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

Abstract

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.

More than just snowmelt: integrated watershed science for changing climate and permafrost at the Cape Bounty Arctic Watershed Observatory

“…This work highlights the important control of highly variable thaw depth in channel and adjacent floodplain and slope systems. Similar research has been initiated at CBAWO and provides some initial indications of hyporheic flow pathways and localized inflows of subsurface water in channels . However, these processes remain poorly understood in the High Arctic, and recent channel temperature work at CBAWO has demonstrated that the accumulation of thick winter snowpack due to wind redistribution of snow can maintain highly protected channel thermal settings.…”

“…Similar research has been initiated at CBAWO and provides Advanced Review wires.wiley.com/water some initial indications of hyporheic flow pathways and localized inflows of subsurface water in channels. 25 However, these processes remain poorly understood in the High Arctic, and recent channel temperature work at CBAWO has demonstrated that the accumulation of thick winter snowpack due to wind redistribution of snow can maintain highly protected channel thermal settings. Bonnaventure et al 27 noted that the influence of snow on winter heat loss and freeze dates was substantial, and in one instance where several meters of snow accumulated, shallow channel bed temperatures were 30 C warmer than ambient air temperatures.…”

“…The transition layer is typically ice‐rich, and frozen core sampling indicates this is the case at CBAWO as well . Warmer climate will continue to contribute to thawing this layer with poorly understood hydrological effects, but results from CBAWO in years with record summer warmth indicate that soil water properties and flow pathways appear substantially different during times when the transition layer is subject to thaw. The contribution of altered subsurface flow pathways and structures remains poorly understood in the High Arctic.…”

Spatial Variability of Dissolved Organic Carbon, Solutes, and Suspended Sediment in Disturbed Low Arctic Coastal Watersheds

“…Subsurface flow is important to mobilize solutes from the active layer as also found by Coch et al (). Isotopic composition along a longitudinal profile had also been measured in West River on Cape Bounty, Melville Island, in the High Arctic by Bolduc et al (). They also find an increase of stable isotopes through rainfall, and progressively downstream from the headwaters.…”

Hyperpycnal flows control the persistence and flushing of hypoxic high conductivity bottom water in a High Arctic lake

“…7). This is likely an overestimate, since ground ice melt and increased baseflow will likely moderate river water temperatures (Bolduc 2015). The lake is unlikely to warm by a similar amount due to thermal inertia of the lake and isolation of the lake from the atmosphere by persistent ice cover.…”