Ice cores recovered from the polar regions of the Earth contain the most comprehensive, direct record of the Earth's high-latitude climate for the past 800,000 years. In addition to providing a proxy temperature record (through the record of the stable isotope ratios of water preserved in the ice) and a direct observational record of net accumulation, ice cores also provide the only direct record of atmospheric composition (direct gases, total gas content, and isotopic ratios) available in the field of paleoclimatology. As a result, the primary evidential basis for much of the current scientific thinking about past rates of climate change and the irrefutable evidence for the past linkage between atmospheric greenhouse gas concentrations and mean atmospheric temperature reside in the ice core record.
In its 2007 report, the UN's Intergovernmental Panel on Climate Change recognized the limited understanding of ice sheet dynamics (the motion and deformation of large bodies of ice) as a significant and poorly-characterized factor affecting our ability to model sea-level rise attributable to potential melting of the polar ice sheets. Studies of the physical properties of ice cores improve our understanding of how bodies of glacier ice respond to changes in accumulation rate, temperature, and external dynamics and provide constraints on the rates of those responses.
The interpretation of both the paleoclimate record and the past dynamical state of an ice sheet depends, in part, on the establishment of temporal continuity and a robust timescale, each of which can, in part, be determined from the analysis of the physical properties of an ice core recovered from it. The purpose of the work carried out in this task is to provide this analysis for ice cores recovered through the National Science Foundation's Office of Polar Programs from both the Arctic and Antarctic regions of the Earth.
The Ice Dynamics, Paleoclimate, and Ice Cores Project is funded by the Research and Development program of the USGS Climate and Land Use Change Program.
Objectives
- Provide understanding of the physical characteristics of ice sheets. Assess their stratigraphic continuity; identify anomalies that can potentially impact the interpretation of the climate records derived from them; reconstruct the flow history and the conditions for enhanced flow as an aid to reconstructing climate.
- Extract high-resolution hemispheric records of climate from ice cores to improve understanding of mechanisms of slow and abrupt climate change on glacial/interglacial and faster timescales.
- Collect a comprehensive suite of physical-property information to improve the general characterization of the past and present behavior of ice sheets.
- Participate in national and international field campaigns to acquire and provide analyses of the physical properties of deep ice cores from the polar regions.
- Contribute the results of laboratory analysis of physical properties of deep ice cores to national and international multi-disciplinary project teams working on creating high-resolution global climate history records.
- Develop numerical models for dynamic recrystallization and bubble evolution and assess their impact on ice dynamics.
- Ensure ready availability of analytical results to collaborators and team members through electronic dissemination of results.
Facilities
The Ice Dynamics, Paleoclimate, and Ice Cores Project maintains a laboratory for ice microstructure characterization at the U.S. National Ice Core Laboratory. Equipment for the preparation of thin and thick sections of ice includes:
- Bright field microscopy in plane polarized and cross-polarized light
- 90-degree illumination microscopy optimized for bubble characterization
- Reflected-light microscopy utilizing coaxial illumination
- Universal and Rigsby stages
- Digital image capture and video
- Fabric analysis is carried out in collaboration with the Ice and Climate Research Group at the Pennsylvania State University
Image processing and analysis software provide the capability to extract quantitative information from digital images, and microstructural modeling software is used to investigate the deformation and recrystallization mechanisms active at depth in an ice sheet. Microstructural visualization of measured parameters can be created in ArcGIS.
Below are publications associated with this project.
Physical properties of the WAIS Divide ice core
Digital-image processing and image analysis of glacier ice
Late-Holocene climate evolution at the WAIS Divide site, West Antarctica: Bubble number-density estimates
History of the Greenland Ice Sheet: paleoclimatic insights
Developing a bubble number-density paleoclimatic indicator for glacier ice
Fabric and texture at Siple Dome, Antarctica
Conditions for bubble elongation in cold ice-sheet ice
The geochemical record in rock glaciers
Old ice in rock glaciers may provide long-term climate records
Saline minerals in the Lewis Cliff ice tongue, Buckley Island Quadrangle, Antarctica
Borax in the supraglacial moraine of the Lewis Cliff, Buckley Island quadrangle--first Antarctic occurrence
- Overview
Ice cores recovered from the polar regions of the Earth contain the most comprehensive, direct record of the Earth's high-latitude climate for the past 800,000 years. In addition to providing a proxy temperature record (through the record of the stable isotope ratios of water preserved in the ice) and a direct observational record of net accumulation, ice cores also provide the only direct record of atmospheric composition (direct gases, total gas content, and isotopic ratios) available in the field of paleoclimatology. As a result, the primary evidential basis for much of the current scientific thinking about past rates of climate change and the irrefutable evidence for the past linkage between atmospheric greenhouse gas concentrations and mean atmospheric temperature reside in the ice core record.
The Greenland Ice Sheet contains approximately 2.9 million km3 of ice that would raise sea level by about 7.3 m if it were to melt completely. (Credit: NASA) In its 2007 report, the UN's Intergovernmental Panel on Climate Change recognized the limited understanding of ice sheet dynamics (the motion and deformation of large bodies of ice) as a significant and poorly-characterized factor affecting our ability to model sea-level rise attributable to potential melting of the polar ice sheets. Studies of the physical properties of ice cores improve our understanding of how bodies of glacier ice respond to changes in accumulation rate, temperature, and external dynamics and provide constraints on the rates of those responses.
The interpretation of both the paleoclimate record and the past dynamical state of an ice sheet depends, in part, on the establishment of temporal continuity and a robust timescale, each of which can, in part, be determined from the analysis of the physical properties of an ice core recovered from it. The purpose of the work carried out in this task is to provide this analysis for ice cores recovered through the National Science Foundation's Office of Polar Programs from both the Arctic and Antarctic regions of the Earth.
The Ice Dynamics, Paleoclimate, and Ice Cores Project is funded by the Research and Development program of the USGS Climate and Land Use Change Program.
Objectives
- Provide understanding of the physical characteristics of ice sheets. Assess their stratigraphic continuity; identify anomalies that can potentially impact the interpretation of the climate records derived from them; reconstruct the flow history and the conditions for enhanced flow as an aid to reconstructing climate.
- Extract high-resolution hemispheric records of climate from ice cores to improve understanding of mechanisms of slow and abrupt climate change on glacial/interglacial and faster timescales.
- Collect a comprehensive suite of physical-property information to improve the general characterization of the past and present behavior of ice sheets.
- Participate in national and international field campaigns to acquire and provide analyses of the physical properties of deep ice cores from the polar regions.
- Contribute the results of laboratory analysis of physical properties of deep ice cores to national and international multi-disciplinary project teams working on creating high-resolution global climate history records.
- Develop numerical models for dynamic recrystallization and bubble evolution and assess their impact on ice dynamics.
- Ensure ready availability of analytical results to collaborators and team members through electronic dissemination of results.
Snowpits dug into the surface of an ice sheet reveal annual layers that can be identified hundreds of meters deep. Counting these layers provides one of several measurements used to create a robust timescale for an ice core. (Credit: Kendrick Taylor) Facilities
Joan Fitzpatrick at work in the U.S. National Ice Core Laboratory. The Ice Dynamics, Paleoclimate, and Ice Cores Project maintains a laboratory for ice microstructure characterization at the U.S. National Ice Core Laboratory. Equipment for the preparation of thin and thick sections of ice includes:
- Bright field microscopy in plane polarized and cross-polarized light
- 90-degree illumination microscopy optimized for bubble characterization
- Reflected-light microscopy utilizing coaxial illumination
- Universal and Rigsby stages
- Digital image capture and video
- Fabric analysis is carried out in collaboration with the Ice and Climate Research Group at the Pennsylvania State University
Image processing and analysis software provide the capability to extract quantitative information from digital images, and microstructural modeling software is used to investigate the deformation and recrystallization mechanisms active at depth in an ice sheet. Microstructural visualization of measured parameters can be created in ArcGIS.
- Publications
Below are publications associated with this project.
Physical properties of the WAIS Divide ice core
The WAIS (West Antarctic Ice Sheet) Divide deep ice core was recently completed to a total depth of 3405 m, ending ∼50 m above the bed. Investigation of the visual stratigraphy and grain characteristics indicates that the ice column at the drilling location is undisturbed by any large-scale overturning or discontinuity. The climate record developed from this core is therefore likely to be continuoAuthorsJoan J. Fitzpatrick, Donald E. Voigt, John M. Fegyveresi, Nathan T. Stevens, Matthew K. Spencer, Jihong Cole-Dai, Richard B. Alley, Gabriella E. Jardine, Eric Cravens, Lawrence A. Wilen, T. J. Fudge, Joseph R. McConnellDigital-image processing and image analysis of glacier ice
This document provides a methodology for extracting grain statistics from 8-bit color and grayscale images of thin sections of glacier ice—a subset of physical properties measurements typically performed on ice cores. This type of analysis is most commonly used to characterize the evolution of ice-crystal size, shape, and intercrystalline spatial relations within a large body of ice sampled by deeAuthorsJoan J. FitzpatrickLate-Holocene climate evolution at the WAIS Divide site, West Antarctica: Bubble number-density estimates
A surface cooling of ∼1.7°C occurred over the ∼two millennia prior to ∼1700 CE at the West Antarctic ice sheet (WAIS) Divide site, based on trends in observed bubble number-density of samples from the WDC06A ice core, and on an independently constructed accumulation-rate history using annual-layer dating corrected for density variations and thinning from ice flow. Density increase and grain growthAuthorsJohn M. Fegyveresi, R. B. Alley, M. K. Spencer, J. J. Fitzpatrick, E.J. Steig, J.W.C. White, J.R. McConnell, K.C. TaylorHistory of the Greenland Ice Sheet: paleoclimatic insights
Paleoclimatic records show that the GreenlandIce Sheet consistently has lost mass in response to warming, and grown in response to cooling. Such changes have occurred even at times of slow or zero sea-level change, so changing sea level cannot have been the cause of at least some of the ice-sheet changes. In contrast, there are no documented major ice-sheet changes that occurred independent of temAuthorsRichard B. Alley, John T. Andrews, J. Brigham-Grette, G.K.C. Clarke, Kurt M. Cuffey, J. J. Fitzpatrick, S. Funder, S.J. Marshall, G. H. Miller, J.X. Mitrovica, D.R. Muhs, B. L. Otto-Bliesner, L. Polyak, J.W.C. WhiteDeveloping a bubble number-density paleoclimatic indicator for glacier ice
Past accumulation rate can be estimated from the measured number-density of bubbles in an ice core and the reconstructed paleotemperature, using a new technique. Density increase and grain growth in polar firn are both controlled by temperature and accumulation rate, and the integrated effects are recorded in the number-density of bubbles as the firn changes to ice. An empirical model of these proAuthorsM. K. Spencer, R. B. Alley, J. J. FitzpatrickFabric and texture at Siple Dome, Antarctica
Preferred c-axis orientations are present in the firn at Siple Dome, West Antarctica, and recrystallization begins as shallow as 200 m depth in ice below –20°C, based on digital analysis of c-axis fabrics, grain-sizes and other characteristics of 52 vertical thin sections prepared in the field from the kilometer-long Siple Dome ice core. The shallowest section analyzed, from 22 m, shows clusteringAuthorsC. L. Diprinzio, Lawrence A. Wilen, R. B. Alley, J. J. Fitzpatrick, M. K. Spencer, A. J. GowConditions for bubble elongation in cold ice-sheet ice
Highly elongated bubbles are sometimes observed in ice-sheet ice. Elongation is favored by rapid ice deformation, and opposed by diffusive processes. We use simple models to show that vapor transport dominates diffusion except possibly very close to the melting point, and that latent-heat effects are insignificant. Elongation is favored by larger bubbles at pore close-off, but is nearly independenAuthorsR. B. Alley, J. J. FitzpatrickThe geochemical record in rock glaciers
A 9.5 m ice core was extracted from beneath the surficial debris cover of a rock glacier at Galena Creek, northwestern Wyoming. The core contains clean, bubble-rich ice with silty debris layers spaced at roughly 20 cm intervals. The debris layers are similar in appearance to those in typical alpine glaciers, reflecting concentration of debris by melting at the surface during the summer ablation seAuthorsE.J. Steig, J. J. Fitzpatrick, N. Potter, D.H. ClarkOld ice in rock glaciers may provide long-term climate records
[No abstract available]AuthorsD.H. Clark, E.J. Steig, N. Potter, J. Fitzpatrick, A.B. Updike, G. M. ClarkSaline minerals in the Lewis Cliff ice tongue, Buckley Island Quadrangle, Antarctica
No abstract available.AuthorsJ. J. Fitzpatrick, D.R. Muhs, A.J.T. JullBorax in the supraglacial moraine of the Lewis Cliff, Buckley Island quadrangle--first Antarctic occurrence
During the 1987-1988 austral summer field season, membersof the south party of the antarctic search for meteorites south-ern team* working in the Lewis Cliff/Colbert Hills region dis-covered several areas of unusual mineralization within theLewis Cliff ice tongue and its associated moraine field (figure1). The Lewis Cliff ice tongue (84°15'S 161°25'E) is a meteorite-stranding surface of ablating bAuthorsJ. J. Fitzpatrick, D.R. Muhs - Partners