Presentation Information
[U11-07]Decreased typhoon activity affecting Taiwan during the Holocene compared to the last glacial period★Invited Papers
*Pierrick Fenies1, Sze Ling Ho1, Maria-Angela Bassetti2, Natalia Vazquez Riveiros3, Jens Hefter4, Yuan-Pin Chang5, Ludvig Löwemark6, Nathalie Babonneau3, Gueorgui Ratzov7, Shu-Kun Hsu8, Chih-Chieh Su1 (1.Institute of Oceanography, National Taiwan University, Taiwan, 2.CEFREM, University of Perpignan, France, 3.GEO-OCEAN, UMR 6538 CNRS-UBO-Ifremer-UBS, France, 4.Alfred-Wegener-Institute, Helmholtz-Center for Polar- and Marine Research, Germany, 5.Department of Oceanography, National Sun Yat-sen University, Taiwan, 6.Department of Geosciences, National Taiwan University, Taiwan, 7.GEOAZUR, University of Côte d’Azur, France, 8.Department of Earth Sciences, National Central University, Taiwan)
Keywords:
Land-to-sea transport,Typhoon,Taiwan,Carbon cycle,Deglaciation
Typhoons exert a strong control on hydrological variability and land-ocean carbon transfer in the western North Pacific, yet their evolution at glacial-interglacial timescales remains poorly constrained due to the scarcity of long terrestrial archives and the uncertainty of numerical simulations. In Taiwan, typhoons dominate sediment and particulate organic carbon (POC) export, with more than 75% of the annual flux occurring within less than 1% of the year, and typhoon-induced floods accounting for up to 90% of the annual biospheric/fresh (vegetation- and soil-derived) POC flux. Marine sediments deposited on submarine canyon levees offshore eastern Taiwan, fed directly by rivers irrespective of relative sea level change due to the absence of a broad continental shelf, hence provide a unique archive to investigate past typhoon variability.
Building upon modern observations, in this study we combined lipid biomarker, sedimentological, and geochemical analyses from a sediment core collected offshore eastern Taiwan to reconstruct changes in terrestrial organic carbon transfer, and therefore on typhoon activity over the last glacial-interglacial cycle. Coarser grain sizes, higher total organic carbon content, increased long chain n-alkanes and soil-derived brGDGTs accumulation rates during the deglaciation relative to the Holocene indicate substantially enhanced land-to-sea carbon transport linked to more frequent and/or more energetic turbidity current activity. In addition, the higher dominance of odd over even long-chain n-alkanes and reduced radiocarbon age offsets between planktonic foraminifera and bulk organic matter over the same interval point to a larger fraction of biospheric terrestrial POC transfer to the marine sediments compared to the Holocene. Together, these results point to an enhanced typhoon activity during the deglaciation, in agreement with recent model simulations indicating a higher typhoon genesis potential at that time. Given the difficulties in simulating past typhoon activity in Taiwan, or in recording it from terrestrial archives, our approach provides an alternative way to constrain past changes in typhoon activity affecting the island.
Building upon modern observations, in this study we combined lipid biomarker, sedimentological, and geochemical analyses from a sediment core collected offshore eastern Taiwan to reconstruct changes in terrestrial organic carbon transfer, and therefore on typhoon activity over the last glacial-interglacial cycle. Coarser grain sizes, higher total organic carbon content, increased long chain n-alkanes and soil-derived brGDGTs accumulation rates during the deglaciation relative to the Holocene indicate substantially enhanced land-to-sea carbon transport linked to more frequent and/or more energetic turbidity current activity. In addition, the higher dominance of odd over even long-chain n-alkanes and reduced radiocarbon age offsets between planktonic foraminifera and bulk organic matter over the same interval point to a larger fraction of biospheric terrestrial POC transfer to the marine sediments compared to the Holocene. Together, these results point to an enhanced typhoon activity during the deglaciation, in agreement with recent model simulations indicating a higher typhoon genesis potential at that time. Given the difficulties in simulating past typhoon activity in Taiwan, or in recording it from terrestrial archives, our approach provides an alternative way to constrain past changes in typhoon activity affecting the island.