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

合作研究：北美北极永久冻土融化和古气候的洞穴记录

• 批准号: 1607968
• 负责人: William McGee
• 金额: $ 10.85万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1607968&HistoricalAwards=false
• 关键词: Collaborative; Research; Speleothem; records; permafrost

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.

考虑到在温暖的未来，永久冻土融化可能会释放出大量温室气体，以及永久冻土融化对基础设施造成的威胁，了解永久冻土对过去温暖的反应就显得至关重要。当上面的永久冻土融化并且不再成为从地表渗入洞穴的不可渗透屏障时，它们就会生长在北极洞穴中。主要研究人员将开发一个网站，旨在向普通观众介绍如何利用洞穴生物来研究过去的气候。科学节的“街头科学”项目为科学家提供了一个与参加社区活动的公众进行研究交流的渠道。该项目还将帮助启动三名早期职业科学家的研究项目，从而促进 STEM 劳动力的发展。作为支持两名研究生和三名本科生的培训。提出了一种新的方法来重建过去的永久冻土融化事件？他们的工作将利用铀-钍地质年代学的进步，并利用来自加拿大三个偏远地区（横跨纬度 17°、孤立的连续永久冻土区）的现有洞穴化石藏品来记录过去 600 凯尔的不同间冰期条件下，洞穴的生长程度以及永久冻土融化程度如何？其中一些冰期温度比今天温暖。他们还将对选定的样本进行铀铅测年，以将测年范围扩大到数百万个。北极地区历史悠久、高分辨率的陆地古气候记录也很少见，尽管这对于了解该地区对辐射强迫的响应和确定气候至关重要。因此，他们将测量洞穴中的稳定同位素记录，以重建它们生长期间的气候变化，尽管这些变化可能是碎片性的，并且仅限于温暖时期。记录本质上将提供格陵兰冰芯ä18O记录到许多过去间冰期的地下延伸。