5. CONCLUSIONS
Because of their remoteness and inhospitality, high-altitude (as well as high-latitude) snow-melt dominated catchments remain understudied. These catchments contribute a significant fraction of global streamflow (Viviroli et al., 2007) and are also among the most susceptible to the effects of changing climate (Adam et al., 2009). Mobilization and downstream transport by river networks are critical processes in carbon and nitrogen cycles. This makes developing a generalized understanding of the solute dynamics of snowmelt dominated catchments, and in particular the response to hydroclimatic perturbation, of global importance. Como Creek represents one of the highest elevation locations we yet have data for.
Using big, open-data is the new frontier in hydrological and ecological sciences (Hampton et al., 2013), and this study relied entirely on publicly available data. We took a network-of-networks approach to combine historical and high-frequency precipitation, snowpack, discharge, and solute data to assess drivers of carbon and nitrogen export from a high altitude stream in the Rocky Mountains. We found that DOC and NO3-N fluxes were strongly controlled with discharge, over time scales ranging from minutes to decades. Seasonal snowmelt pulses are the dominant driver of annual solute export. Interannually, the magnitude and timing of the snowmelt pulse, and by extension solute export, was strongly correlated with both the depth and persistence of the snowpack. As in prior studies, we found that clockwise C-Q hysteresis over the snowmelt pulse was suggestive of seasonal depletion of solute pools. Yet, the high-frequency data revealed pulses within pulses from individual events wherein concentrations where enriched and C-Q hysteresis was counter-clockwise - indicating that additional DOC and NO3-N pools persist and can be readily mobilized, particularly through rain on snow events. While the historical low-frequency grab sample data suggest that reduced snowpack and earlier snowmelt may result in reduced export of DOC and NO3-N, the sensor data make this conclusion uncertain, as increasingly prevalent rain on snow events appear equally capable of mobilizing solutes.