Preprints
https://doi.org/10.5194/egusphere-2023-2549
https://doi.org/10.5194/egusphere-2023-2549
07 Dec 2023
 | 07 Dec 2023
Status: this preprint is open for discussion.

Novel approach to estimate the water isotope diffusion length in deep ice cores with an application to MIS 19 in the EPICA Dome C ice core

Fyntan Shaw, Andrew Mark Dolman, Torben Kunz, Vasileios Gkinis, and Thomas Laepple

Abstract. Accurate estimates of water isotope diffusion lengths are crucial when reconstructing and interpreting water isotope records from ice cores. This is especially true in the deepest, oldest sections of deep ice cores, where thermally enhanced diffusive processes have acted over millennia on extremely thinned ice. Previous estimation methods, used with great success in shallower, younger ice cores, falter when applied to these deep sections, as they fail to account for the statistics of the climate on millennial timescales. Here, we present a new method to estimate the diffusion length and apply it to the Marine Isotope Stage 19 (MIS 19) interglacial at the bottom of the EPICA Dome C (EDC) ice core. In contrast to the conventional estimator, our method uses other interglacial periods taken from further up in the ice core to estimate the structure of the variability before diffusion. Through use of a Bayesian framework, we are able to constrain our fit while propagating the uncertainty in our assumptions. We estimate a diffusion length of 31 ± 5 cm for the MIS 19 period, which is significantly smaller than previously estimated (40 cm–60 cm). Similar results were obtained for each interglacial used to represent the undiffused climate signal, demonstrating the robustness of our estimate. Our result suggests better preservation of the climate signal at the bottom of EDC and likely other deep ice cores, offering greater potentially recoverable temporal resolution and improved reconstructions through deconvolution.

Fyntan Shaw, Andrew Mark Dolman, Torben Kunz, Vasileios Gkinis, and Thomas Laepple

Status: open (until 30 Mar 2024)

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Fyntan Shaw, Andrew Mark Dolman, Torben Kunz, Vasileios Gkinis, and Thomas Laepple
Fyntan Shaw, Andrew Mark Dolman, Torben Kunz, Vasileios Gkinis, and Thomas Laepple

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Short summary
Water isotope diffusion poses a challenge for recovering high frequency variability from ice cores, but can be partially resolved if the diffusion length is known. We propose a new diffusion length estimation method, adapting the conventional method for deep ice. We estimate a diffusion length of 31 ± 5 cm for the deepest section of the EDC ice core, almost half that of the conventional method. Our result offers a more optimistic outlook for recovering millennial variability from deep ice cores.