Tracing paleo-permafrost with meteoric 10Be and in-situ 26Al/10Be - A proof of concept

确定覆盖西伯利亚东北部的厚含碳永久冻土的过去热状态对于理解上新世-更新世的碳封存、长期气候冷却和限制未来碳库释放的潜力至关重要。该项目将开发和应用一种新型的大气铍-10 （10Be）技术，与原位铝-26/铍-10 （26Al/10Be）计时器相结合，以确定西伯利亚北极地区El 'gygytgyn撞击坑内从上新世中期撞击到今天的永久冻土的热历史。这些结果不仅可以提供2008年钻取的141米岩心下部的年表，因为没有其他年龄控制，而且还可以通过使用最近开发的等时线方法来解释沉积物中的26Al/10Be比率，从而更好地了解冻土堆积的速度和类型。在这里，我们试图以一种新的方式使用一种已知的地球化学示踪剂，它提供了来自降水（大气）10Be的土壤热状态记录。冻结时，土壤不会形成大气中的二氧化碳；解冻后，10Be通过活动层迁移。我们的研究将调查使用这种同位素示踪剂来确定自沉积以来土壤经历解冻条件的相对持续时间。当这些信息与El 'gygytgyn湖岩心的气候代用物联系起来时，将得出过去温度与永久冻土融化深度之间的关键联系，并在预期的全球变暖背景下，为过去的冷暖事件对永久冻土产生和维持的影响提供现实的限制条件。该方法可以推广到其他北极地区，以确定其他碳库的历史和命运。

Determining the past thermal regime of thick carbon-bearing permafrost soil blanketing northeastern Siberia is critical for understanding Plio-Pleistocene carbon sequestration, longterm climate cooling and constraining the potential for release of this pool of stored carbon in the future. This project will develop and apply a novel meteoric Beryllium-10 (10Be) technique in concert with the in-situ Aluminum-26/Beryllium-10 (26Al/10Be) chronometer in order to determine the thermal history of permafrost within the El’gygytgyn impact crater in the Siberian Arctic from time of the mid-Pliocene impact to today. The results will provide not only a chronology within the lower parts of the 141 m core drilled in 2008 where no other age control exists, but will also allow a better understanding of the rate and style of frozen ground build-up by using a recently developed isochron method for interpreting 26Al/10Be ratios in sediments. Here, we attempt to use a known geochemical tracer in a new way, which provides a record of the thermal regime of the soil from precipitation-derived (meteoric) 10Be. When frozen, soil does not build up meteoric 10Be; when thawed, 10Be migrates through the active layer. Our research will investigate the use of this isotope tracer for determining the relative duration soils have experienced thawed conditions since deposition. This information, when linked with climate proxies from the Lake El’gygytgyn cores, will yield key connections between past temperatures and depth of permafrost thaw and to provide realistic constraints on the impact of past warm and cold episodes on permafrost generation and maintenance in the context of anticipated global warming. The method can be extended to other Arctic terrains to determine the history and fate of other carbon reservoirs.