The influence of precipitation weighting on interannual variability of stable water isotopes in Greenland



[1] We investigate the effect of precipitation weighting on annual δ values of stable water isotopes in ice cores from Greenland. This effect can explain the observation from ice cores that δ values in northwestern Greenland are less related to annual coastal temperatures than are the δ values in southern and central Greenland ice cores. Furthermore, the precipitation weighting can explain the result of Vinther et al. (2010) that exclusion of summer layers increases information about annual temperature in Greenland ice core records. We study these effects by comparing arithmetic annual means of a regional temperature signal to annual means of the same signal weighted by local precipitation. Specifically, we apply the ERA-40 reanalysis of meteorological observations to compute time series of southwest Greenland temperatures in annual means and in annual precipitation weighted means. We find that the correlation between these temperature series is highest in southern Greenland, decreasing toward the north, and that the correlation is controlled by the seasonal time scale precipitation weighting. A statistical model is developed to understand the role of climatic parameters in this correlation. The low correlation in northwestern Greenland is caused in equal parts by a relatively lower mean fraction of precipitation during winter in this sector and a larger year-to-year variability of this fraction.