* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download New Zealand glacier response to climate change of the past 2
Climate change adaptation wikipedia , lookup
Climate sensitivity wikipedia , lookup
Politics of global warming wikipedia , lookup
Solar radiation management wikipedia , lookup
Climate change in Tuvalu wikipedia , lookup
Climate change and agriculture wikipedia , lookup
Instrumental temperature record wikipedia , lookup
Global warming wikipedia , lookup
Effects of global warming on human health wikipedia , lookup
Media coverage of global warming wikipedia , lookup
Scientific opinion on climate change wikipedia , lookup
Climate change feedback wikipedia , lookup
Attribution of recent climate change wikipedia , lookup
Climate change and poverty wikipedia , lookup
Effects of global warming wikipedia , lookup
Effects of global warming on humans wikipedia , lookup
Climate change in New Zealand wikipedia , lookup
Climate change, industry and society wikipedia , lookup
Public opinion on global warming wikipedia , lookup
Surveys of scientists' views on climate change wikipedia , lookup
Years of Living Dangerously wikipedia , lookup
Future sea level wikipedia , lookup
Global and Planetary Change 22 Ž1999. 155–168 www.elsevier.comrlocatergloplacha New Zealand glacier response to climate change of the past 2 decades T.J. Chinn ) Alpine and Polar Processes Consultancy, C r -NIWA, P.O. Box 6414, Dunedin, New Zealand Received 22 September 1997; accepted 19 February 1999 Abstract Oblique aerial photography of 111 glaciers during the past 2 decades has recorded a reversal of the past century glacier-recession trend. Cirque glaciers show little response to the recent mass balance increase; mountain glaciers show visible advances. Some valley glaciers have advanced, some have thickened in the upper trunk, and the larger ones and those with proglacial lakes continue to recede. The shift to advance is driven by an average lowering of snowlines of 67 m, equivalent to a cooling of 0.478C if other factors are held constant. q 1999 Elsevier Science B.V. All rights reserved. Keywords: glaciers; fluctuations; New Zealand 1. Introduction From a programme begun in 1977, which records end-of-summer snowlines on selected glaciers throughout the Southern Alps, data are available on glacier length and mass balance changes. This paper takes the opportunity of a recent trend towards positive glacier balances to examine the change in length of New Zealand glaciers in response to the climate of the last 2 decades, in an attempt to isolate the timing of the climate change responsible for the ) Corresponding author. Tel.: q64-3-477-8615; fax: q64-3479-0134. E-mail address: [email protected] ŽT.J. Chinn. glacier changes. Responses are discussed in terms of different types of glaciers. 2. Glacier observations in New Zealand The Southern Alps of New Zealand lie athwart the prevailing westerly weather systems, and generate a strong west–east orographic precipitation gradient with an associated steep eastward rise of glacier equilibrium line altitudes. Extreme maritime glaciers occur west of the Main Divide, with ‘dry’ balance glaciers and rock glaciers lying to the east. New Zealand glaciers are mainly high activity maritime types with precipitation at or well above 3 mra. A total of 3149 glaciers has been inventoried for New Zealand ŽFig. 1. ŽChinn, 1991., but few glacier termini have been systematically monitored. The most comprehensive set of fluctuations are recorded 0921-8181r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 8 1 8 1 Ž 9 9 . 0 0 0 3 3 - 8 156 T.J. Chinnr Global and Planetary Change 22 (1999) 155–168 Fig. 1. Distribution of the glaciers of the Southern Alps, South Island, New Zealand. T.J. Chinnr Global and Planetary Change 22 (1999) 155–168 157 Table 1 Summary of glacier size changes of the past century Žfrom Chinn, 1996.. DL Žkm., average change in glacier length. DL Ž%., average change in length as a proportion of original length. Rate Žmra., average rate of recession. DElev Žm., average rise of glacier mean elevations. D Area Ž%., average change in area of a limited number of glaciers DL Žkm. DL Ž%. Rate Žmra. DElev Žm. D Area Ž%. Cirque glaciers Alpine glaciers Valley glaciers Glaciers with lakes y0.78 y48 y7.8 y84 – y1.17 y44 y11.7 y137 y32 y1.77 y29 y17.7 y68 y25 y1.8 y24 y18 y16 y23 for Franz Josef Glacier Žeg, Suggate, 1950; Sara, 1968. and Stocking Glacier ŽSalinger et al., 1983.. The two glaciers show a high degree of conformity in terminus behaviour. Sporadic terminus measurements are also available for the Fox Glacier ŽSara, 1968., Ivory Glacier ŽAnderton and Chinn, 1978., Dart Glacier ŽBishop and Forsyth, 1988. and Whakapapanui Glacier ŽKrenek, 1959; Heine, 1962.. Observations of the large valley glaciers; Tasman, Hooker, Mueller and Godley Glaciers of Mount Cook National Park, have been summarised by Gellatly Ž1985a.. Many intermittent and opportunistic obser- Fig. 2. Fluctuations of the terminus position of Franz Josef Glacier. Amplitude of the changes are the greatest of all glacier fluctuations measured in the New Zealand Southern Alps. 158 T.J. Chinnr Global and Planetary Change 22 (1999) 155–168 vations of other glaciers are available from various sources. 2.1. Glacier length–climate correlations Correlations of glacier terminus fluctuations with temperature and precipitation have been attempted only for the Franz Josef Glacier ŽSuggate, 1950; Hessell, 1983; Gellatly and Norton, 1984. and Stocking Glaciers ŽSalinger et al., 1983., but results are ambiguous. Hessell Ž1980. argued that an implied warming was artificial and that the terminus changes could be explained by precipitation changes; whereas Salinger Ž1982. showed that the termius changes were related to a 0.58C warming. A more refined result was obtained by Woo and Fitzharris Ž1992., who modelled the mass balance of the Franz Josef Glacier and related the results to variations of the terminus position. Glacier length variations have been compared with variations in atmospheric circulation patterns reconstructed back to 1911 ŽFitzharris et al., 1992., where a strong linkage was found. The frequent and intensive measurements required for mass balance studies have been carried out at Fig. 3. Example of cumulative length changes of three characteristic glacier types from the Swiss Alps. Small cirque glaciers such as the Pizol, have low basal shear stresses and respond directly to annual mass balance and snowline variability through depositionrmelting of snowrfirn at the glacier margin. Medium-size mountain glaciers, such as the Trient, flow under high basal shear stresses and react dynamically to decadal mass–balance variations in a delayed and strongly smoothed manner. The Franz Josef Glacier is of this type. Large valley glaciers, such as the Aletsch, damp decadal mass–balance variations but exhibit strong signals of secular trends. The Tasman Glacier is an example of this type Žfrom Haeberli, 1995.. T.J. Chinnr Global and Planetary Change 22 (1999) 155–168 only a few New Zealand glaciers, with the longest and most complete record of 7 balance years from the Ivory Glacier ŽAnderton and Chinn, 1978.. 2.2. Termination of the little ice age in New Zealand The glaciers of New Zealand have retreated dramatically during the past century ŽTable 1.. Between about A.D. 1750 and 1890, persistent retreat appears to have begun at different times on different glaciers, and to have proceeded at different rates. Recession has been spectacular at some glaciers, but others have shown very little change in length. Dates from moraines indicate that for many glaciers, the maximum was reached around 1600 ŽWardle, 1973; Gellatly et al., 1988. followed only by minor retreat before the rapid wasting during the 20th century ŽGellaty, 1985b.. The most rapid collapse of all glaciers occurred in the mid 20th century ŽFig. 2... Within the general recession, some glaciers made minor resurgences while others have steadily diminished, with variations similar to the Swiss examples of Fig. 3. Literature on the Franz Josef and Fox Glaciers deals mainly with retreat since the 1890s, but moraines indicate that these glaciers attained a maximum in 1750 ŽLawrence and Lawrence, 1965.. 3. Glaciers and climate Glacier fluctuations are among the clearest signals of climate change because glaciers are effectively highly sensitive, large-scale climate instruments. However, they do not measure simple temperature or snowfall changes, rather they indicate a complex combination of mass and energy exchange at the Earth’s surface. Air temperature and precipitation, the two elements most commonly correlated with glacier fluctuations, are only two elements of the complex chain of processes linking climate and glacier fluctuations ŽHaeberli, 1995.. 3.1. Response time Direct, undelayed changes to a glacier result from annual cycles of mass–balance change at the glacier surface which are subsequently transmitted downglacier to produce the indirect, delayed reaction to climate forcing of the glacier front. Following a 159 change in mass balance, there is a lag before the length of a glacier starts to change, and it will continue to change until a new equilibrium length is reached. This time taken for a glacier to fully adjust to a change in its mass balance is the ‘filling time’ or ‘ volume response time’ ŽPaterson, 1994, p. 319; Ruddell, 1995.. Volume response time has been found to be related to an index of glacier thickness and ablation loss at the terminus ŽJohannesson et al., 1989.. Response times for most valley glaciers are in the order of 10–50 years ŽOerlemans, 1994.. The lag between a change in mass balance and the first significant response at the terminus Žnot including the immediate effects of terminus ablation changes. is the ‘lag time’ or ‘terminus response time’ ŽPaterson, 1994, p. 319. which occurs many years before the volume response time. These varying terminus response times for the onset of observed glacier readvances, which constitute an expression of differing glacier responses to the same climate change, is the subject of this study. 3.2. Glacier length changes Different types of glaciers have different response times, making it inappropriate to compare or combine terminus behaviour of different types of glaciers, or indeed, to use length changes of a single glacier as being representative of climate change. Differing responses to climate forcing of different types of glaciers is demonstrated in Fig. 3, which gives length changes for three Swiss glaciers Žcomparative measurements of this nature are not available for New Zealand glaciers.. These differing responses indicate that glaciers should be separated into different categories, and that it is normally inappropriate to compare the terminus behaviours of Franz Josef Glacier with the Tasman Glacier. However it may be appropriate to compare them over periods longer than their response times, say over 100 years. 4. Method 4.1. Data from annual snowline programme flights Annual oblique aerial photography flights have been made at the end of summer over the Southern Alps since 1977, originally to record glacier occurrence for the New Zealand glacier inventory, ŽChinn 160 T.J. Chinnr Global and Planetary Change 22 (1999) 155–168 and Whitehouse, 1980. and latterly to record endof-summer snowlines as an indicator of net mass balance change. After completion of the inventory, 49 selected ‘index’ glaciers, arranged in transects across the Southern Alps, were selected for continuing annual end-of-summer snowline surveys. This monitoring programme is ongoing and uses the position of the end-of-summer snowline or equilibrium line elevation ŽELA. as defined by Meier and Post Ž1962. as a surrogate for mass balance ŽChinn, 1995.. During the 20-year period of monitoring, the trend of glacier recession has reversed, with positive balances occurring in most years since 1980, and more recently all glaciers have shown positive balances ŽFig. 4.. Some of the values given in this figure differ by small amounts from Chinn Ž1995. as the position of the estimated long term, or steady state ELA, has been revised for a number of glaciers to improve consistency with regional trends. For a few glaciers the range of measured ELAs has also been compressed to conform with the Southern Alps measured average. There were no snowline survey flights in 1979, 1990 and 1991. Photographs on these flights were both of the ‘index’ glaciers and the termini of the larger glaciers, the majority of which were re-photographed in 1995. One hundred and eleven glaciers selected from those photographed over the past 20 years on the snowline monitoring flights are used in this study. All available photographs for each glacier were examined in chronological order and the terminus changes noted in Tables 2–4 as advance ŽA., stationary ŽS., or recession ŽR.. Because of the photograph quality or angle of view, changes at some glaciers could not be defined and are tabulated as undefined ŽU.. Medium-altitude oblique photographs, taken from about 3000 m, have limited resolution, making it impractical to measure the changes as absolute distances. Although some spectacular changes have occurred, the majority of changes were only minor and difficult to detect on the photographs; it was impossible to detect changes of the small cirque glaciers. From simple mass balance processes, however, it follows that, where snow cover remains over the glacier terminus after the end of summer, there has been no ice loss and the glacier must have advanced by an amount equal to ice flow. The ‘advance’ of these cirque glaciers is immediate and was initiated in the year of observation, consequently they are not included in the estimates of response times. Fig. 4. The percentage of all index glaciers measured each year indicating positive proxy mass balances. Numbers indicate total number of glaciers observed each year. Table 2 Fluctuations of mountain glaciers, 1977 to 1997, with terminus response times to a 1976"1 positive balance T.J. Chinnr Global and Planetary Change 22 (1999) 155–168 161 162 Table 3 Fluctuations of valley glaciers, 1977 to 1997, with terminus response times to a 1976"1 positive balance. Vs valley glaciers; Dsdebris mantled glaciers T.J. Chinnr Global and Planetary Change 22 (1999) 155–168 Table 4 Fluctuations of glaciers with lakes, 1977 to 1997, with terminus response times to a 1976"1 positive balance. C s cirque; Vs valley; M s mountain; Dsdebris mantled; L s proglacial lake T.J. Chinnr Global and Planetary Change 22 (1999) 155–168 163 164 T.J. Chinnr Global and Planetary Change 22 (1999) 155–168 The dataset has been subdivided into the three sizertype classifications of Haeberli Ž1995 and Fig. 3. in order to compare glaciers of similar response times. The subdivision is basically by glacier size, but also takes some account of shape and slope. Ž1. Small, low-shear–stress cirque glaciers ŽC. reflect changes in climate and mass balance almost without delay. Ž2. Large, high-shear–stress mountain glaciers ŽM. react to decadal variations in climate and mass balance forcing with an enhanced amplitude after a delay of several years. Ž3. Valley glaciers ŽV. with low-gradient tongues and frequently debris mantled give strong and efficiently-smoothed signals of secular trends with a delay of several decades. Glaciers entering proglacial lakes ŽL. are frequetly decoupled from climate response ŽKirkbride, 1993. and these have been placed into a separate category. Debris covered glaciers ŽD. have been identified but not separated from the valley glaciers. Debris cover is proportionally highest on large valley glaciers, with an average of more than 25% of their surfaces mantled, whereas alpine glaciers average - 10% cover ŽChinn, 1996.. 5. Results The 2-decade record of terminus behaviour of 78 glaciers interpreted from oblique photographs is presented for 38 mountain glaciers ŽTable 2.; 26 valley glaciers ŽTable 3. and 14 glaciers having proglacial lakes ŽTable 4.. 5.1. Response times Tables 2–4 identify the first occurrences of the reversal of terminus recession within the limits of the Fig. 5. Tasman Glacier equilibrium line elevations from 1959 to 1997. T.J. Chinnr Global and Planetary Change 22 (1999) 155–168 intervals of the surveys. Assuming that the majority of these readvances are in response to the same climate variation, then the table indicates comparative terminus response times. Using the long, detailed record of the Franz Josef glacier, which has strongly enhanced responses to climate ŽFig. 2., the time of the general change from negative to positive balances may be isolated. Terminus response times for this glacier have been variously estimated to be 5 years ŽSuggate, 1952.; 4 to 8 years ŽSoons, 1971.; 5 to 7 years ŽHessell, 1983.; 5 to 7 years ŽHooker, 1995.; and 4 to 5 years ŽTyson et al., in press.. At the nearby Stocking Glacier Salinger et al. Ž1983. also found a 5 to 7 year terminus response. The Franz Josef Glacier had a well documented vigorous advance commencing in the 1983–1984 ablation season. From the above response times, the positive mass balances responsible for this advance would have occurred during the 1976–1978 period. A long record of ELA values for the nearby Tasman 165 Glacier is available since 1959 ŽChinn, 1995..This record ŽFig. 5. clearly shows a series of low ELAs from 1974 to 1977. This is slightly earlier by 1 or 2 years than the positive balance period predictable from the response times found for the Franz Josef Glacier. Positive balances dominated in 1977, the year that snowline surveys commenced. This information suggests that the positive mass balances responsible for glacial readvances occurred towards the end of the 1974 to 1977 period. 1976 " 1 year has been selected for use in this study as the time of commencement of the wave of positive mass balance that has reversed the general recession. Terminus response times of the glaciers to a 1976 pulse are listed in Tables 2–4. 5.2. Cirque glaciers (C) From aerial observations of form and changes, all cirque glaciers appear to have regained equilibrium Fig. 6. Percentage of 38 mountain glaciers advancing. 166 T.J. Chinnr Global and Planetary Change 22 (1999) 155–168 since the end of the LIA by the time this study commenced. Therefore, their response to climate change since the end of the LIA has taken less than 100 years. However, despite 2 decades of dominantly positive balances, the slow advance of these glaciers remains undectable at the resolution of the photographs. balances prior to the 1974–1977 event. The dominant resurgence took place in 1983, followed by a decline in the number of glaciers advancing. A second advance pulse is evident from 1989 to 1995 ŽFig. 6.. Response times range from 5 years to more than 20 years as a few glaciers have yet to commence the general readvance. 5.3. Mountain glaciers (M) 5.4. Valley glaciers (V) Thirty eight mountain glaciers ŽTable 2. includes the steep responsive glaciers which are expected to have attained equilibrium with climate change since the end of last century. The data for the changes to these glaciers are from direct observations of changes at the termini, although many of the changes are small and barely detectable. The advances recorded in 1978–1979 and 1981 may indicate exceptionally short response times Žas in the case of the steep Crow Glacier., or may be a response from positive Twenty six valley glaciers ŽTable 3. exhibit a characteristic slow, dampened response of low-gradient glaciers of Fig. 2. The 1983 initial pulse evident in mountain glaciers has been dampened into a more general resurgence culminating in 1986, some 2 to 4 years later than that for the mountain glaciers ŽFig. 7.. Again, there appears to be a second pulse of advances peaking in 1994. This group includes the debris covered glaciers which may go through a long period of loss by Fig. 7. Percentage of 26 valley glaciers advancing. T.J. Chinnr Global and Planetary Change 22 (1999) 155–168 lowering before entering a phase of catastrophic retreat by glacierkarst decay. Many have detached stagnant debris-covered ice plus avalanche ice obscuring ill-defined trunk positions. However, the wave of positive balances has travelled the full length of many of these glaciers. Table 3 indentifies the glaciers yet to show a readvance. Response times for this group range from 9 to well over 20 years. 5.5. Glaciers haÕing proglacial lakes (L) The 13 mainly large valley glaciers entering lakes ŽTable 4. show that these glaciers had yet to attain equilibrium with the climate before the recent increase in balances occurred. A thickening pulse travelling down the trunk, may be observed on many of them, but this has served only to retard the expansion of the proglacial lakes. Although only one of these is advancing, the cliffed termini on a few of them have ceased retreating and are now stationary. Response times for this group are more than 20 years and may be as much as hundreds of years. 6. Discussion Despite the nearly continuous period of positive mass balances during the past 20 years, with end-ofsummer snow commonly remaining over the entire lower glacier surfaces, the advance of cirque glaciers remains undetectable on the aerial photographs. On a few of these glaciers, small proglacial lakes which had developed by the beginning of the period have persisted. In contrast, larger, more active mountain glaciers have responded with visible advances. Valley glaciers, both clean and debris-mantled, have also shown either a re-advance or visible thickening in the upper trunk areas. Conversely, larger debriscovered glaciers have demonstrated continued recession that many have yet to fully respond to the climate warming of the past century while others display a continuing thinning of the lower trunk, with glacierkarst formation suggesting that proglacial lakes may be about to develop. Those with proglacial lakes are continuing to recede as their lakes expand. Response times are a result of a complex interaction between the climate signal and the geometry of 167 the glacier. Correlations of the observed response times with glacier lengths and surface gradients are very poor; For response time ; length, r 2 s 0.125; ; gradient, r 2 s 0.205 and for response time ; lengthrgradient, r 2 s 0.123. If precipitation has remained constant, then a temperature change responsible for the observed lowering of the ELAs may be estimated from the atmospheric lapse rate. From the 49 snowline ‘index’ glaciers, 672 ELA readings are available for the period 1977 to 1997 where the average difference between the estimated steady state ELAs and the observed annual ELAs, gives a snowline depression of 67 m. Using a standard lapse rate of 0.78C per 100 m, the downward shift represents a general cooling of 0.478C since the late 1970s. A mean trend fitted through the ELA record for the Tasman Glacier ŽFig. 5. suggests a fall of 160 m in the ELA since 1960. In a study of a century of glacier recession to the late 1970s, Chinn Ž1996. found an upward ELA shift of circa 84 m for cirque glaciers. This is equivalent to a warming of circa 0.68C. This comparison indicates that the present ‘cool climate’, if continued, will not bring the glaciers to near their LIA size. This is demonstrated by the fluctuations of the Franz Josef Glacier, which although its active advance has slowed as it presumably approaches equilibrium with the recent climate, has only regained its 1960 extent. In a study of past and present glaciers of the Waimakariri basin, Chinn Ž1975. found an ELA rise of 200 m, equivalent to 1.48C warming since the end of the LIA. Salinger Ž1979. suggests that measured temperatures over the past century show a warming of circa 1.08C, with most of the rise occurring since the 1950s. This study demonstrates the complexity of glacier response to climate forcing. To derive climate inferences from glacier-length changes, sophisticated methods must be used to accomodate differences in response times due to differences in glacier geometry. Acknowledgements This work was carried out under contract No. CO5624 of the New Zealand Foundation for Research, Science and Technology. I am grateful for 168 T.J. Chinnr Global and Planetary Change 22 (1999) 155–168 the helpful comments by Dr C. Raymond and an anonymous journal reviewer. References Anderton, P.W., Chinn, T.J., 1978. Ivory Glacier, New Zealand, an IHD basin study. J. Glaciol. 20, 67–84. Bishop, G., Forsyth, J., 1988. Vanishing Ice, an Introduction to Glaciers Based on the Dart Glacier. John McIndoe and NZ Geological Survey, Dunedin, 56 pp. Chinn, T.J., 1975. Late Quaternary snowlines and cirque moraines within the Waimakariri watershed. Unpublished MSc thesis, University of Canterbury, Christchurch, New Zealand. 213 pp. Chinn, T.J., 1991. Glacier inventory of New Zealand. Institute of Geological and Nuclear Sciences, unpublished. Chinn, T.J., 1995. Glacier fluctuations in the Southern Alps of New Zealand determined from snowline elevations. Arct. Alp. Res. 27 Ž2., 187–198. Chinn, T.J., 1996. New Zealand glacier response to climate change of the past century. N. Z. J. Geol. Geophys. 39, 415–428. Chinn, T.J.H., Whitehouse, I.E., 1980. Glacier snow line variations in the Southern Alps, New Zealand. In: World Glacier Inventory. International Association of Hydrological Sciences Publication 126, pp. 219–228. Fitzharris, B.B., Hay, J.E., Jones, P.D., 1992. Behaviour of New Zealand glaciers and atmospheric circulation changes over the past 130 years. The Holocene 2, 97–106. Gellatly, A.F., 1985a. Glacier fluctuations in the central Southern Alps, New Zealand: documentation and implications for environmental change during the last 1000 years. Z. Gletscherkd. Glazialgeol. 21, 259–264. Gellatly, A.F., 1985b. Historical records of glacier fluctuations in Mt. Cook National Park, New Zealand: a century of change. The Geogr. J. 151, 86–99. Gellatly, A.F., Norton, D.A., 1984. Possible warming and glacier recession in the South Island, New Zealand. N. Z. J. Sci. 27, 381–388. Gellatly, A.F., Chinn, T.J.H., Rothlisberger, 1988. Holocene ¨ glacier variations in New Zealand: a review. Quat. Sci. Rev. 7, 227–242. Haeberli, W., 1995. Glacier fluctuations and climate change detection — operational elements of a worldwide monitoring strategy. World Meteorological Organisation Bulletin 44, 23–31. Heine, A.J., 1962. Glacier changes on Mount Ruapehu New Zealand — 1957–1961. In: Proceedings of the Symposium of Obergurgl. ‘‘Variations in the regime of existing glaciers’’ 10–18 Sept 1962. IUGG Internat. Assoc. Sci. Hydrology, Gentbrugge, pp. 173–178, Publication No. 58, 312 pp. Hessell, J.W.D., 1980. Apparent trends of mean temperature in New Zealand since 1930. N. Z. J. Sci. 23, 1–9. Hessell, J.W.D., 1983. Climatic effects on the recession of the Franz Josef Glacier. N. Z. J. Sci. 26, 315–320. Hooker, B.L., 1995. Advance and retreat of Franz Josef Glacier in relation to climate. Diploma of Science Dissertation. Otago University Geography Department, Dunedin 62 pp. Johannesson, T., Raymond, C., Waddinton, E., 1989. Time-scale for adjustment of glaciers to changes in mass balance. J. Glaciol. 35, 355–369. Kirkbride, M.P., 1993. The temporal significance of transitions from melting to calving termini at glaciers in the central Southern Alps of New Zealand. The Holocene 3 Ž3., 232–240. Krenek, L.O., 1959. Changes in the glaciers of Mt. Ruapehu in 1955. N. Z. J. Geol. Geophys. 2, 644–653. Lawrence, D.B., Lawrence, D.G., 1965. Glacier Studies in New Zealand. Mazama 47, 17–27. Meier, M.F., Post, A.S., 1962. Recent variations in mass net budgets of glaciers in western North America. In: Proceedings of Obergurgl Symposium International Association of Hydrological Sciences Publication 58, pp. 63–77. Oerlemans, J., 1994. Quantifying global warming from the retreat of glaciers. Science 264, 243–245. Paterson, W.S.B., 1994. The Physics of Glaciers, 3rd edn. Pergamon, Oxford, 480 pp. Ruddell, A., 1995. Recent glacier and climate change in the New Zealand Alps. Unpublished PhD thesis, Meteorology Department, University of Melbourne, Australia. Salinger, M.J., 1979. New Zealand climate; the temperature record, historical data and some agricultural implications. Climate Change 2, 109–126. Salinger, M.J., 1982. On the suggestion of post-1950 warming over New Zealand. N. Z. J. Sci. 25, 77–86. Salinger, M.J., Heine, M.J., Burrows, C.J., 1983. Variations of the Stocking ŽTe Wae Wae. Glacier, Mount Cook and climatic relationships. N. Z. J. Sci. 26, 321–338. Sara, W.A., 1968. Franz Josef and Fox Glaciers, 1951–1967. N. Z. J. Geol. Geophys. 11, 768–780. Soons, J., 1971. Recent Changes in the Franz Josef Glacier. Proceedings of the Sixth New Zealand Geography Conference, pp. 195–200. Suggate, R.P., 1950. Franz Josef and other glaciers of the Southern Alps, New Zealand. J. Glaciol. 1 Ž8., 422–429. Suggate, R.P., 1952. Franz Josef Glacier, March 1951. N. Z. J. Sci. Technol. 33 Ž4., 299–304. Tyson, P.D., Sturman, A.P., Fitzharris, B.B., Mason, S.J., Owens, I.F., in press. Circulation changes and teleconnections between glacial advances on the West Coast of New Zealand and extended spells of drought years in South Africa. Int. J. Climatol. Wardle, P., 1973. Variations of the glaciers of Westland National Park and the Hooker Range, NZ. N. Z. J. Bot. 11, 349–387. Woo, M., Fitzharris, B.B., 1992. Reconstruction of mass balance variations for Franz Josef Glacier, New Zealand, 1913 to 1989. Arct. Alp. Res. 24, 281–290.