We’re studying Arctic deltas to examine their morphologies, dynamics, and effects of ice cover and permafrost. We’ve been using remote sensing to characterize and quantify their morphologies, and will soon start comparing to temperate systems. We’ve also been examining patterns of ice retreat during the spring and summer that control channel fluxes and activity. We use the reduced complexity model DeltaRCM to examine the effects of ice and permafrost on longer term channel dynamics, large-scale delta morphology, and sediment transport and depositional patterns. This work is part of the HiLAT-RASM project, funded by DOE BER RGMA.
River deltas distribute fluxes of water, sediments, nutrients, and heat to the coastal ocean and can alter the timing, magnitude, and spatial distribution of fluxes. We’re combining a remote sensing analysis of Arctic delta morphology and channel network structure with a network-based analysis using the python package RivGraph to estimate the spatial distribution of fluxes at delta shorelines. The ultimate goal is to test the sensitivity of things like coastal ice melting rates and patterns and marine primary production to the spatial distribution of fluxes in regional and Earth system models.
Alaska coastal change
The North Slope of Alaska is comprised of a wide variety of environments that are responding to climate change. Coastal erosion in some locations exceeds rates of 5 m/yr, while other low-lying areas are prone to flooding from sea level rise, storm-surge, and permafrost thaw-driven subsidence. We are working to characterize the environments of the North Slope coastal zone to understand the variability in coastal conditions and to generate a set of typologies (i.e.., idealized or generalized environments) to be used to model future rates of coastal erosion and flooding. This work is part of the InteRFACE project, funded by DOE BER.
Hydrologic connectivity on river deltas
Hydrologic connectivity on river deltas affects the coastal transport pathways and residence times for nutrients, as well as sediment transport and depositional patterns. We typically observe river deltas while considering only their long-term, structural connectivity, but surface hydrologic connectivity can change on short, seasonal timescales in response to changing river discharge, tides, waves, and storms. This project examines seasonal and annual variability in surface hydrologic connectivity on two Arctic and two temperate river deltas to estimate residence time distributions as a function of hydrologic connectivity and to compare differences in connectivity between flashy Arctic systems and less flashy temperate deltas. This work is funded by the Center for Space and Earth Sciences.
Arctic river hydrology
Arctic rivers are changing in response to the rapid rate of warming at high latitudes. Several studies have recorded changes, such as earlier snowmelt peaks in the spring and higher winter baseflows associated with increased permafrost thaw. We are conducting a pan-Arctic analysis of changes in river hydrology to look for other changes to river hydrographs that may be attributable to different flood generating mechanisms or watershed conditions. This is a collaboration between the HiLAT-RASM project and the InteRFACE project.
Wetland restoration and carbon storage
The Valles Caldera in northern New Mexico used to have abundant wetlands with lush, healthy ecosystems. Human modifications within the preserve, increased grazing, and extensive gulleying have drastically altered the landscape, leading to wetland loss. Recent ecosystem restoration efforts have tried to reroute water to rewet previous wetlands and restore wetland plant communities. We are working with several small businesses through the New Mexico Small Business Assistance program to do a carbon inventory of restored and unrestored landscapes to estimate the effects of restoration on carbon sequestration and storage.
Thermokarst lakes are a uniquely permafrost feature that cover more than 40% of the Arctic coastal plains. Some thermokarst lakes have distinct shelves or terraces along their perimeters whose formation processes are unknown. We have been analyzing lake morphologies on Alaska’s North Slope to understand the regional variability in terrace abundance and morphometrics to gain insights about the processes that may have formed them. This work was funded by the Center for Space and Earth Sciences and was led by former post-MS researcher Mulu Fratkin.
Permafrost riverbank erosion
Arctic rivers are bounded by permafrost floodplains. The addition of ice to floodplain soils has an influence on soil cohesion and strength, but past research has shown that the presence of permafrost in riverbanks can either increase or decrease riverbank erosion rates, depending on the temporal and spatial scale of the measurement. We’ve been studying the Koyukuk River in central Alaska to understand river migration rates, the abundance and patterns of riverbank and floodplain permafrost, and how permafrost may affect river channel mobility and soil organic carbon transport.
Tie channels and hydrodynamics on the Wax Lake Delta
Islands on the Wax Lake delta contain numerous tie channels that connect the main channel network to the interdistributary bays. We surveyed the main channels and tie channels around Greg Island (left) to understand how flow magnitudes and directions change seasonally and with the tidal cycle. Results suggest that flow directions in tie channels sometimes reverse but it varies spatially and seasonally, likely as a function of both river discharge and vegetation cover that alter water surface elevations and gradients.