Abstract
Abstract. The isotopic signal (δ18O and δD) imprinted in ice cores from Antarctica is not solely generated by the temperature sensitivity of the isotopic composition of precipitation, but it also contains the signature of the intermittency of the precipitation patterns, as well as of post-deposition processes occurring at the surface and in the firn. This leads to a proxy signal recorded by the ice cores that may not be representative of the local climate variations. Due to precipitation intermittency, the ice cores only record brief snapshots of the climatic conditions, resulting in aliasing of the climatic signal and thus a large amount of noise which reduces the minimum temporal resolution at which a meaningful signal can be retrieved. The analyses are further complicated by isotopic diffusion, which acts as a low-pass filter that dampens any high-frequency changes. Here, we use reanalysis data (ERA-Interim) combined with satellite products of accumulation to evaluate the spatial distribution of the numerical estimates of the transfer function that describes the formation of the isotopic signal across Antarctica. As a result, the minimum timescales at which the signal-to-noise ratio exceeds unity range from less than 1 year at the coast to about 1000 years further inland. Based on solely physical processes, we are thus able to define a lower bound for the timescales at which climate variability can be reconstructed from the isotopic composition in ice cores.
Highlights
Ice cores are key archives of past climatic conditions (Jouzel and Masson-Delmotte, 2010, and references therein) as a wide range of climatic parameters are recorded in the physical and chemical composition of the ice itself and of the air bubbles trapped within
What is the theoretical lower limit for the timescale at which a meaningful climatic signal can still be reconstructed from water isotopes in ice cores? Here, we present two simple modelling approaches involving virtual ice cores to identify the minimum resolution at which a climatic signal can be retrieved from the snow’s isotopic composition in Antarctica at a predefined level of quality
A first virtual core is generated for the pure climatic signal (Fig. 2b) which corresponds to a perfect record as each day is archived and no information is lost
Summary
Ice cores are key archives of past climatic conditions (Jouzel and Masson-Delmotte, 2010, and references therein) as a wide range of climatic parameters are recorded in the physical and chemical composition of the ice itself and of the air bubbles trapped within. Antarctic ice cores have been used to reconstruct continuous high-resolution temperature time series dating back 800 000 years (Petit et al, 1999; EPICA Community Members, 2004; Kawamura et al, 2017). Ice cores from high accumulation areas such as coastal Antarctica (Morgan, 1985; Masson-Delmotte et al, 2003; Küttel et al, 2012; Vega et al, 2016; Caiazzo et al, 2017; Goursaud et al, 2018) and West Antarctica (Markle et al, 2017) could be used to achieve up to seasonal resolution in temperature reconstructions, while ice cores from low Published by Copernicus Publications on behalf of the European Geosciences Union
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