气候变化领域集成服务门户(CCPortal): On the similarity and apparent cycles of isotopic variations in East Antarctic snow pits

CCPortal

DOI	10.5194/tc-12-169-2018
	On the similarity and apparent cycles of isotopic variations in East Antarctic snow pits
	Laepple T.; Münch T.; Casado M.; Hoerhold M.; Landais A.; Kipfstuhl S.
发表日期	2018
ISSN	19940416
卷号	12 期号:1
英文摘要	Stable isotope ratios δ18O and δD in polar ice provide a wealth of information about past climate evolution. Snow-pit studies allow us to relate observed weather and climate conditions to the measured isotope variations in the snow. They therefore offer the possibility to test our understanding of how isotope signals are formed and stored in firn and ice. As δ18O and δD in the snowfall are strongly correlated to air temperature, isotopes in the near-surface snow are thought to record the seasonal cycle at a given site. Accordingly, the number of seasonal cycles observed over a given depth should depend on the accumulation rate of snow. However, snow-pit studies from different accumulation conditions in East Antarctica reported similar isotopic variability and comparable apparent cycles in the δ18O and δD profiles with typical wavelengths of ∼ 20cm. These observations are unexpected as the accumulation rates strongly differ between the sites, ranging from 20 to 80mmĝ€†w. e. ĝ€†yr-1 ( ∼ 6-21cm of snow per year). Various mechanisms have been proposed to explain the isotopic variations individually at each site; however, none of these are consistent with the similarity of the different profiles independent of the local accumulation conditions.Here, we systematically analyse the properties and origins of δ18O and δD variations in high-resolution firn profiles from eight East Antarctic sites. First, we confirm the suggested cycle length (mean distance between peaks) of ∼ 20cm by counting the isotopic maxima. Spectral analysis further shows a strong similarity between the sites but indicates no dominant periodic features. Furthermore, the apparent cycle length increases with depth for most East Antarctic sites, which is inconsistent with burial and compression of a regular seasonal cycle. We show that these results can be explained by isotopic diffusion acting on a noise-dominated isotope signal. The firn diffusion length is rather stable across the Antarctic Plateau and thus leads to similar power spectral densities of the isotopic variations. This in turn implies a similar distance between isotopic maxima in the firn profiles.Our results explain a large set of observations discussed in the literature, providing a simple explanation for the interpretation of apparent cycles in shallow isotope records, without invoking complex mechanisms. Finally, the results underline previous suggestions that isotope signals in single ice cores from low-accumulation regions have a small signal-to-noise ratio and thus likely do not allow the reconstruction of interannual to decadal climate variations. © Author(s) 2018.
学科领域	climate conditions; firn; ice core; isotopic analysis; paleoclimate; reconstruction; seasonal variation; signal-to-noise ratio; snow accumulation; spectral analysis; stable isotope; Antarctic Plateau; Antarctica; East Antarctica
语种	英语
scopus关键词	climate conditions; firn; ice core; isotopic analysis; paleoclimate; reconstruction; seasonal variation; signal-to-noise ratio; snow accumulation; spectral analysis; stable isotope; Antarctic Plateau; Antarctica; East Antarctica
来源期刊	Cryosphere
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/119236
作者单位	Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Telegrafenberg A43, Potsdam, 14473, Germany; Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, Potsdam, 14476, Germany; Laboratoire des Sciences du Climat et de l'Environnement - IPSL, UMR 8212, CEA-CNRS-UVSQ, Gif-sur-Yvette, France; Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 26, Bremerhaven, 27568, Germany
推荐引用方式 GB/T 7714	Laepple T.,Münch T.,Casado M.,et al. On the similarity and apparent cycles of isotopic variations in East Antarctic snow pits[J],2018,12(1).
APA	Laepple T.,Münch T.,Casado M.,Hoerhold M.,Landais A.,&Kipfstuhl S..(2018).On the similarity and apparent cycles of isotopic variations in East Antarctic snow pits.Cryosphere,12(1).
MLA	Laepple T.,et al."On the similarity and apparent cycles of isotopic variations in East Antarctic snow pits".Cryosphere 12.1(2018).