EAR-PF: The impact of varying sediment supply on Arctic delta-front transport processes

An NSF EAR Postdoctoral Fellowship has been awarded to Dr. Brandee N. Carlson to carry out research and education activities under the mentorship of Dr.

Irina Overeem at the University of Colorado, Boulder. The project seeks to assess how enhanced sediment supply from melting ice sheets and glaciers, and thawing permafrost impacts the growth of Arctic deltas. The sand delivered to Arctic deltas, particularly those in West Greenland, is recognized as a potential resource for coastal restoration efforts and for industrial use (primarily concrete production) worldwide.

This project will investigate the processes that control sediment retention along Arctic coastlines using field observations and remote sensing. This work will inform policy and economic decisions for sand-use in Greenland. Furthermore, the information gained from this project will be used to develop a learning module geared toward introductory undergraduate students that allows the user to explore controls on delta growth.

The model will be housed at SedEdu, which is a suite of educational tools related to geomorphology and sedimentology.

Subaqueous delta-front sediment transport processes are an important control on coastal evolution. Rivers and subaqueous density flows are the largest mechanisms for sediment redistribution on Earth's surface. Subaerial coastal evolution is easily-observable through historical and satellite imagery, however quantifying subaqueous sediment movement is inherently difficult because it typically requires observation in the field.

Delta-front sediment transport processes become especially important to consider for rapidly growing deltas with high sedimentation rates. Under warming climate conditions, Arctic deltas, particularly those in Greenland, are rapidly growing as they receive enhanced sediment supply from melting and retreating glaciers and thawing permafrost. While there is evidence for delta-front failures that transport substantial volumes of sediment, it is unclear to what degree they influence delta progradation rates and sediment retention along coastlines.

This study links readily observable data (images of subaerial delta activity) to subaqueous sediment transport processes. The objectives of this study are to determine how subaerial delta activity links to sediment transport at the subaqueous delta front and how enhanced sediment supply impacts marine sediment transport processes on Arctic deltas. In turn, the influence of delta-front failures on delta topset dynamics will be evaluated.

These questions will be addressed over different temporal and spatial scales. Dr. Carlson will evaluate individual delta-front transport events at one field location during variable discharge conditions, using repeat bathymetric data.

During this field campaign, changes in the subaerial delta topset (e.g. wetted area) will be evaluated using satellite imagery. Correlations between delta topset activity and delta-front transport timing/location will be used to infer relationships under past conditions (evaluated using 34-years of Landsat data) and to consider delta-front sediment transport under future conditions (e.g. how do Arctic delta-front failures vary under higher water and sediment discharge conditions in a waring climate?).

These findings may offer insight into the conditions and potential effects of shifting sediment delivery for other fjord deltas in Greenland. The Geomorphology and Land-use Dynamics program in the Earth science division is co-funding this fellowship.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.