P2C2: New Analyses of Paleo-Seasonality and Climate Variability Using Fossil Wood

该项目旨在利用现有的化石木材标本和新开发的模型，在三个实地地点产生关于季节性和气候变化的新数据：1)加拿大北极班克斯岛（始新世早期）；2)中国南宁盆地（晚渐新世）；3)西伯利亚Finish Stream（晚中新世）。这些地点以前收集的化石标本超过100个。初步数据显示，这些化石中保存了足够的纤维素，适合进行高分辨率氧同位素分析。这些新数据与已发表的碳同位素记录相结合，使我们能够以年分辨率对一整套季节性气候参数（夏季降水、冬季降水、寒冷月平均温度、温暖月平均温度）进行新的定量估计。这些数据将允许对北极和季风气候的大气二氧化碳（CO2）浓度的多个水平进行季节性变化评估。研究人员计划生成新的高分辨率稳定同位素数据集来测试：1)渐新世晚期东亚季风的年际变化，当时大气二氧化碳浓度与预计的21世纪末水平相似；2)亚热带和北极环境中冬季和夏季气温如何随着年平均气温的增加而变化。最近的模拟工作预测，在年平均气温较暖的情况下，降水时间和强度会发生变化，冬季比夏季变暖更大，这在北极环境中被放大；然而，代理通常缺乏合适的分辨率来测试化石记录中的这些假设。潜在的更广泛的影响包括始新世、渐新世和中新世的次年分辨率的新古气候记录。这些高分辨率代用物是罕见的，将提供关于不同大气CO2浓度时间间隔内高纬度和低纬度年际气候变率和季节性的新信息。这些数据将有利于古气候群落的代理和建模。该项目将资助一名博士和一名本科生以及处于不同职业阶段的研究人员。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

This project aims to leverage existing fossil wood specimens and a newly developed model to generate new data on seasonality and climate variability across three field sites: 1) Banks Island, Arctic Canada (early Eocene); 2) Nanning Basin, China (late Oligocene); and 3) Finish Stream, Siberia (late Miocene). More than 100 fossil specimens are available from previous collections at these sites. Preliminary data show sufficient cellulose preserved in these fossils is suitable for high-resolution oxygen isotope analysis. These new data, combined with published carbon isotope records, allow for new quantitative estimates of a full suite of seasonal climate parameters (summer precipitation, winter precipitation, cold month mean temperature, warm month mean temperature) at annual resolution. Such data will allow for changes in seasonality to be assessed across multiple levels of atmospheric carbon dioxide (CO2) concentrations for both Arctic and monsoon climates. The researchers plan to generate new high-resolution stable isotope datasets to test: 1) inter-annual variability in the East Asian Monsoon during the late Oligocene, when atmospheric CO2 concentrations were similar to projected late 21st century levels, and 2) how winter versus summer temperatures change with increases in mean annual temperature, across both subtropical and Arctic environments. Recent modeling work predicts changes in precipitation timing and intensity occur under warmer mean annual temperatures, and greater wintertime versus summertime warming, which is amplified in Arctic environments; however, proxies generally lack suitable resolution to test these hypotheses in the fossil record.The potential Broader Impacts include new paleoclimate records at sub-annual resolution during the Eocene, Oligocene and Miocene. These high-resolution proxies are rare and will provide new information about inter-annual climate variability and seasonality at high and low latitudes during time intervals with different atmospheric CO2 concentration. Such data will benefit proxy and modeling paleoclimate communities. The project will support one PhD and one undergraduate student as well as researchers at various career-stages.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.