Search

Millennial-scale climate variability was persistent feature for Greenland ice core and North Atlantic marine records during the Marine Isotope Stage (MIS) 3. Studying high quality climatic archives outside of the Greenland and North Atlantic with precise constraint of absolute dating and high resolution sampling is a prerequisite to understand how the millennial-scale changes well expressed in North Hemisphere (NH) high latitudes had been propagated out to the other regions. Here, we generated the surface and subsurface hydrography (U k’ 37 and TEX H 86 temperatures) and terrestrial material input ( n -alkanes) records with precise AMS 14 C dated control for the 45 ka from a core (MD972146) retrieved from the northern South China Sea (SCS). Then, we compared our records to the oxygen isotope record from a Greenland NGRIP ice core, and the mean grain size record from a loess sequence at Gulang, China. We found that the millennial-scale oscillations of hydrolography and terrestrial material inputs records during the time since the last deglaciation and of ∼33–45 ka share similar patterns in timing and amplitude of the NH high latitude climate. However, we found that a non-NH pattern of millennial-scale oscillations for the late MIS 3, ∼20–33 ka of our hydrography and terrestrial material inputs records. Our studies imply that the changes of obliquity also may be important in determining the timing and amplitude of millennial-scale East Asian Monsoon (EAM) variability expressed in the northern SCS hydrography and terrestrial material inputs. [ABSTRACT FROM AUTHOR]

Abstract: High sedimentation rate (SR) cores retrieved from the South China Sea (SCS) form the basis for studying the marine components of millennial-scale Asian monsoon (AM) variability and for comparison with the AM reconstructions from cave records on land (e.g. Dongge and Hulu). However, carefully correlating the SCS sedimentary records to the cave records that are precisely dated by U/Th methods with resolution of decadal-scale, has not been completed. Such a correlation is essential when comparing AM influences expressed over land and sea, but requires a construction of marine AMS 14C age models that are precise enough to be compared to the cave U/Th age models. For the purpose of establishing such a correlation, this study presents new data from intensive AMS 14C dated marine cores retrieved from the northern SCS (MD972146, MD972148). The discrepancy of marine and cave δ18O record for the interval of ∼18–30ka might be due to the change of marine 14C reservoir age in SCS surface water during the glacial period, and to the change in interhemispheric dominance of the AM systems. With the new AMS 14C dating on MD972146 and MD972148, we examined the millennial-scale records of planktonic foraminifer δ18O and carbonate contents of MD972146, MD97248, and SONNE 17940-2 and compared those records with Dongge–Hulu δ18O record of the past 30ka. Our results show that in the intervals corresponding to the high-latitude Northern Hemisphere (NH) Younger Dryas (YD) and Heinrich I event (H1), the AMS 14C dated millennial-scale oscillations show relatively heavy δ18O and low carbonate contents, but H2 and H3 are in the opposite direction. Our results indicate the complexity for the marine cores which were used in interpreting the millennial-scale AM variability. [Copyright &y& Elsevier]

Abstract: This study presents a high-resolution, multi-proxy analysis of sediments from IMAGES core MD972146 in the northern South China Sea (SCS). Analyses include detailed measurements of planktonic foraminifer oxygen isotopes, sediment carbonate, total organic carbon (TOC), opal, and phosphorus concentrations, as well as a Holocene interval of planktonic foraminifer sea surface temperature (SST) estimates. The age model of MD972146 was constructed by adopting oxygen isotope stratigraphy and AMS 14C dating, and fine-tuned further by correlation with nearby, well-studied SONNE 17940 and Hulu stalagmite isotope records. The age model indicates that this record covers the past 70,000 yr—from isotope stage 4 to the Holocene—with a nearly constant, very high sedimentation rate of ∼50 cm/kyr. Such sedimentation rates allow for intensive investigations of millennial-scale climate variability expressed in the SCS and its potential global linkages. We constructed a composite terrestrial index (CTI) for MD972146 through a principal component analysis of a suite of the core proxies that are sensitive to terrestrial sediment input. During the last glacial of stage 4 to stage 2, warm interstadials appear to coincide with high terrestrial sediment pulses inferred from the CTI, suggesting humid conditions in the SCS and Southern China. Intervals of high terrestrial input are also correlated with Heinrich events, suggesting an increase of eolian and possibly also of fluvial terrestrial input to the northern SCS. Our high resolution Holocene SST and salinity estimates show warm, stable and humid conditions during short episodes of quasi-periodic, millennial-scale cooling in the North Atlantic, superimposed on generally more humid conditions during the middle Holocene (4–6 ka) compared to the dry late Holocene (0–4 ka). The presented data provide evidence that a variety of mechanisms involving the strength of East Asian summer monsoons, migration of the Intertropical Convergence Zone, and processes that are analogous to those governing the El Niño Southern Oscillation and the Arctic Oscillation might play important roles in modulating tropical climate during the last glacial stages and the Holocene. [Copyright &y& Elsevier]