National Institute of Polar Research, Tokyo 190-8518, Japan
Meteorological Research Institute, Japan Meteorological Agency, Tsukuba 305-0052, Japan
Abstract. Previous studies reconstructing summer temperature from an ice core relied on statistical relationship between melt feature and instrumental temperature observed at a nearby station. This study demonstrates a novel method to reconstruct summer temperature from ice layer thickness in an ice core using an energy balance model, in which heat conduction and refreezing of meltwater in firn are taken into account. Using seasonal patterns of the ERA-Interim reanalysis dataset for an ice core site, we calculated amounts of refreezing water within firn under various settings of summer mean temperature (SMT) and annual precipitation, and prepared lookup tables containing these three variables. We then estimated SMT from the refreezing amount and annual accumulation, both available in an ice core. We applied this method to four ice cores drilled in the sites of different climates; two sites on the Greenland Ice Sheet, one in Alaska, and one in Russian Altai Mountains. Reconstructed SMTs show comparable variations to the temperatures observed at nearby stations. Relationships between SMT and ice layer thickness differ site by site, indicating that a single approximation cannot be applicable to estimate SMT. Sensitivity analyses suggest that annual temperature range, amount of annual precipitation and firn albedo setting significantly affect the relationship between SMT and ice layer thickness. This new method provides alternative and independent estimation of SMT from ice cores affected by melting.
How to cite. Fujita, K., Matoba, S., Iizuka, Y., Takeuchi, N., and Aoki, T.: Physically based summer temperature reconstruction from ice layers in ice cores, Clim. Past Discuss. [preprint], https://doi.org/10.5194/cp-2019-97, 2019.
Received: 04 Aug 2019 – Discussion started: 19 Aug 2019
This study presents a novel method for reconstructing summer temperatures from ice-layer thickness and annual accumulation in an ice core using an energy balance model. The method calculates a lookup table by considering heat conduction and meltwater refreezing in firn. We applied the method to four ice cores in different climates. Sensitivity analyses reveal that the annual temperature range, amount of annual precipitation, and firn albedo significantly affect the estimated summer temperature.
This study presents a novel method for reconstructing summer temperatures from ice-layer...