Analysis of the frequency of the Kuroshio large meander over the past 20,000 yearsfrom Mg/Ca-derived temperature of individual foraminiferal analysis

Abstract

The frequency of past occurrences of the Kuroshio large meander is analyzed by examining the Mg/Ca ratio of planktonic foraminiferal shells in marine sediment cores using Individual Foraminifera Analysis (IFA). The core samples were collected off the coast of the Tokai region, where there is a temperature difference between non-large meander periods and large meander periods. IFA involves picking approximately 100 individual planktonic foraminifera from a single stratigraphic layer and analyzing the Mg/Ca ratio temperature of each individual. From the temperatures of 100 individuals, the temperature frequency distribution recorded over an approximate 100-year sedimentation period is reconstructed. The frequency of large meander occurrences is analyzed from the distribution characteristics of the high-temperature side of the bimodal temperature distribution.