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

Abstract

The Cape Bounty Arctic Watershed Observatory (CBAWO) was established in 2003 to investigate the hydrological processes and impacts associated with climate and permafrost change in the High Arctic. Comprehensive data collection at the paired watersheds has spanned a period containing both the coldest and warmest melt season conditions, including the recent decade that is the warmest on record. Through this period, the hydrological regime has transitioned from a nival (snowmelt) dominated to increased importance of rainfall runoff and baseflow. This hydrological shift and associated environmental changes have altered the seasonality and magnitude of fluxes. Permafrost degradation has resulted in both localized and catchment-wide soil and runoff perturbations, broadly increasing solute and nutrient flushing, with more intense sediment and solute impacts where physical disturbances have occurred. The recovery time to perturbations diverges with sedimentary systems responding in approximately 5 years, while dissolved fluxes remaining high due to repeated thermal perturbations. Permafrost carbon in this setting is relatively old and labile, both in particulate and dissolved phases. Permafrost degradation has altered microbial activity in soils, and increased nitrification in disturbed settings, which points to complex biogeochemical responses to climate and permafrost change. Sustained research activity at CBAWO has revealed new complexity in the hydrological and biogeochemical functioning of High Arctic watersheds. Long-term observatories like CBAWO provide critical context to place observations in, especially during periods of change, and are necessary to develop a comprehensive understanding of hydrological change and water security in the region.

Summer rainfall dissolved organic carbon, solute, and sediment fluxes in a small Arctic coastal catchment on Herschel Island (Yukon Territory, Canada)

“…Thus, the summer of 2016 did not seem to be influenced by the event anymore. This short-lived sediment mobilization differs from major disturbances such as active-layer detachments or retrogressive thaw slumps, which impact sediment delivery in streams over many seasons (Bowden et al 2008;Frey and McClelland 2009;Lamoureux and Lafrenière 2009;Kokelj et al 2013;Lamoureux and Lafrenière 2017). Along with the increased sediment flux in 2015, we observe higher chloride concentrations and a slightly reduced alkalinity compared with the other years.…”

“…Hysteresis patterns for calcium and potassium are clockwise across catchments with varying permafrost coverage (Petrone et al 2007). The majority of SS is transported during the snowmelt season (Braun et al 2000;Forbes and Lamoureux 2005;Cockburn and Lamoureux 2008;Lamb and Toniolo 2016;Lamoureux and Lafrenière 2017), although high amounts of sediment may also be mobilized during summer rainfall events (Lewis et al 2005;Dugan et al 2012;Lamb and Toniolo 2016). Clockwise suspended sediment discharge hysteresis behaviour suggests a limitation and therefore rapid exhaustion of sediment that can be mobilized during rainfall (Dugan et al 2009).…”

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

“…Kokelj et al () examined solute concentrations in the subarctic Peel River (Canada) and found that summer Na:SO 4 significantly decreased in the past 40 years as a result of RTSs increase. We do not have long‐term data for this site, but based on the scientific literature (Lafrenière & Lamoureux, ; Lamoureux & Lafrenière, ), we assume that past disturbances have influenced hydrochemical composition.…”

“…Further, our data only provide insights into catchment processes during the summer. Snowmelt is the largest hydrological event of the year (M. Woo, 2012) and responsible for major matter export from Arctic rivers (Fouché et al, 2017;Lamoureux & Lafrenière, 2018;Laudon et al, 2004;Petrone et al, 2006). Incorporating all seasons into the water balance and hydrochemical export studies is essential to assess lateral fluxes into the ocean.…”

“…Understanding the interplay between snowmelt, precipitation, and physical and thermal disturbances is essential to quantify lateral biogeochemical fluxes. Research from the High Arctic suggests that physical disturbances such as ALDs or thaw slumps lead to increased solute and sediment fluxes (Lamoureux & Lafrenière, ). They found that sediment concentrations generally recover to predisturbance conditions in approximately 5 years, while solute concentrations are impacted for more than 5 years.…”