For this mountain there is photographic evidence of massive glacial retreat since the region was first extensively explored by airplane in 1936 in preparation for the peak's first ascent. Between then and 2010, the mountain lost 80 percent of its ice — two-thirds of which since another scientific expedition in the 1970s. That research between 1973 and 1976 showed glacier retreat for the Meren Glacier of while the Carstensz Glacier lost . The Northwall Firn, the largest remnant of the icecap that once was atop Puncak Jaya, has itself split into two separate glaciers after 1942. IKONOS satellite imagery of the New Guinean glaciers indicated that by 2002 only glacial area remained, that in the two years from 2000 to 2002, the East Northwall Firn had lost 4.5%, the West Northwall Firn 19.4% and the Carstensz 6.8% of their glacial mass, and that sometime between 1994 and 2000, the Meren Glacier had disappeared altogether. An expedition to the remaining glaciers on Puncak Jaya in 2010 discovered that the ice on the glaciers there is about thick and thinning at a rate of annually. At that rate, the remaining glaciers were expected to last only to the year 2015.