Typhoon and Climate History of Northeastern Taiwan During the Holocene: Inferences From Dahu Lake Sediment Core, Ilan Plain

Abstract

To investigate Holocene typhoon variability in Taiwan, a multiproxy sediment core from Dahu Lake in the Ilan Plain, northeastern Taiwan, was analysed. Radiocarbon dating established that the Dahu Lake core spans the last 7.8 kyr, and combined information from geochemical elements (Ti and Al), diatoms, total organic carbon (TOC), total nitrogen (TN), the TOC/TN ratio, and carbon isotopic compositions (delta 13Corg) was used to investigate the variations in runoff and typhoon activity. These signals reflected high-energy runoff conditions, likely triggered by intense typhoon-related precipitation, during the periods 7.5, 7.3, 6.7-6.5, 6.0-5.7, 5.5-4.8, 4.3-3.6, 3.3-2.8, 2.2-2.0, 1.5-0.8, and 0.5-0.3 cal kyr BP. These events likely caused overflow conditions in the Lanyang River. Diatom records further indicated that at the end of, or during some of these events, the Lanyang River retreated, and the basin temporarily functioned as a lacustrine environment. During the intervening phases, the Dahu Lake was primarily sustained by the Dahu stream under lower runoff conditions. Comparison with other Taiwanese records shows broad coherence, including a prolonged wet phase between similar to 7.8 and 4.8 ka. In a wider regional context, both coherence and divergence emerge: Dahu Lake aligns with the northern South China Sea and, at times, the Okinawa Trough, but diverges from the East China Sea record. Periods of enhanced typhoon activity at Dahu Lake broadly coincide with La Ni & ntilde;a-like and negative PDO phases, suggesting that Holocene typhoon variability in the northwestern Pacific reflects ENSO-PDO-driven shifts in storm pathways rather than a uniform regional signal.