Glacial discharge along the west Antarctic Peninsula during the Holocene

Jennifer Pike,George E A Swann,Melanie J Leng,Andrea M Snelling

doi:10.1038/ngeo1703

Abstract

The causes for rising temperatures along the Antarctic Peninsula during the late Holocene have been debated, particularly in light of instrumental records of warming over the past decades1. Suggested mechanisms range from upwelling of warm deep waters onto the continental shelf in response to variations in the westerly winds2, to an influence of El Nino–Southern Oscillation on sea surface temperatures3. Here, we present a record of Holocene glacial ice discharge, derived from the oxygen isotope composition of marine diatoms from Palmer Deep along the west Antarctic Peninsula continental margin. We assess atmospheric versus oceanic influences on glacial discharge at this location, using analyses of diatom geochemistry to reconstruct atmospherically forced glacial ice discharge and diatom assemblage4 ecology to investigate the oceanic environment. We show that two processes of atmospheric forcing—an increasing occurrence of La Nina events5 and rising levels of summer insolation—had a stronger influence during the late Holocene than oceanic processes driven by southern westerly winds and upwelling of upper Circumpolar Deepwater. Given that the evolution of El Nino–Southern Oscillation under global warming is uncertain6, its future impacts on the climatically sensitive system of the Antarctic Peninsula Ice Sheet remain to be established.

Highlights

World-wide, the west Antarctic Peninsula (WAP) has experienced one of the greatest and fastest rates of atmospheric warming since observations began[1]
We show that increasing occurrence of La Niña[5] and increasing summer insolation, atmospheric forcing, had a stronger influence on glacial discharge to the west Antarctic Peninsula margin during the late Holocene than oceanic processes driven by southern westerly winds and upwelling of upper circumpolar deepwater
We interpret our δ18Odiatom record (Fig. 1a) from Palmer Deep, WAP (ODP Site 1098A, 64°51.72’S, 64°12.47’W)[9] as being forced by variations in glacial discharge (δ18O < –20‰) and our record, together with planktonic diatom assemblage data[4], provides a unique opportunity to assess the relative contributions to past glacial discharge of (i) glacial ice discharge forced by atmospheric processes, and (ii) frontal melt driven by oceanic warmth

Summary

Introduction

World-wide, the west Antarctic Peninsula (WAP) has experienced one of the greatest and fastest rates of atmospheric warming since observations began[1]. We show that increasing occurrence of La Niña[5] and increasing summer insolation, atmospheric forcing, had a stronger influence on glacial discharge to the west Antarctic Peninsula margin during the late Holocene than oceanic processes driven by southern westerly winds and upwelling of upper circumpolar deepwater.

Results

Conclusion