Spatial pattern of accumulation at Taylor Dome during Marine Isotope Stage 4: stratigraphic constraints from Taylor Glacier

James A Menking,Shaun Marcott,Jeffrey P Severinghaus,Stephen Barker,Rachael H Rhodes,Vasilii Petrenko,Michael N Dyonisius,Sarah A Shackleton,Thomas K Bauska,Joseph R Mcconnell,Edward J Brook,Daniel Baggenstos

doi:10.5194/cp-15-1537-2019

Abstract

Abstract. New ice cores retrieved from the Taylor Glacier (Antarctica) blue ice area contain ice and air spanning the Marine Isotope Stage (MIS) 5–4 transition, a period of global cooling and ice sheet expansion. We determine chronologies for the ice and air bubbles in the new ice cores by visually matching variations in gas- and ice-phase tracers to preexisting ice core records. The chronologies reveal an ice age–gas age difference (Δage) approaching 10 ka during MIS 4, implying very low snow accumulation in the Taylor Glacier accumulation zone. A revised chronology for the analogous section of the Taylor Dome ice core (84 to 55 ka), located to the south of the Taylor Glacier accumulation zone, shows that Δage did not exceed 3 ka. The difference in Δage between the two records during MIS 4 is similar in magnitude but opposite in direction to what is observed at the Last Glacial Maximum. This relationship implies that a spatial gradient in snow accumulation existed across the Taylor Dome region during MIS 4 that was oriented in the opposite direction of the accumulation gradient during the Last Glacial Maximum.

Highlights

Trapped air in ice cores provides a direct record of the Earth’s past atmospheric composition (e.g., Bauska et al, 2016; Petrenko et al, 2017; Schilt et al, 2014)
Ice containing the full Marine Isotope Stage (MIS) 5–4 transition was formerly considered to be missing from the glacier (Baggenstos, 2015; Baggenstos et al, 2017), but we show here that a new ice core near the main transect contains an intact record with ice dating from 76.5–60.6 ka and air dating from 74.0–57.7 ka
In order to obtain exploratory gas age information and verify the continuous CH4 data, discrete ice core samples were measured for CH4 concentration in the field using a Shimadzu gas chromatograph coupled to a custom melt–refreeze extraction line, a manually operated version similar to the automated system used at Oregon State University (OSU) (Mitchell et al, 2011, 2013)

Summary

Introduction

Trapped air in ice cores provides a direct record of the Earth’s past atmospheric composition (e.g., Bauska et al, 2016; Petrenko et al, 2017; Schilt et al, 2014). Measurements of trace gas species, their isotopic composition, create a demand for large-volume glacial ice core samples. Effective techniques for dating ablation zone ice include matching globally well-mixed atmospheric trace gas records (e.g., CH4, CO2, δ18Oatm, N2O) and correlating glaciochemical records (e.g., δ18Oice, Ca2+, insoluble particles) with existing ice core records with precise chronologies

Methods

Results

Discussion

Conclusion