Continuous synchronization of the Greenland ice-core and U-Th timescales using probabilistic inversion
This study presents the first continuously measured transfer function that quantifies the age difference between the Greenland Ice-Core Chronology 2005 (GICC05) and the U-Th timescale during the last glacial period. The transfer function was estimated using an automated algorithm for Bayesian invers...
| Main Authors: | , |
|---|---|
| Format: | Text |
| Language: | English |
| Published: |
2023
|
| Subjects: | |
| Online Access: | https://doi.org/10.5194/cp-2023-65 https://cp.copernicus.org/preprints/cp-2023-65/ |
| Summary: | This study presents the first continuously measured transfer function that quantifies the age difference between the Greenland Ice-Core Chronology 2005 (GICC05) and the U-Th timescale during the last glacial period. The transfer function was estimated using an automated algorithm for Bayesian inversion that allows inferring a continuous and objective synchronization between Greenland ice-core and East Asia Summer Monsoon speleothem data. The algorithm is based on an alignment model that considers prior knowledge on the GICC05 counting error, but also samples synchronization scenarios that exceed the differential dating uncertainty of the annual-layer count in ice cores, which are currently not detectable using conventional alignments techniques. The transfer function is on average 52 % more precise than previous estimates and significantly reduces the absolute dating uncertainty of the GICC05 back to 48 kyr ago. The results reveal that GICCC05 is, on average, systematically younger than the U-Th timescale by 0.97 %. However, they also highlight that the annual-layer counting error is not strictly correlated over extended periods of time, and that within the coldest Greenland Stadials the differential dating uncertainty is likely underestimated by ~10–15 %. Importantly, the analysis implies for the first time that during the Last Glacial Maximum GICC05 overcounts ice layers by ~15 % –a bias attributable to a higher frequency of sub-annual layers due to changes in the seasonal cycle of precipitation and mode of dust deposition to the Greenland Ice Sheet. The new timescale transfer function provides important constraints on the uncertainty surrounding the stratigraphic dating of the Greenland age-scale and enables an improved chronological integration of ice cores, U-Th-dated and radiocarbon-dated paleoclimate records on a common timeline. The transfer function is available as supplements to this study. |
|---|