Eclipse Ice Core Accumulation and Stable Isotope Variability as an Indicator of North Pacific Climate

Abstract

The high accumulation rate and negligible amount of melt at Eclipse Icefield (3017 m) in the Saint Elias Range of Yukon, Canada, allows for the preservation of a high-resolution isotopic and glaciochemical records valuable for reconstruction of climatic variables. Each of the three Eclipse ice cores have a well-constrained depth-age scale with dozens of reference horizons over the twentieth century that permits an exceptional level of confidence in the results of the current calibration exercise. Stacked time series of accumulation and stable isotopes were divided into cold and warm seasons and seasons of extreme high and extreme low accumulation and stable isotope values (eight groups). For each group, season-averaged composites of 500-hPa geopotential height grids, and the individual seasons that constitute them, were analyzed to elucidate common anomalous flow patterns.This analysis shows that the most fractionated isotopes and lowest accumulation cold seasons reflect a more zonal height pattern in the North Pacific associated with negative Pacific-North American (PNA) and Pacific decadal oscillation (PDO) indices. Conversely, the least fractionated isotopes and highest accumulation cold seasons are associated with a positive PNA pattern. Although only a maximum of approximately 20% of the total number of accumulation and stable isotope seasons exhibit a relatively consistent relationship with 500-hPa geopotential height patterns, these results support the hypothesis that the most extreme accumulation and extreme isotope cold-season values in the Saint Elias Mountains are related to consistent atmospheric circulation and oceanic sea surface temperature patterns.

Southern Tibetan Plateau ice core δ18O reflects abrupt shifts in atmospheric circulation in the late 1970s

“…Following earlier works of Hoffmann (2003) and Vuille et al (2003) for the Andes, Brown et al (2006) identified strong imprints of monsoons, meridional migration of the ITCZ and ENSO in tropical precipitation isotopic composition, through processes affecting rainout intensity and convection height. Other ice cores in the central TP, Arctic, Antarctic, and subpolar regions were also interpreted to depict rapid changes in atmospheric circulation after the mid-1970s (Kang et al 2002;Kaspari et al 2007;Schneider et al 2012;Kelsey et al 2012).…”

Ice Cores from the St. Elias Mountains, Yukon, Canada: Their Significance for Climate, Atmospheric Composition and Volcanism in the North Pacific Region

“…In contrast to those from the NWC and PRC cores, snow accumulation records developed from cores drilled on the Eclipse Icefield in 1996 and 2002 (Wake et al, 2002;Kelsey et al, 2012) are highly and significantly correlated over their period of overlap (│R│ = 0.50; AD 1895 -1994), implying a much higher signal-to-noise ratio than in the Mt. Logan plateau records .…”

“…Years with anomalously high (low) accumulation in the PRC record, which were identified using the same criteria as Moore et al (2002a) and Rupper et al (2004), differ from the anomalous years identified by those authors for their composite meteorological field analyses, and (Holdsworth et al, 1992;Moore et al, 2002b); (b) the Mt. Logan PRC core ; and (c) the Eclipse Icefield cores (Kelsey et al, 2012) these differences cannot be accounted for solely by dating discrepancies.…”

“…3c), as would be expected given the altitudinal decoupling between lower and mid-tropospheric air and moisture flow previously noted in δ 18 O records. Kelsey et al (2012) Kelsey et al (2012) also found that unlike those in the Mt. Logan PRC record, variations in d (sensitive to moisture source conditions) in the Eclipse core records are poorly correlated to specific atmospheric circulation patterns and therefore unlikely to serve as reliable moisture source tracers.…”

“…Fisher et al (2008) hypothesize that the shifts in the moisture flow regime recorded in Mt. Logan cores may be linked to variations in the ENSO regime (on this, see also Barron and Anderson, 2011 Wake et al, 2002;period AD 1895period AD -1994 and in 2001 (δD; in black; Kelsey et al, 2012;period AD 1700period AD -2000; (f) pollen grain counts in the Mt. Logan PRC core, period AD 1770 -2000 (J.…”