Drought or Deluge? Columbia River flows to the North Pacific under a variable Holocene climate.

干旱还是洪水？全新世气候变化下的哥伦比亚河流入北太平洋，哥伦比亚河的流量大致反映了太平洋西北地区的供水情况。在20世纪之前，气候变率对供水的长期影响知之甚少，导致目前气候变暖对区域水权、农业生产和渔业的影响存在不确定性。本研究旨在通过对哥伦比亚河口附近海洋沉积层中保存的过去表面盐度的化学和生物测量来重建河流流量的自然变化，并将河流流量变化置于过去~12,000年的气候背景中，这段时间跨越了比今天更温暖和更冷的气候间隔。通过调查过去气候变化与这一主要河流系统流量之间的关系，这项研究将有助于更好地了解未来可能发生的情况。该项目利用了一套新的沉积物岩心，这些岩心是最近通过两次海上研究考察在哥伦比亚河沿岸的大陆斜坡上收集的，非常适合重建全新世气候和河流流量。这些地点位于哥伦比亚河沿岸冬季和夏季低盐度羽流的范围内。该研究将分析浮游生物化石壳的氧同位素，钡：钙和镁：钙的比例，海洋有孔虫浮游生物以及海洋和淡水硅藻的物种丰度，以重建海面温度和海面盐度（与排放有关）。对已知季节演替的多种物种的分析将允许调查季节性和流量的间歇性。这些数据将解决一个假设，即东北太平洋的高温与内陆干旱有关，相对于另一个假设，即海洋温度升高通过增加大气湿度导致净降水（雪和雨）增加。这次重建的高分辨率独立年表将把PNW水文气候和东北太平洋温度变率纳入全球时间框架，提高我们对世界部分地区大尺度区域气候动力学的理解，这些地区受到数据和模式的限制较少。这项研究的结果将促进对区域尺度气候动态敏感性的基本理解，并将为长期规划提供有关潜在未来水供应的实用知识。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。

Drought or Deluge? Columbia River flows to the North Pacific under a variable Holocene Climate The discharge of the Columbia River broadly reflects the water supply of the Pacific Northwest region. Little is known about the long-term influence on climate variability on this water supply prior to the 20th century, leading to uncertainty surrounding the impacts of the currently warming climate on regional water rights, agricultural production, and fisheries. This research aims to reconstruct the natural variability in river discharge via chemical and biotic measures of past surface salinity preserved in marine sedimentary layers accumulating off the Columbia River mouth, and to place that river discharge variability into the climatologic context of the past ~12,000 years, a time that spans intervals of both warmer and cooler climate than today. By investigating the relationship between climate variability and discharge of this major river system in the past, this research will contribute to a better understanding of what is likely in the future. This project leverages a new suite of sediment cores recently collected via two seagoing research expeditions to the continental slope off the Columbia River, well suited for reconstructions of Holocene climate and river discharge. The sites bracket the offshore Columbia River low salinity plume in its winter and summer extents. The study will analyze fossil plankton shells for oxygen isotopes, barium:calcium and magnesium:calcium ratios, the species abundances of marine foraminiferal plankton and both marine and freshwater diatoms to reconstruct sea-surface temperatures and sea-surface salinity (related to discharge). Analysis of multiple species of known seasonal succession will allow for investigation of seasonality and intermittency of discharge. These data will address a hypothesis that higher temperatures in the NE Pacific are associated with inland drought, relative to an alternate hypothesis that warmer ocean temperature drive higher net precipitation (snow and rain) through an increase in atmospheric moisture. The highly resolved independent chronology of this reconstruction will place PNW hydroclimate and NE Pacific temperature variability into a global temporal framework, improving our understanding of large-scale regional climate dynamics in a part of the world poorly constrained by data and models. Results of this study will advance fundamental understanding of regional-scale dynamic sensitivity of climate and will yield practical knowledge about potential future water supplies of value for long-term planning.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.