Tropical glaciers can provide climatic information through changes in ice area through time and from ice core records contained within them. The glaciers near Puncak Jaya in Papua, Indonesia are the last remaining glaciers in the tropical West Pacific. Several satellite based studies have been conducted to assess the glacier recession through the area, but few intensive field and no ice cores studies have been conducted on these glaciers. A field expedition to Papua highland was conducted in May - June 2010 to drill ice cores from these glaciers and to collect rain samples from different elevation in the vicinity.
Three ice cores were drilled, two to bedrock measuring 32.13 m (D1) and 31.25 m (D1B) in length and the third measuring 26.19 m (D2) in length. The stable isotope records were reproducible between the longer cores with significant δ18O variability of 5 to 6‰. High aerosol events were identified between 20 and 29 meters depth and in the top eight meters. This suggests that there is no melting throughout the glacier. The dating of D1 core has not been completed yet. Low tritium concentration in D1 core and high tritium concentration recorded in precipitation at the northern sites of Papua suggests that the glaciers may have melted below the 1950s/1960s bomb horizons.
Eighty three rain samples were collected from different altitudes in the southern part of Papua. The analysis results suggest that the altitude effect dominates in the Papua region. The isotopic lapse rate is about 0.23‰/100 m and 1.80‰/100 m for δ18O and δD, respectively, greater than the continentality effect of 0.09‰/km. The isotopic compositions of the rain samples generally fall on the global meteoric water line. The meteorological data analysis from automated weather stations arrayed extending from the southern coastal region up to near the glaciers shows that the surface lapse rate is about 5°C/km. Greater diurnal temperature differences are identified at below 2,500 m a.s.l and at above 3,500 m a.s.l. The highest average precipitation of ~12,500 mm/ year is recorded at an elevation of 617 m. Above 600 m a.s.l, the daytime precipitation is higher than during the night.
For short-term assessment of controls on precipitation isotopic composition, the results indicate that the temperature effect, in association with the altitude effect, is stronger than the amount effect on a daily basis for June 2010. In longer term, the amount effect is stronger than the temperature effect on a monthly basis, while on six-month average basis both the temperature effect and the amount effect prevail in this region. The monthly d-excess value of precipitation is positively correlated with relative humidity and negatively correlated with local wind speed on 12-month running mean.
Comparisons were made of the top 32 meters of ice cores from Kilimanjaro, Tanzania (NIF3); Quelccaya, Peru (SD); and Papua, Indonesia (D1). The results show that similar mean isotopic compositions are found between D1 core and SD core. This may indicate an ENSO connection between these glacier locations. The more enriched isotopic composition in NIF3 core may result from drier conditions in tropical Africa. The highest dust and major ion concentrations occur in NIF3 core, which may be due primarily to low precipitation and to the existence of deserts as possible main aerosol sources. The dust and major ions in the Quelccaya ice core may come from the Amazon Basin. The Papua ice core is the cleanest of the three sites since its location is surrounded by oceans.