Glacial-Interglacial Variations in Organic Carbon Burial in the Northwest Pacific Ocean Over the Last 380 kyr and its Environmental Implications

Abstract

The carbon cycle on the Earth’s surface is linked to long-term variations in atmospheric CO2 as well as carbon sequestration in various pools. The burial of particulate organic carbon (OC) in marine sediments is also highly sensitive to the global climate over geological time scales, but with little known about OC burial and its regulations over glacial-interglacial cycles. Here, we present a long-term OC record over the past ∼380 kyr, from the Northwest Pacific Ocean, an ideal region for studying OC burial and its environmental implications on glacial-interglacial timescales. We observed a distinct cyclicity of higher OC burial in glacial periods, which was coupled with input from Asian dust and the Kuroshio Current but seemingly decoupled from biogenic element contents, implying a limited effect of marine productivity on OC burial. Moreover, the sedimentary record of OC was synchronous with oceanic redox conditions, especially the redox sensitive elements at the sediment-water interface, indicating a relatively reducing conditions that enhanced OC preservation during glacial periods. The overall glacial-interglacial OC burial regime in the Northwest Pacific Ocean was conceptually constructed. It showed a higher efficiency of OC burial during glacial periods and significant degradation during interglacial periods. The findings of this study highlighted the important contribution of environmental redox conditions on OC burial in the deep Northwest Pacific, demonstrating the sensitivity of the carbon cycle to global climate on an orbital scale.

Organic carbon burial and their implication on sea surface primary productivity in the middle Okinawa Trough over the past 200 ka

“…The deeper trough is mainly affected by NPIW, SCSIW or North Pacific Deep Water (NPDW) (Dou et al, 2015;Zhao et al, 2021). In a recent reconstruction of OC burial in the Northwest Pacific (water depth: 2670 m), it was shown that vertical water exchange was hindered due to the barrier formed by the enhanced glacial NPIW, so a hypoxic reducing environment was formed in the bottom water, which promoted the burial of OC (Zhang et al, 2022). We assumed that the water depth and topography of the site were crucial considering that core Z1 was collected from the west slope of the OT and the water depth was only 940 m. This location has been greatly affected by terrigenous materials and NPIW, so ventilation and related mineralization play important roles in regulating organic OC burial.…”

“…Many large rivers flow into the ECS, which causes the trough to receive tremendous detrital matter from East Asia. Compared with the continental shelf, the deeper water and slower sedimentation rate of the OT are conducive to preserving longscale paleoenvironmental information, providing high-resolution sedimentary records for the reconstruction of tectonic evolution, hydrological environmental changes, and global climate change during the Quaternary (Shinjo et al, 1999;Jian et al, 2000;Kao et al, 2005;Kao et al, 2006;Chang et al, 2009;Ujiiéet al, 2016;Li et al, 2017;Zhao et al, 2021;Zhang et al, 2022).…”