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

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.