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Collaborative Research: Constraining West Antarctic Ice Sheet Elevation during the last Interglacial
Start Date:
2018-09-01
End Date:
2023-08-31
Description/Abstract
Understanding the geometry of a reduced West Antarctic Ice Sheet (WAIS) during the last interglacial (~125,000 years ago) when the planet was warmer than present provides a possible analogue for future environmental conditions given predicted temperature trends. A reduction of WAIS results in rising sea levels which threatens coastal communities across the globe. Data constraining WAIS elevation during the interglacial will help improve numerical ice sheet models to better predict WAIS response to current and future climate trends. The goal of this project is to constrain WAIS elevation changes at Mt. Waesche, a volcano in Marie Byrd Land, near an ice dome of WAIS (2000 m elevation) by obtaining rock samples from beneath the WAIS through shallow (<80 m) drilling.
The first field season (2018-19) focused on identifying appropriate locations for drilling using ground penetrating radar (GPR) to map the subglacial topography under the blue ice area adjacent to the volcano and mapping and dating the adjacent exposed lava flows to identify lava flows of appropriate age and lithology. 40Ar/39Ar data obtained on samples collected indicate several lava flows on the volcano flank that date to the last interglacial. Based on GPR these flows continue beneath the present ice surface; thus cosmogenic nuclides measured in rock cores from beneath the ice surface will indicate exposure during periods of reduced ice elevation, most likely, during the last interglacial. The lithologies of lava flows exposed on the flank of the volcano are well-suited for cosmogenic 3He and 36Cl to determine the duration of exposure and cover by ice. 40Ar/39Ar measurements will establish eruption age and provide independent evidence of lower levels at that time.
The second field season (2024-25) focused on drilling through blue ice with the Winkie drill near the ice margin to obtain rock cores from the sub-ice lava flows. Three cores from a lava flow 40m, 60m, and 80 m beneath the ice surface were recovered. Based on the lithology of the cores, the lava flow was subaerial, indicating lower Ice levels at the time of eruption. Assuming the subglacial flows correlate to the 40Ar/39Ar dated lava flow exposed directly up slope on Mt Waesche, the eruption and hence lower ice levels occurred during the last interglacial. This assumption will be tested through 40Ar/39Ar dates on the cores. The concentration of cosmogenic nuclides (3He and 36Cl) will be analyzed to determine the duration of exposure and t when the surface became overridden by the ice sheet.
WAIS elevation changes inferred from geologic data have inherent uncertainties due to changes in bedrock elevation due to isostatic adjustments to changing ice loads. In order to better constrain Antarctic bedrock elevation history changes over the last glacial cycle were modelled using available ice histories.
This study collected a novel dataset to determine how the West Antarctic Ice Sheet (WAIS) responded to a warmer climate during the last interglacial period. Exposure ages will constrain the duration and minimum extent of past surface lowering of the WAIS near the dome in Marie Byrd Land. Results from this study will be compared with the modeled ice elevation histories at Mt. Waesche to validate ice sheet modeling efforts
Personnel
Funding
AMD - DIF Record(s)
Deployment
Data Management Plan
Product Level:
4 (model output and interpretations)
Datasets
Publications
Keywords
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This project has been viewed 6 times since May 2019 (based on unique date-IP combinations)
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Hosted at Lamont-Doherty Earth Observatory of Columbia University. Site licensed under Creative Commons Attribution-Noncommercial-Share Alike 3.0 |
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Funded by the US National Science Foundation (NSF) |