Abstract. The loess-soil sequence in northern China is among the best long-term terrestrial climate records in the Northern Hemisphere that documented the history of the Asian summer and winter monsoon circulations, dust emission and aridity of inland deserts. In the Southern Hemisphere, the Antarctica ice cores provided a 800-thousand year (ka) history of the atmospheric methane (CH4) and carbon dioxide (CO2) concentrations, eolian dust and Antarctica temperature. We correlate the two records to address the hemispheric climate link in the past 800 ka and the potential roles of Asian dust and monsoon on the atmospheric CO2 and CH4 levels. The results show a broad coupling between the Asian and Antarctic climates at the glacial-interglacial scale and support a potential role of Asian dust and monsoon in modulating the atmospheric concentration of greenhouse gases. However, a number of decoupled aspects are revealed, among which marine isotope stage (MIS) 13 exhibits the strongest anomalous link compared with the other interglacials. It is characterized by the greatest interglacial global ice volume, carbon isotope (δ13C) maxima in the world oceans, cooler Antarctic temperature, more extended sea ice in the Southern Ocean, lower CO2 and CH4 concentrations, but by unusually strengthened Asian, Indian and African monsoons, weakest Asian winter monsoon, lowest Asian dust and iron fluxes. Particularly warm conditions were also reported for the elevated Tibetan Plateau and northern high-latitude regions. These lines of evidence consistently suggest an increased ice volume in the Southern Hemisphere, a substantially reduced ice volume in the Northern Hemisphere during MIS-13, and hence, an enhanced hemispheric asymmetry of polar ice-conditions. This event has deeply affected the continental, marine and atmospheric conditions at the global scale. Similar anomalies of lesser extents also occurred during MIS-11 and MIS-5e. These suggest that hemispheric climate coupling at the glacial-interglacial scale was significantly unstable during the mid-Pleistocene, and that the degree of asymmetry of polar ice-conditions has prominent impacts on the global climate system, including the Asian monsoon climate. Because global sea ice is likely evolving towards a similar trend now, the scenario may also be helpful for future climate evaluation.
The History of Early Polar Ice Cores