Increased precipitation during the Little Ice Age in northern Taiwan inferred from diatoms and geochemistry in a sediment core from a subalpine lake

Abstract

We studied diatoms in a 55.5-cm-long sediment core from a subalpine lake in northern Taiwan, Tsuifong Lake (TFL), to investigate environmental changes from AD 490 to present. Diatom assemblages of the last century were dominated by acidophilous species, whereas alkaliphilous taxa dominated the record between AD 1480 and 1910. Over the studied time frame, four decadal periods with high precipitation were inferred from evidence of elevated soil input from the watershed, supported by the stable isotope signatures (d 15 N, d 13 C) of organic matter and magnetic susceptibility of the sediments. We compared the inferred changes in pH of TFL to values obtained from three other Taiwanese subalpine lakes. The present study revealed that elevated precipitation was associated with increased solar irradiance over the last five centuries, with a stable dry period between AD 490 and 1450. Acidification of TFL in the last *100 years was a consequence of deforestation and acid rain.

Late Holocene environmental reconstructions and their implications on flood events, typhoon, and agricultural activities in NE Taiwan

“…7), indicating Figure 8. Variations of diatom-inferred precipitation during the last 1000 years in subalpine lake (TFL) (Wang et al, 2013), lowland lake (DHL), and offshore marine sediments (SOT) the stable lacustrine environment.. During this period the DHL hydrological conditions are similar to today, which is an enclosed lake without the influence of alluviums. Although the flood variations cannot be reflected by the proxy of overflows, such as pollen PC2, the variations in diatom assemblages imply changes in the lake level.…”

“…The continuously high percentages of Cyperaceae pollen and epiphytic diatoms reflect that the wetland expanded in the vicinity of the DHL. Although the climate records in Taiwan indicated a wetter LIA (Liew et al, 2014;Wang et al, 2013Wang et al, , 2014, the reduction in flood events in the Ilan Plain during the early LIA was likely related to the local depositional environment in the alluvial plain transition phase. The human activities are reduced during this period.…”

“…This view has been challenged by findings of increased rainfall during the LIA in South China (Chen et al, 2005;Chu et al, 2002) and Taiwan Wang et al, 2011Wang et al, , 2013. Such spatial variations in precipitation reflect the regional climate characteristics, such as monsoonal precipitation or TC-triggered heavy rainfall.…”

“…Such spatial variations in precipitation reflect the regional climate characteristics, such as monsoonal precipitation or TC-triggered heavy rainfall. However, studies on the influences of TC intensity and frequency on local hydrology during the Holocene epoch are rare (Chen et al, 2012;Wang et al, 2013;Woodruff et al, 2009), even though the hydrological conditions, especially flooding, on the East Asian coast are strongly affected by TCs today.…”

“…Diatom analysis followed the method described by Wang et al (2013). Half gram of dry weight sediment was digested with 32 % H 2 O 2 and 10 % HCl, then mounted on slides using mounting media (Wako).…”