Multi-proxy records of Holocene hydroclimatic and environmental changes on the southern coast of South Korea

Abstract

A well-dated sediment core from the Goheung area of the southern coast of the Korean Peninsula was used to reconstruct the history of environmental and vegetation changes in response to variability in the East Asian summer monsoon (EASM) and the sea-level change during the Holocene. A multi-proxy analysis (palynomorphs, mean grain size, TOC, TS, C/N ratio, and δ13CTOC data) indicated that the study area underwent a change in environment from a fluvio-coastal (a fluvial to intertidal zone) to a subtidal zone due to a sea-level rise at ca. 7500 cal yr BP. Since ca. 6000 cal yr BP, it has gradually returned to a brackish-dominant environment (intertidal zone) due to coastal regression, with a decrease in relative sea-level. Palynological data show that the climate of the southern coast of the Korean Peninsula underwent a gradual cooling trend after ca. 5900 cal yr BP, due to weakening EASM intensity in response to decreasing insolation in the Northern Hemisphere. Therefore, the long-term vegetation dynamics in this study area were controlled primarily by solar insolation–driven temperature changes during the Holocene. They were also associated with sea surface temperature (SST) changes in the western tropical Pacific (WTP). The vegetation dynamics (sharp reduction of broad-leaved trees and freshwater discharge indicators) in our study area indicate cold and dry climatic conditions since ca. 4500 cal BP, which may have been caused by the decreasing SST in the WTP. In addition, the strong link between the Holocene vegetation dynamics in the East Asian coastal area (especially, Quercus-Lepidobalanus and Pinus-Diploxylon) and SST variation in the WTP may suggest that the centennial-timescale recurring variations in EASM activity have been controlled by low-latitude ocean forcing induced by El Niño Southern Oscillation activity.