Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial

Chris S M Turney,Christopher J Fogwill,Jonathan Palmer,David K Hutchinson,Zoë Thomas,Richard T Jones,Konrad A Hughen ,Alan G Hogg ,Gretel Boswijk,Simon Haberle,Andrew Lorrey,Mark Grosvenor,Christopher Bronk Ramsey,Steven J Phipps,Nicholas R Golledge,Sune Olander Rasmussen,Richard A Staff,A Peter Kershaw,Florian Adolphi,Raimund Muscheler,Alan Cooper

doi:10.1038/s41467-017-00577-6

Abstract

Contrasting Greenland and Antarctic temperatures during the last glacial period (115,000 to 11,650 years ago) are thought to have been driven by imbalances in the rates of formation of North Atlantic and Antarctic Deep Water (the ‘bipolar seesaw’). Here we exploit a bidecadally resolved 14C data set obtained from New Zealand kauri (Agathis australis) to undertake high-precision alignment of key climate data sets spanning iceberg-rafted debris event Heinrich 3 and Greenland Interstadial (GI) 5.1 in the North Atlantic (~30,400 to 28,400 years ago). We observe no divergence between the kauri and Atlantic marine sediment 14C data sets, implying limited changes in deep water formation. However, a Southern Ocean (Atlantic-sector) iceberg rafted debris event appears to have occurred synchronously with GI-5.1 warming and decreased precipitation over the western equatorial Pacific and Atlantic. An ensemble of transient meltwater simulations shows that Antarctic-sourced salinity anomalies can generate climate changes that are propagated globally via an atmospheric Rossby wave train.

Highlights

Contrasting Greenland and Antarctic temperatures during the last glacial period (115,000 to 11,650 years ago) are thought to have been driven by imbalances in the rates of formation of North Atlantic and Antarctic Deep Water
We identify a ~460-year-long radiocarbon plateau at ~26.4 14C kyr BP coincident with Greenland Interstadial (GI)-5.1 and a ~480-year duration ~25.4 14C kyr BP plateau during a period of enhanced delivery of freshwater and debris-laden icebergs into the North Atlantic associated with HE3
The parallel changes in Cariaco Basin surface water and atmospheric 14C levels argue against a stratification of surface waters[20] and collapse of the Meridional Overturning Circulation (MOC)[8,9,10] implying the ocean circulation was not appreciably shutdown during the 2000 years captured by our tree-ring series

Summary

Introduction

Contrasting Greenland and Antarctic temperatures during the last glacial period (115,000 to 11,650 years ago) are thought to have been driven by imbalances in the rates of formation of North Atlantic and Antarctic Deep Water (the ‘bipolar seesaw’). We observe no divergence between the kauri and Atlantic marine sediment 14C data sets, implying limited changes in deep water formation. Oceanic meridional heat transport variations are recorded through most of this period, recent work on North Atlantic marine sediments has highlighted limited changes in ocean circulation between 33 and 18 kyr BP8–10, and yet a pervasive antiphase temperature relationship continues to be observed between Greenland and Antarctica[4, 6], implying that additional mechanism (s) may have operated during the glacial. Calendar age uncertainties for synchronization of records shown at 2σ (95% confidence limits) a

Methods

Results

Conclusion