The Bjerknes Centre is a collaboration on climate research, between the University of Bergen, NORCE, the Institute of Marine Research, Nansen Environmental and Remote Sensing Centre.

Seminar: The Sahara greening during the African humid period: An overview of its regional and global impacts

Welcome to a seminar talk by Francesco S.R. Pausata from University of Quebec in Montreal

Francesco Pausata
Francesco Pausata

 

Short biography:

My research focuses on understanding past climate dynamics with particular focus on the last deglaciation, interpreting the signal recorded in proxy records with the help of climate models. I am currently working on the last African Humid Period assessing the role played by changes in dust and vegetation cover in altering regional and global climate and investigating the associated mechanisms. I also use global climate models to characterize variations in atmospheric and ocean circulation associated to large high-latitude and tropical volcanic eruptions.

 

PhD Univ. of Bergen (Paleoclimate modeling);

Post doc European Commission (air quality and atmospheric dynamics)

Post doc Stockholm University (many different topics)

current:

Assistant Professor University of Quebec in Montreal

 

 

Abstract:

In the Sahara and Sahel, rainfall is closely linked to the intensity of the West African Monsoon (WAM), which is crucial for the socio-economic stability of millions of people living in the region. Severe droughts have ravaged the region in the last three decades of the 20th century. However, our incomplete understanding of the complex interactions between global and local drivers of the WAM casts uncertainty in the prediction of future climate change. Past changes in WAM can offer an opportunity to better understand the mechanisms affecting its dynamics. One of the most dramatic changes in the WAM occurred between 12,000–5,000 years BP, when increased summer rainfall led to an expansion of the North African lakes and wetlands and an extension of grassland and shrubland into areas that are now desert, giving origin to the so-called “Green Sahara” or African Humid Period. However, model experiments have not been able to fully reproduce the intensification and geographical expansion of the WAM during this period and its potential teleconnections has hardly been investigated. In recent studies, we highlighted the feedbacks of land cover and the associated dust emission changes as critical factors in enhancing WAM strength as well as its far afield impacts on the El Nino-Southern Oscillation (ENSO) variability, tropical cyclone (TC) activity as well as Arctic Amplification. For example, we show through a modeling study that the strengthening of the WAM during the African Humid Period may have been able to reduce ENSO variability by up to 25%, more than twice the decrease obtained using orbital forcing alone (10%). We identify changes in tropical Atlantic mean state and variability as fundamental agents driving ENSO variations through changes in the Walker circulation. These changes in the large-scale circulation, and the thermodynamic and kinetic state of the atmosphere also have strong impacts on worldwide TC development. The African Humid Period offers a unique opportunity to leverage the past to elucidate the implications of a potential natural or geoengineered regreening of the Sahel and Sahara region.

 

Arranged date for the seminar talk: Jun 13, 2019