Collaborative Research: P2C2--Cool and Warm Season Moisture Reconstruction and Modeling over North America

由近2,000个北美树木年轮年表组成的网络是一个出色的高分辨率古气候数据集，已被用于重建整个大陆的长期土壤水分平衡。然而，这些现有的重建代表了在年环宽度年表中编码的不同季节气候信号的平均值，并不提供冬季和夏季条件的离散重建。需要明确古代干旱和湿润时期的精确季节性，以便为气候模型模拟提供最真实的过去气候重建和最有用的约束。许多北美树木年轮年表编码了不同的季节气候信号，可用于分别重建该大陆大部分地区的冷季和暖季湿度。这项研究将使用数百个新的和现有的树木年轮年表来重建热带、亚热带和温带北美大部分地区的凉季和暖季湿度水平。季节性重建将在两个固定的时间段内每年在0.5°网格上进行：公元1500年至今和公元1000年至今。它们将基于现有的年表，重新测量现有的树轮收藏，以得出季节性明确的早材和晚木宽度年表，并选择性地收集新的年表。不是所有地方都可能进行单独的冷暖季节水汽重建，但在热带和亚热带北美地区可能是最连续的，那里太平洋海面温度的气候强迫特别强烈，并随着纬度和季节的变化而变化。新的重建将与气候模式模拟一起使用，以检验以下假设：北美地区冷暖季节气候的海洋-大气强迫，每个季节十年干旱和湿季的气候动力学，以及人为微量气体和陆地表面变化对季节性干旱和湿季的影响。重建和气候模拟也将被用来识别古代与现代见证的极端十年干旱和潮湿时期的相似之处。这一合作研究项目将涉及阿肯色大学、哥伦比亚大学拉蒙特-多尔蒂地球天文台、孟菲斯大学和美国宇航局戈达德空间研究所。这项研究将提供冷季和暖季湿度异常的长时间、空间详细的重建，这些异常目前不存在，但需要为北美气候变率的模式模拟提供更现实的季节性约束。新的重建将具有重大的跨学科应用，为评估史前、殖民和现代时代季节性气候极端对社会和生态变化的影响提供了一个客观、准确的框架。重建工作将在具有互动分析能力的网络界面上进行，以最大限度地利用季节性重建[北美季节性干旱地图集]。学生将在科学研究和出版方面获得真实的野外和实验室经验。该项目将支持一名早期职业科学家，将启动与美国宇航局科学家的新合作，并将加强与墨西哥森林研究服务局(墨西哥托雷恩INIFAP)的长期合作。

The network of nearly 2,000 North American tree-ring chronologies is an outstanding high-resolution paleoclimate data set and has been used to reconstruct the long-term soil moisture balance across the continent. However, these existing reconstructions represent an average of the differing seasonal climate signals encoded in the annual ring width chronologies and do not provide discrete reconstructions of winter and summer conditions. The precise seasonality of ancient droughts and wet periods needs to be specified to provide the most realistic reconstructions of past climate and the most useful constraints for climate model simulations. Many North American tree-ring chronologies encode distinct seasonal climate signals that can be used for the separate reconstruction of cool and warm season moisture amounts over large sectors of the continent. The research will use hundreds of new and existing tree-ring chronologies to reconstruct both cool and warm season moisture levels across much of tropical, subtropical, and temperate North America. The seasonal reconstructions will be developed on a 0.5° grid for every year during two fixed time periods: AD 1500-present and AD 1000-present. They will be based on existing chronologies, re-measurements of existing tree-ring collections to derive seasonally explicit earlywood and latewood width chronologies, and selective field collections of new chronologies. Separate cool and warm season moisture reconstructions will not be possible everywhere, but are likely to be most continuous over tropical and subtropical North America where climate forcing from Pacific sea surface temperatures is particularly strong and changes sign with latitude and season. The new reconstructions will be used with climate model simulations to test hypotheses concerning the ocean-atmospheric forcing of cool and warm season climate over North America, the climate dynamics responsible for decadal droughts and wet periods in each season, and the influence of anthropogenic trace gas and land surface changes on seasonal droughts and wet periods. The reconstructions and climate simulations will also be used to identify ancient analogues for the extreme decadal droughts and wet periods witnessed during the modern era. This collaborative research project will involve the University of Arkansas, Lamont-Doherty Earth Observatory of Columbia University, the University of Memphis, and NASA's Goddard Institute for Space Studies. The research will provide the long, spatially detailed reconstructions of cool and warm season moisture anomalies that currently do not exist but are needed to provide more realistic seasonal constraints on model simulations of North American climate variability. The new reconstructions will have major interdisciplinary applications by providing an objective exactly dated framework for evaluating the impacts of seasonal climate extremes on social and ecological change during the prehistoric, colonial, and modern eras. The reconstructions will be served on a web-based interface with interactive analytical capabilities to leverage the widest possible use of the seasonal reconstructions [the North American Seasonal Drought Atlas (NASDA)]. Students will be provided with authentic field and laboratory experience in scientific research and publication. This project will support an early career scientist, will initiate a new collaboration with NASA scientists, and will strengthen a long-term collaboration with the Mexican Forest Research Service (INIFAP, Torreon, Mexico).