Alpine and Polar Processes Consultancy

Lake, New Zealand

Alpine and Polar Processes Consultancy

Lake, New Zealand
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Kaplan M.R.,Lamont Doherty Earth Observatory | Schaefer J.M.,Lamont Doherty Earth Observatory | Schaefer J.M.,Columbia University | Denton G.H.,University of Maine, United States | And 10 more authors.
Geology | Year: 2013

The timing and magnitude of postglacial climatic changes around the globe provide insights into the underlying drivers of natural climate change. Using geomorphologic mapping of moraines,10Be surface-exposure dating, snowline reconstructions, and numerical modeling, we quantified glacier behavior during Late Glacial (15-11.5 ka) and Holocene (the past ̃11.5 k.y.) time in the Ben Ohau Range, New Zealand. Glaciers were more extensive during the Antarctic Cold Reversal (ACR), than subsequently, and the margins underwent a punctuated net withdrawal over the Holocene. Numerical modeling experiments that achieve the best fit to the moraines suggest that air temperature during the ACR was between 1.8°C and 2.6°C cooler than today, with similar (±20%) prescribed precipitation. After the ACR, a net snowline rise of ̃100 m through the Younger Dryas stadial (12.9-11.7 ka) was succeeded by a further "long-term," or net, rise of ̃100 m between ̃11 k.y. and ̃500 yr ago. Glacier snowline records in New Zealand show generally coherent Late Glacial and Holocene climate trends. However, the paleoclimate record in the southwest Pacific region shows important differences from that in the Northern Hemisphere. © 2013 Geological Society of America.

Putnam A.E.,Lamont Doherty Earth Observatory | Putnam A.E.,University of Maine, United States | Schaefer J.M.,Lamont Doherty Earth Observatory | Schaefer J.M.,Columbia University | And 7 more authors.
Nature Geoscience | Year: 2012

Mountain glaciers worldwide have undergone net recession over the past century in response to atmospheric warming, but the extent to which this warming reflects natural versus anthropogenic climate change remains uncertain. Between about 11,500 years ago and the nineteenth century, progressive atmospheric cooling over the European Alps induced glacier expansion, culminating with several large-scale advances during the seventeen to nineteenth centuries. However, it is unclear whether this glacier behaviour reflects global or a more regional forcing. Here we reconstruct glacier fluctuations in the Southern Alps of New Zealand for the past 11,000 years using 10 Be exposure ages. We use those fluctuations to estimate the associated temperature variations. On orbital to submillennial timescales, changes in glacier snowlines in New Zealand were linked to regional climate and oceanographic variability and were asynchronous with snowline variations in European glaciers. We attribute this asynchrony to the migration of the intertropical convergence zone. In light of this persistent asynchrony, we suggest that the net glacier recession and atmospheric warming in both regions over the past century is anomalous in the context of earlier Holocene variability and corresponds with anthropogenic emissions of greenhouse gases. © 2012 Macmillan Publishers Limited. All rights reserved.

Purdie H.,University of Canterbury | Rack W.,University of Canterbury | Anderson B.,Victoria University of Wellington | Kerr T.,Aqualinc Research Ltd | And 3 more authors.
Geografiska Annaler, Series A: Physical Geography | Year: 2015

Glacier mass balance is more sensitive to warming than cooling, but feedbacks related to the exposure of previously buried firn and ice in very warm years is not generally considered in sensitivity studies. A ground-penetrating radar survey in the accumulation area of Rolleston Glacier, New Zealand shows that five years of previous net accumulation was removed by melt from parts of the glacier above the long-term equilibrium line altitude during a single negative mass balance year. Rolleston Glacier receives a large amount of accumulation from snow avalanches, which may temporarily buffer it from climate warming by providing additional mass that has accumulated at higher elevations, effectively increasing the elevation range of the glacier. However, glaciers reliant on avalanche input may have high sensitivity to climatic variations because the extra mass is concentrated on a small part of the glacier, and small variations in avalanche input could have a large impact on overall glacier accumulation. Further research is needed to better estimate the amount and spatial distribution of accumulation by avalanche in order to quantify the climate sensitivity of small avalanche-fed glaciers. © 2015 Swedish Society for Anthropology and Geography.

Winkler S.,University of Canterbury | Chinn T.,Alpine and Polar Processes Consultancy | Gartner-Roer I.,University of Zürich | Nussbaumer S.U.,University of Bern | And 2 more authors.
Erdkunde | Year: 2010

Summary: This article gives an introduction to the spatial and temporal diversity of mountain glaciers as climate indicators. Alongside some information about the present extent of mountain glaciation and available databases, some specific problems with the interpretation of mountain glacier changes are highlighted.

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