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The purpose of this study is to improve prehistoric knowledge of paleo-typhoon and winter monsoon activity in the western North Pacific after 8 cal. ka BP. We examine two sediment cores derived from lakes located to the south and north of the Ilan Plain in northeastern Taiwan. Seasonal and typhoon rainfall data over the past several decades are collected for this study region. We also use mineral indicators, K/Rb ratios and grain size to estimate sediment sources, intensity of chemical weathering and rainfall intensity. The results show that the chemical weathering index (K/Rb ratio) of Meihua Lake indicates the continuing effects of autumn rainfall, while coarse grain sizes of Dahu Lake sediments suggest increased intensity in typhoon rainfall. Grain size results reveal that increasing El Niño-Southern Oscillation intensity in the tropical Pacific has intensified the activity of super typhoons in the western North Pacific. Finally, we find that frequent activity of super paleo-typhoons occurred in Taiwan during the La Niña-like state, and the strengthening winter monsoon activity and higher sea surface temperature enhanced plentiful autumn rainfall in El Niño-like state. After comparing our results with the paleo-typhoon data in Japan and south China, we suggest that the tracks of super typhoon are mainly affected by variations in the warm pool and subtropical Northwestern Pacific High in the western Pacific. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The formation, evolution, and potential as a climate archive of Tienchi Pond was evaluated using geomorphology, sedimentology, geochemistry, and AMS radiocarbon measurements of tree ring cores. Tienchi Pond is a small ephemeral lake situated on the subtropical Lanyu Island in the Western Pacific Ocean about 90 km east of southern Taiwan. The lake is situated on a mountain ridge and is today characterized by numerous dead trees and stumps. The position at the boundary between the two main components of the SE Asian monsoon system, the Asian landmass and the Western Pacific, makes this lake particularly interesting as a potential natural climate archive. Since previous studies have shown that the bedrock underlying the lake formed over 2 my ago, a volcanic crater origin was ruled out. Rather, element ratios of K/Ti and Ca/Fe together with 210 Pb dating suggest a recent origin for the lake, probably as the result of a natural damming event in the southern, narrower, part of the lake basin, or as a result of increased precipitation at the end of the Little Ice Age (or a combination of both). Radiocarbon measurements on a dead tree near the lake perimeter show 14 C levels of more than 1.7% modern radiocarbon near the bark, suggesting that the tree died in the early 1970s. In contrast, by correlating a large number of radiocarbon measurements to a northern hemisphere reference curve, it was shown that trees closer to the center of the lake died in the early 20th century. This agrees with a scenario where a small lake formed by initial damming, and gradually grew larger through erosion of the surrounding shore lines caused by rapid lake level oscillations. [ABSTRACT FROM AUTHOR]

A detailed oxygen isotope time-scale based on planktonic foraminifera Globigerinoides sacculifer at site MD012380 in the Banda Sea was established for the past 820 kyrs by correlating the record to the astronomically tuned benthic oxygen isotope chronology of MD972143. Ages for marine isotope stratigraphic (MIS) events from 2.0 back to 21.1 were designated for this western tropical Pacific record. Spectral analysis of the δ18O time-series reveals distinct periodicities of 100, 41, and 23 kyrs, indicating strong orbital forcing, yet the power of each band varies through time. The time-series of three other paleo-proxies, namely, coarse fraction (CF), lightness of sediments and δ 13C of Globigerinoides sacculifer, were subjected to cross-spectral analyses against the oxygen isotope record. The Mid-Brunhes (MIS 13 - 10, 535 - 333 ka) divides the record into two time domains characterized by different spectral behaviors. Before the Mid-Brunhes, the analyzed proxies show relatively stronger powers at the 41-kyr band, and the coherence among various proxies is relatively high. After the Mid-Brunhes, 100-kyr periodicity becomes to dominate the δ 18O and coarse fraction records while coherence among the various proxies becomes weaker. The spectral behaviors of the various paleo-proxies appear to vary through the late Quaternary and are fundamentally changed by the Mid-Brunhes event, suggesting the existence of an ever changing, internally complicated system of the Banda Sea under the influence of orbital forcing during the last 820 kyrs. [ABSTRACT FROM AUTHOR]