TEMPORAL AND SPATIAL VARIABILITY OF SNOW ACCUMULATION IN CENTRAL GREENLAND

Snow accumulation records from central Greenland are explored to impro ve the understanding of the accumulation signal in Greenland ice core records. Results from a ''forest'' of 100 bamboo poles and automated a ccumulation monitors in the vicinity df Summit as well as shallow core s collected in the Summit and Crete areas are presented. Based on thes e accumulation data, a regression has been calculated to quantify the signal-to-noise variance ratio of ice core accumulation signals on a v ariety of temporal (1 week to 2 years) and spatial (20 m to 200 km) sc ales. Results are consistent with data obtained from year-round automa ted accumulation measurements deployed at Summit which suggest that it is impossible to obtain regional snow accumulation data with seasonal resolution using four accumulation monitors positioned over a length scale of similar to 30 km. Given this understanding of the temporal an d spatial dependence of noise in the ice core accumulation signal, the accumulation records from 17 shallow cores are revisited. Each core s pans the time period from 1964 to 1983. By combining the accumulation records, the regional snow accumulation record has been obtained for t his period. The results show that 9 of the 20 years can be identified as having an accumulation different from the 20 year mean with 99% con fidence. The signal-to-noise variance ratio for the average accumulati on signal sampled at annual intervals is 5.8 +/- 0.5. The averaged acc umulation time series may be useful to climate modelers attempting to validate their models with accurate regional hydrologic data sets.