| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | July 23, 2020 |
| Latest Amendment Date: | July 23, 2020 |
| Award Number: | 2002520 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Margaret Fraiser
mfraiser@nsf.gov (703)292-0000 EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | September 1, 2020 |
| End Date: | August 31, 2024 (Estimated) |
| Total Intended Award Amount: | $363,128.00 |
| Total Awarded Amount to Date: | $363,128.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
940 GRACE HALL NOTRE DAME IN US 46556-5708 (574)631-7432 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
940 Grace Hall Notre Dame IN US 46556-5708 |
| 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
Historically, much of our understanding of significant environmental change in the past glacial cycles has primarily come from high latitude regions. However, the spatial pattern of glacial-interglacial climate and environmental variability in the tropics underscores the need for longer and better constrained data sets from the region to fully understanding forcings and potential feedbacks. The tropics play a crucial role in global moisture balance and heat redistribution. Additionally, environmental change in continental systems is also generally greater in amplitude and more spatially heterogeneous than in marine environments, where many of the early records of tropical climate variability are located. Thus, terrestrial records from the tropics are particularly necessary to fully resolve regional variability of glacial-interglacial climate variability and for comparison to existing high latitude records. This project will contribute to an enhanced understanding of Neotropical paleoclimate over the last 400 thousand years, and will illuminate temperature, hydroclimate, and vegetation shifts for a key location in Central America, Lake Petén Itzá. The researchers will mentor students in scientific communication with the broader public, focusing on the societal relevance of paleoclimate research, and will develop a paleoclimate-based, data-integrated exercise that will be used for hands-on undergraduate classes. Additionally, the project team will develop an open-access article describing paleoclimate science in an online journal aims to inspire and educate the next generation of scientists, reaching a large global student audience.
Lake Petén Itzá, Guatemala, lies in a region dominated by trade wind migration and is influenced by sea surface temperature changes in the subtropical Atlantic basin. It thus represents a key spatial node for understanding large-scale climate variability of the northern tropics of the Americas. The investigators will use existing, archived drill cores from Lake Petén Itzá to develop records of changing Neotropical temperature (using brGDGTs) and precipitation (using ?D values of leaf waxes), and the response of terrestrial vegetation (using ?13C values of leaf waxes) to these changes, in order to examine climate and ecosystem evolution over the past 400 ka. The investigators will integrate findings from the organic geochemical sedimentary reconstructions with previously published and currently on-going sedimentological and palynological research from Petén Itzá. Proxy-model comparison work will also be completed using these integrated reconstructions and other regionally available records with water isotope-enabled GCM experiments.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
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 overarching goal of this project was to reconstruct past temperatures and past rainfall using organic geochemical remains preserved in sediments from Lake Petén Itzá, Guatemala. These sediments were previously collected and thought to go back 400,000 years and were available for our study to examine climate and ecosystem changes. We combined our findings from organic geochemical reconstructions with previously published and currently on-going sedimentological and palynological research from Petén Itzá and globally.
We focused our climate reconstructions on high resolution analysis of ~260-170 ka, covering the period of time known as Marine Isotope Stage (MIS) 7. MIS 7 is the coldest interglacial following the Mid-Brunhes Event ~430 ka, an interval characterized by an increase in the amplitude of glacial-interglacial variability. MIS 7 was marked by high-amplitude solar insolation changes, but less significant changes in high latitude ice volume and greenhouse gas concentrations. Global temperature and ice volume variability do not seem to respond proportionally to precessional solar insolation forcing (due to axial rotation, ~23 kyr cycle on average), but it is unknown what influence, if any, this may have had on climate of the region near Lake Petén Itzá.
We found that precipitation, as reconstructed using compound specific hydrogen isotopes measured from preserved plant leaf wax compounds, was strongly similar to LR04, the oxygen isotope record from deep sea marine foraminifera. Wetter (drier) intervals, as seen in more D depleted (enriched) wax compounds, occur during globally warmer (cooler) intervals with less (more) ice volume as reconstructed in LR04. The glacial-interglacial hydroclimate variability is striking and is the only record of its kind for MIS 7 in the neotropics. Additional biomarker data based on the quantified abundances of sedimentary leaf wax compounds suggest ecosystem-wide terrestrial and aquatic vegetation changes were occurring at the same time.
In addition to the scientific discoveries that we made via this project, the broader impacts of this award focused on student education and mentoring, developing climate-focused curricula, and communicating results with those outside of the university setting. The award supported an underrepresented graduate student in STEM and undergraduate students, broadening participation in climate sciences from underrepresented groups. This graduate student has continued in academics following their experiences with this project. In addition to mentoring these students, supported participants joined university and national mentoring programs to encourage the next generations of scientists. The supported graduate student gave presentations in English and Spanish at multiple meetings in Guatemala in the US about climate and water issues. University curricula was developed and introduced as a part of this award in Global Change class taught at the University of Notre Dame. Finally, beyond formal scientific presentations of the results, this research was discussed with the public in local ‘science days.’
Last Modified: 01/17/2025
Modified by: Melissa A Berke
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