Accumulation-rate variations around Summit, Greenland

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Abstract
Shallow cores to about 17 m depth were recovered at nine sites distributed on a 150 km × 150 km survey grid centered Summit in central Greenland. Measurements of the stable oxygen-isotope ratio and the gross β activity as a function of depth enable annual summer horizons to be identified and dated. From these data, average accumulation rates were computed with an uncertainty of about 5–8%. The contours of constant accumulation rate in the region suggest a primary moisture flux from the southwest of the grid. Similarly, contours of the average oxygen-isotope ratio are consistent with the progressive isotopic depletion of a precipitating air mass moving from the southwest, and automatic weather-station data indicate that the moisture flux tends to be largest from the southwest quadrant. The annual variation in the total accumulation over the grid shows no persistent trend over the interval 1964–87 common to all cores.