Two millennia of intense tropical cyclone activity in the western North Pacific: Insights from coastal boulder deposits

Tropical cyclones (TCs) are among the most destructive hydrodynamic disturbances, yet our knowledge of their long-term climatology is limited by the short length of observational records. Geological records provide valuable insights into TC activity before modern observation. Although the western North Pacific (WNP) is the most active TC basin, little is known about how intense TCs have responded to long-term climate variability. Here, this study presents a new two-millennia record of intense TC activity from coastal boulder deposits on Amami-Oshima Island in the Ryukyu Islands, Japan. The results indicate reduced TC activity during colder periods, including the Late Antique Little Ice Age (LALIA; 540–660 CE) and the Little Ice Age (LIA; 1400–1700 CE), and increased activity from the end of cold periods to warm periods, including the Medieval Climate Anomaly (MCA; 950–1250 CE) and the Current Warm Period (CWP; 1850 CE–present). Our integration of paleo-TC and paleoclimate records shows that TC activity had been synchronously activated during warm periods at middle latitudes in the WNP; however, it had been enhanced during the LIA at low latitudes. These meridional anti-phase patterns are likely driven by the variability in air and sea surface temperature and associated shifts in the Hadley circulation. Given the unprecedented rise in global mean temperature, ongoing climate change may drive significant changes in TC behavior, potentially mirroring or exceeding past warm-period trends.