气候变化领域集成服务门户(CCPortal): Firn microstructure in the lock-in zone for three polar ice cores

CCPortal

DOI	https://doi.org/10.1594/PANGAEA.879577
	Firn microstructure in the lock-in zone for three polar ice cores
	Schaller; Christoph Florian; Freitag; Johannes; Eisen; Olaf
发布日期	2017-08-14
数据集类型	dataset
英文简介	In order to interpret the paleoclimatic record stored in the air enclosed in polar ice cores, it is crucial to understand the fundamental lock-in process. Within the porous firn, bubbles are sealed continuously until the respective horizontal layer reaches a critical porosity. Present-day firn models use a postulated temperature dependence of this value as the only parameter to adjust to the surrounding conditions of individual sites. However, no direct measurements of the firn microstructure could confirm these assumptions. Here we show that the critical porosity is a universal constant by providing a statistically solid data set of µm-resolution 3D X-ray computer tomographic measurements for ice cores representing different extremes of the temperature and accumulation ranges. We demonstrate why indirect measurements yield misleading data and substantiate our observations by applying percolation theory as a theoretical framework for bubble trapping. Incorporation of our results does significantly influence the dating of trace gas records, changing gas age-ice age differences by up to more than 1000 years. This will help resolve inconsistencies, such as differences between East Antarctic d15N records (as a proxy for firn height) and model results. We expect our findings to be the basis for improved firn air and densification models, leading to lower dating uncertainties. The reduced coupling of proxies and surrounding conditions may allow for more sophisticated reinterpretations of trace gas records in terms of paleoclimatic changes and will foster the development of new proxies, such as the air content as a marker of local insolation.
空间范围	Median Latitude: -33.988802 * Median Longitude: 21.371651 * South-bound Latitude: -76.790000 * West-bound Longitude: 0.220000 * North-bound Latitude: 71.304194 * East-bound Longitude: 31.910000
时间范围	2013-01-15T00:00:00 - 2015-05-15T00:00:00
语种	英语
国家	国际
学科大类	气候变化
学科子类	气候变化
文献类型	数据集
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/215307
推荐引用方式 GB/T 7714	Schaller,Christoph Florian,Freitag,et al. Firn microstructure in the lock-in zone for three polar ice cores.2017-08-14.https://doi.org/10.1594/PANGAEA.879577.