Seasonal-Scale Dating of a Shallow Ice Core From Greenland Using Oxygen Isotope Matching Between Data and Simulation

A precise age scale based on annual layer counting is essential for investigating past environmental changes from ice core records. However, subannual scale dating is hampered by the irregular intraannual variabilities of oxygen isotope (delta O-18) records. Here we propose a dating method based on matching the delta O-18 variations between ice core records and records simulated by isotope-enabled climate models. We applied this method to a new delta O-18 record from an ice core obtained from a dome site in southeast Greenland. The close similarity between the delta O-18 records from the ice core and models enables correlation and the production of a precise age scale, with an accuracy of a few months. A missing delta O-18 minimum in the 1995/1996 winter is an example of an indistinct delta O-18 seasonal cycle. Our analysis suggests that the missing delta O-18 minimum is 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 is reconstructed as 1.02 m yr(-1) in water equivalent. The annual accumulation rate shows an increasing trend with a slope of 3.6 mm yr(-1), which is mainly caused by the increase in the autumn accumulation rate of 2.6 mm yr(-1). This increase is likely linked to the enhanced hydrological cycle caused by the decrease in Arctic sea ice area. Unlike the strong seasonality of precipitation amount in the ERA reanalysis data in the southeast dome region, our reconstructed accumulation rate suggests a weak seasonality.