Temperature change in subtropical southeastern Africa during the past 790,000 yr

Manuel Chevalier,Lydie M Dupont,Brian M Chase,Thomas C Johnson,Lynne J Quick

doi:10.1130/g47841.1

Abstract

Abstract Across the glacial-interglacial cycles of the late Pleistocene (∼700 k.y.), temperature variability at low latitudes is often considered to have been negligible compared to changes in precipitation. However, a paucity of quantified temperature records makes this difficult to reliably assess. In this study, we used the Bayesian method CREST (Climate REconstruction SofTware) to produce a 790,000 yr quantified temperature reconstruction from a marine pollen record from southeast Africa. The results reveal a strong similarity between temperature variability in subtropical Africa and global ice volume and CO2 concentrations, indicating that temperature in the region was not controlled by local insolation, but followed global trends at these time scales, with an amplitude of ∼4 °C between glacial minima and interglacial maxima. The data also enabled us to make an assessment of the impact of temperature change on pollen diversity, with results showing there is no link between glacial-age temperatures/CO2 and a loss of diversity in this record.

Highlights

Hydrological conditions have been shown to be highly variable during the late Pleistocene in tropical and subtropical southeastern Africa (e.g., Schefuß et al, 2011; Johnson et al, 2016; Caley et al, 2018)
In the case of MD96–2048, the region is dominated by easterly onshore winds year-round (Tyson and Preston-White, 2000), which is not favorable for eolian pollen transport to the coring location, and studies indicate that most of the terrestrial sediment flux is fluvial in origin (Dupont et al, 2011; Castañeda et al, 2016)
The MD96–2048 mean annual temperature (MAT) reconstruction is strikingly similar to glacial-interglacial signatures of global temperature (Pearson’s correlation index ρ = 0.76 [last 342 k.y.]/0.72 [entire record]; Jouzel et al, 2007), atmospheric CO2 concentration (ρ = 0.77/0.74; Lüthi et al, 2008; Bereiter et al, 2015), and ice volume (ρ = –0.79/−0.66; Lisiecki and Raymo, 2005) throughout the past 790 k.y. (Fig. 4; Appendix S2)

Summary

Introduction

Hydrological conditions have been shown to be highly variable during the late Pleistocene in tropical and subtropical southeastern Africa (e.g., Schefuß et al, 2011; Johnson et al, 2016; Caley et al, 2018). The development of the Bayesian climate reconstruction method CREST (Climate REconstruction SofTware) has enabled the reconstruction of quantified records of past climate change from fossil pollen data (Chevalier et al, 2014), with recent results highlighting a strong connection between terrestrial temperatures and sea-surface temperatures (SSTs) from the Mozambique Channel (Truc et al, 2013; Chevalier and Chase, 2015) These reconstructions are too short (20 k.y. and 45 k.y., respectively) to determine responses to a more complete suite of Pleistocene conditions, periods of high eccentricity, when variations in direct insolation were substantially greater than during the last 50 k.y. These reconstructions are too short (20 k.y. and 45 k.y., respectively) to determine responses to a more complete suite of Pleistocene conditions, periods of high eccentricity, when variations in direct insolation were substantially greater than during the last 50 k.y. (Laskar et al, 2004)

Methods

Results

Conclusion