80-1 Revising Records of Antarctic Ice Sheet Thinning with an Updated in-situ 14C Production Rate

Session: Recent Advances in Glacial Geology, Geomorphology, and Chronology

Presenting Author:

Authors:

Abstract:

We present a revised Antarctic in situ ¹⁴C production rate calibrated using over a decade of measurements of the CRONUS-A intercomparison material. The production rate of a cosmogenic nuclide (the number of cosmogenic atoms produced in a gram of sample per year) relates the measured concentration of an Earth surface material to its exposure time. An inaccurate production rate may result in an offset between the estimated exposure age and the true exposure age by up to thousands of years, leading to misinterpretations of the rate and timing of ice sheet thinning. Therefore, an accurate production rate is critical for interpreting the timing and rate of Antarctic ice sheet thinning from the geologic record.

We calculate the maximum likelihood concentration of in situ ¹⁴C for CRONUS-A as 6.91±0.58×10^5 14C atoms g^-1 (n=102). This concentration yields an in situ ¹⁴C production rate in quartz of 14.73 atoms g^-1 year^-1 for Antarctica when scaled to SLHL using the LSDn scaling model. Production rates used in recent Antarctic studies, calibrated using a subset of our compilation or alternate calibration datasets, are 11-17% lower than our updated production rate. Additionally, our production rate is closer to a theoretical production rate of 15.8 atoms g^-1 year^-1 than previous calibration studies. This significant difference in production rate necessitates the recalculation of published exposure ages. In each sector of Antarctica we analyzed (Weddell, Amundsen, Ross), we find lower exposure ages corresponding to later ice thinning than discussed in the original publications–illustrating the importance of this work for interpreting glacial history in Antarctica.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9479

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.