| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | December 19, 2017 |
| Latest Amendment Date: | May 20, 2021 |
| Award Number: | 1703041 |
| Award Instrument: | Standard Grant |
| Program Manager: |
David Verardo
AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | January 1, 2018 |
| End Date: | June 30, 2022 (Estimated) |
| Total Intended Award Amount: | $563,483.00 |
| Total Awarded Amount to Date: | $703,487.00 |
| Funds Obligated to Date: |
FY 2021 = $140,004.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
815 N BROADWAY SARATOGA SPRINGS NY US 12866-1632 (518)580-8052 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
815 North Broadway Saratoga Springs NY US 12866-1632 |
| 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: |
01002122DB NSF RESEARCH & RELATED ACTIVIT |
| 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 project aims to use speleothems from caves on the Yucatan Peninsula to reconstruct quantitative precipitation and tropical cyclone (TC) records affecting the Caribbean and Gulf of Mexico regions spanning hundreds of thousands of years.
The success of such reconstructions depends on understanding the relationship between local precipitation amount and precipitation delta 18-Oxygen isotope values (i.e. the amount effect) and how this relationship is preserved in stalagmite deposits. TC precipitation can shift the amount effect and it has been hypothesized that TC rain may therefore bias quantitative stalagmite delta 18-Oxygen isotope precipitation records (i.e. the TC masking hypothesis).
Recent studies based on stalagmite delta 18-Oxygen isotope precipitation records, however, suggest that TC variability was linked to the collapse of the ancient Maya civilization (i.e., the tropical storm hypothesis). Available stalagmite delta 18-Oxygen isotope precipitation records to test this hypothesis have not yet been replicated and their precipitation estimates may reflect TC masking. Replication, furthermore, may be hindered by chronological uncertainty, the lack of equilibrium stalagmite delta 18-Oxygen isotope values and regional climate variability.
The researchers therefore will: (i) apply a promising approach for replication of available stalagmite delta 18-Oxygen isotope based precipitation records during selected intervals spanning the last 2000 years; (ii) examine quantitatively the TC masking influence on the amount effect and on stalagmite precipitation records; and (iii) test the tropical storm hypothesis by applying an ultrahigh resolution sampling approach to detect the particular isotopic signature from individual TCs in three known stalagmites (i.e., CH-1, Chaac, Itzamna).
The potential Broader Impacts include improved understanding of tropical cyclone (TC)-climate relationships under different climate states and over long timescales. Such understanding is critical for accurate projections and TC risk assessment and mitigation in a changing climate. This project supports a female lead investigator at an undergraduate liberal arts college. It will provide significant research experience for several undergraduates and the researchers have a strong history of supporting women and underrepresented minority students.
One of the lead researchers is an early-career Hispanic faculty member and this project would support the work of this researcher and two female Hispanic PhD students. This work would potentially help further develop methods for speleothem-based paleotempestology and would highlight the need to consider TC masking in other tropical speleothem records. Finally, this work will be of interest to the archaeology research community as it can help address the role of TCs in societal changes in Latin America.
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.
We focused on three previously-studied stalagmites from the Yucatan Peninsula in Mexico during three time periods of interest: the modern period when historical or instrumental weather data is available, the drier Maya Terminal Classic Period between 800 and 950 C.E., and the wetter Maya late Pre-Classic at about 250 to 150 B.C.E. We used a computer-controlled CM-2 micromilling system to shave mineral powders at 4 to 6 micron intervals from stalagmites Chaac, CH-1, and Itzamna, and analyzed the ratios of oxygen and carbon isotopes. We developed more detailed age models to incorporate the new data. With close to 14,000 new analyses, we detected tropical weather changes over weeks to months.
The additional detail reveals considerably more rainfall variability than previously recognized over decades, years, and within seasons. We found that previously-recognized prolonged drought intervals during the Maya Terminal Classic Period shared dramatic fluctuations between wet and dry weather patterns, but differ in drought severity. We successfully replicated Terminal Classic stable isotope records from stalagmites found in different caves, increasing confidence in paleoclimate patterns. Related cave monitoring results helped us develop more advanced and accurate rainfall reconstructions, for example identifying flash drought and rapid drought-breaking rain events, and avoiding under-estimates of drought intensity. We continue to investigate the influence of tropical cyclone rainfall found throughout the records. Interestingly, the new stalagmite data also detects a pattern of wet and dry conditions over one to two month intervals that corresponds to an important influence on global tropical weather known as the Madden-Julien Oscillation. This is the first time that the Madden-Julien Oscillation has been detected in a paleoclimate record, and we are currently working on a publication describing this discovery. Overall, this study improved understanding of the links between extreme rainfall and severe drought in the tropics, and better uncertainty estimates for oxygen isotope-based paleo-rainfall records from stalagmites.
Last Modified: 01/13/2023
Modified by: Amy Frappier
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