Impacts of permafrost change on landscape stability and water quality

Abstract:

Communities and northern development depend on knowledge to support safe infrastructure design and to define appropriate environmental targets. Projected climate change is expected to have substantial impacts on permafrost through increased seasonal thaw. These changes will likely result in changing hydrological processes that will alter surface and subsurface water flow and quality. Similarly, in settings with ice-rich surficial materials, changing active layer depth and hydrological conditions can contribute to permafrost degradation and land instability. Predicting these impacts is an important need for sustainable development in permafrost regions.

We have investigated these processes through a long term integrated watershed program at the Cape Bounty Arctic Watershed Observatory (CBAWO) in the Canadian Arctic. Surface water discharge and quality has been assessed since 2005 and in particular, through a period of record summer temperatures that resulted in substantial active layer perturbation and resulted in widespread localized disturbance. Research has documented the impact and recovery from these permafrost changes and demonstrate several key linkages between changing hydrological conditions, quality, and landscape sensitivity to disturbance. Deeper active layer thaw appears to alter subsurface flow paths, resulting sustained changes to water quality through increased solute fluxes and changes to nutrients. These effects are widespread across the landscape, while physical disturbance due to permafrost slope failures are dispersed and generate impacts ranging from minimal to locally-significant increases in downstream sediment and solute transport. We note that this strong spatial contrast between “thermal” and “physical” perturbation of the shallow permafrost system represents a key impact in these settings. Further, subsurface water pressurization appears to be localized but linked to physical disturbance. Hence, results indicate the benefit of an integrated approach to investigating impacts to the permafrost system through both hydrological and geomorphic perspectives.