After hauling their equipment to 5325 m above sea level, scientists set up a small gas-powered drill. While there are minor variations in drilling technology and techniques, all drills use the
same basic idea: a drill bit is lowered into the core hole and cuts out a cylinder of ice that is then carefully extracted from the core sleeve and analyzed both on site and in the laboratory. Since Quelccaya is at the edge of the moist Amazon Basin
while Dunde is wedged between two deserts, it is not surprising that accumulation rates are much higher at Quelccaya. Indeed, the annual average accumulation at Quelccaya in meters of water equivalent is 1.15 m compared to just .43 m at Dunde. Like
Quelccaya, around 80% of Dunde's precipitation falls during the wet season. The dry season is clearly identified in the core record by the layers of dust from surrounding deserts visible in this ice segment.
Since snow accumulates more slowly
at Dunde, ice from its ~140 m cores is significantly older than that from Quelccaya. While Quelccaya provides high-resolution clues to the last 1500 years of climate, Dunde stretches back over 40,000 years, well into the last ice age.
Byrd Polar Research Center, The Ohio State University
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