Holocene erosion processes dominated by the East Asian Summer Monsoon: Evidence from the radiocarbon age offset of lacustrine sediments in Gonghai Lake, Chinese Loess Plateau

Abstract

Soil and water loss due to erosion in the Chinese Loess Plateau (CLP) has been a persistent ecological issue of significant concern to both the government and society. However, the limited timespan of existing measurements has resulted in a poor understanding of the long-term processes and mechanisms underlying erosion in the region. Changes in the ¹⁴C reservoir age in enclosed lacustrine sediments are linked to the input of old carbon into lakes due to erosion. These changes can, to some extent, reflect the intensity of erosion within the surrounding catchment. In this study, we analyzed a sediment core GH09B from the central part of Gonghai Lake, a hydrologically closed alpine lake located on the northeastern margin of the CLP. The core provides a high-precision chronological framework spanning approximately the last 14.7 ka, based on 25 AMS ¹⁴C dates of terrestrial plant remains. To complement this, we obtained 24 AMS ¹⁴C dates of bulk samples within the same core (GH09B). By comparing the ¹⁴C ages of the bulk samples with those of terrestrial plant remains at corresponding depths, we reconstructed changes in the ¹⁴C reservoir age of Gonghai Lake on a millennial timescale during the Holocene. The results reveal that the ¹⁴C reservoir age was more pronounced during the early and late Holocene, while it was comparatively smaller during the middle Holocene. Drawing on high-resolution paleoclimate data from Gonghai Lake, we propose that during the middle Holocene, a relatively stronger East Asian Summer Monsoon (EASM) fostered greater vegetation coverage, which enhanced soil and water conservation, mitigated erosion, and, a result, reduced the carbon reservoir effect. In contrast, the weaker EASM during the early and late Holocene, coupled with lower vegetation coverage, led to increased erosion intensity and stronger carbon reservoir effect. Changes in vegetation coverage, primarily driven by fluctuations in the EASM, were the primary factor influencing catchment erosion intensity in the CLP during the Holocene.