Ice layers as an indicator of summer warmth and atmospheric blocking in Alaska

Abstract

Samples were collected from a snow pit and shallow firn core near Kahiltna Pass (2970 m a.s.l.), Denali National Park, Alaska, USA, in May 2008. The record spans autumn 2003 to spring 2008 and reveals clusters of ice layers interpreted as summertime intervals of above-freezing temperatures. High correlation coefficients (0.75–1.00) between annual ice-layer thickness and regional summertime station temperatures for 4 years (n = 4) indicate ice-layer thickness is a good proxy for mean and extreme summertime temperatures across Alaska, at least over the short period of record. A Rex-block (aka high-over-low) pattern, a downstream trough over Hudson Bay, Canada, and an upstream trough over eastern Siberia occurred during the three melting events that lasted at least 2 weeks. About half of all shorter melting events were associated with a cut-off low traversing the Gulf of Alaska. We hypothesize that a surface-to-bedrock core extracted from this location would provide a high-quality record of summer temperature and atmospheric blocking variability for the last several hundred years.

High‐frequency observations of melt effects on snowpack stratigraphy, Kahiltna Glacier, Central Alaska Range

“…In terms of melt layer mass as a percentage of total snow with a column, melt layers at Kbase increased from less than 1% on May 26 to 10% by June 10. This is already more than an entire season's worth of melt layers in 4 of the 5 years studied at Kahiltna Pass (Kelsey et al ., ). For our study, 35% of meltwater infiltrates deeper than 1.8 m, the depth of our pits.…”

“…This finding is supported by the work of Kelsey et al . () at a nearby site, who found stratigraphic alteration (melt layer formation) to be proportional to temperature‐induced melting.…”

“…How snow properties such as albedo, grain size, density, and permeability change with the addition of melt has important implications for feedback in various glacial systems. Also, by establishing how melt layers form in the snowpack, ice core palaeoclimate studies, such as those by Das and Alley (2005) and Kelsey et al (2010), will better be able to reconstruct temperature and energy balance records based on physical stratigraphy, addressing some of the issues raised by Koerner (1997).…”

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

“…yr −1 at Kahiltna Pass (2970 m a.s.l. ), Denali National Park, Alaska (Kelsey et al, 2010). However, the average annual accumulation rate at Aurora Peak (1.87 w.eq.…”

“…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).…”