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

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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.

Conceptual relative sediment and solute fluxes and recovery trajectories (insets, red, sediment, blue, solutes) from slope tributaries resulting from localized physical disturbance (ALD, yellow polygons) and widespread thermal perturbation. Increased low‐solute fluxes are widespread due to deep active layer thaw and release of solutes from the transient layer. Higher solute loads are generated locally by ALD physical disturbance. By contrast, sediment fluxes are minimal except where physical disturbance has occurred. Highly connected, channelized ALD generate high sediment loads, while loads are reduced by limited connectivity or internal channelization. Recovery times appear to be approximately more than 5 years for solutes, while sediment erosion rapidly diminishes in poorly connected or channelized systems. Higher sediment yields from connected‐channelized systems also show rapid reduction in sediment fluxes, but maintain relatively high yields.
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Seasonal runoff, suspended sediment, hydrochemical, and nutrient fluxes from the West (a,c,e,g,i) and East (b,d,f,h,j) rivers. Fluxes are separated by hydrological season (SF, stormflow, BF, baseflow, and SM, snow melt). Note the variation from primarily snow melt dominated fluxes in 2006 to substantial fluxes associated with rainfall runoff (2009). (Reprinted with permission from Ref . Copyright 2003 Wiley)
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Images illustrating permafrost thermokarst disturbances at Cape Bounty that formed during late July 2007. (a) An active layer detachment (ALD) located on an upland slope with fractured soil (foreground) and exposed marine clay in the scar zone (mid‐ground). (b) Post‐disturbance channelization in the scar zone of Ptarmigan Creek (Figure ), June 2010, 3 years after initial disturbance. (c) Exposed massive ice along river bank in the upper West River watershed. Ice was exposed by bank erosion initiated by slope disturbance on the opposite bank forcing flow to undercut and expose the ice (August 3, 2009). Rapid ice retreat generated sustained sediment mobilization for many years. Photographs: S.F. Lamoureux.
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Long‐term and seasonal climate and hydrological data observed at CBAWO. (a) Long‐term total discharge for West River, mean summer (June–July) temperature and total summer rainfall indicate the wide range of hydroclimatic conditions. Seasonal hydrological contributions are indicated and demonstrate the variable influence of water timing in this environment. Note that discharge data is not available for 2011, 2013, and 2015 following a shift to biannual gauging due to the resource‐intensive requirements of hydrometric measurements in this setting. West River hydrograph and seasonal climate data for two representative seasons. (b) Conditions in 2004, the coldest season on record were dominated by nival runoff and muted rainfall and baseflow contributions. (c) In 2009 two major rainfall events resulted in seasonal high discharge in late July. (Reprinted with permission from Ref . Copyright 2017 Springer)
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Images of landscape, vegetation, and channel environments at Cape Bounty. (a) Late snow melt (June 21, 2012) and receding discharge in the West River, with residual channel snowpack. (b) Slope water track during snow melt (June 16, 2010, Goose Creek; Figure ). (c) Riparian seep and associated algal mat draining a sedge wetland adjacent to the West River (August 20, 2015). Photographs: S.F. Lamoureux.
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A schematic chronology of major research and monitoring programs at CBAWO. Lighter colors are indicated in cases where programs were of limited scope or short lived. Three major events are indicated for reference, including: the warmest and coldest summer seasons, and the episode of widespread permafrost disturbance.
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Overview of the Cape Bounty Arctic Watershed Observatory (CBAWO). Paired watersheds drain into similar freshwater lakes. In addition to hydrometric stations at the outlet of both watersheds, slope subcatchments in the West River provide focused investigations, particularly related to varying amounts of permafrost slope disturbance. A network of meteorological, soil, and permafrost stations support hydrological research. The International Tundra Experiment (ITEX, http://ibis.geog.ubc.ca/itex/) site was established in 2008 and includes snow and temperature experiments. Lake stations are locations for systematic water column measurements and sampling. Contour interval 10 m.
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Integrated climate‐permafrost effects on sediment and solute fluxes in rivers and downstream lakes. Thermal perturbation of the upper permafrost occurs during individual warm summers, mobilizing solutes in the transient layer, especially following heavy rainfall. Downstream effects are cumulative in lakes, resulting in substantial changes to water chemistry. The conditions that lead to physical disturbance appear less common, but result in an abrupt increase in sediment yield and short‐term recovery and no measurable cumulative impact in downstream lakes.
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