| NSF Org: |
OPP Office of Polar Programs (OPP) |
| Recipient: |
|
| Initial Amendment Date: | March 9, 2012 |
| Latest Amendment Date: | April 28, 2014 |
| Award Number: | 1142173 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Julie Palais
OPP Office of Polar Programs (OPP) GEO Directorate for Geosciences |
| Start Date: | June 1, 2012 |
| End Date: | May 31, 2015 (Estimated) |
| Total Intended Award Amount: | $348,384.00 |
| Total Awarded Amount to Date: | $348,384.00 |
| Funds Obligated to Date: |
FY 2013 = $109,239.00 FY 2014 = $116,530.00 |
| History of Investigator: |
|
| Recipient Sponsored Research Office: |
1608 4TH ST STE 201 BERKELEY CA US 94710-1749 (510)643-3891 |
| Sponsor Congressional District: |
|
| Primary Place of Performance: |
CA US 94704-5940 |
| Primary Place of
Performance Congressional District: |
|
| Unique Entity Identifier (UEI): |
|
| Parent UEI: |
|
| NSF Program(s): | ANT Glaciology |
| Primary Program Source: |
|
| Program Reference Code(s): |
|
| Program Element Code(s): |
|
| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.078 |
ABSTRACT
1142010/Talghader
This award supports a project to combine the expertise of both glaciologists and optical engineers to develop polarization- preserving optical scattering techniques for borehole tools to identify changes in high-resolution crystal structure (fabric) and dust content of glacial ice. The intellectual merit of this work is that the fabric and impurity content of the ice contain details on climate, volcanic activity and ice flow history. Such fabric measurements are currently taken by slicing an ice core into sections after it has started to depressurize which is an extremely time-intensive process that damages the core and does not always preserve the properties of ice in its in-situ state. In addition the ice core usually must be consumed in order to measure the components of the dust. The fabric measurements of this study utilize the concept that singly-scattered light in ice preserves most of its polarization when it is backscattered once from bubbles or dust; therefore, changes to the polarization of singly-backscattered light must originate with the birefringence. Measurements based on this concept will enable this program to obtain continuous records of fabric and correlate them to chronology and dust content. The project will also develop advanced borehole instruments to replace current logging tools, which require optical sources, detectors and power cables to be submerged in borehole fluid and lowered into the ice sheet at temperatures of -50oC. The use of telecommunications fiber will allow all sources and detectors to remain at the surface and enable low-noise signal processing techniques such as lock-in amplification that increase signal integrity and reduce needed power. Further, fiber logging systems would be much smaller and more flexible than current tools and capable of navigating most boreholes without a heavy winch. In order to assess fabric in situ and test fiber-optic borehole tools, field measurements will be made at WAIS Divide and a deep log will also be made at Siple Dome, both in West Antarctica. If successful, the broader impacts of the proposed research would include the development of new analytical methods and lightweight logging tools for ice drilling research that can operate in boreholes drilled in ice. Eventually the work could result in the development of better prehistoric records of glacier flow, atmospheric particulates, precipitation, and climate forcing. The project encompasses a broad base of theoretical, experimental, and design work, which makes it ideal for training graduate students and advanced undergraduates. Collaboration with schools and classroom teachers will help bring aspects of optics, climate, and polar science to an existing Middle School curriculum.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
Note:
When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external
site maintained by the publisher. Some full text articles may not yet be available without a
charge during the embargo (administrative interval).
Some links on this page may take you to non-federal websites. Their policies may differ from
this site.
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 atmospheric dust preserved in glacial ice and the crystal structure, or fabric, of that ice contain vital information about climate, glacier flow history and future stability of ice sheets, volcanism and extraterrestrial impacts. Historically, high resolution records of dust and fabric have required painstaking measurements on ice core samples, once those samples have been retrieved to the surface to depressurize. This time-intensive process does not always preserve the properties of ice in its glacial state and measurements cannot be made with existing instruments without destroying the core.
A main goal of this program has been to combine the expertise of glaciologists, physicists and optical engineers to develop optical borehole tools capable of rapidly measuring ice impurities and identifying changes in fabric. We obtained and analyzed multiple profiles of the WAIS Divide ice core borehole, taken with a laser borehole dust logger in 2011-12 and an improved instrument in 2014-15. We synchronized these WAIS Divide logging records of dust, volcanic ash and climate change with ice core and logging data from other Antarctic sites including South Pole, Dome C and Siple Dome (see Figures). We found evidence for shape-preferred orientation of dust grains at WAIS Divide related to ice fabric, motivated by our discovery of the effect at the South Pole in the IceCube neutrino observatory. Optical borehole dust logging has become an essential part of glaciology and is more active than ever before.
The tools developed in this research program will be used in boreholes created by the Rapid Access Ice Drill (RAID). RAID is a multidisciplinary platform to rapidly access the ice sheet bed for glaciology, subglacial biology, geophysics, and bedrock geology. Among other science objectives, the chronological information provided by our tools will underpin a rapid reconnaissance survey for 1.5 million year old ice, a centerpiece objective of the International Partnerships in Ice Core Sciences (IPICS). The ultimate goal is to acquire a 1.5 million year ice core record of greenhouse gases and climate, doubling the length of the current ice core record. Such a core will ultimately address the questions: What caused the shift from regular 41,000 year glacial cycles to irregular, 100,000 year cycles, about a million years ago? Was atmospheric carbon dioxide concentration higher during the 41,000 year cycles? Was the transition to 100,000 cycles caused by falling greenhouse gases? These questions are vitally important for understanding the workings of our climate system, with implications for our future.
By incorporating our detailed dust records with the discovery of oriented dust grains, we were able to significantly improve performance of the IceCube observatory, which was awarded the 2013 Breakthrough of the Year by Physics World.
The research and technology in this program impacts our understanding of the Polar Regions and climate change, and the future direction of glaciology and climate research. The techniques developed here address the need within the Antarctic sciences for dense spatial sampling of ice sheets using powerful, portable instruments, for analysis of current and future boreholes.
Last Modified: 07/13/2015
Modified by: Ryan Bay
