Abstract
The onset of deglaciation in the Southern Hemisphere mid-latitudes has been attributed to the southward transmission of climate anomalies in response to slow-down of Atlantic meridional overturning circulation (AMOC) during Heinrich Stadial 1 (HS-1; 18–14.6 ka). However, inferences on the response of former ice sheets to sub-millennial palaeoclimate shifts are limited by a shortage of high-resolution terrestrial archives. Here we use a ~1000-year duration, annually-resolved lake sediment record to investigate the deglacial retreat dynamics of the Lago General Carrera–Buenos Aires ice lobe (46.5°S) of the former Patagonian Ice Sheet. We attribute the onset of glacier retreat at 18.0 ± 0.14 cal ka BP to abrupt southward migration of the Southern Westerly Winds that enhanced solar radiation receipt (and ablation) at the ice sheet surface. We infer that accelerated retreat from 17.77 ± 0.13 cal ka BP represents a lagged Southern Hemisphere response to gradual ocean-atmosphere warming associated with the centennial-scale transmission of Northern Hemisphere climate anomalies through the oceanic bipolar seesaw. By 17.38 ± 0.12 cal ka BP, the glacier margin had receded into a deepening proglacial lake, instigating sustained calving losses and more rapid ice recession.
Highlights
The mid-latitude ice masses of Patagonia and New Zealand are ideally located to investigate the response of the cryosphere to climatic changes that occurred during the global Last Glacial Maximum (LGM) and succeeding deglacial period[1,2,3]
Through detailed sedimentological investigation of these sequences, Bendle et al developed the Fenix Chico Master Varve Chronology (FCMC17), a composite record derived from five varve series located in the eastern parts of the LGC–BA basin
The FCMC17 varves are composed of two main sedimentary layers (Fig. 2): a silt and/or fine sand layer deposited during the melt season in response to glacier ablation and sediment transport through the glaciohydraulic system; and a clay layer that settled from suspension during the quiescent non-melt season when glacier ablation ceased, and meltwater/sediment fluxes to the lake diminished[25]
Summary
The mid-latitude ice masses of Patagonia and New Zealand are ideally located to investigate the response of the cryosphere to climatic changes that occurred during the global Last Glacial Maximum (LGM) and succeeding deglacial period[1,2,3]. Increased varve thickness has been linked to transitional periods of (i) rapid glacier advance (i.e. increased ice-margin proximity) or (ii) the initial phases (one-to-two decades) of glacier retreat (i.e. enhanced glacier ablation and meltwater/sediment flux)[31,36]. Using these established glacier-varve relationships, high-resolution (
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