| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | May 17, 2012 |
| Latest Amendment Date: | May 17, 2012 |
| Award Number: | 1203910 |
| Award Instrument: | Standard Grant |
| Program Manager: |
David Verardo
AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | June 1, 2012 |
| End Date: | May 31, 2016 (Estimated) |
| Total Intended Award Amount: | $603,737.00 |
| Total Awarded Amount to Date: | $603,737.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
101 COMMONWEALTH AVE AMHERST MA US 01003-9252 (413)545-0698 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
MA US 01003-9242 |
| 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
The project is a study of an extreme, short-lived climate oscillation that occurred at the Oligocene-Miocene boundary about 23 million years ago. The event is characterized by a 150,000-year oscillation in the stable oxygen isotope composition (delta18O) of benthic foraminifera, generally thought to reflect a rapid advance and retreat in the Antarctic ice sheet, as well as a perturbation in the global carbon cycle and evidence of biotic impacts in marine and terrestrial systems. The magnitude of the event and its short duration are unusual and in apparent contradiction to our understanding of ice sheet behavior.
The researchers will use proxy measurements of past climate and general circulation model simulations to address four overarching questions:
What were the primary drivers of the event: carbon cycle dynamics and atmospheric carbon dioxide (CO2), orbits?
What was the magnitude of the event in terms of temperature and ice volume change?
Could Northern Hemispheric ice sheets have grown, given near-modern atmospheric CO2 levels at the time, and if so, what is their impact on the benthic delta18O signal?
How can a polar-centered, terrestrial ice sheet experience such variability if CO2 levels remained as low as suggested by proxy records?
The broader impacts include graduate student mentoring, participation in an important summer school focused on past climate history, and the development of undergraduate education modules for climate history.
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.
This interdisciplinary project targeted a long-standing geological and climatological conundrum: how could global ice volume (and sea-level) have varied so much during the Miocene, when atmospheric CO2 concentrations were similar to today’s levels, and there were presumably no varying ice sheets in the northern hemisphere. This is particularly problematical, given previous modeling studies that suggest that the Antarctic Ice Sheet should be very stable, once it grows large enough to cover the continent. This conundrum was resolved by 1) considering the effects of ancient ocean temperatures on Antarctic climate, 2) using new reconstructions of Antarctic topography in our ice sheet model, 3) considering new records of Miocene atmospheric CO2, 4) adding new physical treatments of ice sheet dynamical processes (hydrofracturing of ice shelves, and ice-cliff mechanical failure) to our ice-sheet model, and 5) coupling our numericial ice sheet model to a high-resolution atmospheric model.
This work produced a number of papers published in high-impact journals including Nature, Nature Communications, Geology, Geophysical Research Letters, Earth and Planetary Science Letters, Science, etc. In summary, the key findings indicate that the volume of the Antarctic Ice Sheet could have varied substantially during the Miocene; just as indicated by Miocene geological and geochemical records. These variations in ice volume represent changes in global mean sea level >30m. Importantly, this range of sea-level is demonstrated to be possible at levels of atmospheric CO2 as low as 500 ppmv, which is surprisingly close to the current level of 400 ppmv. A broader impact of this result is that the potential for long-term, future sea-level rise might be substantially higher than previously thought.
Other products of this work include the development of new, numerical models of the Antarctic atmosphere and ice sheet, new reconstructions of ancient ocean temperature at times when the Antarctic ice sheet was variable, and new estimates of atmospheric CO2 at the time of maximum ice-sheet retreat.
This award supported the successful completion of a Ph.D. dissertation project and a post-doctoral fellowship, both at the University of Massachusetts, Amherst.
Last Modified: 08/27/2016
Modified by: Robert M Deconto
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