002; but see Wolfe et al, 2011), there are several examples of recent biological changes within aquatic ecosystems in the region.…”

“…It is a region characterized by low topographic relief that is overlain with poorly drained glacial and marine silts and clays, with lakes and ponds covering an estimated 25% (Macrae et al, 2004) to >40% of the landscape (Bello and Smith, 1990). Many of these water bodies are shallow and provide excellent habitat for waterfowl and other wildlife (Wolfe et al, 2011). They also influence biogeochemical dynamics at local, regional, and perhaps global scales (Vincent et al, 2013), serving as important sinks or sources of carbon, the balance of which is closely tied to hydrology and climate (Macrae et al, 2004).…”