Abstract
Proglacial lakes can affect the stability of mountain glaciers and can partly disengage glacier behaviour from climatic perturbations. However, their role in controlling the onset and progression of deglaciation from the Last Glacial Maximum (LGM) remains poorly understood. This lack of understanding is partly because the evidence required to consistently and robustly identify the location and evolution of ice-contact lakes is not standardised. In this paper we therefore firstly present a new set of criteria for identifying the landform and sedimentary evidence that defines and characterises ice-marginal lakes. Secondly, we then apply these key criteria with the aid of high-resolution topographic mapping to produce the first holistic definition and assessment of major proglacial lake landforms and sediments pertaining to the end of the LGM across South Island, New Zealand. The major findings of this assessment can be grouped to include that: (i) The localised constraints to proglacial lake extent were topography, glacier size and meltwater/sediment fluxes, (ii) Lake damming was initiated by outwash fan-heads that interrupted water and sediment flows down-valley, and (iii) New Zealand LGM lakes were unequivocally in contact with a calving ice margin. These findings will be useful for reconstructing ice dynamics and landscape evolution in this region.
Highlights
Introduction and aimsProglacial lakes are pervasive globally within contemporary mountain environments
We provide an overview of the distribution and geometry of nine proglacial lakes situated within parallel valleys east of the Main Divide (Fig. 1)
With lakes presently persisting at moraine limits (Supplementary Fig. 1A) it is likely that large proglacial lakes would have formed on the Westland piedmont, occupying glacial troughs during ice retreat and there would have been more Last Glacial Maximum (LGM) lakes on the western side of the Southern Alps than we see evidence for
Summary
Introduction and aimsProglacial lakes are pervasive globally within contemporary mountain environments. Ice-contact proglacial lakes are important for determining glacier geometry and behaviour (Carrivick and Tweed, 2013) They play a significant role in controlling proglacial landform evolution and effectively buffer the delivery of meltwater and sediment to proglacial areas and to the oceans (Larsen et al, 2011; Tsutaki et al, 2011; Carrivick and Tweed, 2013; Staines et al, 2015). They can provide an effective buttress to the ice margin, evidenced by periods of instability following rapid and sudden drainage events (Kirkbride and Warren, 1999; Diolaiuti et al, 2006; Ro€hl, 2008). Large floods from proglacial lakes are known to have affected global circulation and global climate during the Quaternary (Barber et al, 1999; Clark et al, 2001 Teller et al, 2002; Mangerud et al, 2004)
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