Development and Application of Cryo-Cell –UV-Laser Ablation Mass Spectrometry (UV-LA-ICPMS) to Greenland Ice Cores: Implications for Abrupt Climate Change and Ice Physics. / Della Lunga, Damiano.

2015. 232 p.

Research output: ThesisDoctoral Thesis

Unpublished

Documents

Abstract

Ice cores from Greenland preserve a continuous ~125 kyrs record of climate change at very high resolution. The most remarkable of these changes are Dansgaard-Oeschger (DO) cycles, which are characterized by very rapid Greenland temperature shifts of 5-16°C recorded in δ18O and reflected in many other proxies such as dust (Ca, Al, Fe) and sea salt (Na, Mg). DO events also are recorded in other northern and southern hemisphere archives such as speleothems and thus show the large-scale extent of these climate variations.
By applying cryo-cell UV-LA-ICPMS (Ultra-Violet Laser-Ablation Inductively-Coupled-Plasma-Mass-Spectrometry) directly to frozen NGRIP ice samples, we investigated elemental proxies of dust and sea salt at an unprecedented spatial resolution of ≤200 µm while maintaining ppb detection limits. For the investigated DO event 22 (87.6-84.7 ka), we thus achieve approximately bi-monthly time resolution. Using a series of suitably homogenous reference ice standards specifically prepared during this project, fully quantitative external concentration calibration is achieved.
This high resolution dataset for the main GS22 transitions as well the GS21 precursor shows (1) the phasing of dust, sea salt and temperature proxies, where dust precedes temperature change by three to ten years, (2) the ~ten-fold change in dust concentrations within one year at the GS21.2 and GI21 warming events, (3) a transient phase from interstadial to stadial lasting several decades and characterized by high amplitude oscillations before the onset of the cold/warm phase (‘flickering of climate signal’), (4) the confirmation that dust and sea salt proxies vary significantly even during minor precursor climatic events, and (5) the quantification of rapid changes in dust provenance as deduced from elemental ratio signatures. We also investigated the role of soluble and insoluble impurities during ice grain growth and recrystallization, and show that impurities distribute preferentially on grain boundaries for relatively low concentration ice but not for ‘dirtier’ ice. This difference is interpreted to be related to the size of impurities. While in clear ice impurities are mostly mobile soluble micro-inclusions with sub-micron dimensions that are easily harvested by moving boundaries, in impurities-enriched layers (cloudy-bands) large insoluble particles prevail, reducing the mobility of grain boundaries.
Original languageEnglish
QualificationPh.D.
Awarding Institution
Supervisors/Advisors
Award date1 Sep 2015
Publication statusUnpublished - 2015
This open access research output is licenced under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

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