Collaborative Research: Partitioning early Holocene Laurentide v. Antarctic ice melt from high-resolution reconstruction of sea-level rise and glacial isostatic adjustment modeling

合作研究：从海平面上升的高分辨率重建和冰川均衡调整模型中划分全新世早期的劳伦泰德诉南极冰融化

• 批准号: 1502588
• 负责人: Torbjorn Tornqvist
• 金额: $ 39.02万
• 依托单位: Tulane University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2020-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1502588&HistoricalAwards=false
• 关键词: Collaborative; Research; Partitioning; early; Holocene

Sea-level rise is a defining issue for the future of densely populated low-lying coastal regions. Within this context, the fate of the remaining large ice sheets is arguably the primary concern. Therefore, numerous studies over the past few decades have focused on the retreat of ice sheets during the end of the last ice age, 20,000 to 7,000 years ago. The North American and Antarctic continents collectively account for up to 80% of total ice melt, but the amount and timing of their contributions is not well known. Resolving this is important because the location of meltwater input is likely to have major implications for ocean-atmosphere circulation across the globe. The period between 12,000 and 7,000 years ago that witnessed about half (the last ~60 m) of the total sea-level rise is particularly poorly studied, despite the fact that the Earth's climate was roughly comparable to that of the present-day. Thus, this time interval could serve as a useful analog for the future. The present project will reconstruct the rate of sea-level rise in the Mississippi Delta during this period with unprecedented resolution. Combining this new record with state-of-the art computer models of ice sheets and the solid earth, it will be possible to calculate the relative contribution of North American v. Antarctic ice sheets to global sea-level rise during this time interval. The project will support a postdoctoral scholar as well as undergraduate students, and also contain numerous outreach activities. This includes instruction and field demonstrations at a New Orleans urban farm that educates local youth leaders on sustainable food production. Educational materials will be provided for high school teachers throughout Florida and for an exhibit on sea-level rise in the Tampa Bay-St. Petersburg area. Finally, all new sea-level data will be publicly released through the NOAA-WDC Paleoclimatology database.Uncertainty about the meltwater contribution from different ice sheets during the last deglaciation is particularly well reflected by the sea-level history during the early Holocene, where recent end-member estimates of the Laurentide Ice Sheet (LIS) contribution to global sea-level rise between 11 and 7 ka vary from ~20 to 30 m sea-level equivalent. This difference corresponds to about 1.5 times the volume of the present-day Greenland Ice Sheet. Possibly even larger uncertainties exist about the retreat history of the Antarctic Ice Sheet (AIS). Ice-sheet volumes during this time window are equally poorly constrained. The Mississippi Delta is uniquely suited to produce a highly detailed early Holocene relative sea-level (RSL) record, extending to ~9.5 ka and possibly older. Wherever conventional approaches (AMS 14C dating of plant macrofossils extracted from basal peat) are not feasible, ramped pyrolysis 14C dating of brackish wetland paleosols, a novel geochronological technique, will be used to obtain sea-level index points of sufficiently high resolution. The new early Holocene RSL record will be combined with a synthesis of lower resolution records from across the globe, with the primary goal to determine the rate of RSL rise and its spatial variability from 7 to 10 ka. Glacial isostatic adjustment modeling that considers a large suite of ice-sheet histories will be used to correct RSL records for viscoelastic and rotational effects. The residual signal should provide new information on the contribution from the LIS and AIS to early Holocene sea-level rise, due to their distinctly different sea-level fingerprints. Specific questions that the work will answer include: (1) Was the early Holocene sea-level rise predominantly smooth or was it punctuated by distinct sea-level jumps akin to (and possibly larger than) those around the 8.5 to 8.2 ka time window? and (2) What was the relative contribution of the LIS v. AIS to early Holocene sea-level rise, in particular during the time interval from ~9.5 to 8 ka?

海平面上升是人口稠密的低洼沿海地区未来的一个决定性问题。在这种情况下，可以说，剩下的大冰盖的命运是主要的担忧。因此，在过去的几十年里，许多研究都集中在20,000到7,000年前最后一个冰河时代结束时冰盖的消退。北美大陆和南极大陆总共占冰川融化总量的80%，但它们的贡献数量和时间尚不为人所知。解决这个问题很重要，因为融化水输入的位置可能会对全球海洋-大气循环产生重大影响。12000至7000年前见证了海平面总上升的大约一半(最后~60米)的时期，尽管地球的气候与现在大致相当，但对这段时期的研究特别少。因此，这一时间间隔可以作为未来有用的类比。本项目将以前所未有的分辨率重建这一时期密西西比河三角洲的海平面上升速度。将这一新记录与最先进的冰盖和固体地球计算机模型相结合，将有可能计算出在这一时间间隔内北美和南极冰盖对全球海平面上升的相对贡献。该项目将支持一名博士后学者和本科生，并包含许多外联活动。这包括在新奥尔良的一个城市农场进行指导和实地演示，该农场对当地青年领袖进行可持续粮食生产方面的教育。将为佛罗里达州的高中教师和坦帕湾-圣彼得堡的海平面上升展览提供教育材料。彼得堡地区。最后，所有新的海平面数据将通过NOAA-WDC古气候学数据库公开发布。关于最后一次冰川消融期间不同冰盖对融水的贡献的不确定性，特别是在早期全新世的海平面历史中得到了很好的反映，最近终端成员估计劳伦蒂德冰盖(LIS)对11至7 ka之间的全球海平面上升的贡献在~20至30米海平面当量之间变化。这一差异相当于今天格陵兰冰盖体积的1.5倍左右。南极冰盖(AIS)的退缩历史可能存在更大的不确定性。在这个时间窗口期间，冰盖的数量也受到了同样糟糕的限制。密西西比三角洲是唯一适合产生高度详细的全新世早期相对海平面(RSL)记录的地区，该记录延伸到约9.5ka或更早。当常规方法(从基泥中提取的植物大型化石的AMS14C测年)不可行时，将使用微咸水湿地古土壤的斜坡式热解14C测年，这是一种新的年代学技术，可以获得足够高分辨率的海平面指标点。新的全新世早期RSL记录将与来自全球各地的较低分辨率记录相结合，主要目标是确定RSL上升的速度及其7至10ka的空间变异性。考虑了一大套冰盖历史的冰川均衡调整模型将用于校正粘弹性和旋转效应的RSL记录。由于LIS和AIS的海平面指纹截然不同，残余信号应该会提供有关LIS和AIS对全新世早期海平面上升的贡献的新信息。这项工作将回答的具体问题包括：(1)全新世早期海平面上升主要是平稳的，还是被类似于(可能比8.5ka至8.2ka时间窗左右)更大的海平面跳跃所打断？以及(2)LIS和AIS对全新世早期海平面上升的相对贡献是什么，特别是在~9.5-8ka的时间段？