SEDIMENTARY EVIDENCE OF THE 13TH CENTURY KAMIKAZE TYPHOONS FROM SOUTHWESTERN JAPAN

Approximately a third of all tropical cyclones occurring throughout the world form within the western North Pacific, making this region the most active tropical cyclone basin on earth. Large uncertainties exist about how climate shifts affect tropical cyclone activity in this region, largely in part due to limited reliable instrumental records for typhoon activity, which merely go back to only a few decades. Consequently, longer data sets are needed to decipher dominant climatic controls that influence typhoon activity on centennial-to-millennial timescales.

Here we provide results from sediment cores from two coastal lagoons on western Kyushu in southwestern Japan (Lake Daija and Lake Kawahara) that provide evidence of episodic coastal inundation over the last 2500 years. Sediment cores collected along transects connecting beach to river inlet in both lakes contain periodically finely laminated organic mud, interbeded with dense units containing both marine and terrigenous materials (a finding consistent with typhoon-induced flooding from both storm surge and extreme precipitation). Two prominent event layers are dated to approximately the late 13^th century at both sites, with the timing of these deposits concurrent to two devastating typhoons that occurred during the late 13^th century that closely correlate to failed Mongol invasions of 1274 AD and 1281 AD. These deposits occur during a period of more frequent marine-sourced deposition, which potentially indicates that these historical typhoons occurred during a time when tropical cyclones were more prone to making landfall along the southwestern coast of Japan.