Zhisheng An Prof. Zhisheng An Institute of Earth Environment Chinese Academy of Sciences China If you would like to interview this scientist, please contact Leah Christen. > biographical information > abstract > paper

Biographical Information:

Prof. An gradated from the Department of Geology, Nanjing University, China in 1962, and finished his postgraduate studies at the Chinese Academy of Sciences (CAS) in 1966. He has been researching loess and the Chinese environment, and its linkage to climate, for almost 40 years. In collaboration with Prof. Liu Tungsheng, he was responsible for establishing the importance of Chinese Loess as a climatic record for global environmental studies by the successful comparison of its sequence with that of deep-sea sediments. In addition, he has proposed the monsoon mechanism for East Asian environmental changes, reasoned out the instability, periodicity and diachroneity of the monsoon climate, and explicated the coupling linkage between the phased uplift of Tibetan Plateau and the Asian monsoon evolution. He is currently a Professor at the Institute of Earth Environment, CAS, Chairmen of the Xi’an Branch of the CAS and Shaanxi Provincial Academy of Sciences, Vice President of INQUA, and Vice President of IGBP.

Abstract:

The Evolutional Process of Asian Dust and its Role for the Earth System in the Past

Records of dust deposition in the past may be used to evaluate global iron connections under different conditions from today. Dust production, ocean paleoproductivity, pCO2 and past climate have co-varied over glacial-interglacial cycles, which has been observed in paleoclimatic studies. Here we review our current understanding and research results regarding biogeochemical records for the past global iron connections on different timescales. Paleo-records, such as terrestrial (loess) deposits, marine sediments and ice cores, suggest that average eolian deposition rates were approximately 2-20 times higher during glacial periods than during interglacial periods. During glacial times, enhanced dust supply to the ocean, particularly in the main HNLC areas of the open ocean (i.e., the Pacific subarctic, the equatorial Pacific, and the Southern Ocean), could have ‘fertilized’ the marine biota, enhanced the ocean productivity (1-2 times) and driven atmospheric CO2 lower. Current models yield various results, predicting that glacial-interglacial changes in dust fluxes could produce changes in atmospheric pCO2 ranging from 5-45 ppm as a contribution to the total glacial-interglacial change of 80-100 ppm. The positive correlations among Asian dust, ocean productivity and atmospheric CO2 in the last 2,500 kyrs, 1,000 kyr, 130 kyr, and 2 kyr indicate an important role of dust/iron in global biogeochemistry cycles in the past. A simple estimation confirms that a fourth of the glacial-interglacial CO2 change induced from iron fertilization might be due to dust supply change in Asia and its associated productivity change in the Pacific Ocean.

Paper:

The Evolutional Process of Asian Dust and its Role for the Earth System in the Past

What is Asian Dust?
In spring each year, heavy dust storms sweep across vast areas of central and eastern Asia, destroying public infrastructures, disrupting daily life, and throwing communication and transportation schedules into disarray. These large amounts of Asian dust are carried by prevailing winds of middle latitude and deposited in East Asia. They are also found in the near-surface atmosphere and deep-sea sediments of the remote Pacific and in Greenland ice cores.

Why is Asian Dust important in the Earth System?
The changing emissions and rising concentrations of Asian dust have important implications for atmospheric chemistry, regional climate, hemispheric to global-scale biogeochemical cycles, and human health and welfare.

What is the role of Asian dust in past climate?
Paleorecords of dust in continental sediments, marine sediments and ice cores can be used to verify the links between dust, ocean productivity and atmospheric carbon dioxide under conditions different from those today. For example, data from these paleorecords suggest that average eolian deposition rates were approx. 2-20 times higher during glacial periods than during interglacials. Increased Asian dust to the oceans, particularly to the main high-nutrient/low-chlorophyll (HNLC) areas of the open ocean (i.e. the Pacific subarctic, the equatorial Pacific), may have ‘fertilized’ marine biota, thereby enhancing ocean productivity and driving atmospheric carbon dioxide down. Since the connections between dust supplies to the ocean and atmospheric carbon dioxide are neither simple nor direct, the role of Asian dust in past global change needs to be re-evaluated to enable a deeper understanding of the driving mechanisms of climate change.