| NSF Org: |
OPP Office of Polar Programs (OPP) |
| Recipient: |
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| Initial Amendment Date: | August 27, 2013 |
| Latest Amendment Date: | December 22, 2017 |
| Award Number: | 1341680 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Michael E. Jackson
OPP Office of Polar Programs (OPP) GEO Directorate for Geosciences |
| Start Date: | January 1, 2014 |
| End Date: | December 31, 2018 (Estimated) |
| Total Intended Award Amount: | $239,093.00 |
| Total Awarded Amount to Date: | $239,093.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
4333 BROOKLYN AVE NE SEATTLE WA US 98195-1016 (206)543-4043 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
Johnson Room 070, 4000 15TH AVE Seattle WA US 98195-1310 |
| 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): |
ANT Instrum & Facilities, ANT Earth Sciences |
| Primary Program Source: |
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| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.078 |
ABSTRACT
Intellectual Merit:
This project will yield new information on the long term Antarctic climate and landscape evolution from measurements of cosmogenic nuclides in quartz sand from two unique permafrost cores collected in Beacon Valley, Antarctica. The two cores have already been drilled in ice-cemented, sand-rich permafrost at 5.5 and 30.6 meters depth, and are currently in cold storage at the University of Washington. The cores are believed to record the monotonic accumulation of sand that has been blown into lower Beacon Valley and inflated the surface over time. The rate of accumulation and any hiatus in the accumulation are believed to reflect in part the advance and retreat of the Taylor Glacier. Preliminary measurements of cosmogenically-produced beryllium (10Be) and aluminum (26Al) in quartz sand in the 5.5 meter depth core reveal that it has been accreting at a rate of 2.5 meter/Myr for the past million years. Furthermore, prior to that time, lower Beacon Valley was most likely covered (shielded from the atmosphere thereby having no or very low production of cosmogenic nuclides in quartz) by Taylor Glacier from 1 to 3.5 Myr BP. These preliminary measurements also suggest that the 30.6 meter core may provide a record of over 10 million years. The emphasis is the full characterization of the core and analysis of cosmogenic nuclides (including cosmogenic neon) in the 30.6 meter permafrost core to develop a burial history of the sands and potentially a record the waxing and waning of the Taylor Glacier. This will allow new tests of our current understanding of surface dynamics and climate history in the McMurdo Dry Valleys (MDV) based on the dated stratigraphy of eolian sand that has been accumulating and inflating the surface for millions of years. This is a new process of surface inflation whose extent has not been well documented, and holds the potential to develop a continuous history of surface burial and glacial expansion. This project will provide a new proxy for understanding the climatic history of the Dry Valleys and will test models for the evolution of permafrost in Beacon Valley.
Broader impacts:
The landscape history of the McMurdo Dry Valleys is important because geological deposits there comprise the richest terrestrial record available from Antarctica. By testing the current age model for these deposits, we will improve understanding of Antarctica?s role in global climate change. This project will train one graduate and one undergraduate student in geochemistry, geochronology, and glacial and periglacial geology. They will participate substantively in the research and are expected to develop their own original ideas. Results from this work will be incorporated into undergraduate and graduate teaching curricula, will be published in the peer reviewed literature, and the data will be made public.
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.
This project focuses on analyzing a 30-m ice-rich permafrost core collected in Beacon Valley, Antarctica, BV4, in a previously funded National Science Foundation project, and kept in storage at -30 degrees C. Beacon Valley is part of the McMurdo Dry Valleys and is one of the few percents of land area in Antarctica that is not covered by ice due to its location in the precipitation shadow for snow.
The project analyses the chemical and physical characteristics of the permafrost core. The motivation for this work is to understand the dynamics of the surface inflation in this area of polygonal patterned ground located in front of the Taylor Glacier. As ice-rich permafrost cools, it contracts and cracks, much like lake sediments form contraction crack polygons as they dry out and shrink. The cracks are open primarily when the ground is coldest (due to thermal contraction), and sand may blow or ravel into the cracks. As the ground warms during the Austral summer, the ice-cemented permafrost will expand (due to thermal expansion) and since the cracks have filled with some sand, they cannot close fully, thereby resulting in the ground surrounding the cracks to be deformed and pushed upward. The sand that is filling the open cracks leads to the inflation of the surfaces. The soils with the polygonal patterned ground in lower Beacon Valley appear to have inflated at least 7 meters over the past 2-3 million years.
The age of the core was determined by measuring cosmogenic nuclides, which increase near the surface over time due to the input of high-energy cosmic radiation to quartz grains. The radiation leads to an increase of the isotopes beryllium-10, aluminum-26, and neon-21. The buildup and decay of these isotopes allow the modeling of the erosion (or inflation) rate and surface age. Above 7 meters, the input of the sediments was slower than at depth. Below about 7 meters to about the full depth of 30 meters the age was more tightly constrained to 4.5-5.5 million years and accumulated quickly based on the cosmogenic modeling and the core chemistry. The quick accumulation may be due to a large meltwater event of Taylor Glacier.
The indication of a melt event in Beacon Valley at 2-3 million years ago is unprecedented for the Dry Valleys; however, based on marine cores collected in the ANDRILL project, there is evidence of warming occurring during this period. If correct, this finding has significant implications for the longterm climate stability of the Dry Valleys and challenges the paradigm that the Dry Valleys have been in a deep freeze since the Miocene (10-15 million years ago).
Another new finding from this study was evidence of the mineral dolerite weathering in permafrost. Based on the soluble salt content and stable magnesium isotopes, it appears that weathering in the permafrost accounts for up to ? of the soluble Mg found in the ice-cemented permafrost. This finding is significant since permafrost, which covers 20% of the ice-free of Earth, is generally believed to be inert. This study revealed that even at subfreezing temperatures, significant weathering occurs if that is enough salt present to allow liquid films to exist. This finding has implications for weathering on Mars since the entire planet is permafrost, particularly since salts are abundant.
Last Modified: 01/28/2020
Modified by: Ronald S Sletten
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