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Mass Balance of Glaciers

The Intergovernmental Panel on Climate Change (IPCC) has provided the strongest and clearest statements about the nature and impacts of climate change to date. The recent Fourth Assessment states that over the 20th century 'warming of the climate system is unequivocal, and is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level' (IPCC, 2007). Global average sea level has risen at a rate of 3.2 mm/yr between 1993 and 2003 as a result of thermal expansion and the melting of glaciers, ice caps and the polar ice sheets. The earth's climate system is now in a no-analogue state, i.e. it has not experienced the present climatic configuration in the recent geological past. Consequently, studies of the behaviour of the impact of past climate change are of secondary importance in research on global environmental processes and change. The urgent research imperative is knowledge and understanding of the impacts of climate change now and the likely impacts in the future.

 

New Zealand Glaciers 

Global climate change has major implications for the environment and economy of New Zealand. One of the most vulnerable parts of the earth's system in New Zealand is the cryosphere which can be defined as the part of the earth that is characterised by the presence of snow and ice. The lack of systematic study of glaciers in New Zealand and the Ross Dependency, particularly the absence of a mass balance experiment in which the inputs and outputs of a glacier are monitored is a major deficiency in New Zealand's research profile. In New Zealand there are about 3153 glaciers with a total area of 116 km² which is about 5% of the area of the South Island (Chinn 1989). Most of the glacier-covered area is in the South Island with approximately the same areas on the west and east coasts but a greater volume on the east coast (Figure 1).

PieGraph_NZ_GlaciersFigure 1: Regional distribution of the New Zealand glaciers by volume

Figure 1: Regional distribution of the New Zealand glaciers by volume.

The largest glacier in New Zealand is the 29km-long Tasman Glacier, which is likely to respond the slowest to climate change because of its size. Widespread increased rates of snow and ice melt in temperate mountainous regions has contributed to the rise in sea level experienced during the last century. Consequently, a high priority is placed on understanding mid-latitude glaciers by the international scientific community. The lack of data from glaciers in the Southern Hemisphere has been identified as a significant gap in existing knowledge. Although it is widely accepted that New Zealand glaciers will diminish in size and about one third may disappear entirely, our knowledge of the behaviour of glaciers largely depends on the application of glacier models derived from studies of glaciers located in the Northern Hemisphere.

Laurel measuring snow stakeThere is very little direct data that informs us about the behaviour of glaciers in the Southern Hemisphere and sparce information on the mass balance state of glaciers in New Zealand. We believe that the lack of knowledge of the behaviour of glaciers is a major deficiency in research on natural environments in New Zealand. This deficiency needs urgent attention because glaciers in the Southern Alps are likely to undergo profound and sustained changes in the near future. The Intergovernmental Panel on Climate Change has concluded that a chain of events is in progress that cannot be stopped. While the risk posed by climate change cannot be averted we can understand what is likely to happen, where and how fast thereby mitigating the impacts. These insights provide information necessary for planning the mitigation of impacts on vulnerable sectors like tourism and electricity generation, thereby managing the environmental risks associated with glacier response to a changing climate.

 

Tropical Glaciers

Glaciers in the tropical regions of South America, Africa and New Guinea are good indicators of the climate in these regions, which is generally characterised by temperatures that do not exhibit high seasonal fluctuations. This lack of temperature variation leads to particular glacier behaviour and where changes in the behaviour can be attributed to disturbances in climatic parameters.

Glaciers in these regions have been retreating since the end of the Little Ice Age, though this retreat was punctuated by advancements or stagnant conditions (Kaser, 1999). However, the retreat has not been uniform. The retreat of the tabular glaciers on the summit plateau of Kilimanjaro (>5700m) is different to that of other tropical glaciers due to their high, nearly vertical walls at the margins (Mölg et al. 2003). Research into melt processes on these tabular glaciers has been carried out with particular regard to the energy balance at the vertical walls (Cullen et al. 2007). Even so there is still a poor understanding of glacier and climate interactions as observations are scares for the Tropics, thus highlighting the need for continued research on these glaciers.


Research questions

  • How are glaciers in the Southern Alps and different regions of the world responding to climate change?
  • What is the nature of regional variability in glacier response to climate change and what are the key environmental controls of regional differentiation?
  • How are the glaciers likely to respond to climate change in the future?
  • What are the implications of change in glaciers for contrasting alpine, tropical & polar ecosystems?
  • What are the likely impacts on the tourism and power generation industries?

 

Research Strategy

The proposed research clearly spans a wide latitudinal gradient from the topics to the high latitudes. The large environmental gradient will permit identification of a wide range of response timescales from the rapid responses of temperate, mid-latitude glaciers to the slow response of cold-based polar glaciers. Another advantage offered by the approach is to capitalise on research programmes already in progress and to cross-pollinate experiences of working in both environments.

Climate Station on Brewster Glacier

The research design consists of several aims:

  • To develop and implement mass balance monitoring programmes on several New Zealand glaciers (for example the Brewster Glacier)

  • To calculate and develop an understanding of the controls of altitudinal gradients of mass balance from the mass balance measurements. As well as calibrating remotely sensed-observations of snow cover and snowlines (ground-based photography by NIWA)

  • To develop predictive models of future glacier behaviour in New Zealand and elsewhere in the world.

 

References

Chinn, T. J. H., 1989: Glacier of New Zealand. In: Satellite Image Atlas of Glaciers in the World; Irian Jaya, Indonesia, and New Zealand. U.S. Geological Survey Professional Paper 1386-H: H25-48.

Cullen, N. J., Mölg, T., Kaser, G., Steffen, K. and Hardy, D. R. 2007. Energy-balance model validation on the top of Kilimanjaro, Tanzania, using eddy covariance data. Annals of Glaciology, 46, 227-233.

Kaser. G. 1999. A review of the modern fluctuations of tropical glaciers. Global and Planetary Change, 22, 93-103.

Mölg, T., Hardy, D. R. and Kaser, G. 2003. Solar-radiation-maintained glacier recession on Kilimanjaro drawn from combined ice-radiation geometry modelling. Journal of Geophysical Research Letters, 108 (D23), 4731.

 

Related Student Theses and Dissertations

Gillet, S. 2008. Modelling sumer ablation on the Brewster Glacier, New Zealand. Unpublished MSc thesis, in Geography, at the University of Otago, Dunedin, New Zealand. 109 pp.

Cutler, E. 2002. High elevation seasonal snow melt at the Tasman Glacier névé, Southern Alps, New Zealand. Unpublished MSc thesis, in Geography, at the University of Otago, Dunedin, New Zealand. 208 pp.

Evans, E. 2003. Ablation at the terminus of the Franz Josef Glacier. Unpublished BSc (hons) dissertation, in Geography, University of Otago, Dunedin, New Zealand. 58 pp. [abstract]

George, L. 2005. Mass balance and climate interactions at Brewster Glacier 2004-5. Unpublished MSc thesis, in Geography, University of Otago, Dunedin, New Zealand. [abstract]

Hooker, B.L. 1995. Advance and retreat of Franz Josef Glacier in relation to climate. Unpublished Postgraduate Diploma of Science dissertation, in Geography, at the University of Otago, New Zealand. 62 pp. [abstract]

Purdie, J.M. 1996. Ice loss at the terminus of the Tasman Glacier. Unpublished MSc thesis, in Geography, University of Otago, Dunedin, New Zealand. 191 pp. [abstract]

BrewsterGlacier


© 2009 Department of Geography, University of Otago, Dunedin, New Zealand