Abstract
Abstract. To evaluate the impact of vapor diffusion on isotopic composition variations in snow pits and then in ice cores, we introduced water isotopes in the detailed snowpack model Crocus. At each step and for each snow layer, (1) the initial isotopic composition of vapor is taken at equilibrium with the solid phase, (2) a kinetic fractionation is applied during transport, and (3) vapor is condensed or snow is sublimated to compensate for deviation to vapor pressure at saturation. We study the different effects of temperature gradient, compaction, wind compaction, and precipitation on the final vertical isotopic profiles. We also run complete simulations of vapor diffusion along isotopic gradients and of vapor diffusion driven by temperature gradients at GRIP, Greenland and at Dome C, Antarctica over periods of 1 or 10 years. The vapor diffusion tends to smooth the original seasonal signal, with an attenuation of 7 to 12 % of the original signal over 10 years at GRIP. This is smaller than the observed attenuation in ice cores, indicating that the model attenuation due to diffusion is underestimated or that other processes, such as ventilation, influence attenuation. At Dome C, the attenuation is stronger (18 %), probably because of the lower accumulation and stronger δ18O gradients.
Highlights
The isotopic ratios of oxygen or deuterium measured in ice cores have been used for a long time to reconstruct the evolution of temperature over the Quaternary (EPICA comm. members, 2004; Johnsen et al, 1995; Jones et al, 2018; Jouzel et al, 2007; Kawamura et al, 2007; Lorius et al, 1985; Petit et al, 1999; Schneider et al, 2006; Stenni et al, 2004, 2011; Uemura et al, 2012; WAIS Divide project members, 2013)
If we compare attenuation for heights 11.46 and 11.56 m in the first and second simulation, we note that including temperature gradients leads to an increased attenuation by 50 %
Water vapor transport and water isotopes have been implemented in the Crocus snow model, enabling the depiction of the temporal δ18O variations in the top 50 cm of the snow in response to new precipitation, the evolution of the temperature gradient in the snow, and densification
Summary
The isotopic ratios of oxygen or deuterium measured in ice cores have been used for a long time to reconstruct the evolution of temperature over the Quaternary (EPICA comm. members, 2004; Johnsen et al, 1995; Jones et al, 2018; Jouzel et al, 2007; Kawamura et al, 2007; Lorius et al, 1985; Petit et al, 1999; Schneider et al, 2006; Stenni et al, 2004, 2011; Uemura et al, 2012; WAIS Divide project members, 2013). Members, 2004; Johnsen et al, 1995; Jones et al, 2018; Jouzel et al, 2007; Kawamura et al, 2007; Lorius et al, 1985; Petit et al, 1999; Schneider et al, 2006; Stenni et al, 2004, 2011; Uemura et al, 2012; WAIS Divide project members, 2013). They are, subject to alteration during post-deposition through various processes. Humidity and temperature in the region of evaporation (Landais et al, 2008; Masson-Delmotte et al, 2011) or the seasonality of precipitation
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