Abstract
AbstractIce cores provide a robust reconstruction of past climate. However, development of timescales by annual-layer counting, essential to detailed climate reconstruction and interpretation, on ice cores collected at low-accumulation sites or in regions of compressed ice, is problematic due to closely spaced layers. Ice-core analysis by laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) provides sub-millimeter-scale sampling resolution (on the order of 100 μm in this study) and the low detection limits (ng L−1) necessary to measure the chemical constituents preserved in ice cores. We present a newly developed cryocell that can hold a 1 m long section of ice core, and an alternative strategy for calibration. Using ice-core samples from central Greenland, we demonstrate the repeatability of multiple ablation passes, highlight the improved sampling resolution, verify the calibration technique and identify annual layers in the chemical profile in a deep section of an ice core where annual layers have not previously been identified using chemistry. In addition, using sections of cores from the Swiss/Italian Alps we illustrate the relationship between Ca, Na and Fe and particle concentration and conductivity, and validate the LA-ICP-MS Ca profile through a direct comparison with continuous flow analysis results.
Highlights
Ice-core proxies for past atmospheric circulation patterns (Mayewski and others, 1997), sea-ice extent (O’Dwyer and others, 2000), snow accumulation rates (Meese and others, 1994; Kaspari and others, 2004), pollution histories (Wagenbach and others, 1988) and volcanic eruptions (Hammer and others, 1981; Zielinski and others, 1996) have all been developed through a variety of chemical analytical techniques
How, laser ablation (LA)-inductively coupled plasma–mass spectrometry (ICP-MS) measurements change with depth of laser penetration, we ablated multiple passes along the same line on a section of the Greenland Ice Sheet Project 2 (GISP2) deep ice core (72.6° N, 38.5° W) which was collected between 1989 and 1993
We have developed a laser ablation cryocell (Sayre Cell) for use in ICP-MS analysis, capable of holding and keeping frozen up to 1 m sections of ice core
Summary
Ice-core proxies for past atmospheric circulation patterns (Mayewski and others, 1997), sea-ice extent (O’Dwyer and others, 2000), snow accumulation rates (Meese and others, 1994; Kaspari and others, 2004), pollution histories (Wagenbach and others, 1988) and volcanic eruptions (Hammer and others, 1981; Zielinski and others, 1996) have all been developed through a variety of chemical analytical techniques. These techniques include ion chromatography (IC), gas chromatography, continuous flow analysis (CFA), stable-isotope mass spectrometry and elemental analysis. Laser ablation offers a technique with the ultra-high sampling resolution necessary under these conditions to be used as a complementary tool for climate reconstruction together with more traditional analytical methods
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