| NSF Org: |
OPP Office of Polar Programs (OPP) |
| Recipient: |
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| Initial Amendment Date: | June 6, 2014 |
| Latest Amendment Date: | June 6, 2014 |
| Award Number: | 1418000 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Gregory Anderson
greander@nsf.gov (703)292-4693 OPP Office of Polar Programs (OPP) GEO Directorate for Geosciences |
| Start Date: | January 1, 2015 |
| End Date: | December 31, 2018 (Estimated) |
| Total Intended Award Amount: | $753,204.00 |
| Total Awarded Amount to Date: | $753,204.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
601 S KNOLES DR RM 220 FLAGSTAFF AZ US 86011 (928)523-0886 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
NAU Box 4099 Flagstaff AZ US 86011-0001 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | ARCSS-Arctic System Science |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.078 |
ABSTRACT
Nontechnical
Accurate records of natural variability that cover broad temporal and spatial scales, and that capture intervals of non-linear change are needed to fully comprehend the arctic system. This project aims to develop the first system model to simulate the full chain of processes that control how weather and climate affect the processes that lead to deposition of a sediment record in lakes in glaciated watersheds. This model provides an alternative approach to previous statistically-based models traditionally used by paleo-climatologists to infer past climate variability from lake sediment records. The new process-based quantitative understanding will lay the groundwork for future studies that will be aimed at recovering records of environmental and climate change that extend back thousands of years.
This project will contribute to ongoing efforts through collaborations with: utility managers of the Municipality of Anchorage who are planning for diminished glacier meltwater input to Eklutna Lake, a major source of their electricity and freshwater and with resource managers at US Fish and Wildlife Service who are developing a monitoring network for the Arctic Refuge and who are striving to foresee future changes in habitat quality associated with glacier retreat. This project will benefit climate science researchers by leading to more accurate climate reconstructions, which will be used as benchmarks for validating global climate model output. Finally, it will support four early-career scientists and will train graduate and undergraduate students in system-science research.
Technical
The primary goal of this project is to develop a system model that encodes the major processes that govern the amount and grain size of sediment that accumulates in arctic lakes in glaciated catchments, and to acquire the field-based data for model input and testing. Sediments that accumulate at the bottom of arctic lakes contain a wealth of information about how major features of the surrounding watershed have varied on seasonal to millennial time scales, as well as how they have responded to natural and anthropogenic forcings. Lakes in glaciated watersheds record changes in the melt rate of upstream glaciers, which are among the most dynamic components of the evolving arctic system. The sediment stored in glacier-fed lakes often comprise distinct rhythmic layers that represent annual cycles. These varved sediments are among the most valuable of all natural archives on Earth because they can be placed on a precise time line, and because they accumulate at a rate that is sufficiently high to track environmental variability on annual, and often seasonal, scales. They have been used extensively to reconstruct past climate changes in the Arctic, most often relying on statistical correlations between records from long-term weather stations and varve thickness. These statistical correlations disregard the complex and time-evolving interactions within the glacier-hydrology-lake-sedimentation system that link climate to changing properties of sediment deposited at the lake bottom. A more process-based understanding of the interactions that control sedimentation within lakes of glaciated catchments is needed to provide the next generation of paleoclimate reconstructions. By incorporating a system-modeling approach, a process-based system model will be developed to capture dynamic nonlinearities in the glacier-hydrology-lake-sedimentation system. The system model will couple three existing model components: a physically based, spatially explicit hydrological model, which includes a glacier sub-model; an empirically based sediment-flux model; and a process-response, basin-filling sedimentation model. The system model will be applied to three glaciated watersheds that fall along an environmental gradient spanning from the sub-Arctic to the High Arctic, including Lake Linne (Svalbard), Lake Peters (near McCall Glacier, Arctic National Wildlife Refuge), and Eklutna Lake (near Anchorage, Alaska). This study builds on extensive previous and on-going process studies at or near each of the study sites. Existing data and proposed glacier, hydrology, limnology, and sediment process studies will provide the input data to run the system model and to validate its output.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Sediments that accumulate in Arctic lakes contain a wealth of information about how major features of the Arctic system vary on seasonal to millennial time scales, as well as how they respond to natural and anthropogenic forcings. Lakes in glaciated watersheds record changes in weather, the melt rate of upstream glaciers, changes in river systems, and dynamics within the lake. Each of these components leaves its own fingerprint, filtering this information and archiving it in the sediments of these lakes.
In this project, we worked to develop a more process-based understanding of the interactions that control sedimentation within lakes of glaciated catchments. To do this, we studied three glaciated watersheds that fall along an environmental gradient spanning from the sub-Arctic to the High Arctic, including Lake Linne (Svalbard), Lake Peters (near McCall Glacier, Arctic National Wildlife Refuge), and Eklutna Lake (near Anchorage, Alaska).
For this award, we: established a watershed observatory at Lake Peters, Alaska, from 2015-2018, where we observed a large suite of weather, glacier, river and lake data, many of which were geared toward understanding how and why sediment moves through the catchment (Figures 1 & 2). We also continued and extended ongoing observations at Eklutna Lake, and recovered and synthesized seven years of disparate observations at Lake Linne. These observations led to key insights, specifically:
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We have documented substantial interannual variability in sediment transport at all three lakes. This is both a result, and a challenge, as it emphasizes need for long-term monitoring studies and the difficulty of making robust conclusions from short instrumental records. This motivates the use of proxy records to infer long-term trends and variability.
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Rainfall dominates discharge hydrography and controls sediment transport, in both the sub-Arctic, and Arctic sites. This was expected for south Alaska, but is surprising in the Arctic, and has significant implications for the future of the Arctic where rainfall is projected to continue to increase. This finding also runs contrary to some proxy reconstructions that relate sediment accumulation to summer melt temperature, although the extent to which this result can be applied to other glaciated catchments remains uncertain.
A key component of this project was to work to understand the key processes that drive sediment transport in these catchments, and then to build, calibrate and ultimately link models of varying complexity that simulate the primary patterns of deposition over time. For this project, we developed simple models of river sediment transport for each of the catchments. In all three regions, we found that discharge, primarily driven by rainfall, was a key predictor variable, although the models performed best when meteorological or temporal explanatory variables were also used.
We linked the river sediment transport model for Lake Peters to a lake sedimentation model, allowing us to simulate how changes in discharge, driven by precipitation and glacier melt, are ultimately recorded as sedimentation events in the lake. The model does a good job of simulating the overall amount of annual and total sediment deposition from 2015-2017, as well as the relative amounts in each year, and the changes in deposition rates as a function of distance from the inlet (Figure 3). However, on a finer scale, the agreement is worse, as the model is particularly sensitive to the large discharge events that transport most of the sediment to the lake. The model shows those events settling out unrealistically quickly, and although in general the result that most of the sedimentation occurs in short intervals is consistent with our observations, this is exaggerated in the simulations.
We were able to communicate and increase the impact of this project in multiple ways. In 2017, PolarTREC high school teacher Rebecca Harris joined us for a field campaign at Lake Peters. Rebecca documented her experience through written and audio journals, available here: https://www.polartrec.com/expeditions/arctic-glacial-lakes . In addition, Rebecca Harris and NAU Ph.D. student Ellie Broadman gave a presentation at the Kaktovik school and a webinar for PolarTREC, and throughout the project we communicated regularly to the interested public, land managers, and to other scientists https://www.facebook.com/LakePetersProject/ . We also maintained our project webpage to disseminate information about the project http://www2.nau.edu/arcss-p/ .
Last Modified: 04/02/2019
Modified by: Nicholas P Mckay
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