| NSF Org: |
OPP Office of Polar Programs (OPP) |
| Recipient: |
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| Initial Amendment Date: | April 23, 2018 |
| Latest Amendment Date: | June 1, 2021 |
| Award Number: | 1744771 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Michael E. Jackson
OPP Office of Polar Programs (OPP) GEO Directorate for Geosciences |
| Start Date: | June 1, 2018 |
| End Date: | August 31, 2022 (Estimated) |
| Total Intended Award Amount: | $229,463.00 |
| Total Awarded Amount to Date: | $262,203.00 |
| Funds Obligated to Date: |
FY 2021 = $32,740.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
2455 RIDGE RD BERKELEY CA US 94709-1211 (510)644-9200 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
2355 Ridge Road Berkeley CA US 94709-1211 |
| 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 Earth Sciences, ANT Glaciology |
| 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): | 47.078 |
ABSTRACT
The purpose of this project is to use geological data that record past changes in the Antarctic ice sheets to test computer models for ice sheet change. The geologic data mainly consist of dated glacial deposits that are preserved above the level of the present ice sheet, and range in age from thousands to millions of years old. These provide information about the size, thickness, and rate of change of the ice sheets during past times when the ice sheets were larger than present. In addition, some of these data are from below the present ice surface and therefore also provide some information about past warm periods when ice sheets were most likely smaller than present. The primary purpose of the computer model is to predict future ice sheet changes, but because significant changes in the size of ice sheets are slow and likely occur over hundreds of years or longer, the only way to determine whether these models are accurate is to test their ability to reproduce past ice sheet changes. The primary purpose of this project is to carry out such a test. The research team will compile relevant geologic data, in some cases generate new data by dating additional deposits, and develop methods and software to compare data to model simulations. In addition, this project will (i) contribute to building and sustaining U.S. science capacity through postdoctoral training in geochronology, ice sheet modeling, and data science, and (ii) improve public access to geologic data and model simulations relevant to ice sheet change through online database and website development.
Technical aspects of this project are primarily focused on the field of cosmogenic-nuclide exposure-dating, which is a method that relies on the production of rare stable and radio-nuclides by cosmic-ray interactions with rocks and minerals exposed at the Earth's surface. Because the advance and retreat of ice sheets results in alternating cosmic-ray exposure and shielding of underlying bedrock and surficial deposits, this technique is commonly used to date and reconstruct past ice sheet changes. First, this project will contribute to compiling and systematizing a large amount of cosmogenic-nuclide exposure age data collected in Antarctica during the past three decades. Second, it will generate additional geochemical data needed to improve the extent and usefulness of measurements of stable cosmogenic nuclides, cosmogenic neon-21 in particular, that are useful for constraining ice-sheet behavior on million-year timescales. Third, it will develop a computational framework for comparison of the geologic data set with existing numerical model simulations of Antarctic ice sheet change during the past several million years, with particular emphasis on model simulations of past warm periods, for example the middle Pliocene ca. 3-3.3 million years ago, during which the Antarctic ice sheets are hypothesized to have been substantially smaller than present. Fourth, guided by the results of this comparison, it will generate new model simulations aimed at improving agreement between model simulations and geologic data, as well as diagnosing which processes or parameterizations in the models are or are not well constrained by the data.
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.
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.
The purpose of this project is to use geological data that record past changes in the size of the Antarctic ice sheets to test computer models for ice sheet change. The geologic data mainly consist of glacial deposits that are preserved above the level of the present ice sheet. Their ages have been measured using geologic dating methods, and range from thousands to millions of years. These deposits therefore provide information about the size, thickness, and rate of change of the ice sheets during past times when the ice sheets were larger than present. In addition, some of these data are from below the present ice surface and therefore also provide some information about past warm periods when ice sheets were most likely smaller than present. The primary purpose of the computer models is to predict future ice sheet changes, but because significant changes in the size of ice sheets are slow and likely occur over hundreds of years or longer, the only way to determine whether these models are accurate is to test their ability to reproduce past ice sheet changes.
Thus, what we did in this project was to compile large amounts of these geologic data and compare them to model simulations. First, we completed an online database (the 'ICE-D:ANTARCTICA' database at www.ice-d.org/antarctica) that includes all the data of this type that we know about in Antarctica. Second, we built a prototype system to generate comparisons between the geologic data and a variety of ice sheet model simulations that had been performed in previous research by others. Third, we performed a series of new ice sheet model runs to try to investigate what properties of the ice sheet model improved or worsened comparison with the geologic data. This led to several broader outcomes. First, we were able to systematically identify several areas in which model simulations differ from observational data with regard to the timing, rate, or amount of ice sheet change. Although we have not completely determined the reasons for these differences, these observations can be used as a guide to future improvement of ice sheet model simulations. Second, we were able to determine that certain types of ice sheet model tend to produce predictions that are a better match for geologic data than other models. Again, this provides guidance for how to improve model simulations in future. Finally, this project also provided training and research experience for recent undergraduates and postdoctoral researchers in Earth and climate science, thus contributing to US scientific expertise both inside and outside academia.
Last Modified: 11/23/2022
Modified by: Gregory A Balco
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