TY - JOUR

T1 - Numerical experiments on firn isotope diffusion with the Community Firn Model

AU - Gkinis, Vasileios

AU - Holme, Christian

AU - Kahle, Emma C.

AU - Stevens, Max C.

AU - Steig, Eric J.

AU - Vinther, Bo M.

PY - 2021/6/1

Y1 - 2021/6/1

N2 - Advances in analytical methods have made it possible to obtain high-resolution water isotopic data from ice cores. Their spectral signature contains information on the diffusion process that attenuated the isotopic signal during the firn densification process. Here, we provide a tool for estimating firn-diffusion rates that builds on the Community Firn Model. Our model requires two main inputs, temperature and accumulation, and it calculates the diffusion lengths for delta O-17, delta O-18 and delta D. Prior information on the isotopic signal of the precipitation is not a requirement. In combination with deconvolution techniques, diffusion lengths can be used in order reconstruct the pre-diffusion isotopic signal. Furthermore, the temperature dependence of the isotope diffusion and firn densification makes the diffusion length an interesting candidate as a temperature proxy. We test the model under steady state and transient scenarios and compare four densification models. Comparisons with ice core data provide an evaluation of the four models and indicate that there are differences in their performance. Combining data-based diffusion length estimates with information on past accumulation rates and ice flow thinning, we reconstruct absolute temperatures from three Antarctic ice core sites.

AB - Advances in analytical methods have made it possible to obtain high-resolution water isotopic data from ice cores. Their spectral signature contains information on the diffusion process that attenuated the isotopic signal during the firn densification process. Here, we provide a tool for estimating firn-diffusion rates that builds on the Community Firn Model. Our model requires two main inputs, temperature and accumulation, and it calculates the diffusion lengths for delta O-17, delta O-18 and delta D. Prior information on the isotopic signal of the precipitation is not a requirement. In combination with deconvolution techniques, diffusion lengths can be used in order reconstruct the pre-diffusion isotopic signal. Furthermore, the temperature dependence of the isotope diffusion and firn densification makes the diffusion length an interesting candidate as a temperature proxy. We test the model under steady state and transient scenarios and compare four densification models. Comparisons with ice core data provide an evaluation of the four models and indicate that there are differences in their performance. Combining data-based diffusion length estimates with information on past accumulation rates and ice flow thinning, we reconstruct absolute temperatures from three Antarctic ice core sites.

KW - Glaciological model experiments

KW - ice and climate

KW - ice core

KW - ice temperature

KW - polar firn

KW - STABLE WATER ISOTOPES

KW - CONTINUOUS-FLOW ANALYSIS

KW - DRONNING MAUD LAND

KW - ICE-CORE

KW - POLAR FIRN

KW - DOME C

KW - TEMPERATURE

KW - FRACTIONATION

KW - RECORDS

KW - DENSIFICATION

U2 - 10.1017/jog.2021.1

DO - 10.1017/jog.2021.1

M3 - Journal article

VL - 67

SP - 450

EP - 472

JO - Journal of Glaciology

JF - Journal of Glaciology

SN - 0022-1430

IS - 263

ER -