Learning from the past: Impact of the Arctic Oscillation on sea ice and marine productivity off northwest Greenland over the last 9,000 years.

Audrey Limoges,Katrine E Hansen,Marit‐Solveig Seidenkrantz,Philippe Martinez,Eleanor Georgiadis,Jacques Giraudeau,Guillaume Massé,Kaarina Weckström,Xavier Crosta,Sofia Ribeiro

doi:10.1111/gcb.15334

Abstract

Climate warming is rapidly reshaping the Arctic cryosphere and ocean conditions, with consequences for sea ice and pelagic productivity patterns affecting the entire marine food web. To predict how ongoing changes will impact Arctic marine ecosystems, concerted effort from various disciplines is required. Here, we contribute multi‐decadal reconstructions of changes in diatom production and sea‐ice conditions in relation to Holocene climate and ocean conditions off northwest Greenland. Our multiproxy study includes diatoms, sea‐ice biomarkers (IP25 and HBI III) and geochemical tracers (TOC [total organic carbon], TOC:TN [total nitrogen], δ13C, δ15N) from a sediment core record spanning the last c. 9,000 years. Our results suggest that the balance between the outflow of polar water from the Arctic, and input of Atlantic water from the Irminger Current into the West Greenland Current is a key factor in controlling sea‐ice conditions, and both diatom phenology and production in northeastern Baffin Bay. Our proxy record notably shows that changes in sea‐surface conditions initially forced by Neoglacial cooling were dynamically amplified by the shift in the dominant phase of the Arctic Oscillation (AO) mode that occurred at c. 3,000 yr BP, and caused drastic changes in community composition and a decline in diatom production at the study site. In the future, with projected dominant‐positive AO conditions favored by Arctic warming, increased water column stratification may counteract the positive effect of a longer open‐water growth season and negatively impact diatom production.

Highlights

Climate change is causing an accelerating decline in the seasonal duration and thickness of Arctic sea ice (Serreze and Stroeve, 2015), with important implications for marine primary production (e.g., Comeau et al 2011; Tremblay et al 2012; Bergeron and Tremblay 2014)
Our multiproxy record supports the hypothesis of a pervasive effect of the dominant Arctic Oscillation (AO) phase on seaice conditions and diatom production on the northwest Greenland shelf
We show that an important and rapid decline in primary production starting around 3 cal kyrs BP was coeval with a shift from low to high AO polarity values

Summary

Introduction

Climate change is causing an accelerating decline in the seasonal duration and thickness of Arctic sea ice (Serreze and Stroeve, 2015), with important implications for marine primary production (e.g., Comeau et al 2011; Tremblay et al 2012; Bergeron and Tremblay 2014). For the Arctic Ocean, satellite-based measurements suggest that annual net primary production has increased by 30% between 1998 and 2012 (Arrigo and van Dijken 2015) This increase is largely attributed to thinning sea ice and more abundant and larger melt ponds that allow greater light transmittance and earlier onset of seasonal sea-ice melt, thereby enhancing both the under-ice productivity and the length of the growing season (Arrigo et al 2012; Mundy et al 2009). On the Holocene timescale, studies suggest linkages between hemispheric atmospheric circulation and hydrographical conditions in the North Atlantic region (e.g., Andersen et al 2004; Solignac et al 2004; Giraudeau et al 2010; Moros et al 2012; Staines-Urías et al 2013; Van Nieuwenhove et al 2018), and along the Southeast and Western Greenland shelves (e.g., Jennings et al 2011; Sha et al 2011; Krawczyk et al 2013)

Methods

Results

Discussion

Conclusion