Layering of surface snow and firn at Kohnen Station, Antarctica: Noise or seasonal signal?

Laepple, Thomas; Hörhold, Maria; Münch, Thomas; Freitag, Johannes; Wegner, Anna; Kipfstuhl, Sepp

doi:10.1002/2016jf003919

Cited by 43 publications

(51 citation statements)

References 60 publications

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“…Table 1. Climatic conditions at the different sites used in this study (Alley, 1980;Petit et al, 1982;Wendler and Kodama, 1984;Oerter et al, 2000;Ekaykin et al, 2002;van As et al, 2007;Lazzara et al, 2012;Casey et al, 2014;Genthon et al, 2015;Touzeau et al, 2016;Laepple et al, 2016) Site Location Altitude AWS mean 10 m firn Accumulation Mean wind (m a.s.l.) temperature ( Table 2).…”

Section: Sitesmentioning

confidence: 99%

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Archival of the water stable isotope signal in East Antarctic ice cores

Casado

Landais

Picard

et al. 2016

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Abstract. The oldest ice core records are obtained from the East Antarctic plateau. Water stable isotopes records are key for reconstructions of past climatic conditions both over the ice sheet and at the evaporation source. The accuracy of such climate reconstructions crucially depends on the knowledge of all the processes affecting the water vapour, precipitation and snow isotopic composition. Atmospheric fractionation processes are well understood and can be integrated in Rayleigh distillation and complex isotope enabled climate models. However, a comprehensive quantitative understanding of processes potentially 5 altering the snow isotopic composition after the deposition is still missing, especially for exchanges between vapour and snow.In low accumulation sites such as found on the East Antarctic Plateau, these poorly constrained processes are especially likely to play a significant role. This limits the interpretation of isotopic composition from ice core records, specifically at short time scales. 10Here, we combine observations of isotopic composition in the vapour, the precipitation, the surface snow and the buried snow from various sites of the East Antarctic Plateau. At the seasonal scale, we highlight a significant impact of metamorphism on surface snow isotopic signal compared to the initial precipitation isotopic signal. In particular, in summer, exchanges of water molecules between vapour and snow are driven by the sublimation/condensation cycles at the diurnal scale. Using highly resolved isotopic composition profiles from pits in five East Antarctic sites, we identify a common 20 cm cycle which 15 cannot be attributed to the seasonal variability of precipitation. Altogether, the smaller range of isotopic compositions observed in the buried and in the surface snow compared to the precipitation, and also the reduced slope between surface snow isotopic composition and temperature compared to precipitation, constitute evidences of post-deposition processes affecting the variability of the isotopic composition in the snow pack. To reproduce these processes in snow-models is crucial to understand the link between snow isotopic composition and climatic conditions and to improve the interpretation of isotopic composition as a 20 paleoclimate proxy.

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Section: Sitesmentioning

confidence: 99%

“…can be attributed to the mixture of the potential climate signal and non-climate noise (Fisher et al, 1985;Münch et al, 2016;Laepple et al, 2016).…”

mentioning

confidence: 99%

Archival of the water stable isotope signal in East Antarctic ice cores

Casado

Landais

Picard

et al. 2016

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…Table 1. Climatic conditions at the different sites used in this study (Alley, 1980;Petit et al, 1982;Wendler and Kodama, 1984;Oerter et al, 2000;Ekaykin et al, 2002;van As et al, 2007;Lazzara et al, 2012;Casey et al, 2014;Genthon et al, 2015;Touzeau et al, 2016;Laepple et al, 2016) Site Table 2). Because different teams were in charge of the different sampling activities, the protocols differ between the years.…”

Section: Sitementioning

confidence: 99%

“…Yet, the profiles are highly variable, exhibiting strong differences in between sites and as well as in between pits from a single site, even if sampled the same year. This can be attributed to the mixture of the potential climate signal and non-climate noise (Fisher et al, 1985; Laepple et al, 2016). Here, when we compare several snow pits dug the same year at the same sites (for instance at Kohnen as presented on Fig.…”

mentioning

confidence: 99%

Archival processes of the water stable isotope signal in East Antarctic ice cores

Casado¹,

Landais²,

Picard³

et al. 2017

Preprint

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Abstract. The oldest ice core records are obtained from the East Antarctic plateau. Water isotopes records are key to reconstructing past climatic conditions over the ice sheet and at the evaporation source. The accuracy of climate reconstructions depends on knowledge of all the processes affecting water vapour, precipitation and snow isotopic compositions. Fractionation processes are well understood and can be integrated in Rayleigh distillation and isotope enabled climate models. However, a quantitative understanding of processes potentially altering the snow isotopic composition after the deposition is still missing. 5In low accumulation sites, such as those found in Antarctica, these poorly constrained processes are likely to play a significant role and limit the interpretation of isotopic composition.Here, we combine observations of isotopic composition in the vapour, the precipitation, the surface snow and the buried snow from Dome C, a deep ice core site on the East Antarctic Plateau. At the seasonal scale, we suggest a significant impact of 10 metamorphism on surface snow isotopic signal compared to the initial precipitation signal. Particularly, in summer, exchanges of water molecules between vapour and snow are driven by the sublimation/condensation cycles at the diurnal scale. Using highly resolved isotopic composition profiles from pits in five Antarctic sites, we identify common patterns, despite different accumulation rates, which cannot be attributed to the seasonal variability of precipitation. Altogether, the difference in the signals observed in the precipitation, surface snow and buried snow isotopic composition constitute evidences of post-deposition 15 processes affecting ice core records in low accumulation areas. 1The Cryosphere Discuss., https://doi

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“…To quantify these effects, certain site-specific parameters have to be known. Firn densities are provided independently of the trench data by high-resolution X-ray Computer Tomography data (Freitag et al, 2013a) of the firn cores B41 and B42 (core distance ∼ 10 m, Laepple et al, 2016) drilled in vicinity to the trenches (∼ 1 km, Fig. 2).…”

Section: Quantification Of Downward Advection Firn Densification Andmentioning

confidence: 99%

Constraints on post-depositional isotope modifications in East Antarctic firn from analysing temporal changes of isotope profiles

et al. 2017

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Abstract. The isotopic composition of water in ice sheets is extensively used to infer past climate changes. In lowaccumulation regions their interpretation is, however, challenged by poorly constrained effects that may influence the initial isotope signal during and after deposition of the snow. This is reflected in snow-pit isotope data from Kohnen Station, Antarctica, which exhibit a seasonal cycle but also strong interannual variations that contradict local temperature observations. These inconsistencies persist even after averaging many profiles and are thus not explained by local stratigraphic noise. Previous studies have suggested that post-depositional processes may significantly influence the isotopic composition of East Antarctic firn. Here, we investigate the importance of post-depositional processes within the open-porous firn ( 10 cm depth) at Kohnen Station by separating spatial from temporal variability. To this end, we analyse 22 isotope profiles obtained from two snow trenches and examine the temporal isotope modifications by comparing the new data with published trench data extracted 2 years earlier. The initial isotope profiles undergo changes over time due to downward advection, firn diffusion and densification in magnitudes consistent with independent estimates. Beyond that, we find further modifications of the original isotope record to be unlikely or small in magnitude ( 1 ‰ RMSD). These results show that the discrepancy between local temperatures and isotopes most likely originates from spatially coherent processes prior to or during deposition, such as precipitation intermittency or systematic isotope modifications acting on drifting or loose surface snow.

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Layering of surface snow and firn at Kohnen Station, Antarctica: Noise or seasonal signal?

Cited by 43 publications

References 60 publications

Archival of the water stable isotope signal in East Antarctic ice cores

Archival of the water stable isotope signal in East Antarctic ice cores

Archival processes of the water stable isotope signal in East Antarctic ice cores

Constraints on post-depositional isotope modifications in East Antarctic firn from analysing temporal changes of isotope profiles

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