气候变化领域集成服务门户(CCPortal): Radiocarbon dating of alpine ice cores with the dissolved organic carbon (DOC) fraction

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DOI	10.5194/tc-15-1537-2021
	Radiocarbon dating of alpine ice cores with the dissolved organic carbon (DOC) fraction
	Fang L.; Jenk T.M.; Singer T.; Hou S.; Schwikowski M.
发表日期	2021
ISSN	19940416
起始页码	1537
结束页码	1550
卷号	15 期号:3
英文摘要	High-Alpine glaciers are valuable archives of past climatic and environmental conditions. The interpretation of the preserved signal requires a precise chronology. Radio carbon (14C) dating of the water-insoluble organic carbon (WIOC) fraction has become an important dating tool to con strain the age of ice cores from mid-latitude and low-latitude glaciers. However, in some cases this method is restricted by the low WIOC concentration in the ice. In this work, we report first 14C dating results using the dissolved organic car bon (DOC) fraction, which is present at concentrations of at least a factor of 2 higher than the WIOC fraction. We eval uated this new approach by comparison to the established WIO14C dating based on parallel ice core sample sections from four different Eurasian glaciers covering an age range of several hundred to around 20 000 years; 14C dating of the two fractions yielded comparable ages, with WIO14C re vealing a slight, barely significant, systematic offset towards older ages comparable in magnitude with the analytical un certainty. We attribute this offset to two effects of about equal size but opposite in direction: (i) in-situ-produced 14C con tributing to the DOC resulting in a bias towards younger ages and (ii) incompletely removed carbonates from particulate mineral dust (14C-depleted) contributing to the WIOC frac tion with a bias towards older ages. The estimated amount of in-situ-produced 14C in the DOC fraction is smaller than the analytical uncertainty for most samples. Nevertheless, under extreme conditions, such as very high altitude and/or low snow accumulation rates, DO14C dating results need to be interpreted cautiously. While during DOC extraction the removal of inorganic carbon is monitored for completeness, the removal for WIOC samples was so far only assumed to be quantitative, at least for ice samples containing average levels of mineral dust. Here we estimated an average removal effi ciency of 98 ± 2 %, resulting in a small offset of the order of the current analytical uncertainty. Future optimization of the removal procedure has the potential to improve the accuracy and precision of WIO14C dating. With this study we demon strate that using the DOC fraction for 14C dating not only is a valuable alternative to the use of WIOC but also ben efits from a reduced required ice mass of typically ∼ 250 g to achieve comparable precision of around ±200 years. This approach thus has the potential of pushing radiocarbon dat ing of ice forward even to remote regions where the carbon content in the ice is particularly low. © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License.
英文关键词	alpine environment; dissolved organic carbon; fractionation; geochronology; ice core; radiocarbon dating
语种	英语
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/202302
作者单位	Laboratory for Environmental Chemistry, Paul Scherrer Institute, Villigen, PSI 5232, Switzerland; Department of Chemistry and Biochemistry, University of Bern, Bern, 3012, Switzerland; Oeschger Centre for Climate Change Research, University of Bern, Bern, 3012, Switzerland; School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing, 210023, China; School of Oceanography, Shanghai Jiao Tong University, Shanghai, 200240, China
推荐引用方式 GB/T 7714	Fang L.,Jenk T.M.,Singer T.,et al. Radiocarbon dating of alpine ice cores with the dissolved organic carbon (DOC) fraction[J],2021,15(3).
APA	Fang L.,Jenk T.M.,Singer T.,Hou S.,&Schwikowski M..(2021).Radiocarbon dating of alpine ice cores with the dissolved organic carbon (DOC) fraction.Cryosphere,15(3).
MLA	Fang L.,et al."Radiocarbon dating of alpine ice cores with the dissolved organic carbon (DOC) fraction".Cryosphere 15.3(2021).