Research
The geologic record helps us understand the climatic history of our planet. Information preserved in the Greenland and Antarctic ice sheets plays a critical role in understanding past natural climate change, through information about past temperatures, snowfall, and many other properties of the environment. Moreover, the ice traps small samples of the atmosphere, preserving a unique and highly accurate record of greenhouse and other gases, providing the best evidence for a strong link between atmospheric carbon dioxide (CO2) and Earth’s climate on geologic timescales.
The oldest ice cores are from East Antarctica, the largest and most stable of the polar ice sheets. Existing ice core data add tremendously to our understanding of climate. However, these cores do not extend back far enough to provide information from periods when Earth’s climate was significantly warmer and/or greenhouse gas levels were higher than today. Such information is vital for understanding how climate will evolve as greenhouse levels rise, and for developing a deeper understanding of long-term trends in Earth history.
The challenge is to locate the rare places where old ice is still present in Antarctica. The oldest continuous ice core is 800,000 years. Radar imaging and ice sheet models suggest that ice as old as 1.5 Ma or older could be preserved in the interior. Recent results indicate that discontinuous ice as old as 2.7 million years is preserved in at least one mountain region in East Antarctica (Yan et al. (2019).
The Center for OLDest Ice EXploration (COLDEX), founded in 2021 and funded by the National Science Foundation, will extend the ice core record to at least 1.5 million years B.P. by ultimately drilling and analyzing a continuous ice core in East Antarctica, and to much older times using discontinuous ice sections at the base and margin of the ice sheet. COLDEX is addressing fundamental questions critical for understanding past and future climate change, including sensitivity to higher levels of greenhouse gases, the role of greenhouse gases in the evolution of ice age cycles, and behavior of the Antarctic ice sheet in warmer climates. Required technological advances will set new standards in data collection and analysis in glaciology and climate science. To accomplish its goals, COLDEX has formed a strong collaboration among ice core geochemists, geophysicists, glaciologists, and engineers from 13 U.S. universities, integrating knowledge of past climate, ice dynamics, subglacial geology, and technologies for direct and remote measurement of subsurface properties.
COLDEX is conducting research in four broad areas: exploration, ice sheet modelling, ice coring and ice core analysis.
Our exploration program seeks sites to drill ice cores in the Antarctic interior and near the ice margin to obtain samples older than 800,000 years. This work includes deploying airborne and surface-based radar to image the ice sheet structure, with development of novel radar methods to determine ice movement in slow flowing areas and over large regions from airborne data. It also includes development of a new thermal probe that directly measures the dust content of the ice while rapidly melting through the ice sheet; the dust data can be used to determine the age structure of the ice.
COLDEX is also collaborating with the US RAID (Rapid Access Ice Drill) program; COLDEX participants John Goodge and Jeff Severinghaus are the RAID PIs. RAID is designed to drill a borehole through the Antarctic ice sheet and in to the bedrock below. Optical and temperature logging, and ice coring, from RAID boreholes will provide additional tools for searching for Antarctica’s oldest ice. Understanding the composition of Antarctica’s bedrock geology will be a key component of constraining geothermal flux, also critical for predicting the preservation of old ice.
Overall exploration lead: Jeff Severinghaus, UCSD.
Aerogeophysics leads: Paden (CReSIS) and Young (UTIG). Key participants: Blankenship, (UTIG), Hale, Rodriguez, Arnold (CReSIS), Koutnik, Fudge, Waddington, Christianson, Conway (UW), Greenbaum (UCSD). Ground-based radar lead: Christianson (UW). Key participants: Holschuh (Amherst College), Conway, Koutnik, Waddington, Fudge (UW), Paden (Kansas). Ice Diver Lead: Winebrenner (UW-APL). Key participants: Bay (UC Berkeley). RAID leads: Goodge (UMN Duluth), Severinghaus (UCSD).
Ice sheet modelling and studies of ice dynamics are underway to understand where a stratigraphic sequence of old ice may be preserved. These modelling efforts, which include thermal and mechanical ice-flow models, are critical for COLDEX because the preservation of old ice depends on details of ice flow and deformation, basal temperature, and ice-sheet and climate history. Our new modeling is focusing on details of individual interior East Antarctic sites by incorporating the new COLDEX airborne and surface geophysical data. The models applied to meet our objectives are being developed together with geophysical surveys, providing constraints on ice sheet history.
Lead: Koutnik (UW). Key Participants: Fudge, Waddington, Conway (UW), Holschuh (Amherst College), Pettit (OSU).
During the first 5 year phase of COLDEX, ice coring is being conducted at several places along the Antarctic ice sheet margin. Shallow (~ 200 m) coring will be conducted in locations that are expected to preserve very old (>2 million years) ice in the Transantarctic Mountains based on previous work, including Allan Hills, Elephant Moraine, as well as other potential locations being evaluated. An intermediate depth core (~1200 m) in the Allan Hills at a location already identified as possibly preserving a 1 million year record is also under consideration.
(Photo by Yuzhen Yan during the 2015/16 field season at Allan Hills, Antarctica.)
Lead: Higgins (Princeton). Key Participants: Bender (Princeton), Conway, Fudge (UW), Kurbatov, Mayewski (Maine), Brook, Buizert (OSU).
Our ice core analysis program is combining both traditional and new measurement techniques to develop climate and environmental histories from COLDEX cores. These efforts include a centralized laboratory for basic isotopic and chemical measurements, improvement in greenhouse gas and other atmospheric measurements, improvements in dating atmospheric gas records from old ice, enhanced ice imaging techniques, isotopic studies of atmospheric dust, and reconstructions of past ocean temperatures from noble gas ratios.
Lead: Buizert (OSU). Key Participants: Steig (UW), Saltzman (UCI), Aarons, Severinghaus (UCSD), Brook (OSU), Bender, Higgins (Princeton), Kurbatov (Maine).