B. B. Fitzharris

The correlation between climatic parameters and the retreat and advance of Franz Josef Glacier, New Zealand

Abstract After a long period of general retreat, the Franz Josef Glacier on the western flanks of the Southern Alps of New Zealand has undergone a major advance, beginning about 1982. Key climatic variables, atmospheric circulation patterns over the Southwest Pacific, and the Southern Oscillation Index (SOI), are compared for two 20-year periods that represent advance and retreat phases of the Franz Josef Glacier. The results show strong links between atmospheric circulation changes, climate variables and glacier behaviour. The retreat phase is characterised by slightly warmer temperatures and markedly lower precipitation in the ablation season, a high pressure anomaly over New Zealand, and a southward shift in the subtropical high pressure zone. In contrast, the advance phase is characterised by anomalous southwest airflow, especially during the ablation season, and higher precipitation. The high pressure anomaly is shifted westward by about 55° of longitude so as to lie south of Australia. The advance phase is also related to a higher frequency of El Nino events.

Behaviour of New Zealand Glaciers and Atmospheric Circulation Changes over the Past 130 years

There is renewed interest as to the impact of future climate change on temperate alpine glaciers because of their role as indicators of past and ongoing changes, and due to their possible involvement in sea-level rise. Substantial changes in termini of New Zealand glaciers since the nineteenth century are compared with variations in atmospheric circulation patterns over the southwest Pacific region. Reconstructed sea-level pressure patterns are used back to 1911. Atmospheric circulation indices obtained from pressure differences between appropriate stations are extended back to the 1860s. Circulation anomalies are examined for winter (related to glacier accumulation), and for summer (related to glacier ablation). Behaviour of glacier termini is found to be strongly linked with circulation changes, especially in summer. Latitudinal shifts in the southern margin of the subtropical high pressure zone are identified as important. An advance of some glaciers since 1980 is consistent with circulation changes over the New Zealand region induced by two large El Niño events.

New eyes in the sky measure glaciers and ice sheets

The mapping and measurement of glaciers and their changes are useful in predicting sea-level and regional water supply, studying hazards and climate change [Haeberli et al., 1998],and in the hydropower industry Existing inventories cover only about 67,000 of the worlds estimated 160,000 glaciers and are based on data collected over 50 years or more [e.g.,Haeberli et al., 1998]. The data available have proven that small ice bodies are disappearing at an accelerating rate and that the Antarctic ice sheet and its fringing ice shelves are undergoing unexpected, rapid change. According to many glaciologists, much larger fluctuations in land ice—with vast implications for society—are possible in the coming decades and centuries due to natural and anthropogenic climate change [Oppenheimer, 1998].

The New Zealand Southern Alps Experiment

The Southern Alps Experiment is being mounted to study the influence of New Zealands Southern Alps on local weather and climate. This paper describes these alpine influences and outlines proposed field and modeling experiments. Experiment goals include understanding and quantifying factors that govern the intensity and spatial distribution of heavy rainfall, the west to east distribution of precipitation across the mountains, and the intensity of lee wind storms and warming. Linked research will explore the use of deterministic rainfall models to predict river flows from mountain watersheds.

Processes and rates of ice loss at the terminus of Tasman Glacier, New Zealand

Abstract The Tasman Glacier is the largest glacier in the Southern Alps of New Zealand. Despite a century of climate warming, the glacier has until recently remained at its “Little Ice Age” terminus position, although there has been substantial downwasting. The lower glacier is covered by an extensive debris layer, which has redistributed ice losses in both space and time compared to the conventional glacier response to climate change. Ice is lost at the terminus through melt of bare ice slopes, melt under the debris layer, and calving of ice into a newly established pro-glacial lake. Over the past ten years, the glacier has evolved from an ablation regime of melt under the debris and around sinkholes, to one where calving into the lake is of greater importance. This study investigates the processes and rates of ice loss at the terminus during the summer of 1995. Melt rates of ice are greatest on bare ice slopes, averaging 96 mm day −1 of ice depth over the summer period. Melt under the debris averaged 7 mm day −1 , and calving accounted for a specific ice loss of 125 mm day −1 . Overall, calving is the dominant form of ice loss at the terminus, accounting for 73% of the total. Melt under the debris layer accounted for 26% of terminus ablation, and melt on bare ice slopes just 1%, due to the relatively small area covered by these. Ice loss at the terminus is therefore largely de-coupled from climatic influences, and due mainly to the effect of the pro-glacial lake. However, when water loss from the whole ablation zone of the glacier is considered, calving accounts for just 4% of ice loss, with the largest portion of ice loss (80%) coming from melt on bare ice upstream of the debris cover. A total amount of 21 million m 3 a −1 of water is estimated to be supplied to Tasman River due to ice loss from the lowest 4 km 2 of glacier. 135 million m 3 a −1 of water is estimated to be lost below Ball Hut (approximately 10 km up-glacier), with 20% of this being calved from the terminus. This proportion will increase as the glacier terminus retreats up the valley, but at present rates, it will take over a century for the glacier to retreat to Ball Hut. Water stored as ice and then released from Tasman Glacier is resulting in a mean annual flow into Lake Pukaki of 4.3 m 3 s −1 . The water released from all glaciers in the region due to glacier ice loss is 6% of the annual inflow to Lake Pukaki.

Glacier balance fluctuations and atmospheric circulation patterns over the Southern Alps, New Zealand

The links between climate and glacier change are investigated by examining the relationships between atmospheric circulation and glacier balance changes over a 17 year period. Altitudes of the end-of-summer snowlines made on some 48 index glaciers provide surrogates for mass balance, and mean atmospheric pressure maps were computer-generated for the south-west Pacific from long-period meteorological station data. Pressure data are separated into accumulation and ablation seasons. The results show that atmospheric circulation patterns exert a strong control on glacier mass balance, with positive balances associated with anomalous south to south-west flow and negative balances associated with enhanced north to north-east flow.

Dependency of summer lake inflows and precipitation on spring SOI

Abstract Inflows to South Island, New Zealand lakes deriving from snowmelt are quantified using a water balance approach and are shown to be between 8% and 24% of annual inflow. A snow accumulation index calculated from climatological data using a snowpack simulation model confirms the general pattern of the year-to-year variability of these estimates. Previous work has shown that summer inflows tend to be relatively low in years when the El Nino Southern Oscillation phenomenon is in a positive phase (i.e. La Nina). We show that this patter is also evident in records of precipitation around the catchments, particularly where precipitation exceeds 1000 mm/yr. Variance of inflows and precipitation appears to be dependent on the magnitude of the SOI. Snowmelt increases somewhat in La Nina years, and this may relate to a general trend for warmer temperatures in these years. A relative absence of La Nina conditions for 1976–1994 may be partially responsible for a significant increase in mean lake inflows over the period 1978–1994.

Circulation changes and teleconnections between glacial advances on the west coast of New Zealand and extended spells of drought years in South Africa

ABSTRACTTwentieth century changes in the terminal position of the Franz Josef Glacier on the west coast of New Zealand are comparedwith an area-averaged mean annual rainfall series for the summer rainfall region of South Africa. Distinctive teleconnectionsare evident in an out-of-phase relationship between the two series, each of which exhibits an oscillation of 18–20 years.Periods of glacial advance are shown to coincide with extended dry spells in South Africa, when drought years are prevalent.Reconstructed pressure anomaly fields are presented for periods of advance and recession of the glacier and for the inter-decadal wet and dry spells in South Africa. In both cases major regional atmospheric circulation adjustments take place in aquasi-regular fashion over time to produce an enhancement in westerly airflow during the periods of drought in Africa andglacial advance on the west coast of New Zealand. Extended wet periods and glacial recession are likewise shown to beassociated with an enhancement of easterly components of the circulation. Changes in precipitation, temperature and moisturetransport are examined and associations with the Southern Oscillation Index are investigated.Franz Josef glacial advances are shown to occur 4–5 years after the onset of enhanced south-westerly airflow on to the westcoast of New Zealand. Advances occur on average 4 years after the onset of extended dry spells in South Africa. Similaratmospheric circulation anomalies in the respective sectors of the Southern Hemisphere and adjustments in the locations of thepositions of the ridges in standing wave three are responsible for this correspondence. # 1997 Royal Meteorological Society.Int. J. Climatol., Vol. 17: 1499–1512 (1997)(No. of Figures: 5. No. of Tables: 0. No. of References: 89)

Slopes of glacier ELAs in the Southern Alps of New Zealand in relation to atmospheric circulation patterns

Abstract The links between climate and glaciers of the Southern Alps are investigated by examining the relationships between atmospheric circulation and glacier mass balance changes, as measured by end-of-summer snowlines (ELAs) over a 21-year period on 48 index glaciers. Trend surfaces are fitted to the ELAs data for each mass balance year, and the elevation and slope of each surface is computed. These are compared to atmospheric pressure anomaly maps generated for the southwest Pacific from long-period climate station data. The results show that atmospheric circulation patterns exert a strong control on elevation and slope of the trend surfaces. A simple “sloping roof” model is suggested to represent the ELAs surface, with its tilt across the Southern Alps varying from year to year, depending upon the nature of the atmospheric circulation. Steeper sloping trend surfaces across the Southern Alps are associated with anomalous southwest to westerly flow, whereas less steep slopes are associated with anomalous airflow from the south, southeast, and easterly directions.

Southwest Pacific temperatures: Diurnal and seasonal trends

Temperature trends are presented for a large part of the southwest Pacific. The trends differ from those documented for Northern Hemisphere land areas, where warming has occurred mainly through increases in minimum temperature. The New Zealand patterns are derived from recently completed analyses of monthly and annual mean maximum and minimum surface temperature records for a newly homogenised historical climate data series for New Zealand and outlying islands. They indicate that the warming in the New Zealand region over the past five decades can be attributed to increases in both mean maximum (mostly daytime) and mean minimum (mostly night time) temperature. All seasons show a temperature increase, with the largest occurring in summer (DJF). Northern Hemisphere evidence suggests that changes in cloud cover and the presence of sulfate aerosols plays a direct role. The present results imply that, while the observed warming in a large portion of the Northern Hemisphere landmass may be significantly affected by both these factors, sulfate aerosol effects may be less important in the Southern Hemisphere.