Climate Change and Glacier Retreat in Irian Jaya Over the Past Half Century

Over the past century, glaciers throughout the tropics have predominately retreated. These small glaciers, which respond quickly to climate changes, are becoming increasingly important in understanding glacier- climate interactions. The glaciers on Mt. Jaya in Irian Jaya, Indonesia, are the last remaining tropical glaciers in the Western Pacific region. Rates of ice loss, calculated from area measurements for the Mt. Jaya glaciers in 1942, 1972, 1987, and 2005, indicate that ice loss on Mt. Jaya has increased during each subsequent period. Preliminary modeling using 600 hPa atmospheric temperature, specific humidity, wind speeds, and surface precipitation and radiation fields, acquired from the NCEP Reanalysis dataset, indicates that the only climate variable having a statistically-significant change with a magnitude great enough to strongly affect ice loss on these glaciers was an increase in atmospheric temperature of 0.24 °C between 1972 and 1987. However, accelerated ice loss occurring from 1988-2005 without large observed changes in climate indicates that a more complex explanation may be required. Small, though statistically-significant changes were found in regional precipitation with precipitation decreasing from 1972-1987 and increasing from 1988-2005. While these changes were not of sufficient magnitude to have greatly affected ice loss on these glaciers, increased precipitation along with a rising freezing level may have resulted in a greater proportion of the glacier surface being affected by rain. This may account for the increased recession rate observed in the latter period. Spatial variation in incoming shortwave radiation may also control the observed pattern of retreat. Further analysis of climate variations over each observational period will be completed. Modeling of the shortwave radiation field over these glaciers should shed additional light on the factors controlling Mt. Jaya glacier retreat.