Exploring ice’s role in river bank migration through permafrost
Icy river dynamics set the rate of material exchange between arctic channels and their floodplains. As they migrate across arctic landscapes, icy rivers limit the residence time of soil organic carbon (SOC) by transferring some river bank material to the fluvial network before it can completely decompose. In this way, bank migration limits SOC oxidation in a deepening permafrost active layer and modulates the landscape-wide carbon budget. Concurrently, arctic river banks are laden with permafrost ice wedges and channels themselves are occupied by ice for a significant portion of the hydrograph; these factors are known to affect fluvial potential to erode and remove material from floodplains. However, we do not know how ice impacts rates of river bank migration through permafrost, especially in small arctic watersheds like the Canning Rivers on Alaska's North Slope. We aim to quantify how much SOC the Canning River removes from its floodplain over a typical year by differencing satellite-collected images. Based on initial results, the Canning seems to migrate much less than expected over the last two decades. We will use similar remote sensing methods - in addition to planned field sampling - to identify the annual cycles of river ice occurrence and bank ice content on the Canning. Ice observations will be compared to locations of actual and expected river bank migration. Expected river bank migration will be predicted from classical river bank migration models based on rivers with no ice content in their banks or channels. We hypothesize that models of bank migration based on non permafrost rivers over predict fluvial erosion into permafrost banks, and that river ice occurrence and bank ice content will correlate with that overprediction. We can also make use of this work in predicting the future contribution of the Canning river, and other arctic landscapes, to the global carbon budget. This work has immediate importance for people who traverse or depend on arctic landscapes, but especially those who live within them. Arctic landscape response to climate change is just as much a story about the loss of place and vanishing resources as it is about a dynamic earth system.
Josephine.Arcuri@colorado.edu
Geology Graduate Student, ÃÛÌÒ´«Ã½Æƽâ°æÏÂÔØ