Marine radiocarbon calibration in polar regions: a simple approximate approach using Marine20
The Marine20 radiocarbon (14C) age calibration curve, and all earlier marine 14C calibration curves from the IntCal group, must be used extremely cautiously for the calibration of marine 14C samples from polar regions (outside ∼ 40ºS–40ºN) during glacial periods. Calibrating polar 14C marine samples...
| Main Authors: | , , , , , , |
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| Format: | Journal article |
| Language: | English |
| Published: |
Cambridge University Press
2023
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| _version_ | 1797110969469501440 |
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| author | Heaton, TJ Butzin, M Bard, E Bronk Ramsey, C Hughen, KA Köhler, P Reimer, PJ |
| author_facet | Heaton, TJ Butzin, M Bard, E Bronk Ramsey, C Hughen, KA Köhler, P Reimer, PJ |
| author_sort | Heaton, TJ |
| collection | OXFORD |
| description | The Marine20 radiocarbon (14C) age calibration curve, and all earlier marine 14C calibration curves from the IntCal group, must be used extremely cautiously for the calibration of marine 14C samples from polar regions (outside ∼ 40ºS–40ºN) during glacial periods. Calibrating polar 14C marine samples from glacial periods against any Marine calibration curve (Marine20 or any earlier product) using an estimate of ΔR, the regional 14C depletion adjustment, that has been obtained from samples in the recent (non-glacial) past is likely to lead to bias and overconfidence in the calibrated age. We propose an approach to calibration that aims to address this by accounting for the possibility of additional, localized, glacial 14C depletion in polar oceans. We suggest, for a specific polar location, bounds on the value of ΔR20(θ) during a glacial period. The lower bound ΔR Hol 20 may be based on 14C samples from the recent non-glacial (Holocene) past and corresponds to a low-depletion glacial scenario. The upper bound, ΔR, representing a high-depletion scenario is found by increasing ΔR Hol 20 according to the latitude of the 14C sample to be calibrated. The suggested increases to obtain are based upon simulations of the Hamburg Large Scale Geostrophic Ocean General Circulation Model (LSG OGCM). Calibrating against the Marine20 curve using the upper and lower ΔR 20 bounds provide estimates of calibrated ages for glacial 14C samples in high- and low-depletion scenarios which should bracket the true calendar age of the sample. In some circumstances, users may be able to determine which depletion scenario is more appropriate using independent paleoclimatic or proxy evidence. |
| first_indexed | 2024-03-07T08:03:36Z |
| format | Journal article |
| id | oxford-uuid:6ec1a660-bad9-4dc9-a318-e5301c97914e |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T08:03:36Z |
| publishDate | 2023 |
| publisher | Cambridge University Press |
| record_format | dspace |
| spelling | oxford-uuid:6ec1a660-bad9-4dc9-a318-e5301c97914e2023-10-12T09:17:39ZMarine radiocarbon calibration in polar regions: a simple approximate approach using Marine20Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:6ec1a660-bad9-4dc9-a318-e5301c97914eEnglishSymplectic ElementsCambridge University Press2023Heaton, TJButzin, MBard, EBronk Ramsey, CHughen, KAKöhler, PReimer, PJThe Marine20 radiocarbon (14C) age calibration curve, and all earlier marine 14C calibration curves from the IntCal group, must be used extremely cautiously for the calibration of marine 14C samples from polar regions (outside ∼ 40ºS–40ºN) during glacial periods. Calibrating polar 14C marine samples from glacial periods against any Marine calibration curve (Marine20 or any earlier product) using an estimate of ΔR, the regional 14C depletion adjustment, that has been obtained from samples in the recent (non-glacial) past is likely to lead to bias and overconfidence in the calibrated age. We propose an approach to calibration that aims to address this by accounting for the possibility of additional, localized, glacial 14C depletion in polar oceans. We suggest, for a specific polar location, bounds on the value of ΔR20(θ) during a glacial period. The lower bound ΔR Hol 20 may be based on 14C samples from the recent non-glacial (Holocene) past and corresponds to a low-depletion glacial scenario. The upper bound, ΔR, representing a high-depletion scenario is found by increasing ΔR Hol 20 according to the latitude of the 14C sample to be calibrated. The suggested increases to obtain are based upon simulations of the Hamburg Large Scale Geostrophic Ocean General Circulation Model (LSG OGCM). Calibrating against the Marine20 curve using the upper and lower ΔR 20 bounds provide estimates of calibrated ages for glacial 14C samples in high- and low-depletion scenarios which should bracket the true calendar age of the sample. In some circumstances, users may be able to determine which depletion scenario is more appropriate using independent paleoclimatic or proxy evidence. |
| spellingShingle | Heaton, TJ Butzin, M Bard, E Bronk Ramsey, C Hughen, KA Köhler, P Reimer, PJ Marine radiocarbon calibration in polar regions: a simple approximate approach using Marine20 |
| title | Marine radiocarbon calibration in polar regions: a simple approximate approach using Marine20 |
| title_full | Marine radiocarbon calibration in polar regions: a simple approximate approach using Marine20 |
| title_fullStr | Marine radiocarbon calibration in polar regions: a simple approximate approach using Marine20 |
| title_full_unstemmed | Marine radiocarbon calibration in polar regions: a simple approximate approach using Marine20 |
| title_short | Marine radiocarbon calibration in polar regions: a simple approximate approach using Marine20 |
| title_sort | marine radiocarbon calibration in polar regions a simple approximate approach using marine20 |
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