Study Lakes
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Propagation of fluvial sediment pulse into Lake Peters
- David Fortin
This project aims to better understand how river discharge, fluvial suspended sediment concentration (SSC), and lake thermal conditions influence sediment dispersion within Lake Peters. During the summer of 2015 fluvial inputs into Lake Peters, including SSC and water temperature, were monitored every 30 minutes for nearly three months. The turbidity and temperature of Lake Peters were measured regularly at sub-meter depth intervals across the lake. In addition three moorings located along the long axis of the lake were equipped with sensors, recording water temperature at different depths, at hourly or sub-hourly resolution. We observed overflows that were quickly transformed into interflows as the density of fluvial inflow changed with water temperature and SSC. During an exceptionally high discharge event in August, a sediment-rich underflow quickly propagated along the lake bed and was later transformed into an interflow as the SSC decreased by apparent settling of the coarser particles. Our results also show that not all sediment pulses reach the distal basin. These data sets highlight the variety of spatial sediment transfer patterns in Lake Peters from one fluvial event to another.
A. Bathymetric map of Lake Peters with 5m contour intervals. The black dots represent the location of the profiles used to produce the interpolated maps in panel B. Figure B, shows a sediment rich plume in Nephelometric Turbidity Unit (NTU) during two consecutive days. On August 4, a storm event translates into a sediment rich underflow, which, after loosing some of its sediment load, travels down the lake as an interflow the next day.
Empirically Based Sediment Flux Model
- Lorna Thurston
Suspended sediment yields provide a useful proxy for environmental change, as they are a function of climate-driven glacial and hydrological processes. The discharge – suspended sediment relationship is often strong enough that it can be used to model suspended sediment yields. This approach produces a statistical relationship between discharge and suspended sediment for a channel cross-section, known as a sediment-rating curve. Once the relationship is established, the rating curve can be used to interpret physical processes and can be extrapolated to predict future sediment yields, at least for the season measurements were taken. This approach has been successfully applied in glacierized Arctic catchments.
Perhaps the main problem hindering the wider application of sediment-rating curves as a proxyfor environmental change is that most catchments are ungauged, or subject to limited gauging records, especially in remote areas such as the Arctic. Extensive field monitoring is the obvious solution, but it is labor-intensive, expensive, and many years of monitoring are required beforehe sought-after data is available. An alternative solution is to monitor in-channel discharge and suspended sediment over a couple of seasons, and compare this with lacustrine sediment cores in order to construct a representative sediment-rating curve. The latter approach is used for this project. This project will also build on the simplistic sediment-rating curve model, adding additional parameters to the model using multiple regression techniques.
Lacustrine indicators of glacier fluctuations
- Stacy Kish
Arctic mountain glaciers are sensitive to climate fluctuations and respond to changes in summer temperature and winter precipitation. I will study sediment from Lake Peters and Lake Schrader located in the northeastern portion of the Brooks Range, Alaska to examine (1) how does modern stream discharge and entrained sediment relate to sedimentation in the lake; (2) how can I use lake sediment to reconstruct glacial dynamics in the region through time; and (3) how do changes in the timing and lake temperature at glacier melt reflect glacial dynamics in the region through time.
DETERMINING MODERN HYDROLOGICAL INPUTS WITH A VOLUMETRIC MIXING MODEL
- Rebecca Ellerbroek
This The glaciers of Arctic Alaska serve a crucial ecological role, regulating streamflow between precipitation events and delivering nutrient-rich sediment to streams and lakes. As global warming melts glaciers and changes precipitation regimes, it is particularly important to understand the hydrological inputs that compose streamflow in quickly evolving Arctic basins. This research will use stable isotopes to constrain relative contributions of rain, snow and glacial melt to Lake Peters, with the objective of contributing to a predictive hydrological model. Lake Peters is an ideal location for a hydrograph separation study because of its numerous inflows that range from completely non-glacial to primarily glacial runoff, allowing for comparison across subbasins. Deuterium and oxygen will be used in a volumetric mixing model with summer precipitation and winter-accumulated melt as end members. While summer precipitation is enriched in heavy isotopes and winter precipitation is depleted, there are several other factors that affect meteoric isotopic composition, such as source water and distance traveled. HYSPLIT storm trajectory modeling will be used to distinguish seasonal isotopic differences from other types of isotopic fractionation.
