Tropical and mid-latitude forcing of continental Antarctic temperatures

C S M Turney,J G Palmer,A D Moy,A R Klekociuk,M A J Curran,T D Van Ommen,C J Fogwill

doi:10.5194/tc-9-2405-2015

Abstract

Abstract. Future changes in atmospheric circulation and associated modes of variability are a major source of uncertainty in climate projections. Nowhere is this issue more acute than across the mid-latitudes to high latitudes of the Southern Hemisphere (SH), which over the last few decades have experienced extreme and regionally variable trends in precipitation, ocean circulation and temperature, with major implications for Antarctic ice melt and surface mass balance. Unfortunately there is a relative dearth of observational data, limiting our understanding of the driving mechanism(s). Here we report a new 130-year annually resolved record of δD – a proxy for temperature – from the geographic South Pole where we find a significant influence from extratropical pressure anomalies which act as "gatekeepers" to the meridional exchange of air masses. Reanalysis of global atmospheric circulation suggests these pressure anomalies play a significant influence on mid- to high-latitude SH climate, modulated by the tropical Pacific Ocean. This work adds to a growing body of literature confirming the important roles of tropical and mid-latitude atmospheric circulation variability on Antarctic temperatures. Our findings suggest that future increasing tropical warmth will strengthen meridional circulation, exaggerating current trends, with potentially significant impacts on Antarctic surface mass balance.

Highlights

Uncertainty surrounding future changes in atmospheric circulation is exacerbated in the Southern Hemisphere (SH) by the acutely short baseline of observations available only since the onset of continuous monitoring during the mid-twentieth century and satellite era (Bracegirdle et al, 2015; Delworth and Zeng, 2014; Hobbs and Raphael, 2010; Marshall, 2003), despite the extreme and often contrasting trends in precipitation, ocean circulation and temperature (Gille, 2014), and Antarctic ice melt (Rye et al, 2014) which it has experienced in recent decades
By extending historical observations over the South Pole and in combination with reanalysis products, we find that meridional circulation changes associated with centres of pressure anomalies are part of a broader change observed over recent decades
Of particular note is the marked decrease in rainfall in southwestern Australia since the 1970s

Summary

Introduction

Uncertainty surrounding future changes in atmospheric circulation is exacerbated in the Southern Hemisphere (SH) by the acutely short baseline of observations available only since the onset of continuous monitoring during the mid-twentieth century and satellite era (post-1979) (Bracegirdle et al, 2015; Delworth and Zeng, 2014; Hobbs and Raphael, 2010; Marshall, 2003), despite the extreme and often contrasting trends in precipitation, ocean circulation and temperature (Gille, 2014), and Antarctic ice melt (Rye et al, 2014) which it has experienced in recent decades. Unlike coastal areas where different precipitation sources contribute to significant amounts of accumulation, diamond dust is continuously formed in the low atmosphere on the plateau during clear days, where most of the crystals are generated in the relatively moist upper part of the surface inversion (approximately 600–700 hPa) (Ekaykin et al, 2004; Fujita and Abe, 2006; Walden et al, 2003). To investigate multidecadal trends and reduce the impact of any missing years in the new combined South Pole record, we undertook a 30-year smoothing through the sequence

Methods

Results and discussion

Conclusions