[{"awards": "1341658 Mukhopadhyay, Sujoy", "bounds_geometry": "POLYGON((-116.45 -84.786,-116.443 -84.786,-116.436 -84.786,-116.429 -84.786,-116.422 -84.786,-116.415 -84.786,-116.408 -84.786,-116.401 -84.786,-116.394 -84.786,-116.387 -84.786,-116.38 -84.786,-116.38 -84.7864,-116.38 -84.7868,-116.38 -84.7872,-116.38 -84.7876,-116.38 -84.788,-116.38 -84.7884,-116.38 -84.7888,-116.38 -84.7892,-116.38 -84.7896,-116.38 -84.79,-116.387 -84.79,-116.394 -84.79,-116.401 -84.79,-116.408 -84.79,-116.415 -84.79,-116.422 -84.79,-116.429 -84.79,-116.436 -84.79,-116.443 -84.79,-116.45 -84.79,-116.45 -84.7896,-116.45 -84.7892,-116.45 -84.7888,-116.45 -84.7884,-116.45 -84.788,-116.45 -84.7876,-116.45 -84.7872,-116.45 -84.7868,-116.45 -84.7864,-116.45 -84.786))", "dataset_titles": "Ohio Range Subglacial rock core cosmogenic nuclide data", "datasets": [{"dataset_uid": "601351", "doi": "10.15784/601351", "keywords": "Aluminum-26; Antarctica; Beryllium-10; Cosmogenic Dating; Cosmogenic Radionuclides; Glaciers/ice Sheet; Glaciers/Ice Sheet; Glaciology; Ice Sheet Fluctuations; Ohio Range; Rocks", "people": "Mukhopadhyay, Sujoy", "repository": "USAP-DC", "science_program": null, "title": "Ohio Range Subglacial rock core cosmogenic nuclide data", "url": "https://www.usap-dc.org/view/dataset/601351"}], "date_created": "Sun, 28 Jun 2020 00:00:00 GMT", "description": "Modeling fluctuations in the extent of the West Antarctic Ice Sheet (WAIS) over time is a principal goal of the glaciological community. These models will provide a critical basis for predictions of future sea level change, and therefore this work great societal relevance. The mid-Pliocene time interval is of particular interest, as it is the most recent period in which global temperatures were warmer and atmospheric CO2 concentrations may have been higher than current levels. However, observational constraints on fluctuations in the WAIS older than the last glacial maximum are rare.\r\nTo test model predictions,sub-glacial rock cores were obtained from the Ohio Range along the Transantarctic Mountains near the present-day WAIS divide using a Winkie drill. Rock cores were recovered from 10 to ~30 m under the present-day ice levels. At the Ohio Range, the glacial to interglacial variations in ice sheet levels is ~120 meters. So 30 meters represent a significant fraction of the variation over the course of an ice age.\r\nHigh concentrations of the cosmic ray produced isotopes were detected in the rock cores, indicating extensive periods of ice-free exposure to cosmic irradiation during the last 2 million years. Modeling of the data suggest that bedrock surfaces at the Ohio Range that are currently covered by 30 meters of ice experienced more exposure than ice cover, especially in the Pleistocene. An ice sheet model prediction for the Ohio Range subglacial sample sites however, significantly underestimates exposure in the last 2 million years, and over-predicts ice cover in the Pleistocene. To adjust for the higher amounts of exposure we observe in our samples, the ice sheet model simulations require more frequent and/or longer-lasting WAIS ice drawdowns. This has important implications for future sea-level change as the model maybe under-predicting the magnitude of sea-level contributions from WAIS during the ice-age cycles. Improving the accuracy of the ice sheet models through model-data comparison should remain a prime objective in the face of a warming planet as understanding WAIS behavior is going to be key for predicting and planning for the effects of sea-level change. The project helped support and train a graduate student in climate research related to Antarctica, cosmogenic nuclide analyses and led to a Master\u2019s Thesis. The project also provide partial support to a postdoctoral scholar obtaining cosmogenic neon measurements and for training and mentoring the graduate student\u0027s cosmogenic neon measurements and interpretation. The project results were communicated to the scientific community at conferences and through seminars. The broader community was engaged through the University of California Davis\u0027s Picnic Day celebration, an annual open house that attracts over 70,000 people to the campus, and through classroom visit at a local elementary school.", "east": -116.38, "geometry": "POINT(-116.415 -84.788)", "instruments": "IN SITU/LABORATORY INSTRUMENTS \u003e CORERS \u003e ROCK CORERS; IN SITU/LABORATORY INSTRUMENTS \u003e SPECTROMETERS/RADIOMETERS \u003e AMS; IN SITU/LABORATORY INSTRUMENTS \u003e CHEMICAL METERS/ANALYZERS \u003e GAS CHROMATOGRAPHS", "is_usap_dc": true, "keywords": "Ice Sheet Fluctuations; ALUMINUM-26 ANALYSIS; BERYLLIUM-10 ANALYSIS; Cosmogenic Radionuclides; USAP-DC; FIELD INVESTIGATION; AMD; Ohio Range; GLACIER THICKNESS/ICE SHEET THICKNESS; ICE SHEETS; LABORATORY", "locations": "Ohio Range", "north": -84.786, "nsf_funding_programs": "Antarctic Earth Sciences", "paleo_time": null, "persons": "Mukhopadhyay, Sujoy", "platforms": "LAND-BASED PLATFORMS \u003e FIELD SITES \u003e FIELD INVESTIGATION; OTHER \u003e PHYSICAL MODELS \u003e LABORATORY", "repo": "USAP-DC", "repositories": "USAP-DC", "science_programs": null, "south": -84.79, "title": "Constraining Plio-Pleistocene West Antarctic Ice Sheet Behavior from the Ohio Range and Scott Glacier", "uid": "p0010113", "west": -116.45}]

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Constraining Plio-Pleistocene West Antarctic Ice Sheet Behavior from the Ohio Range and Scott Glacier

1341658

2020-06-28

Mukhopadhyay, Sujoy

Ohio Range Subglacial rock core cosmogenic nuclide data

USAP-DC

Modeling fluctuations in the extent of the West Antarctic Ice Sheet (WAIS) over time is a principal goal of the glaciological community. These models will provide a critical basis for predictions of future sea level change, and therefore this work great societal relevance. The mid-Pliocene time interval is of particular interest, as it is the most recent period in which global temperatures were warmer and atmospheric CO2 concentrations may have been higher than current levels. However, observational constraints on fluctuations in the WAIS older than the last glacial maximum are rare. To test model predictions,sub-glacial rock cores were obtained from the Ohio Range along the Transantarctic Mountains near the present-day WAIS divide using a Winkie drill. Rock cores were recovered from 10 to ~30 m under the present-day ice levels. At the Ohio Range, the glacial to interglacial variations in ice sheet levels is ~120 meters. So 30 meters represent a significant fraction of the variation over the course of an ice age. High concentrations of the cosmic ray produced isotopes were detected in the rock cores, indicating extensive periods of ice-free exposure to cosmic irradiation during the last 2 million years. Modeling of the data suggest that bedrock surfaces at the Ohio Range that are currently covered by 30 meters of ice experienced more exposure than ice cover, especially in the Pleistocene. An ice sheet model prediction for the Ohio Range subglacial sample sites however, significantly underestimates exposure in the last 2 million years, and over-predicts ice cover in the Pleistocene. To adjust for the higher amounts of exposure we observe in our samples, the ice sheet model simulations require more frequent and/or longer-lasting WAIS ice drawdowns. This has important implications for future sea-level change as the model maybe under-predicting the magnitude of sea-level contributions from WAIS during the ice-age cycles. Improving the accuracy of the ice sheet models through model-data comparison should remain a prime objective in the face of a warming planet as understanding WAIS behavior is going to be key for predicting and planning for the effects of sea-level change. The project helped support and train a graduate student in climate research related to Antarctica, cosmogenic nuclide analyses and led to a Master’s Thesis. The project also provide partial support to a postdoctoral scholar obtaining cosmogenic neon measurements and for training and mentoring the graduate student's cosmogenic neon measurements and interpretation. The project results were communicated to the scientific community at conferences and through seminars. The broader community was engaged through the University of California Davis's Picnic Day celebration, an annual open house that attracts over 70,000 people to the campus, and through classroom visit at a local elementary school.