[세미나] Prof. Martin Claussen

The“Green Sahara”

Prof. Martin Claussen

2019년 2월 13일 (수) 16:00

과학관 551호

Abstract

The“Green Sahara”

Pronounced changes in African climate during the transition between glacials and interglacials have been found in palaeo climatic archives, mainly in the region of today’s Sahara and Sahel. There is ample evidence that the Sahara was much wetter and greener than today during the early and mid-Holocene, some 10.000 to 5.000 years ago. Some geological records suggest that these changes happened rather rapidly. Here, we present an overview of theory and numerical climate system simulations aiming at understanding these changes. African climate and vegetation shifts were likely induced by large changes in ice masses, ocean circulation and monsoon dynamics which, in turn, were triggered by variations in the Earth orbit around the sun and subsequent alteration of meridional insolation gradients. It is shown that abrupt change, sometimes referred to as ‘tipping’, in Saharan climate and vegetation could result from a strong feedback between vegetation and climate at different times at different locations. However, the diversity of plants can affect the strength of biogeophysical feedback. Regions rich in plant diversity may stabilize the system leading to more gradual transitions. Simulations suggest that the Sahara may become somewhat greener, if atmospheric CO2 values strongly increase. This is presumably caused by increased fertilization of plants, while the associate climate change acts to oppose further greening.