Morphological and ice-dynamical changes on the Tasman Glacier, New Zealand, 1990–2007 D.J. Quincey ⁎, N.F. Glasser Centre for Glaciology, Institute of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, SY23 3DB, UK abstract article info Article history: Received 18 July 2008 Accepted 13 May 2009 Available online 21 May 2009 Keywords: New Zealand morphology glacier dynamics proglacial lake remote sensing debris cover This paper presents data concerning recent (1990–2007) surface morphological and ice-dynamical changes on the Tasman Glacier, New Zealand. We use remote-sensing data to derive rates of lake growth, glacier velocities and rates of glacier surface lowering. Between 1990 and 2007, the glacier terminus receded ~3.5 km and a large ice-contact proglacial lake developed behind the outwash head. By 2007 the lake area was ~6 km 2 and had replaced the majority of the lowermost 4 km of the glacier tongue. There is evidence that lake growth is proceeding at increasing rates — the lake area doubled between 2000 and 2007 alone. Measured horizontal glacier velocities decline from 150 m a -1 in the upper glacier catchment to almost zero at the glacier terminus and there is a consequent down-glacier increase in surface debris cover. Surface debris mapping shows that a large catastrophic rockfall onto the glacier surface in 1991 is still evident as a series of arcuate debris ridges below the Hochstetter icefall. Calculated glacier surface lowering is most clearly pronounced around the terminal area of the glacier tongue, with down-wasting rates of 4.2±1.4 m a -1 in areas adjacent to the lateral moraine ridges outside of the current lake extent. Surface lowering rates of approximately 1.9±1.4 m a -1 are common in the upper areas of the glacier. Calculations of future lake expansion are dependent on accurate bathymetric and bed topography surveys, but published data indicate that a further 8–10 km of the glacier is susceptible to calving and further lake development in the future. © 2009 Elsevier B.V. All rights reserved. 1. Introduction The disintegration of debris-covered glaciers in mountain areas and the associated formation of glacial lakes is receiving increasing attention in many parts of the world, most notably the Himalaya (Watanabe et al., 1995; Benn et al., 2001), the Andes (Ames 1998; Huggel et al., 2004) and the European Alps (Haeberli et al., 2001; Huggel et al., 2002). Such morphological changes are of interest predominantly because they are symptomatic of a warming climate, indicating changes in local to regional scale temperature and precipitation gradients (Barry, 2006; Calmanti et al., 2007), but also because they can often provide an interesting insight into ablation mechanisms at a local scale, either through field observation or, where appropriate data are available, remote-sensing analyses. Understanding ablation mechanisms is, in turn, required for accurate modelling of energy balances and the future response of geomorphic and hydrological systems to continued climatic forcing (Kirkbride, 1995a). Recent advances in remote sensing have yielded a range of tech- niques with which to study glacierised terrain in very fine detail. Remote sensing now routinely provides data relating to glacier structure (Bishop et al., 1998), horizontal and vertical dynamics (Kääb, 2005; Luckman et al., 2007; Bolch et al., 2008), historic and contemporary fluctuations in extent (Paul et al., 2004; Rivera et al., 2007) and lake evolution (Watanabe et al., 1994; Quincey et al., 2007). Many of these remote- sensing derived data complement and even improve upon field-based assessments. Their integration can facilitate a wide area analysis of glacial processes, past and present, which would not be possible by other means. This paper uses a range of remotely sensed data to examine recent (1990–2007) morphological and ice-dynamical changes on the Tas- man Glacier, New Zealand; a glacier where the surface features have undergone significant change in recent years. The overall aim of the paper is to document the disintegration of the debris-mantled tongue between 1990 and 2007 and evaluate the roles of glacier dynamics and topography in shaping the current ice-surface morphology. In doing so, we address four specific objectives: 1. To document increases in the expansion of the proglacial lake, and to place this expansion into its historical context; 2. To quantify recent changes in horizontal (velocity) and vertical (surface elevation) dynamics; 3. To describe changes in glacier dynamics and ice-surface geomor- phological and topographic features; and 4. To integrate geomorphological, topographic and glacier dynamic information to assess the future development of the ice-contact proglacial lake. Global and Planetary Change 68 (2009) 185–197 ⁎ Corresponding author. Tel.: +44 1970 622784. E-mail address: djq@aber.ac.uk (D.J. Quincey). 0921-8181/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.gloplacha.2009.05.003 Contents lists available at ScienceDirect Global and Planetary Change journal homepage: www.elsevier.com/locate/gloplacha