Interannual variation in end‐of‐summer snowlines of the Southern Alps of New Zealand, and relationships with Southern Hemisphere atmospheric circulation and sea surface temperature patterns

Abstract

Abstract The end‐of‐summer snowline (EOSS) on 47 glaciers distributed throughout the Southern Alps of New Zealand is related to changes in Southern Hemisphere atmospheric circulation and sea surface temperature patterns over a 23 year period. The EOSS provides an index of the glacier mass balance, as high (low) EOSS elevations relative to the steady‐state mean equilibrium line altitude (ELA m ) indicate a negative (positive) glacier mass balance. Southern Hemisphere atmospheric circulation and sea surface temperature anomaly maps are produced for the accumulation season (April–October) and ablation season (November–March) for both composite high and low EOSS years. There is a high correlation between the EOSS for individual glaciers and the mean EOSS for the Southern Alps (EOSS Alps ). The highest EOSS Alps occurred in 1978, 1990, 1998, and 1999; the lowest EOSS Alps occurred in 1983, 1992, 1993, and 1995. High (low) EOSS Alps values are associated with anomalous northerly (southerly) airflows and weaker (stronger) westerly airflows over the Southern Alps. These patterns are associated with positive (negative) 700 hPa geopotential anomalies to the southeast of New Zealand, a weaker (stronger) subtropical jet, and negative (positive) 700 hPa height anomalies over the southeast Pacific Ocean. High (low) EOSS Alps values are also associated with warm (cool) sea surface temperature anomalies near New Zealand and cool (warm) sea surface temperature anomalies in the eastern equatorial region of the Pacific Ocean. Copyright © 2002 Royal Meteorological Society