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Arctic Shelf sediment fate—an observational and modeling study of sediment pathways and morphodynamic feedbacks in a changing polar environment (NSF)

Emily, Josie, Caroline, and John are teaming up with collaborators Jaap Nienhuis (Utrecht University), Nina Stark and Nick Brilli (Virginia Tech), and Jeff Obelcz (Naval Research Lab) to study sediment transport and seabed properties on the Alaskan Beaufort Shelf. The coastline in many parts of the Arctic is retreating at rates of meters per year, a process expected to accelerate as sea ice extents and durations decrease and wave climate intensifies. Our project focuses on tracking the fate of sediments released from the shoreline into the continental shelf environment, during the summertime months when storm-driven transport likely plays a dominant role in dispersal and depositional processes. We’re also building morphostatic and morphodynamic models in Delft3D to evaluate long-term morphologic feedbacks of changing sediment supplies and energy regimes.

Alaskan Beaufort Shelf. A) Long-term coastal retreat rates along the Alaskan coast (retreat data from Gibbs and Richmond, 2005). B) General conceptual profile of the shelf, highlighting two morphologic zones impacted by shorefast versus pack ice (see Reimnitz et al., 1978; Barnes et al., 1984).

 

 

 

 

 

 

 

 

Bathymetry of the Alaskan Beaufort shelf and slope. A two-dimensional cross-shelf model has been developed for the Harrison Bay region. Additional modeling work in 2020-2021 will evaluate shelf dynamics east of Prudhoe Bay as well.


2021 Harrison Bay field work

In Jul/Aug we conducted our first primary survey in Harrison Bay – it was delayed a year by covid, but worth the wait! Our survey team collected more than 500 km of new multibeam and hi-resolution ADCP tracklines, more than 80 profile measurements of water and sediment properties, and more than 700 geotechnical seabed measurements. We also deployed four mini-moorings near the Colville Delta and nearby bluffs in order to evaluate sediment export from the inner shelf near major sources. We had excellent weather and explored keel scours, unexpected bedforms, submerged peats, strudel scours, and diverse other features that make the Arctic a fascinating place to assess cross-shelf sediment transfer. We’re looking forward to continuing this work in 2022.

 


John – modeling successes (summer 2021)

I have been busy finishing up development of a cross-shore sediment transport model of the Alaskan Beaufort Shelf. This summer I will be running the final model experiments and analyzing the results for a manuscript on the long-term evolution of Arctic shelves in a growing wave climate. How will the increase in wave energy impact sediment transport and the shape of the shelf? How does a future equilibrium shelf shape impact how wave energy propagates to the coast? These exciting questions can provide insight to the feedbacks between the shape of the shelf and the propagation of waves that are driving rapid coastal changes in the Arctic. This winter we have been tuning the model and integrating field data collected on the Beaufort Shelf in the Fall of 2020. Sediment grab samples from Harrison Bay and the region seaward of Flaxman Island were analyzed in the lab to provide observed seabed sediment characteristics, such as grain size and relative proportions of sand and mud. We were also fortunate to utilize several year-long time series from several Beaufort locations generated by the UW-APL CODA Project, which were instrumental for tuning tides, waves, currents, and their associated impacts on sediment transport in the model. My goal is to write the draft manuscript and present my masters work this fall.

In March I gave my Interdisciplinary Seminar to the department where I stepped out of my geologic comfort zone to discuss the transport pathways and fate of terrestrial permafrost-sourced carbon that is entering Arctic marine systems at increasing rates. This was a valuable exercise in applying the interdisciplinary subjects taught in the masters program.

Schematic of hypothesized morphodynamic feedbacks on the Beaufort Shelf.

 


2020-2021 early field work

We teamed up with Jim Thomson’s CODA (Coastal Ocean Dynamics in the Arctic) project in Nov 2019 & Sep/Oct 2020 on the R/V Sikuliaq to collect preliminary data on particle fluxes and seabed sediments – see the Updates page for more details.

 

The UW CODA + UNC ABS team, Arctic Ocean, November 2019 ( (C) John Guillote) (John far left; Emily third from right)

 

 


Recent publications

Our colleagues in the UW-APL CODA team have been publishing new data about wave attenuation in landfast ice, during formation and throughout an annual cycle – check them out:

Hošeková, L., Eidam, E., Panteleev, G., Rainville, L., Rogers, W.E. and Thomson, J., 2021. Landfast ice and coastal wave exposure in northern Alaska. Geophysical Research Letters, p.e2021GL095103.

 

Hošeková, L., Malila, M.P., Rogers, W.E., Roach, L.A., Eidam, E., Rainville, L., Kumar, N. and Thomson, J., 2020. Attenuation of ocean surface waves in pancake and frazil sea ice along the coast of the Chukchi Sea. Journal of Geophysical Research: Oceans, 125(12), p.e2020JC016746.