Variability of accumulation in northwest Greenland over the past 250 years

During summer 1996, a 120-m firn and ice core was drilled to determine annual accumulation rates at a northwest Greenland site (GITS, 77.1392 degreesN, 61.0422 degreesW, 1910 m elevation). Annual layers were identified in the core using multiple parameters: delta O-18 and concentrations of dust, hydrogen peroxide, ammonium, calcium and nitrate. Using all parameters together to define annual layers resulted in a 251-year record with a dating uncertainty of one year within that period, Annual accumulation over the period of record averaged about 0.37 m water equivalent. Comparing this record with four other multi-century long records from the west central and northwest portion of the ice sheet shows many periods when decadal-scale fluctuations in accumulation at the different sites are in phase. Overall variations in accumulation in this portion of the ice sheet were +/- 8-9% per decade, versus +/- 25% for individual cores. Annual accumulation at GITS showed a significant correlation with a 12-month North Atlantic Oscillation index (Pearson's R = -0.32 with a significance level of > 99%). though the correlation was slightly lower than for two cores roughly 350 and 700 km south.