Collaborative Research: Improved Constraints on Holocene Retreat History of the Laurentide and Scandinavian Ice Sheets from Cosmogenic Dating and Implications for Sea-level Rise

合作研究：从宇宙起源年代和海平面上升的意义上改进对劳伦泰德和斯堪的纳维亚冰盖全新世退缩史的约束摘要冰盖与气候研究的主要目标是了解冰盖对气候变化的响应。确定过去冰盖退缩的速度以及在自然气候比现在更温暖的情况下对海平面上升的贡献，为格陵兰冰盖未来对全球变暖的反应提供了背景。在此，该研究小组建议改进冰川消融年表，并调查全新世早期至中期（11.7 ka）劳伦泰德（LIS）和斯堪的纳维亚（SIS）冰盖的退缩率，这段时间提供了一个很好的自然实验，这些陆地冰盖在比现在更温暖的气候下消融，但可能与本世纪末相似。本项目拟利用原位宇宙地表暴露年龄直接测定全新世早期至中期的东南、东部边缘和南、东、北部边缘的退缩年代，显著改善了最大的LIS圆顶和大部分SIS的年代学。由此产生的年表将与魁北克西部、拉布拉多东北部和芬兰南部已经存在的宇宙形成年表以及现有的最低限制放射性碳年代和阀门记录相结合。这些数据将用于计算全新世早期至中期的LIS和SIS退缩率和海平面上升贡献，其余的海平面上升主要归因于南极冰盖。这些结果将提供冰盖在辐射强迫下融化的自然速率的估计，这种强迫可能类似于本世纪末的气候。更广泛的影响考虑到预测未来海平面因全球变暖而上升的最大不确定性是剩余冰盖的贡献，因此在比目前更温暖的气候下限制融化速度至关重要。这项研究的结果将为气候科学家提供在自然气候比现在更温暖的情况下，陆地冰盖的退缩率和随之而来的海平面上升贡献的估计。从这项研究中获得的信息将对政策决定具有重大意义，并对广大地球科学家和一般公众感兴趣。本研究计划将资助2名博士生，他们将接触到包括古气候学、冰川地质学、宇宙成因同位素地球化学和古海洋学在内的多学科科学方法。它还将为未获得终身职位的早期职业助理教授提供支持，以进一步发展他的学术生涯。

Collaborative Research: Improved constraints on Holocene retreat history of the Laurentide and Scandinavian Ice Sheets from cosmogenic dating and implications for sea-level riseAnders E. Carlson (U. of Wisconsin-Madison) EAR-0958872 Peter U. Clark (Oregon State U.) EAR-0958417ABSTRACTA major objective of ice sheet and climate research is to understand the responses of ice sheets to climate change. Ascertaining the past rates of ice-sheet retreat and contributions to sea-level rise under climate that was naturally warmer than present provides context for the future Greenland Ice-Sheet response to global warming. Here, this research team proposes to improve the deglacial chronologies and investigate retreat rates of the Laurentide (LIS) and Scandinavian (SIS) Ice Sheets during the early to mid-Holocene (11.7 ka), a period of time that provides an excellent natural experiment where these terrestrial ice sheets deglaciated under a climate warmer than present but potentially similar to the end of this century. This project proposes to directly date the retreat of the southeastern and eastern LIS margins and the southern, eastern, and northern SIS margins during the early to mid-Holocene using in situ cosmogenic surface exposure ages, significantly improving the chronology for the largest of the LIS domes and the majority of the SIS. The resulting chronologies will be combined with already existing cosmogenic chronologies from western Quebec, northeastern Labrador and southern Finland, and existing minimum limiting radiocarbon dates and varve records. These data will allow calculations of LIS and SIS retreat rates and sea-level rise contributions during the early to mid-Holocene, with the remainder of sea-level rise largely attributable to the Antarctic Ice Sheet. The results will provide estimates of the natural rates at which ice sheets can melt under radiative forcing that may be analogous to the climate of the end of this century. Broader ImpactsGiven that the greatest uncertainty in predicting future sea-level rise in response to global warming are the contributions from the remaining ice sheets, it is critical to constrain melt rates under warmer than present climates. Results of this research will provide climate scientists with estimates of the retreat rates and attendant sea-level rise contributions from terrestrial ice sheets under a climate naturally warmer than present. The information gained from this research will be of significant importance for policy decisions and of interest to a broad range of earth scientists and the public in general. This research proposal will support 2 Ph.D. students who will be exposed to a multi-disciplinary scientific approach that includes paleoclimatology, glacial geology, cosmogenic isotope geochemistry and paleoceanography. It will also provide support for an untenured, early career Assistant Professor furthering his academic career.