Physical properties of shallow ice cores from Antarctic and sub-Antarctic islands

Elizabeth Ruth Thomas,Dorothea Elisabeth Moser,Joel B Pedro,Mariusz Potocki,Amy Constance Faith King,Guisella Gacitúa,Bradley Markle

doi:10.5194/tc-15-1173-2021

Abstract

Abstract. The sub-Antarctic is one of the most data-sparse regions on earth. A number of glaciated Antarctic and sub-Antarctic islands have the potential to provide unique ice core records of past climate, atmospheric circulation, and sea ice. However, very little is known about the glaciology of these remote islands or their vulnerability to warming atmospheric temperature. Here we present melt histories and density profiles from shallow ice (firn) cores (14 to 24 m) drilled on three sub-Antarctic islands and two Antarctic coastal domes. Additionally, complementary ground-penetrating radar (GPR) data were collected to further characterize each site and assess the spatial distribution of the observed melt layers. This study includes the first ever firn cores from Bouvet Island (54∘25′19′′ S, 03∘23′27′′ E) in the South Atlantic, from Peter I Island (68∘51′05′′ S, 90∘30′35′′ W) in the Bellingshausen Sea, and from Young Island (66∘31′44′′ S, 162∘33′21′′ E) in the Ross Sea sector's Balleny island chain. Despite their sub-Antarctic location, surface melt is low at most sites (melt layers account for ∼ 10 % of total core), with undisturbed ice layers in the upper ∼ 40 m, suggesting minimal impact of meltwater percolation. The exception is Young Island, where melt layers account for 47 % of the firn core. Surface snow densities range from 0.47 to 0.52 kg m−3, with close-off depths ranging from 21 to 51 m. Based on the measured density, we estimate that the bottom ages of a 100 m ice core drilled on Peter 1 Island would reach ∼ 1856 CE and ∼ 1874 CE at Young Island.

Highlights

The sub-Antarctic region sits at the interface of polar and mid-latitude climate regimes, making it highly sensitive to shifting climate over time
A recent compilation of climate data spanning the 20th century revealed that of the 692 records that exist globally (Emile-Geay et al, 2017), none are available for the Southern Ocean
ground-penetrating radar (GPR) data obtained at Bouvet Island generally show layers of accumulated snow

Summary

Introduction

The sub-Antarctic region sits at the interface of polar and mid-latitude climate regimes, making it highly sensitive to shifting climate over time. The sub-Antarctic and the Southern Ocean region is one of the most data-sparse regions on earth. The vast expanse of open water makes climate and palaeoclimate observations difficult, but a number of glaciated sub-Antarctic islands (SAIs; defined here as islands south of the Southern Ocean polar front) may be suitable for extracting palaeoclimate information from ice cores (Fig. 1). Many of these SAIs sit within the westerly wind belt and the transitional sea ice zone (Fig. 1).

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