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

海平面上升是人口密集的低洼沿海地区未来的一个决定性问题。在这种情况下，剩下的大冰原的命运可以说是主要关注的问题。因此，在过去的几十年里，许多研究都集中在20000到7000年前的最后一个冰河时代结束时冰盖的退缩上。北美和南极大陆总共占冰融化总量的80%，但其贡献的数量和时间尚不清楚。解决这个问题很重要，因为融水输入的位置可能对全球海洋-大气环流有重大影响。尽管当时地球的气候与现在大致相当，但对12,000至7,000年前海平面上升一半（最后约60米）的时期的研究却特别少。因此，这个时间间隔可以作为将来有用的模拟。本项目将以前所未有的分辨率重建这一时期密西西比三角洲海平面上升的速度。将这一新记录与最先进的冰原和固体地球的计算机模型相结合，将有可能计算出北美和南极冰原在这段时间间隔内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，并包含许多外展活动。这包括在新奥尔良城市农场进行指导和实地示范，向当地青年领袖传授可持续粮食生产的知识。教育材料将提供给整个佛罗里达州的高中教师，并在坦帕湾st。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。在全新世早期的海平面历史中，关于末次消冰期间不同冰盖融水贡献的不确定性得到了特别好的反映，最近对11至7 ka期间劳伦泰德冰盖（LIS）对全球海平面上升贡献的末元估计在~20至30 m海平面当量之间变化。这一差异相当于现在格陵兰冰盖体积的1.5倍。南极冰盖（AIS）的退缩史可能存在更大的不确定性。在这段时间内，冰盖的体积也同样不受约束。密西西比三角洲非常适合制作非常详细的早全新世相对海平面（RSL）记录，可延伸至~9.5 ka甚至更早。在传统方法（从基底泥炭中提取的植物大化石的AMS 14C定年）不可行的地方，将使用一种新的年代学技术——半咸湿地古土壤的斜坡热解14C定年，以获得足够高分辨率的海平面指数点。新的早全新世RSL记录将与全球低分辨率记录相结合，主要目标是确定7 - 10 ka期间RSL上升速率及其空间变化率。考虑大量冰盖历史的冰川均衡调整模型将用于校正RSL记录的粘弹性和旋转效应。由于其明显不同的海平面指纹，残差信号应提供全新世早期海平面上升贡献的新信息。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，还是被明显的海平面上升打断，类似于（可能大于）8.5至8.2 ka时间窗前后的海平面上升？(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 ~ 8 ka的时间间隔内？

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?