Abstract
The mid-Pleistocene transition (MPT) is widely recognized as a shift in paleoclimatic periodicity from 41- to 100-kyr cycles, which largely reflects integrated changes in global ice volume, sea level, and ocean temperature from the marine realm. However, much less is known about monsoon-induced terrestrial vegetation change across the MPT. Here, on the basis of a 1.7-million-year δ13C record of loess carbonates from the Chinese Loess Plateau, we document a unique MPT reflecting terrestrial vegetation changes from a dominant 23-kyr periodicity before 1.2 Ma to combined 100, 41, and 23-kyr cycles after 0.7 Ma, very different from the conventional MPT characteristics. Model simulations further reveal that the MPT transition likely reflects decreased sensitivity of monsoonal hydroclimate to insolation forcing as the Northern Hemisphere became increasingly glaciated through the MPT. Our proxy-model comparison suggests varied responses of temperature and precipitation to astronomical forcing under different ice/CO2 boundary conditions, which greatly improves our understanding of monsoon variability and dynamics from the natural past to the anthropogenic future.
Highlights
The mid-Pleistocene transition (MPT) is widely recognized as a shift in paleoclimatic periodicity from 41- to 100-kyr cycles, which largely reflects integrated changes in global ice volume, sea level, and ocean temperature from the marine realm
As the loess δ13C record of inorganic carbonate (δ13CIC) record is affected by changes in mean annual precipitation (MAP) and temperature (MAT), we focused on these two variables averaged over northern China (30–40°N, 104–120°E), where the precipitation change is more sensitive to summer monsoon intensity[19]
Astronomical parameters and lower boundary configurations are key factors affecting orbital-scale monsoon variability[16,17,18,19]
Summary
The mid-Pleistocene transition (MPT) is widely recognized as a shift in paleoclimatic periodicity from 41- to 100-kyr cycles, which largely reflects integrated changes in global ice volume, sea level, and ocean temperature from the marine realm. The MPT might be triggered by a nonlinear response to astronomical forcing[9] induced by a secular CO2 decrease and/or progressive regolith erosion[10,11,12] This transition is apparent in numerous proxy indicators that are sensitive to changing glacial boundary conditions[3,4,5,6,11,13]. Unlike the conventional expression of the MPT, our results reveal a compelling transition of the dominant rhythm in coupled monsoon–vegetation system from 23-kyr to combined 23-, 41-, and 100-kyr cycles across the MPT
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