High-latitude biomes and rock weathering mediate climate\u2013carbon cycle feedbacks on eccentricity timescales

David De Vleeschouwer,Anna Joy Drury,Fiona Rochholz,Diederik Liebrand,Maximilian Vahlenkamp,Heiko Pälike

doi:10.1038/s41467-020-18733-w

Abstract

The International Ocean Discovery Programme (IODP) and its predecessors generated a treasure trove of Cenozoic climate and carbon cycle dynamics. Yet, it remains unclear how climate and carbon cycle interacted under changing geologic boundary conditions. Here, we present the carbon isotope (δ13C) megasplice, documenting deep-ocean δ13C evolution since 35 million years ago (Ma). We juxtapose the δ13C megasplice with its δ18O counterpart and determine their phase-difference on ~100-kyr eccentricity timescales. This analysis reveals that 2.4-Myr eccentricity cycles modulate the δ13C-δ18O phase relationship throughout the Oligo-Miocene (34-6 Ma), potentially through changes in continental weathering. At 6 Ma, a striking switch from in-phase to anti-phase behaviour occurs, signalling a reorganization of the climate-carbon cycle system. We hypothesize that this transition is consistent with Arctic cooling: Prior to 6 Ma, low-latitude continental carbon reservoirs expanded during astronomically-forced cool spells. After 6 Ma, however, continental carbon reservoirs contract rather than expand during cold periods due to competing effects between Arctic biomes (ice, tundra, taiga). We conclude that, on geologic timescales, System Earth experienced state-dependent modes of climate–carbon cycle interaction.

Highlights

The International Ocean Discovery Programme (IODP) and its predecessors generated a treasure trove of Cenozoic climate and carbon cycle dynamics
Building on the outcomes from these modelling studies, we suggest that the Oligocene climate state could support a system in which CO2 is more efficiently removed from the atmosphere during the colder intervals associated with eccentricity-minima
To explain the suggested shift in weathering regime from the high to the low latitudes, we suggest that Earth underwent a transition from an Oligocene (Interval I) climate state with distinct climate belts and a fully glaciated Antarctica to a Miocene (Interval II) monsoon-dominated climate state with stronger north–south atmospheric circulation, promoted by a main uplift phase of the Himalayan orogen unfolding around that time[64] (Fig. 4a)

Summary

Introduction

The International Ocean Discovery Programme (IODP) and its predecessors generated a treasure trove of Cenozoic climate and carbon cycle dynamics. To date, the evolution and pivotal points of carbon cycle–climate feedback mechanisms throughout the Cenozoic Icehouse are poorly understood This is due to a lack of continuous high-resolution benthic isotope records that span the last 35 Myr of Earth’s history. The δ13Cbenthic megasplice provides a time-continuous geological history of carbon-cycle dynamics over the last 35 Myr (Fig. 1c) by combining records from different ocean basins. The removal of smooth inter-basinal δ13Cbenthic trends from individual isotopic time-series reveals similar astronomical rhythms in δ13Cbenthic time-series from different basins (Supplementary Fig. 1) This highlights an important assumption for this work: Deep-sea δ13Cbenthic records from different basins pick up a strong global astronomical δ13Cbenthic rhythm, despite distinct basin-specific δ13CDIC values.

Methods

Results

Conclusion