Seasonal dynamics in shallow freshwater pond‐peatland hydrochemical interactions in a subarctic permafrost environment

Abstract

Terrestrial and aquatic ecological productivity are often nutrient limited in subarctic permafrost environments. High latitude regions are experiencing significant climatic change, including rapid warming and changing precipitation patterns, which may result in changes in nutrient dynamics within terrestrial and aquatic systems and hydrochemical transport between them. The objective of this research was to characterize changes in runoff quantity and quality within, and between peatlands and ponds throughout the snow‐free summer season. Two ponds and their catchments were monitored over the snow‐free season to measure changes in hydrologic storage, and to determine how water chemistry changed with the evolution of the frost table depth. Thresholds in hydrologic storage combined with frost table position (which inhibited infiltration and storage) produced nonlinear responses for runoff generation through highly conductive shallow peat layers while deeper, less conductive layers retarded flow. Greater inputs were required to exceed hydrologic storage (fill and spill) as a deepening frost table increased the hydrologically active portion of the soil, leading to seasonal variability in runoff pathways between peatlands and ponds. Runoff contributions to ponds were an integral component of the snow‐free water balance during the study period, contributing up to 60% of all snow‐free inputs. Groundwater chemistry (and pond chemistry following runoff events when ponds were connected with peatlands) reflected the different depths of peat and mineral soil accessed throughout the season. This work has improved scientific understanding of the combined controls of hydrologic inputs and ground frost on runoff and nutrient transport between peatlands and ponds, and sheds insight into how nutrient dynamics in cold regions may evolve under a changing climate.

Capturing temporal and spatial variability in the chemistry of shallow permafrost ponds

“…Precipitation data were taken from the Environment Canada "Churchill" station (20 km west of the study site). Runoff was determined as the residual change in pond storage exceeding the input from direct precipitation during and up to 24 h. following a rain event, after Morison et al (2017). The perimeter and area of each pond were surveyed with a Trimble Juno SB GPS unit, with a differentially corrected horizontal accuracy of ±5 m.…”

“…This leads to the dampening of the storm-based concentration variability in Strange pond. Those species that may have elevated concentrations in event water relative to lower concentrations in pond water, such as DON (Morison et al, 2017), show a heightened response in terms of pond concentrations in both Frisbee pond and Strange pond. Species which have event water concentrations which are similar to background pond water concentrations show a dampened response.…”

“…4) was observed, nor were either of these related specifically to total catchment area (Table 1). However, this may be a result of the variable source area concept applying in this filland-spill system (Spence et al, 2010;Morison et al, 2017), in which substantial portions of the catchment are not contributing runoff to the ponds for certain storms which do not provide requisite overfilling of the catchment storage capacity threshold. This effect renders estimates of total catchment area which are delineated by topography less useful without additional knowledge of total subsurface storage capacity and effective contributing area for each runoff event.…”

“…Although climate change may lead to long-term changes in pond permanence and hydrologic exchange, pond hydrologic storage can also vary greatly over the course of a single season or among different hydrologic years (Morison et al, 2017;Woo and Guan, 2006). Annual changes to pond storage often reflect the highly variable local climatic conditions, and ponds may either desiccate completely (e.g.…”

Dissolved organic carbon and major and trace elements in peat porewater of sporadic, discontinuous, and continuous permafrost zones of western Siberia

“…may be even more important in changing the biogeochemical cycle of carbon and metals in permafrost-affected soils (Jorgenson et al, 2013). For these reasons, the peat land zones have received significant attention (Haapalehto et al, 2011;Olefeldt and Roulet, 2012;Charman et al, 2013;Quinton and Baltzer, 2013;Muller et al, 2015;Morison et al, 2017), notably via natural manipulation experiments in order to assess the responses of peat carbon to simulated warming and oxidizing (Dielemann et al, 2016;Liu et al, 2016), water table manipulation (Blodau and Moore, 2003;Strack et al, 2008;Goldberg et al, 2010), and drought (Clark et al, 2012).…”