Large-scale reconstruction of accumulation rates in northern Greenland from radar data

Internal layers in polar ice sheets have been mapped in many areas using information from radio-echo sounding surveys. The layers contain imprints of past accumulation patterns and ice flow and can potentially provide estimates of past accumulation rates. In this study, average accumulation rates for the past 14.7 ka in north and central Greenland are recovered from the mapped depth of one pronounced isochrone using a simple ice flow model, accounting for both vertical and horizontal flow combined with formal inversion techniques. Using this method, upstream variations in the accumulation and flow are taken into account when inferring the accumulation rates from the deep layer. This resulted in larger spatial variations in the inferred accumulation rates compared to approaches using a one-dimensional ice flow model. The largest differences were found in areas of significant horizontal flow. The inferred accumulation rates agree with Holocene estimates from ice cores in the interior of the ice sheet. Across the central ice divide, the inferred accumulation pattern shows a pronounced gradient in accumulation rates, similar to the present-day pattern, suggesting that the large-scale pattern in the interior of central northern Greenland has been consistent throughout the past 14.7 ka.