Palaeo-productivity record from Norwegian Sea enables North Atlantic Oscillation (NAO) reconstruction for the last 8000 years

Lukas W M Becker,Hans Petter Sejrup,Haflidi Haflidason,Heidi Kjennbakken,Johannes P Werner,Berit O Hjelstuen

doi:10.1038/s41612-020-00147-6

Abstract

The North Atlantic Oscillation is the dominant atmospheric driver of North Atlantic climate variability with phases corresponding to droughts and cold spells in Europe. Here, we exploit a suggested anti-correlation of North Atlantic Oscillation-phase and north-eastern North Atlantic primary productivity by investigation of south-eastern Norwegian Sea sediment cores spanning the last 8000 years. Age model uncertainties between 2 and 13 years for the period 1992–1850 AD allows for the proxy to observational data calibration. Our data suggest that Ca/Fe core-scanning results reflect sedimentary CaCO3 variability in the region. Cross-correlating the Ca/Fe record with nearby phytoplankton counts and dissolved O2 data suggests that Ca/Fe can be used as a proxy for primary productivity variability in the region. Our data support an anti-correlation of primary productivity to the winter North Atlantic Oscillation index. Hence, we propose a sub-decadally resolved palaeo-North Atlantic Oscillation reconstruction based on an open-ocean record spanning the last 8000 years.

Highlights

The North Atlantic Oscillation (NAO) is the dominant driver of atmospheric variability in the North Atlantic region, determining the strength and position of the westerlies, which are the prevailing winds from the west across the North Atlantic
The eastern Norwegian Sea is directly influenced by the inflow of warm Atlantic surface water through the North Atlantic Current (NAC) (Fig. 1a)
If bulk sediment CaCO3 variability is reflected in the bulk elemental composition from an ITRAX X-ray fluorescence (XRF) core scanner, we focused on raw, bulk element XRF Ca counts and

Summary

INTRODUCTION

The North Atlantic Oscillation (NAO) is the dominant driver of atmospheric variability in the North Atlantic region, determining the strength and position of the westerlies, which are the prevailing winds from the west across the North Atlantic. There are currently only a few published pre-instrumental NAO reconstructions based on an open-ocean sediment record[5,6] among the numerous reconstructions based on palaeo data[7,8,9,10,11,12,13] This is likely due to challenges such as limited temporal resolution and lack of precise (sub-decadal) age control in marine records. This study investigates which factors influence CaCO3 concentrations in the slope sediments on the southern Norwegian continental margin This is done in order to address the following objectives: (i) can ITRAX-derived Ca/Fe variability be used as a proxy for changes in sea-surface primary productivity in the region and (ii) how this proxy may reflect known modes of oceanic and atmospheric variability in the region. Both core stratigraphies overlap with the late 20th-century observational time series of sea-surface conditions and productivity, enabling the calibration of proxy to observational data

RESULTS

DISCUSSION

METHODS