Mathieu Daëron
Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay
Corresponding Author:[email protected]
Author ProfileAbstract
Clumped-isotope measurements in CO2 and carbonates (Δ47) present a
number of technical challenges and require correcting for various
sources of analytical non-linearity. For now we lack a formal
description of the analytical errors associated with these correction
steps, which are not accounted for in most data processing methods
currently in use. Here we formulate a quantitative description of Δ47
error propagation, fully taking into account standardization errors and
their properties. We find that standardization errors are highly
sensitive to the isotopic compositions (δ47, Δ47) of unknown samples
relative to the standards used for analytical corrections, and in many
cases constitute a non-negligible source of uncertainty, causing true
measurements errors to exceed traditionally reported error estimates by
a factor of 1.5 (typically) to 3.5 (in extreme cases). Using Monte Carlo
simulations based on the full InterCarb data set, we find that this
model yields accurate error estimates in spite of small non-Gaussian
effects which remain entirely negligible in practice. We also describe
various standardization strategies, along with the assumptions they rely
on, in the context of this model, and propose a new, “pooled”
standardization approach designed to yield more robust/accurate
corrections. Among other uses, the mathematical framework described here
may be helpful to improve standardization protocols (e.g.,
anchor/unknown ratios) and inform future efforts to define community
reference materials. What’s more, these models imply that the
inter-laboratory scatter (N = 5329) observed in the InterCarb exercise
[Bernasconi et al., 2021] can be entirely explained as the effects
of current standardization procedures. Based on these findings, we
recommend that future studies systematically report full analytical
uncertainties taking standardization errors into account. In line with
this recommendation, we provide user-friendly online resources and an
open-source Python library designed to facilitate the use of these error
models.