Multi-year impacts of permafrost disturbance and thermal perturbation on High Arctic stream chemistry

et al. 2017

Hydrological Processes

Self Cite

The Arctic has experienced substantial warming during the past century with models projecting continued warming accompanied by increases in summer precipitation for most regions. A key impact of increasing air surface temperatures is the deepening of the active layer, which is expected to alter hydrological processes and pathways. The aim of this study was to determine how one of the warmest and wettest summers in the past decade at a High Arctic watershed impacted water infiltration and storage in deeply thawed soil and solute concentrations in stream runoff during the thaw period. In June and July 2012 at the Cape Bounty Watershed Observatory, we combined active layer measurements with major ion concentrations and stable isotopes in surface waters to characterize the movement of different runoff sources: snowmelt, rainfall, and soil water. Results indicate that deep ground thaw enhanced the storage of infiltrated water following rainfall. Soil water from infiltrated rainfall flowed through the thawed transient layer and upper permafrost, which likely solubilized ions previously stored at depth. Subsequent rainfall events acted as a hydrological flushing mechanism, mobilizing solutes from the subsurface to the surface. This solute flushing substantially increased ion concentrations in stream runoff throughout mid to late July. Results further suggest the importance of rainfall and soil water as sources of runoff in a High Arctic catchment during mid to late summer as infiltrated snowmelt is drained from soil following baseflow. Although there was some evaporation of surface water, our study indicates that flushing from solute stores in the transient layer was the primary driver of increased ion concentrations in stream runoff and not evaporative concentration of surface water. With warmer and wetter summers projected for the Arctic, ion concentrations in runoff (especially in the late thaw season), will likely increase due to the deep storage and subsurface flow of infiltrated water and subsequent flushing of previously frozen solutes to the surface.

Section: Resultssupporting

confidence: 67%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Evaluating the hydrological and hydrochemical responses of a High Arctic catchment during an exceptionally warm summer

Lamhonwah

Lafrenière

et al. 2017

Hydrological Processes

Self Cite

“…As such, we suggest that the thermal observations are consistent with water inflows to the channel rather than hyporheic exchanges. Limited ground ice data from permafrost cores near Lower Goose (Figure ), collected at Cape Bounty in 2012 (Lamhonwah et al, ), suggest that the isotopic composition of ground ice is enriched relative to the West River and cannot explain the observed downstream depletion. However, more broadly, the isotopic composition of various types of ground ice across the Canadian Arctic generally have δ 18 O signatures of −26‰ to −36‰ and δD ranging between −200‰ to −255‰ (Michel, ), which could account for downstream depletion in the West River.…”

Section: Discussionmentioning

confidence: 99%

“…An exponential discharge rating best fit curve was calculated as follows:

Q = 16.77 h^{2} - 2.533 h ((),, r^{2} = 0.90, n = 42),

where Q is the discharge (m 3. s −1 ) and h is the recorded stage (m) and subsequently applied to the stage depth measurements collected at the gauging station. Tributaries flowing into the West River displayed in Figure (Ptarmigan (PT), ALD05 (AL), Goose (GS), Muskox (MX)) were also gauged for the summer season using calibrated cutthroat flumes and rated with calibrated standard discharge curves (Lamhonwah, Lafrenière, Lamoureux, & Wolfe, ).…”

Section: Methodsmentioning

confidence: 99%

Thermal and isotopic evidence for surface and subsurface water contributions to baseflow in a high Arctic river

Bolduc

Franssen

2018

Hydrological Processes

Seven longitudinal water temperature tow surveys were conducted to attempt to identify the location of surface and subsurface river water exchanges along the length of the West River at the Cape Bounty Arctic Watershed Observatory, Melville Island, Nunavut, Canada (74°55′ N, 109°35′ W). Water temperature data were collected using a calibrated thermistor with an accuracy of ±0.002 °C (resolution <0.00005 °C) along the river during July 2014 in conjunction with stable water isotope sampling to support the thermal data and to determine the extent of surface water mixing from different sources such as precipitation, snowmelt, and surface/subsurface water contributions to the river. Atmospheric conditions were found to be the main contributor to seasonal temperature variance in the river, whereas tributary inflows and residual channel snow also had important thermal effects to river temperatures. Residual channel snow was a sustained source of cold water during much of the 2014 summer season (June–August) and substantially offset downstream warming. The longitudinal temperature profiles indicate notable changes to the thermal state of the river, which are interpreted to be indicative of subsurface and surface water exchange through inputs of relatively cold or warm water. Broadly, surface inflows were found to provide warmer water relative to the West River, and contributed to downstream warming of the river, along with downstream enrichment of δD and δ18O. Subsurface inflows provided cooler water relative to the river, and contributed to downstream depletion of δD and δ18O and downstream cooling of river temperatures. These results demonstrate that localized changes in river temperature, in conjunction with isotopic tracers, can be used to track channel–slope water interactions in Arctic hydrological systems, work previously limited to alpine and temperate settings.

Utilizing the TTOP model to understand spatial permafrost temperature variability in a High Arctic landscape, Cape Bounty, Nunavut, Canada

Garibaldi

Bonnaventure

Permafrost & Periglacial

2020

Ground surface and permafrost temperatures in the High Arctic are often considered homogeneous especially when viewed at the scale of climate and environmental models. However, this is generally incorrect due to highly variable, topographically redistributed snow cover, which generates a substantial degree of ground thermal heterogeneity. The objective of this study is to describe and spatially model the variability in the ground thermal regime within the Cape Bounty Arctic Watershed Observatory (CBAWO), Nunavut, Canada, using the TTOP model, for current conditions in addition to a series of future climate change scenarios. While observed air temperature was mostly uniform, annual mean ground surface and permafrost temperatures across the paired watersheds were estimated to range between −3.8 to −13.8°C and −3.9 to −14°C, respectively, similar to the −5 to −15°C magnitude and range identified from boreholes across the High Arctic. The spatial models showed higher ground surface temperatures in topographic hollows (slope bases and stream channels), and lower temperatures in areas of topographic prominence (hilltops and plateaus) following the spatial pattern of snow accumulation and redistribution. Under projected climate change, the models predicted areas with the coldest permafrost to have the largest magnitude of warming (about 9°C), while areas of warm permafrost became closer to 0°C (warming 4–7°C). This thermal heterogeneity may have implications for ground instability such as permafrost‐related mass movements, hydrological connectivity, biogeochemical cycling, and microbial activity, which influence water quality and contaminant mobility.