Colloquium: Anastasia Piliouras

Arctic deltas: Toward understanding process and form on high-latitude coasts
The Arctic is expected to have a pronounced response to climate change, including increased
fluxes of water, sediment, and nutrients to the coast, permafrost thaw, and decreasing sea ice
cover. However, Arctic coasts are understudied due to the difficulties of field-based research. In
this talk, I present results from a remote sensing analysis of six Arctic deltas and a reduced
complexity numerical modeling study, aimed at understanding Arctic delta morphologic
variability, the influence of morphology on the spatial and temporal distribution of land-ocean
fluxes, and the impact of permafrost and sea ice on delta morphology and morphodynamics. I
found an inverse relationship between the evenness of fluxes across the delta front and the lateral
expansiveness of the delta, such that smaller deltas distribute their fluxes evenly while larger
deltas favor fewer flow paths. This indicates that these six deltas may deliver most material to
the coast at discrete locations across a small area. The Mackenzie and Colville deltas have the
highest amount of lake coverage on the delta plain and the most lakes that are structurally
connected to the channel network, thus providing a means for transient storage of material as it
moves to the coast and potentially altering biogeochemical fluxes. Modeling results indicate that
both permafrost and landfast ice tend to make more persistent, stable channels, which changes
the storage and delivery of sediment through the deltas. Ice cover, especially, enhances offshore
deposition and overbank sedimentation, and thick ice cover can obstruct transport pathways until
the ice melts, thus creating temporal and spatial variability in transport pathways through the
deltas. Future work involves investigating these delta dynamics and changes to transport
pathways in response to a changing climate with thawing permafrost and diminishing sea ice
cover over time.