GLACIO-FLUVIAL RESPONSE AND SEDIMENT FLUX IN SOUTHEAST ALASKA DURING THE HISTORIC PARAGLACIAL PERIOD

Glaciers influence landscape evolution across a large range of spatial and temporal scales. Climate variability dictates the extent of glacial expansion and retraction, which, in turn, control the distribution of geomorphic processes throughout landscapes. Heightened geomorphic change within drainage basins marks the paraglacial period, a time interval of landscape response to glacial retreat from glacial expansion. Landsliding from over-steepened valley walls, moraine abandonment, and elevated sediment fluxes reflect transient adjustment to new equilibria as glacial sediments are reworked and glaciers are replaced by rivers, changing the sediment delivery and transport capacity of these systems, in response to a rapidly warming climate. This landscape response potentially amplifies the long-term contributions to sediment fluxes and range-scale erosion from regional tectonics, longer period climate variability, and orographic effects on precipitation, glacier distribution, and river discharge. This study seeks to understand the spatial and temporal scales of changes following glacier retreat since the Little Ice Age (the last ~ 400 years) by quantifying glacier and river evolution in the Chugach-St. Elias Range of southeast Alaska. Remote sensing, hydrologic models, and field mapping will focus on the modulation of landscape changes and deglacial sediment fluxes in Granite Creek, a small catchment on the north side of the Bagley Icefield in which glacial and non-glacial geomorphic domains are present. This small catchment serves as an analog for larger-scale basins such as the Chitina River, a major tributary of the Copper River. These past changes can act as a proxy for understanding how modern climate change will propagate throughout drainage basins as glaciers continue to retreat. Potential effects include impacts on vegetation species and distribution, natural resources and resource management, human land use, river stability, health of fisheries (in rivers, deltas, and the ocean), and even regional tourism. As these once-glaciated regions transition to fluvially-dominated drainage basins, understanding the impact of this change on the landscape is important for effectively anticipating and responding to landscape adjustments associated with Earth's warming climate.