Roles of insolation forcing and CO2 forcing on Late Pleistocene seasonal sea surface temperatures

Kyung Eun Lee,Si Woong Bae,Yoshimi Kubota,Sang-Wook Yeh,Steven C Clemens,Tae Wook Ko,Ann Holbourn,Axel Timmermann

doi:10.1038/s41467-021-26051-y

Abstract

Late Pleistocene changes in insolation, greenhouse gas concentrations, and ice sheets have different spatially and seasonally modulated climatic fingerprints. By exploring the seasonality of paleoclimate proxy data, we gain deeper insight into the drivers of climate changes. Here, we investigate changes in alkenone-based annual mean and Globigerinoides ruber Mg/Ca-based summer sea surface temperatures in the East China Sea and their linkages to climate forcing over the past 400,000 years. During interglacial-glacial cycles, there are phase differences between annual mean and seasonal (summer and winter) temperatures, which relate to seasonal insolation changes. These phase differences are most evident during interglacials. During glacial terminations, temperature changes were strongly affected by CO2. Early temperature minima, ~20,000 years before glacial terminations, except the last glacial period, coincide with the largest temperature differences between summer and winter, and with the timing of the lowest atmospheric CO2 concentration. These findings imply the need to consider proxy seasonality and seasonal climate variability to estimate climate sensitivity.

Highlights

Late Pleistocene changes in insolation, greenhouse gas concentrations, and ice sheets have different spatially and seasonally modulated climatic fingerprints
We investigate the seasonal sensitivity of foraminiferal Mg/Ca and alkenone temperature records from the same core in the East China Sea located at the western margin of the subtropical North Pacific Ocean over the last four interglacialglacial cycles
Comparisons of annual mean and seasonal temperature variability with orbital forcing and greenhouse gas forcing indicate that changes in annual mean and seasonal temperatures differ in response to insolation and CO2 forcing

Summary

Introduction

Late Pleistocene changes in insolation, greenhouse gas concentrations, and ice sheets have different spatially and seasonally modulated climatic fingerprints. The Mg/Ca ratio- and alkenone-based SSTs reflect summer and annual mean temperatures, respectively. The alkenone-based SST record exhibited very pronounced temperature minima at approximately 157, 268, and 364 kyr during the MISs 6, 8, and 10 glacial periods, well before the onset of glacial terminations (Fig. 1a).

Results

Conclusion