The Last Interglacial in the Alps

The Last Interglacial (130,000 to 116,000 years before present) was a time of higher sea level, smaller high-latitude ice sheets and lower greenhouse gas concentrations relative to today. This previous warm period in Earth history was similar to our current interglacial but lacked anthropogenic impact, and therefore provides invaluable insight into the natural backdrop influencing the future of a warming Anthropocene. This proposal will examine the Last Interglacial with a regional focus on the European Alps. The aim is to establish the first precisely dated proxy record spanning the entire interglacial from the penultimate deglaciation to the glacial inception for central Europe based on replicated speleothems. We will for the first time attempt to link these cave-based records to long-known, but undated sediment successions of former lakes in the foreland of the Alps using pollen grains preserved in the calcite of cave deposits. This will allow us to address a long-standing question about leads and lags in the vegetation in response to climate change in Europe. We shall also innovative geochemical methods to quantify temperature changes across the Last Interglacial. If successful, this will be the first precisely dated temperature curve for central Europe, which is based on physical measurements rather than biological proxies.

The last interglacial, which lasted from about 130,000 to 116,000 years ago, was a time of higher sea level, smaller polar ice sheets, and lower greenhouse gas levels than today. It is the next oldest warm climate period in Earth's history similar to today's interglacial, but without any human influence. In this project, we studied this time epoch, which can act as a test bed for the future of the Anthropocene, with a focus on the Alpine region. We sampled stalagmites from caves in the Eastern and Western Alps and produced high-resolution, precisely dated climate curves. For the Swiss Alps, we were able to quantitatively reconstruct the temperature evolution for the first time and show that the last interglacial was up to 3-4C warmer than today. We were also able to find evidence that 125,500 years ago, in the middle of this interglacial, there was an abrupt cooling, the traces of which were also detected in the Atlantic. These observations are relevant to the question of the stability of the Greenland ice sheet. Furthermore, we were able to extract fossil pollen from rapidly growing stalagmites and trace the vegetation development of the last interglacial. Thanks to the precise age determination, it could be shown that reforestation after the Riss Glacial began around 129,400 years ago and that the climatic optimum in the Eastern Alps occurred 128,000 years ago, i.e. early in the interglacial. With the help of pollen data from these cave deposits, it is now possible for the first time to integrate earlier undated vegetation data from lake sediments north and south of the Alps into an accurate chronology.