Warm Pliocene mid-latitude upwelling sites, with implications to future southwestern North America aridity under climate change

温暖的上新世中纬度上升流地点，对气候变化下未来北美西南部干旱的影响

• 批准号: 2303486
• 负责人: Eli Tziperman
• 金额: $ 44.95万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2026-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2303486&HistoricalAwards=false
• 关键词: Warm; Pliocene; mid; latitude; upwelling

The early Pliocene (5.3–3 million years ago) was the most recent naturally-occurring warm period. It had an estimated carbon dioxide concentration of 400 ppm, similar to the level reached at present due to anthropogenic emissions. The Pliocene climate is often held up as a past analog for 21st-century climate. Today, cold deep water rises to the surface in the California coastal ocean upwelling system. Climate reconstructions suggest that the surface water in that region during the Pliocene was dramatically warmer than at present—by some 9 degrees C. Other evidence suggests that southwestern North America was very wet at that time, also in contrast to today. Those Pliocene reconstructions differ significantly from Intergovernmental Panel on Climate Change (IPCC) projections of near future climate. The IPCC projections suggest that parts of the southwestern USA will get drier, not wetter. The IPCC projections of the California upwelling system are very uncertain. The proposed research will examine a possible explanation of the Pliocene observations. It will lead to a better understanding of possible future changes to mid-latitude coastal upwelling systems. Such systems are critical to the fishing industry. The study will also lead to a better understanding of our ability to predict the aridity of southwest North America in a warmer climate. The project Broader Impacts include training of a graduate student, undergraduate students doing term and summer research projects, and high school student summer interns. The Broader Impacts activities will also include outreach to STEM college students via an open course on the science of climate change.The planned work will examine a proposed feedback that may explain these past climate observations. In this feedback, weaker upwelling leads to a warmer upwelling-region sea-surface temperature (SST), which enhances precipitation over the adjacent land and creates wetlands there, and then the existence of wetlands weakens the upwelling-favorable coastal winds and, therefore, further weakens the upwelling itself. The significance of the proposed study arises from the exploration of a novel feedback with important socioeconomic consequences. This work will study some related fundamental aspects of ocean upwelling systems and use a hierarchy of ocean and atmospheric models that will provide the opportunity to test the proposed feedback mechanism and study its consequences.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.

上新世早期（530 - 300万年前）是最近自然发生的温暖时期。其二氧化碳浓度估计为百万分之400，与目前人为排放所达到的水平相似。上新世气候经常被认为是21世纪气候的过去模拟。今天，寒冷的深水在加州沿海海洋上升流系统中上升到表面。气候重建表明，上新世期间该地区的地表水比现在高出9摄氏度。其他证据表明，当时北美西南部非常潮湿，与今天形成鲜明对比。这些上新世重建与政府间气候变化专门委员会（IPCC）对近期气候的预测有很大不同。IPCC的预测表明，美国西南部的部分地区将变得更干燥，而不是更潮湿。IPCC对加州上升流系统的预测是非常不确定的。拟议的研究将审查上新世观测的可能解释。它将导致更好地了解中纬度沿海上升流系统未来可能发生的变化。这些系统对渔业至关重要。这项研究还将使我们更好地了解我们在温暖气候下预测北美西南部干旱的能力。“更广泛的影响”项目包括培训研究生、做学期和夏季研究项目的本科生以及高中生暑期实习生。更广泛的影响活动还将包括通过气候变化科学的公开课程向STEM大学生进行宣传。计划中的工作将审查可能解释这些过去气候观测的建议反馈。在这种反馈中，较弱的上升流导致上升流区域的海表温度（SST）升高，这增强了邻近陆地的降水并在那里创造了湿地，然后湿地的存在削弱了有利于上升流的沿海风，因此进一步削弱了上升流本身。所提出的研究的意义产生于一种新的反馈与重要的社会经济后果的探索。这项工作将研究海洋上升流系统的一些相关的基本方面，并使用海洋和大气模型的层次结构，这将提供一个机会，以测试拟议的反馈机制，并研究其后果。这个奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。