Preliminary Evidence for the Role Played by South Westerly Wind Strength on the Marine Diatom Content of an Antarctic Peninsula Ice Core (1980–2010)

Claire S Allen,Dieter R Tetzner,Richard A Warren,Thomas J Bracegirdle,Emily C Ludlow,Elizabeth R Thomas,Hilary Blagbrough

doi:10.3390/geosciences10030087

Abstract

Winds in the Southern Ocean drive exchanges of heat and carbon dioxide between the ocean and atmosphere. Wind dynamics also explain the dominant patterns of both basal and surface melting of glaciers and ice shelves in the Amundsen and Bellingshausen Seas. Long records of past wind strength and atmospheric circulation are needed to assess the significance of these recent changes. Here we present evidence for a novel proxy of past south westerly wind (SWW) strength over the Amundsen and Bellingshausen Seas, based on diatoms preserved in an Antarctic Peninsula ice core. Ecological affinities of the identified diatom taxa indicate an almost exclusively marine assemblage, dominated by open ocean taxa from the Northern Antarctic Zone (NAZ). Back-trajectory analysis shows the routes of air masses reaching the ice core site and reveals that many trajectories involve contact with surface waters in the NAZ of the Amundsen and Bellingshausen Seas. Correlation analyses between ice core diatom abundance and various wind vectors yield positive and robust coefficients for the 1980–2010 period, with average annual SWW speeds exhibiting the strongest match. Collectively, the data presented here provide new evidence that diatoms preserved in an Antarctic Peninsula ice core offer genuine potential as a new proxy for SWW strength.

Highlights

Introduction20th Century is attributed to a poleward shift of the southern westerly wind (SWW) belt associated with a shift to a more positive phase of the Southern Annular Mode (an index of the pressure gradient between the mid and high southern latitudes) in summer [1]
In the Antarctic Peninsula (AP) region, greatly accelerated warming over the second half of the20th Century is attributed to a poleward shift of the southern westerly wind (SWW) belt associated with a shift to a more positive phase of the Southern Annular Mode in summer [1]
The aim of this work was to assess whether the diatom content of the Ferrigno ice core can provide a valid proxy for SWW

Summary

Introduction

20th Century is attributed to a poleward shift of the southern westerly wind (SWW) belt associated with a shift to a more positive phase of the Southern Annular Mode (an index of the pressure gradient between the mid and high southern latitudes) in summer [1]. These circulation changes contribute to the flow of warmer air masses over the AP, resulting in increased snowfall in the region [2], and propel eddies of relatively warm Circumpolar Deep Water onto the continental shelf [3,4].

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