Annual accumulation over recent centuries at four sites in central Greenland

[1] Accurate accumulation records are fundamental to understanding mass balance of the Greenland ice sheet. Ice cores can provide multicentury, high-resolution ground-based point estimates of water accumulation. In 2003 and 2004, four new ice cores were collected in the central western (D4 and D5) and Summit ( Sandy and Katie) regions of Greenland. Annual layer counting based on multiple glaciochemical parameters ( primarily hydrogen peroxide, sea salt, and dust proxies) was used to date the ice cores, resulting in annual dating. The bottom depth ages for D4, D5, Sandy, and Katie were estimated at 1738, 1673, 1844, and 1934 A. D., with mean annual accumulation rates of 41.4, 35.2, 22.4, and 22.4 cm(weq) yr(-1), respectively. These new records were in good agreement with previous accumulation maps and four previously published records from nearby multicentury ice cores. Spatial variability was quantified through an analysis of variance, thereby allowing for more meaningful comparisons to atmospheric processes. More regionally representative accumulation records were constructed for the central western and Summit regions spanning recent centuries using a principle component analysis of both the new and previously reported ice core measurements. These regional records exhibited 6 - 7% interannual variability ( 1 standard deviation of the mean) and had lower spatial variability uncertainties than individual accumulation records. Correlations indicate that similar to 20% of the variance in the central western region was explained by the North Atlantic Oscillation (NAO), and suggests that an array of more northern ice cores may correlate more closely with NAO.