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Advance and retreat of Franz Josef Glacier in relation to climate

Bronwyn L Hooker
Department of Geography, University of Otago, Dunedin, New Zealand

 
Abstract

Temperate maritime glaciers are good indicators of past and ongoing climate change because of their quick reaction to climate perturbations. With future global warming they will be important contributors to possible sea level rise. During the 20th century, most glaciers retreated worldwide. The Franz Josef Glacier on the West Coast of New Zealand is anomalous to this pattern, in that it has been advancing since 1982, after a century of retreat. Key variables, atmospheric circulation patterns over the Southwest Pacific, and the Southern Oscillation Index (SOI), are compared for the advance and retreat phases of Franz Josef Glacier. Terminus changes have long been recorded at Franz Josef and are available from photographs, maps and articles. End of summer snowline (EOSS) positions are estimated from a former tributary glacier and used as a surrogate for mass balance change. Precipitation and temperature, as measured at Franz Josef, are lapsed to the equilibrium line altitude (ELA). The pressure difference between Hokitika and Taiaroa Head is used to indicate the strength of the westerly airflow. Atmospheric circulation changes are investigated using anomalies constructed from sea-level pressure patterns, the position of the subtropical high pressure zone and the SOI. All data are examined for ablation and accumulation seasons of the glacier year. Results show that the retreat phase is characterised by warmer summer temperatures, a weak north-easterly airflow anomaly over the South Island and a southward shift in the subtropical high pressure zone. These are consistent with a dominance of La Nina events. In contrast, the advance phase is characterised by an anomalous southwest airflow and high precipitation, especially during the accumulation season. These are consistent with a dominance of El Nino events. The results show strong links between atmospheric circulation changes, climate variables and glacier behaviour. Future research requires the continued development of techniques for prediction of glacier response to climate change.

 
Reference

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 Unpublished PGDipSci dissertation, in Geography, at the University of Otago, New Zealand. 62pp.

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