Grant: Alliance Grants

Ongoing climate change is accompanied by rapid, partly chaotic, variations in atmospheric, ocean, cyrospheric and land surface conditions that affect not only air temperature, but also the hydrological cycle, sea ice and ice sheets, sea level, ocean circulation including coastal currents. While observation techniques allow high resolution spatial and temporal monitoring of the climate system under anthropogenic forcing, the "pre-anthropogenic" state and natural variability of the system offer the opportunity to explore the behavior of the climate system under extreme conditions, warmer or colder than present, and during important transitions such as the one that led to the desertification of the Sahara, which was covered by a diverse vegetation until about 6,000-5,000 years ago. Here we aim at investigating potential mutual feedbacks between Arctic and tropical climate. We will use a combination of climate and forced ocean model simulations of different complexity and paleoclimate archives to delve into the rapid ice melting phase of the last deglaciation that led to > 120 m global sea-level rise and the current interglacial period that started about 11,700 years ago. The time interval of interest has been punctuated by abrupt climate change at regional as well as hemispheric scale both in the Arctic and in the tropical regions, like for example the Younger Dryas (12,900 - 11,700 years ago) that was accompanied by cooling close to 8°C in western Europe and the inception and withdrawal of the steppe-forest vegetation in the Sahara during the African Humid Period (14,500 - 5,000 years ago). These events occurred at a pace much faster than the underlining external forcing (changes in solar insolation) not only highlighting the presence of critical tipping points in the climate system but also suggesting potential feedbacks between high and low latitudes. Hence, in this context, by combining modeling and paleoclimate data, the overall goal of this project is to unravel key far-field connections between the Arctic and tropical latitude as they could play a key role in amplifying climate change and ice melt at high latitudes, and in altering monsoonal precipitation and droughts at low latitudes.