Abstract
The concentration of radiocarbon (14C) differs between ocean and atmosphere. Radiocarbon determinations from samples which obtained their 14C
in the marine environment therefore need a marine-specific calibration
curve and cannot be calibrated directly against the atmospheric-based
IntCal20 curve. This paper presents Marine20, an update to the
internationally agreed marine radiocarbon age calibration curve that
provides a non-polar global-average marine record of radiocarbon from
0–55 cal kBP and serves as a baseline for regional oceanic variation.
Marine20 is intended for calibration of marine radiocarbon samples from
non-polar regions; it is not suitable for calibration in polar regions
where variability in sea ice extent, ocean upwelling and air-sea gas
exchange may have caused larger changes to concentrations of marine
radiocarbon. The Marine20 curve is based upon 500 simulations with an
ocean/atmosphere/biosphere box-model of the global carbon cycle that has
been forced by posterior realizations of our Northern Hemispheric
atmospheric IntCal20 14C curve and reconstructed changes in CO2
obtained from ice core data. These forcings enable us to incorporate
carbon cycle dynamics and temporal changes in the atmospheric 14C
level. The box-model simulations of the global-average marine
radiocarbon reservoir age are similar to those of a more complex
three-dimensional ocean general circulation model. However, simplicity
and speed of the box model allow us to use a Monte Carlo approach to
rigorously propagate the uncertainty in both the historic concentration
of atmospheric 14C and other key parameters of
the carbon cycle through to our final Marine20 calibration curve. This
robust propagation of uncertainty is fundamental to providing reliable
precision for the radiocarbon age calibration of marine based samples.
We make a first step towards deconvolving the contributions of different
processes to the total uncertainty; discuss the main differences of
Marine20 from the previous age calibration curve Marine13; and identify
the limitations of our approach together with key areas for further
work. The updated values for ΔR, the
regional marine radiocarbon reservoir age corrections required to
calibrate against Marine20, can be found at the data base http://calib.org/marine/.
Original language | English |
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Pages (from-to) | 779-820 |
Number of pages | 42 |
Journal | Radiocarbon |
Volume | 62 |
Issue number | 4 |
Early online date | 12 Aug 2020 |
DOIs | |
Publication status | Published - 31 Aug 2020 |
Keywords
- Bayesian modeling
- Calibration
- Carbon cycle
- Computer model
- Marine environment
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Marine20 --- the marine radiocarbon age calibration curve (0 – 55,000 cal BP) (dataset)
Austin, W. (Creator) & Burke, A. (Creator), Marine Reservoir Correction, 2020
Dataset