| NSF Org: |
OPP Office of Polar Programs (OPP) |
| Recipient: |
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| Initial Amendment Date: | March 31, 2016 |
| Latest Amendment Date: | March 31, 2016 |
| Award Number: | 1607968 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Marc Stieglitz
mstiegli@nsf.gov (703)292-4354 OPP Office of Polar Programs (OPP) GEO Directorate for Geosciences |
| Start Date: | September 1, 2016 |
| End Date: | August 31, 2019 (Estimated) |
| Total Intended Award Amount: | $108,531.00 |
| Total Awarded Amount to Date: | $108,531.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
77 MASSACHUSETTS AVE CAMBRIDGE MA US 02139-4301 (617)253-1000 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
77 Mass. Ave., Bldg E25-625 Cambridge MA US 02139-4307 |
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Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | ANS-Arctic Natural Sciences |
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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
Given the possibility of substantial greenhouse gas release from thawing permafrost in a warmer future, as well as the threats to infrastructure from thawing permafrost, understanding the response of permafrost to past warmth is of fundamental importance. Speleothems (stalagmites and stalactites) only are expected to grow in Arctic caves when the overlying permafrost has thawed and no longer presents an impermeable barrier to seepage from the surface into the cave. This project will develop a record of when speleothems grew in Arctic caves and, consequently, under what past climatic conditions continuous permafrost thawed. The principal investigators will develop a website designed to educate lay audiences on how speleothems are used to study past climate. They will participate in the Cambridge Science Festival?s Science on the Street program, which provides an outlet for scientists to engage with public audiences attending community events on their research. This project will contribute to STEM workforce development by helping launch the research programs of three early-career scientists, as well as supporting the training of two graduate and three undergraduate students.
The propose a novel approach to reconstruct past episodes of permafrost thaw ? dating cave speleothems from now-frozen areas, which require liquid water to grow and thus imply thawed ground conditions when they were deposited. Their work will take advantage of advances in uranium-thorium geochronology and use existing speleothem collections from three remote areas of Canada spanning 17° of latitude and isolated to continuous permafrost zones to document the extent of speleothem growth, and thus permafrost thaw, across variable interglacial conditions of the past 600 kyr ? some of which were warmer than today. They will also apply uranium-lead dating to a selection of samples to extend the dating range to millions of years. Well-dated, high-resolution records of terrestrial paleoclimate are also rare in the Arctic, though critical for understanding the response of this region to radiative forcings and determining the climate forcing that drove past changes in ice sheets, permafrost, sea ice, and vegetation. Therefore, they will measure stable isotope records along the speleothems to reconstruct climate variability over the intervals during which they grew. While likely fragmentary and confined to warm periods, these records will essentially provide underground extensions of the Greenland ice core ä18O record to numerous past interglacials.
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.
Permafrost, or permanently frozen land, covers nearly a quarter of the Northern Hemisphere land surface. It has warmed significantly over the past few decades and may be highly vulnerable to thaw with continued climate change. This thaw vulnerability has potential global implications because high-latitude permafrost is estimated to contain vast stores of organic carbon, some of which may be released as methane and/or carbon dioxide upon thawing, increasing greenhouse gas-driven warming. However, because the response of permafrost to climate change is affected by a complex array of factors, models of 21st century permafrost thaw have high uncertainty.
In this study, we assessed permafrost thaw during past warm periods in order to understand its vulnerability to sustained warming. We reconstructed permafrost history in western Canada from 131 uranium-thorium ages on 74 speleothems, cave deposits that only accumulate during intervals of deep ground thaw. The samples come from cave sites spanning from southern Canada to the Arctic Circle in the northern Yukon. Our data indicate that the greatest amount of thaw in the past 500,000 years occurred during a period around 400,000 years ago, when there appears to have been substantial thawing of sub-Arctic permafrost and some thawing in the Arctic zone. This finding is important because Arctic temperatures during this warm period were comparable to those expected later this century, suggesting that substantial thawing is possible in the near future. Our results also show that permafrost thaw was even more widespread during one or more periods ~0.5-1.5 million years ago, including thawing in the high Arctic, again suggesting that the permafrost-covered Arctic landscape of today is vulnerable to even small amounts of sustained warming.
Last Modified: 01/02/2020
Modified by: William D Mcgee
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