SE-Dome II Ice Core Dating With Half-Year Precision: Increasing Melting Events From 1799 to 2020 in Southeastern Greenland

Arctic warming has accelerated surface melting even in the highland areas of the Greenland ice sheet (GrIS). Understanding the relationship between climate and surface melting is essential for improving the estimates of ice-sheet mass loss due to warming. Here we analyze a 250 m-long ice core from the southeastern dome of GrIS (SE-Dome site; 67(degrees)19'17" N, 36(degrees)47'03" W, 3,161 m a.s.l.), where the annual mean temperature is -20.9(degrees)C and the accumulation rate is high and there is a large discrepancy among climate models regarding snow accumulation estimates. A time scale was established for 1799-2020 with a half-year uncertainty using annual counting of H2O2 concentration and five time horizons determined by electrical conductivity, melt events, and tritium concentration. The annual accumulation rate from the ice core shows no significant trend over 221 years and has an average of 1.04 +/- 0.20 m w.e. year(-1). In contrast, the frequency and thickness of refrozen melt layer (ML) have increased over 221 years, and are synchronized with temperature changes in the Arctic. The thickness of MLs correlates positively with the time-integrated summer temperature anomaly using a reanalysis of air temperature. The in-situ accumulation records in the southeastern GrIS provide an important basis for correcting reanalysis data such as ERA5, which in turn are valuable for improving regional climate models.