Stepwise coupling of monsoon circulations to global ice volume variations during the late Cenozoic

Author(s): Liu Tungsheng; Ding Zhongli
Author Affiliation(s): Primary:
Chinese Academy of Sciences, Institute of Geology, Beijing, China
Academia Sinica, China
Volume Title: Quaternary Earth system changes
Volume Author(s): Faure, H., editor; Faure-Denard, L.; Liu Tungsheng
Source: Global and Planetary Change, 7(1-3), p.119-130; XIII INQUA Congress, Symposia on Global environmental changes, Beijing, China, Aug. 1992, edited by H. Faure, L. Faure-Denard and Liu Tungsheng. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0921-8181
Note: In English. 42 refs.; illus.
Summary: In the Loess Plateau and adjacent areas, the present summer climate is controlled largely by the warm-moist southeast monsoon with its source in the low-latitude oceans, whereas the cold-dry northwest monsoon from Siberia is predominant in winter. In this study, we use the magnetic susceptibility record of the Xifeng loess section and the grain size profile of the Baoji section as indicators of summer and winter monsoon variations, respectively. The two loess sections have a palaeomagnetic basal age of about 2.5 Ma with a total thickness of 155-170 m. Magnetic susceptibility and grain size were measured at 10-20 cm intervals. Comparison of these monsoon proxies with the oxygen isotope record of DSDP Site 607 shows that summer and winter monsoon variations closely match the global ice volume changes over the past 2.5 Ma. During glacial periods, the winter monsoon was enhanced with a significant southward retreat of the summer monsoon, as indicated by an increase in loess grain size and a decrease in magnetic susceptibility. This sequence was reversed during interglacial periods, suggesting that the ice sheet cycle in high-latitudes was an important factor controlling monsoon variations. Detailed comparison also shows that coupling of long-term monsoon change with the global ice volume sequence shows a stepwise pattern over the past 2.5 Ma. Two critical time periods, one at about 2.5 Ma and the other around 0.9-0.55 Ma, have been noted. At about 2.5 Ma B.P., loess deposition began on an extensive scale across northern China. This marked the initiation or intensification of the winter monsoon circulation which coincided approximately with the onset of continental glaciation in the northern Hemisphere. From 2.5 to about 0.9-0.55 Ma B.P., visual examination indicates the importance of a direct component of orbital forcing, besides an obvious ice forcing component. Since 0.9-0.55 Ma B.P., the ice forcing component has become the most important one. This implies that the coupling relationship is more apparent after 0.9-0.55 Ma B.P. than earlier. We speculate that the stepwise coupling mechanism between the monsoon circulations and global ice volume may be associated with the stepwise uplift of the Tibetan Plateau.
Year of Publication: 1993
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 22 Environmental Geology; 24 Surficial Geology, Quaternary Geology; Asia; Atmosphere; Carbonates; Cenozoic; China; Circulation; Clastic sediments; Climate; DSDP Site 607; Deep Sea Drilling Project; Far East; Global; Grain size; Holocene; IPOD; Ice; Indicators; Isotope ratios; Isotopes; Leg 94; Lishi Loess; Loess; Loess Plateau; Magnetic susceptibility; Malan Loess; Mechanism; Models; Monsoons; Neogene; North-central China; O-18/O-16; Oxygen; Paleoclimatology; Paleomagnetism; Pleistocene; Pliocene; Quaternary; Sea ice; Seasonal variations; Sediments; Stable isotopes; Structural controls; Tertiary; Tibetan Plateau; Upper Pleistocene; Upper Pliocene; Wucheng Loess; Xifeng China
Coordinates: N410004 N410005 W0325726 W0325727
Record ID: 1993019883
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands