Reconstruction of recent climate change in Alaska from the Aurora Peak ice core, central Alaska

A Tsushima,K Yoshikawa,T Shiraiwa,S Matoba,H Sasaki,D J Solie,S Okamoto

doi:10.5194/cp-11-217-2015

A Tsushima, K Yoshikawa + Show 5 more

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https://doi.org/10.5194/cp-11-217-2015

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Abstract

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.

Highlights

Various atmospheric chemical species transported by atmospheric circulation from oceans, forest fires, deserts, volcanic eruptions, and other sources are deposited with falling snow on glacier surfaces
We compared the δD values and annual accumulation rates estimated from the ice core with air temperatures and annual precipitation, respectively, observed at weather stations located in Alaska (Table 2 and Fig. 1; climatological data provided by the Alaska Climate Research Center, http://climate.gi.alaska.edu/index.html, and the U.S Geological Survey, http://ak.water.usgs.gov/glaciology/gulkana/ index.html)
Our results suggest that δD values reflect the air temperatures of both central Alaska and the coastal area of the Gulf of Alaska, and that the annual accumulation rates reflect the precipitation in the coastal area of the Gulf of Alaska

Summary

Introduction

Various atmospheric chemical species transported by atmospheric circulation from oceans, forest fires, deserts, volcanic eruptions, and other sources are deposited with falling snow on glacier surfaces. In the northern North Pacific region, several ice cores have been drilled to study paleoclimate change; e.g., the Mt. Logan, Eclipse Icefield, Mt. Wrangell, and Kahiltna Pass (Holdsworth et al, 1992; Yalcin and Wake, 2001; Moore et al, 2002; GotoAzuma et al, 2003; Shiraiwa et al, 2003; Fisher et al, 2004; Zagorodnov et al, 2005; Kelsey et al, 2010) (Table 1 and Fig. 1). The chemical variations have been reported from the Eclipse Icefield snow pit observation and ice core, drilled in 1996 and 2002, respectively (Yalcin and Wake, 2001; Yalcin et al, 2006).

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