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

Abstract

Coastal ecosystems in the Arctic are affected by climate change. As summer rainfall frequency and intensity are projected to increase in the future, more organic matter, nutrients and sediment could be mobilized and transported into the coastal nearshore zones. However, knowledge of current processes and future changes is limited. We investigated streamflow dynamics and the impacts of summer rainfall on lateral fluxes in a small coastal catchment on Herschel Island in the western Canadian Arctic. For the summer monitoring periods of 2014-2016, mean dissolved organic matter flux over 17 days amounted to 82.7 ± 30.7 kg km −2 and mean total dissolved solids flux to 5252 ± 1224 kg km −2 . Flux of suspended sediment was 7245 kg km −2 in 2015, and 369 kg km −2 in 2016. We found that 2.0% of suspended sediment was composed of particulate organic carbon. Data and hysteresis analysis suggest a limited supply of sediments; their interannual variability is most likely caused by short-lived localized disturbances. In contrast, our results imply that dissolved organic carbon is widely available throughout the catchment and exhibits positive linear relationship with runoff. We hypothesize that increased projected rainfall in the future will result in a similar increase of dissolved organic carbon fluxes.Key words: permafrost, hydrology, lateral fluxes, hysteresis, climate change.Résumé : Les écosystèmes côtiers dans l'Arctique sont touchés par le changement climatique. Comme la fréquence et l'intensité des pluies d'été sont censées augmenter à l'avenir, plus de matière organique, de substances nutritives et de sédiments pourraient être mobilisés et transportés dans les zones proches des côtes. Par contre, la connaissance quant aux processus actuels et quant aux changements futurs est limitée. Nous avons examiné la dynamique de débit d'eau et les impacts des pluies d'été sur les flux latéraux dans un petit

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

“…The runoff ratios ICW and ICE are in the same order of magnitude (0.14 ± 0.0 and 0.15 ± 0.0, respectively), suggesting inefficient water routing and a high storage capacity in the catchments. This finding corresponds with runoff ratios reported from ICW by Coch et al () over the summers 2014, 2015, and 2016. Based on complete data of six rainfall events, they estimated a runoff ratio in ICW of 0.11 ± 0.02.…”

“…Turbidity as a proxy of SSC at the outflow of a stream reflects a source in close proximity and not necessarily the overall conditions of the entire stream. This finding is supported by Coch et al (), who assess discharge sediment relationships for several rainfall events of different magnitudes for ICW between 2015 and 2016. Their data suggest a close proximity of local sediment sources and a rapid exhaustion.…”

“…The very low runoff ratios of 0.14 ± 0.0 for ICW and 0.15 ± 0.0 for ICE show the high storage capacity of the catchments. Subsurface flow is important to mobilize solutes from the active layer as also found by Coch et al (2018). 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 (2018).…”

Characterizing organic matter composition in small Low and High Arctic catchments using terrestrial colored dissolved organic matter (cDOM)

“…Summer baseflow from mid-June onwards is controlled by rainfall events (Coch et al, 2018). The active layer freezes up by mid-November (Burn, 2012). The studied catchments unofficially named Ice Creek West (1.4 km 2 ) and Ice Creek East (1.6 km 2 ) are adjacent to each other and merge into an alluvial fan before draining into the Beaufort Sea (Fig.…”

“…Snowmelt is the largest hydrological event of the year occurring in May to early June. Summer baseflow from mid-June onwards is controlled by rainfall events (Coch et al, 2018). The active layer freezes up by mid-November (Burn, 2012).…”