Faster Atlantic currents drive poleward expansion of temperate phytoplankton in the Arctic Ocean

L Oziel,M Ardyna,M Babin,A Randelhoff,E Devred,J.-B Sallée,A Baudena,R B Ingvaldsen,P Massicotte

doi:10.1038/s41467-020-15485-5

Abstract

The Arctic marine biome, shrinking with increasing temperature and receding sea-ice cover, is tightly connected to lower latitudes through the North Atlantic. By flowing northward through the European Arctic Corridor (the main Arctic gateway where 80% of in- and outflow takes place), the North Atlantic Waters transport most of the ocean heat, but also nutrients and planktonic organisms toward the Arctic Ocean. Using satellite-derived altimetry observations, we reveal an increase, up to two-fold, in North Atlantic current surface velocities over the last 24 years. More importantly, we show evidence that the North Atlantic current and its variability shape the spatial distribution of the coccolithophore Emiliania huxleyi (Ehux), a tracer for temperate ecosystems. We further demonstrate that bio-advection, rather than water temperature as previously assumed, is a major mechanism responsible for the recent poleward intrusions of southern species like Ehux. Our findings confirm the biological and physical “Atlantification” of the Arctic Ocean with potential alterations of the Arctic marine food web and biogeochemical cycles.

Highlights

The Arctic marine biome, shrinking with increasing temperature and receding sea-ice cover, is tightly connected to lower latitudes through the North Atlantic
Emiliania huxleyi (Ehux) is usually associated with the surface layer of the temperate North Atlantic Waters (NAW) in summer, typically in a post-spring bloom context characterized by low nutrients, low light and strong stratification[30,31,32]
Using a Lagrangian tracking approach based on satellitederived current fields, we explore how the advection of Ehux cells from these upstream coastal temperate regions shapes the distribution of the massive Ehux blooms in the Barents Sea (BS)

Summary

Introduction

The Arctic marine biome, shrinking with increasing temperature and receding sea-ice cover, is tightly connected to lower latitudes through the North Atlantic. To document the interannual and decadal variability of surface NAW currents, we first performed an Empirical Orthogonal Function (EOF) analysis of the Sea Level Anomalies (1993–2016, see Material and Methods), on which the seasonal signal was removed.

Results

Conclusion