Calibrated cryo-cell UV-LA-ICPMS elemental concentrations from the NGRIP ice core reveal abrupt, sub-annual variability in dust across the GI-21.2 interstadial period

Damiano Della Lunga,Wolfgang Müller,Sune Olander Rasmussen,Paul Vallelonga,Anders Svensson

doi:10.5194/tc-11-1297-2017

Abstract

Abstract. Several abrupt shifts from periods of extreme cold (Greenland stadials, GS) to relatively warmer conditions (Greenland interstadials, GI) called Dansgaard–Oeschger events are recorded in the Greenland ice cores. Using cryo-cell UV-laser-ablation inductively coupled-plasma mass spectrometry (UV-LA-ICPMS), we analysed a 2.85 m NGRIP ice core section (2691.50–2688.65 m depth, age interval 84.86–85.09 ka b2k, thus covering ∼ 230 years) across the transitions of GI-21.2, a short-lived interstadial prior to interstadial GI-21.1. GI-21.2 is a ∼ 100-year long period with δ18O values 3–4 ‰ higher than the following ∼ 200 years of stadial conditions (GS-21.2), which precede the major GI-21.1 warming. We report concentrations of major elements indicative of dust and/or sea salt (Na, Fe, Al, Ca, Mg) at a spatial resolution of ∼ 200 µm, while maintaining detection limits in the low-ppb range, thereby achieving sub-annual time resolution even in deep NGRIP ice. We present an improved external calibration and quantification procedure using a set of five ice standards made from aqueous (international) standard solutions. Our results show that element concentrations decrease drastically (more than 10-fold) at the warming onset of GI-21.2 at the scale of a single year, followed by relatively low concentrations characterizing the interstadial part before gradually reaching again typical stadial values.

Highlights

Dansgaard–Oeschger (D–O) events are abrupt climatic fluctuations between periods of full glacial conditions and periods of relatively mild conditions during the last glacial (Greenland interstadials, GI) (Rasmussen et al, 2014).During stadials, deposition of dust and sea salt in Greenland ice significantly increases
Results of cryo-cell UV-LA-ICPMS measurements of Na, Mg, Al, Ca, and Fe concentrations across the analysed section of GI-21.2 and GS-21.2 are displayed in Figs. 5–8
The element profiles acquired via cryo-cell LA-ICPMS show a similar pattern (Fig. 5)

Summary

Introduction

Dansgaard–Oeschger (D–O) events are abrupt climatic fluctuations between periods of full glacial conditions (called Greenland stadials, GS) and periods of relatively mild conditions during the last glacial (Greenland interstadials, GI) (Rasmussen et al, 2014).During stadials, deposition of dust and sea salt in Greenland ice significantly increases. This phenomenon is strongest during stadials and varies within a year, with the aerosol deposition peaking in wintertime (Wolff et al, 2003) This is because storminess over the ocean enhances the transport of sea-salt species inland during cold conditions, this effect has to counter the typical increase in sea-ice extent during winter that makes it more difficult for sea-salt aerosols to reach a particular site, since they have to travel further (Petit et al, 1999). This mechanism, which is thought to be the primary reason for sea-salt enrichment in ice cores during cooling events, receives possibly further contributions of sea salt from another source. From a quantitative point of view, the contribution of brine, frost flowers, and blow-

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