| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | March 30, 2015 |
| Latest Amendment Date: | March 30, 2015 |
| Award Number: | 1503133 |
| Award Instrument: | Standard Grant |
| Program Manager: |
David Verardo
AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | June 1, 2015 |
| End Date: | May 31, 2019 (Estimated) |
| Total Intended Award Amount: | $422,718.00 |
| Total Awarded Amount to Date: | $422,718.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
1 UNIVERSITY OF NEW MEXICO ALBUQUERQUE NM US 87131-0001 (505)277-4186 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
NM US 87131-0001 |
| 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): | Paleoclimate |
| 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
This award generally aims to integrate high-precision age-dated 5,000 year-old speleothems with isotopic and chemical data from various environmental proxies in the southwestern United States. This study will focus on climate modulators that impact regional hydrologic cycles on differing time-scales. These modulators include the inter-annual varying El Nino-Southern Oscillation (ENSO), the decadal and multi-decadal Pacific Decadal Oscillation (PDO) and the Atlantic Multi-Decadal Oscillation (AMO), and solar variability which may act across varied time-scales.
This region was chosen for the study because it has well-documented hydrologic sensitivity to climate forcing and modulation. The western United States has a long history of climate induced social disruption, dating back to pre-history. Understanding these natural changes will help contribute to a possible predictive capability of future changes in the hydrologic cycle. Such a predictive capability would be a societal benefit to the United States in that it could result in better resource planning and management. A further benefit of the project is the support of a graduate student at a minority serving university.
Speleothems from regional caves provide an opportunity to observe possible changes in the modalities of these climate modulators over the long term and have demonstrated their fidelity to isotopic, chemical and physical climate proxies that are radiometrically datable using advances in uranium-series based chronometry.
The project will specifically collect and evaluate data from two sites with different seasonal hydrologic cycles with the aim of isolating the seasonal component of observed changes and the responsible climate variables. For example, the North American Monsoon (NAM) is modulated by changes in the AMO. This seasonal delineation is important because it could help solve the puzzle of the change in coherence between the NAM and other recently documented Northern Hemisphere monsoons.
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.
Intellectual Merit: Southwestern North America (SW) had experienced climate extremes during the Late Holocene the causes of which are poorly understood. Understanding climate variability in this vulnerable region becomes that much more urgent in light of warming climate. Our study was focused on documenting high-resolution climate change during the Late Holocene using speleothems. Speleothems from regional caves provide such an opportunity. They contain multiple isotopic, chemical and physical climate proxies and are radiometrically datable. The approach of our project was to integrate high precision chronology of speleothems with multiple isotopic, chemical and physical proxies from two areas: 1) the North American Monsoon dominated desert southwest (SW), and 2) the southern Great Basin, which receives most of its moisture during the winter.
The key questions that we proposed to answer were:
A. What was the cause of the Late Holocene ?greening? of the SW? B. What was the cause of the megadroughts that characterized the hydroclimate of the SW?
Broader impacts: The impact from warming-induced climate change, arguably, is the most pressing societal concern. The western United States has a long history of climate induced social disruptions, dating back to North American pre-history. Contributing towards predictive capability of future changes in the hydrologic cycle would be a huge societal benefit to the extent that it would result in better planning and impact mitigation. The University of New Mexico is a minority serving Research I university. We are committed to training a very diverse student body. Accordingly, we planned to recruit a diverse group of participants.
Summary of results:
New data from our two study areas show that, generally, contrary to previous understanding, the two regions experienced contrasting climate regimes; the southern Great Basin was relatively wet when the SW was going through megadroughts and vice-versa. This eliminates excess winter moisture as the cause of the Late Holocene greening of the SW. Based on our new data, hydroclimate in the SW is best explained by changes in the strength and position of the Bermuda High, which has a strong influence on the North American summer monsoon. As a result, warm Northern Hemisphere (NH) temperatures which cause intensification and westward migration of the Bermuda High, coincide with wet intervals in the SW, while megadroughts seem to occur during NH cold intervals. For example, the most severe extended drought, what we have called the ?Super Drought?, occurred during the Little Ice Age.
Discoveries from this grant, which we have presented at conferences and are readying for publications, contribute towards a mechanistic understanding of climate variability in the SW. With further refinements, we expect to provide policy-actionable conclusions.
Building a diverse scientific community is just as important as the scientific discoveries. As a result, we have tried to be very inclusive in this project. A Hispanic male MS student, a female MS student, a Navy veteran PhD student and a Native American undergraduate student were supported to various degrees by this grant and successfully completed their projects.
Last Modified: 10/12/2019
Modified by: Yemane Asmerom
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