East Asian monsoon climate during the Late Pleistocene: high-resolution sediment records from the South China Sea

Abstract

Based on the study of 10 sediment cores and 40 core-top samples from the South China Sea (SCS) we obtained proxy records of past changes in East Asian monsoon climate on millennial to bidecadal time scales over the last 220,000 years. Climate proxies such as global sea level, estimates of paleotemperature, salinity, and nutrients in surface water, ventilation of deep water, paleowind strength, freshwater lids, fluvial and=or eolian sediment supply, and sediment winnowing on the sea floor were derived from planktonic and benthic stable-isotope records, the distribution of siliciclastic grain sizes, planktonic foraminifera species, and the U K 37 biomarker index. Four cores were AMS-14 C-dated. Two different regimes of monsoon circulation dominated the SCS over the last two glacial cycles, being linked to the minima and maxima of Northern Hemisphere solar insolation. (1) Glacial stages led to a stable estuarine circulation and a strong O 2 -minimum layer via a closure of the Borneo sea strait. Strong northeast monsoon and cool surface water occurred during winter, in part fed by an inflow from the north tip of Luzon. In contrast, summer temperatures were as high as during interglacials, hence the seasonality was strong. Low wetness in subtropical South China was opposed to large river input from the emerged Sunda shelf, serving as glacial refuge for tropical forest. (2) Interglacials were marked by a strong inflow of warm water via the Borneo sea strait, intense upwelling southeast of Vietnam and continental wetness in China during summer, weaker northeast monsoon and high sea-surface temperatures during winter, i.e. low seasonality. On top of the long-term variations we found millennial-to centennial-scale cold and dry, warm and humid spells during the Holocene, glacial Terminations I and II, and Stage 3. The spells were coeval with published variations in the Indian monsoon and probably, with the cold Heinrich and warm Dansgaard-Oeschger events recorded in Greenland ice cores, thus suggesting global climatic teleconnections. Holocene oscillations in the runoff from South China centered around periodicities of 775 years, ascribed to subharmonics of the 1500-year cycle in oceanic thermohaline circulation. 102=84-year cycles are tentatively assigned to the Gleissberg period of solar activity. Phase relationships among various monsoon proxies near the onset of Termination IA suggest that summer-monsoon rains and fluvial runoff from South China had already intensified right after the last glacial maximum (LGM) insolation minimum, coeval with the start of Antarctic ice melt Wang et al. / Marine Geology 156 (1999) prior to the δ 18 O signals of global sea-level rise. Vice versa, the strength of winter-monsoon winds decreased in short centennial steps only 3000-4000 years later, along with the melt of glacial ice sheets in the Northern Hemisphere.

Paleonutrient and productivity records from the subarctic North Pacific for Pleistocene glacial terminations I to V

“…A similar interpretation may apply to a large set of published and unpublished planktic data from sediment traps and core tops in ocean regions as different as the northern and equatorial Atlantic [e.g., Simstich, 1998;Deuser et al, 1981aDeuser et al, , 1981bGanssen, 1983], the Arabian Sea, and South China Sea [Wang et al, 1999]. Overall, the spatial distribution patterns of these data suggest that d 13 C values of various planktic foraminifera species primarily reflect the nutrient concentrations in ocean surface water ambient to shell calcification, besides various secondary forcings such as air-sea exchange of CO 2 , sea surface temperature, secular d 13 C variations, and vital and metabolic effects.…”

Phylogeography of the freshwater catfish Hemibagrus guttatus (Siluriformes, Bagridae): Implications for South China biogeography and influence of sea-level changes

“…It may also be used to explain the close relationship between the H. guttatus populations of these two river systems. There were several ice ages and inter-ice ages and their associated sea-level changes in the northeastern part of the South China Sea during the Quaternary (Wang et al, 1999;Liu et al, 2003). The Hanjiang River System and the Jiulongjiang River System are geographically very close to each other (Fig.…”

“…All these results indicated that there was no significant difference between the North River, the East River and the tributaries of the West River, at least for H. guttatus populations. The similarity among populations of these three rivers might be explained by their possible confluence during several large ice ages in the Pleistocene when sea-level was low (Wang et al, 1999;Liu et al, 2003). Floods might have also created temporary freshwater connections between these rivers, especially between the West River and the North River, which may have facilitated the exchange of H. guttatus populations.…”

“…During the ice ages of the late Pleistocene epoch, the continental shelf of the South China Sea was largely above water (Lin, 1966; Chinese Academy of Sciences, 1980;Wang et al, 1999;Liu et al, 2003) ( Fig. 1).…”

Dysaerobic conditions during Heinrich events 4 and 5: Evidence from phosphorus distribution in a North Atlantic deep-sea core

“…There is convincing evidence that HL deposition was accompanied by the formation of a freshwater lid , which possibly stopped or strongly reduced North Atlantic deep water (NADW) formation and thermohaline circulation (Broecker, 1994;Paillard and Labeyrie, 1994;Maslin et al, 1995;Vidal et al, 1997;Zahn et al, 1997). The signature of Heinrich events has been found not only in North Atlantic sediments (e.g., the Arabian and South China seas; Schulz et al, 1998;Wang et al, 1999) but also in terrestrial records (e.g., Grimm et al, 1993;Lowell et al, 1995;Benson et al, 1996;Sanchez-Goñi et al, 2000) and has been correlated with the Greenland ice core isotope record , pointing to possible teleconnections between high-and low-latitude climates on short time scales.…”