Reconstruction of recent climate change in Alaska from the Aurora Peak ice core, central Alaska
- 1Graduate School of Environmental Science, Hokkaido University, N10W5, Sapporo 060-0810, Japan
- 2Institute of Low Temperature Science, Hokkaido University, N19W8, Sapporo 060-0819, Japan
- 3Graduate School of Environmental Studies, Nagoya University, Nagoya 464-8601, Japan
- 4Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, 99775-7320, USA
- 5Water and Environmental Research Center, University of Alaska Fairbanks, Fairbanks, Alaska, 99775-5860, USA
Abstract. A 180.17 m ice core was drilled at Aurora Peak in the central part of the Alaska Range, Alaska, in 2008 to allow reconstruction of centennial-scale climate change in the northern North Pacific. The 10 m depth temperature in the borehole was −2.2 °C, which corresponded to the annual mean air temperature at the drilling site. In this ice core, there were many melt–refreeze layers due to high temperature and/or strong insolation during summer seasons. We analyzed stable hydrogen isotopes (δD) and chemical species in the ice core. The ice core age was determined by annual counts of δD and seasonal cycles of Na+, and we used reference horizons of tritium peaks in 1963 and 1964, major volcanic eruptions of Mount Spurr in 1992 and Mount Katmai in 1912, and a large forest fire in 2004 as age controls. Here, we show that the chronology of the Aurora Peak ice core from 95.61 m to the top corresponds to the period from 1900 to the summer season of 2008, with a dating error of ± 3 years. We estimated that the mean accumulation rate from 1997 to 2007 (except for 2004) was 2.04 m w.eq. yr-1. Our results suggest that temporal variations in δD and annual accumulation rates are strongly related to shifts in the Pacific Decadal Oscillation index (PDOI). The remarkable increase in annual precipitation since the 1970s has likely been the result of enhanced storm activity associated with shifts in the PDOI during winter in the Gulf of Alaska.