| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | May 12, 2017 |
| Latest Amendment Date: | June 4, 2020 |
| Award Number: | 1702438 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Jonathan G Wynn
jwynn@nsf.gov (703)292-4725 EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | June 1, 2017 |
| End Date: | May 31, 2021 (Estimated) |
| Total Intended Award Amount: | $87,520.00 |
| Total Awarded Amount to Date: | $87,520.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
845 N PARK AVE RM 538 TUCSON AZ US 85721 (520)626-6000 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
818 N. Euclid Avenue Tucson AZ US 85719-4824 |
| 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): | GLOBAL CHANGE |
| 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): | 47.050 |
ABSTRACT
Many regions of the world, including the Americas, are experiencing drought and its political consequences. The critical question is why, and are the causes natural or man-made? The answer to this and other questions will help us plan for what is ahead, as some regions of the planet continue to warm and dry. This project will travel to the central Andes of South America- a region that is both politically fragile and recently drought stricken. The aim is to study the interplay of temperature and drought in the past, for clues to their probable connections in the future.
The main purpose of the project is to create a map of changes in the sizes of ancient lakes in the central Andes, giant ancestors to modern lakes in the region such as Lake Titicaca. Well-preserved shorelines mark the extent of these ancient lakes, and using state-of-the art techniques, the age of these features can be determined. The mapping and dating is vital to relating lake size (and therefore rainfall amounts in the past) to the changing temperature state of the planet, which is well known from other records. In short, these reconstructions will help scientists to better understand how rainfall in this region will change in the coming decades to centuries.
This award is cofunded by the Paleo Perspectives on Climate Change Program and the Office of International Science and Engineering.
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.
The main focus of our project was to study geological deposits in the Salinas de Bebedero basin in central Argentina. We found that this basin contains a continuous 30,000-year record of megafloods from the adjacent high Andes to the west. The flooding was focused in two main periods, between about 18,000 and 11,000 years ago, during the end of the last Ice Age, and during the last 3000 years (see attached figure). To reach the Bebedero basin from the high Andes 200 miles away, these floods had to be massive (hence megafloods), we estimate up to 10 cubic kilometers in size, as big as the largest floods ever documented historically. The exact cause of these floods is not known for certain, but probably involves a mix of large rainfall events and sudden massive outbursts of lakes trapped behind melting ice dams. The clustering of flood events coincides nicely with times of known glaciation in the Andes, when ice dams would have been common. Conversely, the Bebederon basin contains no flood deposits from the period 11,000 to 3000 years ago, pointing to a very dry and probably ice-free central Andes. In a warming world, our record predicts that floods like the lethal 1934 flood of nearby Mendoza, Argentina, should diminish in frequency, as the region dries and the sparse ice fields shrink.
This project required some very careful geological detective work and a caste of colleagues and students. Three students, one of them an undergraduate, were closely mentored throughout their projects in stable isotope analysis. Other specialists were drawn from outside the University of Arizona, most especially Elad Dente (Haifa University), to construct hydrologic models of the size and duration of the megafloods.
An additional component of our project was to support the field studies of David McGee and his student Christine Chen from MIT in documenting lake basin records further north in the sub-tropical Andes. Lake-filling events in those records strongly overlap in time with the record from the Bebedero Basin, suggesting that periods of enhanced rainfall and Alpine ice-formation once correlated across a wide swathe of the central Andes.
Last Modified: 08/13/2021
Modified by: Jay Quade
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