Linking ocean and continental records of paleoclimate: determining accord and discord in the records

摘要

Climate forcing at Milankovitch and sub-Milankovitch frequencies are evaluated by linking climate proxy data from terrestrial and ocean records at two scales of temporal resolution: (1) relatively coarse resolution over the last 500 ka, and (2) higher resolution over the last 200 ka. We determine that climate proxy data from Hole 810C represent regional atmospheric and oceanic processes by comparison to core V21-146, both from the northwest Pacific Ocean. We then compare records that represent regional deposition from China and the western Pacific Ocean to focus on determining Milankovitch-type periodicities. Grain-size and magnetic susceptibility data from Hole 810C and Baoji, China are contrasted using a time-sensitive wavelet analysis. The analyses indicate a general correspondence to Milankovitch frequencies, although there is no specific frequency that dominates throughout the records. Additionally, the dominant 100 000 year frequency does not occur at the same time in the records. These factors suggest that differences in the physical mechanisms of deposition may influence the preserved apparent periodicities in these environments. Lastly, climate events over the last 200 000 years in marine and terrestrial records are correlated at a high resolution in the depth domain. The last interglacial-glacial boundary is consistently placed at the base of a cold period (C20) in the terrestrial and marine records. However, the cold period in the ocean data (#delta#~(18)O) is very subdued relative to terrestrial records. Additionally, over the last 200 ka, periods of minimum insolation intensity do not correspond linearly to periods of maximum grain-size and ice volume variations revealed in the loess and ocean records, respectively. However, during the warm interstadials of the last two glaciations, peaks in insolation intensity compare favourably with the times of strongest pedogenic development in the continental records and minimum ice volume in the ocean records.