Collaborative Research: P2C2--Continental Temperature Variability during Greenland Stadials and Interstadials from Subaqueous Speleothems

缺乏过去气候变化的温度信息仍然是缩小未来气候预测不确定性的一个主要障碍。该项目旨在根据洞穴记录（洞穴沉积物）中测量的新温度指标，测量美国西南部和北方地区过去重要气候时期的绝对古地表温度。新生成的晚更新世和全新世的温度数据可能为气候模型提供有用的约束。具体而言，研究人员的目标是使用双聚集同位素和锶同位素提供北美大陆大区域的温度信息。新的温度记录将用于解决以下问题：1）北美大陆内部和整个大陆内部全新世温度变化的程度如何？ 格陵兰和大陆代理记录之间的协变在多大程度上（例如，美国西南部），反映温度变化，而不是水同位素的变化。研究人员已经从几个洞穴（卡尔斯巴德洞穴-NM，墨西哥龙舌兰洞穴-NM，风洞-SD，猛犸洞穴-KY，神秘洞穴-MN，蜀葵洞-NY以及这些地区鲜为人知的洞穴）收集了样本，这些洞穴从劳伦泰德冰盖延伸到沙漠西南部。从选定的样品中对多个子样品粉末（~200 mg）进行精确的铀系定年，将为更重要时期（例如，中全新世，新仙女木，极外气候恢复（神秘间隔），末次冰期最大期，末次间冰期）。这项工作还将描述这些时期美国西南部和北方地区之间的温度梯度。潜在的更广泛的影响包括新的古温度记录，可用于基准气候模型和评估温度对水文气候和水资源的影响。此外，应用双聚集同位素和锶数据的研究可以产生定量古气候重建的新方法。该项目将为新墨西哥州和密歇根州大学的两名研究生提供研究培训。这项工作的结果将通过外展和媒体报道传播给更广泛的公众。这个奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。

The lack of temperature information for past episodes of climate change remains a major hinderance to narrowing uncertainties of future climate projections. This project aims to measure absolute paleo-surface temperatures for important past climate periods in both the southwestern and northern regions of the United States based on novel temperature indicators measured in cave records (speleothems). The newly generated temperature data for the late Pleistocene and Holocene can potentially provide useful constraints for climate models.Specifically, the researchers aim to provide temperature information for a large region of the North American continent using dual clumped isotope and strontium isotopes. The new temperature records will be used to address the following questions: 1) what was the extent of Holocene temperature variability in and across the continental interior of North America? To what extent does the covariation between Greenland and continental proxy-records (e.g., southwestern United States), reflect temperature changes and not water isotope variability. The researchers have already the samples in hand collected from several caves (Carlsbad Cavern-NM, Lechuguilla Cave-NM, Wind Cave-SD, Mammoth Cave-KY, Mystery Cave-MN, Hollyhock Hollow caves-NY, and lesser-known caves in these areas) extending from the Laurentide ice sheet to the Desert southwest. Accurate uranium-series dating of multiple subsample powders (~200 mg) from selected samples will provide suitable subsample powders for clumped and Sr isotope analyses of the more important time periods (e.g., Middle Holocene, Younger Dryas, Extrapolar Climate Reversal (Mystery Interval), Last Glacial Maximum, the Last Interglacial). This work will also characterize temperature gradients between the southwestern United States and the more northern sites for these periods.The potential Broader Impacts include new paleotemperature records that can be used to benchmark climate models and to evaluate the impact of temperature on hydroclimate and water resources. Additionally, the research with the application of dual clumped isotopes and strontium data can yield novel methodological approaches for quantitative paleoclimate reconstructions.The project will provide research training for two graduate students at the universities of New Mexico and Michigan. The results of this work will be disseminated to the broader public via outreach and media coverage.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.