Collaborative Research: Speleothem records of permafrost thaw and paleoclimate in the North American Arctic

考虑到在未来变暖的情况下，永久冻土融化可能会释放大量温室气体，以及永久冻土融化对基础设施的威胁，了解永久冻土对过去温暖的反应至关重要。 只有当覆盖的永久冻土层融化，不再是从地表渗透到洞穴的不透水屏障时，洞穴沉积物（石笋和钟乳石）才会在北极洞穴中生长。 该项目将记录北极洞穴中的洞穴沉积物何时生长，以及在过去的气候条件下连续的永久冻土融化的情况。 主要研究人员将开发一个网站，旨在教育外行观众如何利用洞穴沉积物研究过去的气候。 他们会参加剑桥科学节吗？该计划为科学家提供了一个与参加社区活动的公众参与其研究的渠道。 该项目将通过帮助启动三名早期职业科学家的研究计划，以及支持两名研究生和三名本科生的培训，为STEM劳动力的发展做出贡献。从现在冻结的地区，这需要液态水的增长，从而意味着解冻的地面条件时，他们沉积洞穴洞穴沉积物的日期。他们的工作将利用铀钍地质年代学的进展，并使用来自加拿大三个偏远地区的现有洞穴沉积物收集，跨越纬度17°，与连续的永久冻土区隔离，以记录洞穴沉积物生长的程度，从而记录永久冻土融化的程度，跨越过去600 kyr的可变间冰期条件？其中有些天气较今天温暖。他们还将对一些样本进行铀铅测年，将测年范围扩大到数百万年。 在北极地区，关于陆地古气候的高分辨率、年代久远的记录也很罕见，尽管这对于理解该地区对辐射强迫的响应以及确定推动冰盖、永久冻土、海冰和植被过去变化的气候强迫至关重要。 因此，他们将测量沿着洞穴沉积物的稳定同位素记录，以重建它们生长期间的气候变化。 虽然这些记录可能是零碎的，并仅限于温暖时期，但这些记录将基本上提供格陵兰冰芯18O记录的地下延伸到许多过去的间冰期。

Given the possibility of substantial greenhouse gas release from thawing permafrost in a warmer future, as well as the threats to infrastructure from thawing permafrost, understanding the response of permafrost to past warmth is of fundamental importance. Speleothems (stalagmites and stalactites) only are expected to grow in Arctic caves when the overlying permafrost has thawed and no longer presents an impermeable barrier to seepage from the surface into the cave. This project will develop a record of when speleothems grew in Arctic caves and, consequently, under what past climatic conditions continuous permafrost thawed. The principal investigators will develop a website designed to educate lay audiences on how speleothems are used to study past climate. They will participate in the Cambridge Science Festival?s Science on the Street program, which provides an outlet for scientists to engage with public audiences attending community events on their research. This project will contribute to STEM workforce development by helping launch the research programs of three early-career scientists, as well as supporting the training of two graduate and three undergraduate students.The propose a novel approach to reconstruct past episodes of permafrost thaw ? dating cave speleothems from now-frozen areas, which require liquid water to grow and thus imply thawed ground conditions when they were deposited. Their work will take advantage of advances in uranium-thorium geochronology and use existing speleothem collections from three remote areas of Canada spanning 17° of latitude and isolated to continuous permafrost zones to document the extent of speleothem growth, and thus permafrost thaw, across variable interglacial conditions of the past 600 kyr ? some of which were warmer than today. They will also apply uranium-lead dating to a selection of samples to extend the dating range to millions of years. Well-dated, high-resolution records of terrestrial paleoclimate are also rare in the Arctic, though critical for understanding the response of this region to radiative forcings and determining the climate forcing that drove past changes in ice sheets, permafrost, sea ice, and vegetation. Therefore, they will measure stable isotope records along the speleothems to reconstruct climate variability over the intervals during which they grew. While likely fragmentary and confined to warm periods, these records will essentially provide underground extensions of the Greenland ice core ä18O record to numerous past interglacials.