diffusion.length: Diffusion lengths

In EarthSystemDiagnostics/proxysnr: Separate Signal and Noise in Climate Proxy Records

Diffusion lengths

Description

A dataset containing calculated diffusion lengths for all firn-core sites used in Münch and Laepple (2018). The diffusion lengths are provided as a function of firn-core age at semi-annual resolution and in units of years.

Usage

diffusion.length

Format

A list with 3 elements:

dml1:

a data frame with 338 rows and 16 variables:

Time:

age of the firn core, in yr

columns "B31"-"FB9817":

15 columns with 338 rows with diffusion lengths corresponding to the firn-core ages in Time, in yr

dml2:

a data frame with 1990 rows and 4 variables:

Time:

age of the firn core, in yr

columns "B31"-"B33":

3 columns with 1990 rows with diffusion lengths corresponding to the firn-core ages in Time, in yr

wais:

a data frame with 402 rows and 6 variables:

Time:

age of the firn core, in yr

columns "WDC2005A"-"ITASE-2000-5":

5 columns with 402 rows with diffusion lengths corresponding to the firn-core ages in Time, in yr

Details

Diffusion lengths as a function of firn-core depth are calculated from Eq. (8) in Gkinis et al. (2014); firn diffusivity is modelled following Eqs. (17-19) in Johnsen et al. (2000), firn density with the Herron–Langway model (Herron and Langway, 1980; Eqs. 7 and 10). For the surface firn density we assume a constant value of 340 kg/m^3 for all sites, for all other relevant site parameters, see ?clim.site.par. The depth-dependent diffusion length values are converted into units of yr using the Herron-Langway firn density with a constant accumulation rate, related to the firn-core age and then linearly interpolated onto an equidistant time axis at semi-annual resolution. All steps are documented in the package source (data-raw/calculate-diffusion-length.R).

References

Gkinis, V., et al.: Water isotope diffusion rates from the North-GRIP ice core for the last 16,000 years – Glaciological and paleoclimatic implications, Earth Planet. Sci. Lett., 405, 132–141, https://doi.org/10.1016/j.epsl.2014.08.022, 2014.

Herron, M. M. and Langway, Jr., C. C.: Firn Densification: An Empirical Model, J. Glaciol., 25(95), 373–385, https://doi.org/10.3189/S0022143000015239, 1980.

Johnsen, S. J., et al.: Diffusion of stable isotopes in polar firn and ice: the isotope effect in firn diffusion, in: Physics of Ice Core Records, edited by Hondoh, T., vol. 159, pp. 121–140, Hokkaido University Press, Sapporo, Japan, 2000.

Münch, T. and Laepple, T.: What climate signal is contained in decadal- to centennial-scale isotope variations from Antarctic ice cores? Clim. Past, 14, 2053–2070, https://doi.org/10.5194/cp-14-2053-2018, 2018.

EarthSystemDiagnostics/proxysnr documentation built on Sept. 15, 2024, 7:47 a.m.