Late Quaternary glacier sensitivity to temperature and precipitation distribution in the Southern Alps of New Zealand

Abstract

Glaciers respond to climate variations and leave geomorphic evidence that represents an important terrestrial paleoclimate record. However, the accuracy of paleoclimate reconstructions from glacial geology is limited by the challenge of representing mountain meteorology in numerical models. Precipitation is usually treated in a simple manner and yet represents difficult-to-characterize variables such as amount, distribution, and phase. Furthermore, precipitation distributions during a glacial probably differed from present-day interglacial patterns. We applied two models to investigate glacier sensitivity to temperature and precipitation in the eastern Southern Alps of New Zealand. A 2-D model was used to quantify variations in the length of the reconstructed glaciers resulting from plausible precipitation distributions compared to variations in length resulting from change in mean annual air temperature and precipitation amount. A 1-D model was used to quantify variations in length resulting from interannual climate variability. Assuming that present-day interglacial values represent precipitation distributions during the last glacial, a range of plausible present-day precipitation distributions resulted in uncertainty in the Last Glacial Maximum length of the Pukaki Glacier of 17.1 km (24%) and the Rakaia Glacier of 9.3 km (25%), corresponding to a 0.5°C difference in temperature. Smaller changes in glacier length resulted from a 50% decrease in precipitation amount from present-day values (À14% and À18%) and from a 50% increase in precipitation amount (5% and 9%). Our results demonstrate that precipitation distribution can produce considerable variation in simulated glacier extents and that reconstructions of paleoglaciers should include this uncertainty.

A beryllium-10 chronology of late-glacial moraines in the upper Rakaia valley, Southern Alps, New Zealand supports Southern-Hemisphere warming during the Younger Dryas

“…Anderson and Mackintosh, 2006;Rowan et al, 2014). However, we note that atmospheric temperature is observed to be the predominant control on recent glacier mass-balance changes in the central Southern Alps (Anderson et al, 2010;Rowan et al, 2014). The results of our modeling indicate that a mean annual air temperature of about 2 °C cooler than present values could have sustained the glacier margin at the position of the Reischek knob III and Reischek knob IV moraines (Fig.…”

“…We are aware that temperature is not the sole control on glacier mass balance, and recognize that large changes in precipitation amount can mimic the effects of small temperature changes (e.g. Anderson and Mackintosh, 2006;Rowan et al, 2014). However, we note that atmospheric temperature is observed to be the predominant control on recent glacier mass-balance changes in the central Southern Alps (Anderson et al, 2010;Rowan et al, 2014).…”

The Last Glacial Maximum in the central North Island, New Zealand: palaeoclimate inferences from glacier modelling

“…The paucity of highaltitude precipitation data for the present-day represents an important source of uncertainty in both modern and palaeoapplications of glacier mass balance models. For example, Rowan et al (2014) find that uncertainty in present-day precipitation distribution imparts uncertainty of up to 25 % in modelled LGM glacier length in the central Southern Alps, which equates to about 0.5 • C in the palaeotemperature estimate. The good agreement between observed ice distribution on Mt Ruapehu and ice geometries simulated using the 30-year (AD 1981(AD -2010 average climate data sets (Fig.…”

Cosmogenic 10be Surface Exposure Dating and Numerical Modeling of Late pleistocene glaciers and Lakes in Northwestern Nevada

“…The coupled energy-mass balance and ice-flow models used in this study were originally developed by Plummer and Phillips (2003) and have been used to estimate paleo-climate conditions for paleo-glaciers in various mountain glacier settings (Rowan et al, 2014;Harrison et al, 2014;Leonard et al, 2017). The modeling approach aims to match simulated ice extents produced under specific paleoclimate conditions (e.g., temperature depression from modern and precipitation) to known ice extents reconstructed from glacial deposits and landforms identified in the field (e.g., terminal and lateral moraines).…”