[A-CC37] [EJ] Ice cores and past environmental changes

[ACC37-P04] Seasonal scale dating of a shallow ice core from Greenland using oxygen isotope matching between data and simulation

Ryoto Furukawa¹, *Ryu Uemura², Koji Fujita³, Jesper Sjolte⁴, Kei Yoshimura⁵, Sumito Matoba¹, Iizuka Yoshinori¹ (1.Institite of Low Temperature Science, Hokkaido University, 2.Department of Chemistry, Biology, and Marine Science, Faculty of Science, University of the Ryukyus, 3.Graduate School of Environmental Studies, Nagoya University, 4.Department of Geology, Quaternary Science, Lund University, 5.Institute of Industrial Science, the University of Tokyo)

Keywords:Greenland, ice core, seasonal scale dating, oxygen isotope, air temperature, annual accumulation rate

A precise age scale based on annual layer counting is essential for investigating past environmental changes from ice core records. However, the uncertain seasonal cycle (i.e., non-sinusoidal pattern) of oxygen isotope (δ¹⁸O) records causes inevitable errors in the dating. Here, we propose a dating method based on matching the δ¹⁸O variations between ice-core records and records simulated by isotope-enabled climate models. We applied this method to a new δ¹⁸O record from an ice core obtained from a dome site in southeast Greenland. The close similarity between the δ¹⁸O records from the ice core and models enabled correlation and the production of a precise age scale, whose accuracy was ±2 months. A missing δ¹⁸O minimum in the 1995/1996 winter is an example of the uncertain δ¹⁸O seasonal cycle, which hampers annual layer counting. Our analysis suggests that the missing δ¹⁸O minimum was likely caused by a combination of warm air temperature, weak moisture transport, and cool ocean temperature. Based on the age scale, the average accumulation rate from 1960 to 2014 was reconstructed as 1.02 m yr^-1. The annual accumulation rate increases with a slope of 3.6 (mm year^-1), which is mainly caused by the increase in the autumn accumulation rate (2.6 mm year^-1), which is likely linked to the enhanced hydrological cycle caused by the decrease in Arctic sea ice area. On a seasonal time-scale, our reconstructed accumulation suggests that the ERA re-analysis data overestimates the seasonality in this southeast dome region.