The response of the water cycle under elevated temperatures - lessons from the past

人们普遍认为，全球变暖导致了水循环的加剧以及极端降雨事件的数量和强度的增加。然而，水循环的区域变化仍然是气候系统中最不为人所知的方面之一。地球的历史包括过去的气候状态——“古气候”——它为我们未来的温暖气候提供了经验，并有助于提高对地球系统的理解。渐新世（距今约3400万~ 2300万年前）是一个以高温为特征的古气候区间（比现在高约0.8℃），可以用来研究高温下水循环的响应。然而，在这个关键的气候区间内，没有连续和直接的水文变化记录。叶蜡生物标志物的氢同位素组成是用来推断降雨、水分来源和大气环流变化的有力工具（见下文）。在这个项目中，学生将：i)利用叶蜡生物标志物的氢同位素组成在渐新世期间开发新的水文气候记录，ii)合成渐新世期间新的和现有的水文记录，以及iii)确定在更温暖的世界中水文循环的响应。

Global warming is widely considered to cause intensification of the water cycle and an increase in the number and magnitude of extreme rainfall events. However, regional variations in the water cycle remain one of the worst understood aspects of the climate system. Earth's history includes past climate states-"paleoclimates"-that hold lessons for our future warm climate and have contributed towards an improved understanding of the Earth system. The Oligocene (~34 to 23 million years ago) is a paleoclimate interval characterised by high temperatures (> 8 Celsius higher than today) and can be used to study the response of the water cycle under elevated temperatures. However, there are no continuous and direct records of hydrological change during this key climate interval. The hydrogen isotopic composition of leaf wax biomarkers is a powerful tool used to infer changes in rainfall, moisture sources, and atmospheric circulation (see below). In this project, the student will: i) develop new hydroclimate records during the Oligocene using the hydrogen isotopic composition of leaf wax biomarkers, ii) synthesise new and existing hydrological records during the Oligocene, and iii) determine the response of the hydrological cycle in a warmer world.