Methods and codes for reservoir-atmosphere C-14 age offset calculations

Reservoir C-14 age offsets are invaluable tracers for past changes in carbon cycle and oceanic circulation. Reconstruction of reservoir age offsets with time is also required for calibration purposes (reconstruction of atmospheric calibration curve, calibration of non-atmospheric radiocarbon ages). Thus, properly propagating the various uncertainties linked to reservoir age offset is important for proper interpretation. However, approaches for reservoir age offset calculation especially when considering pairs of reservoir-derived C-14 and calenidar ages are usually not detailed and inadequate for proper propagation of uncertainties. Here, the various ways to properly calculate reservoir age offsets are described with a focus on a new approach when considering pairs of C-14 and calendar ages. This approach maps the calendar age distribution onto the C-14 time scale prior to reservoir age offset calculation the ``uncalibration-convolution process{''}. R codes computing reservoir age offsets based on available data are presented. Finally, a case study focusing on the reconstruction of the speleothem-atmosphere C-14 age offsets of speleothem C-14 data used in the latest release of the atmospheric calibration curve is discussed. (C) 2015 Elsevier B.V. All rights reserved.