In-situ observations of solid particulate impurities in glacial ice retrieved at NEEM, Greenland
Abstract
Concentrations and size distributions of solid particulate impurities (particulates hereafter) in ice cores provide us with valuable information on the past climate and environment. It is also important to investigate locations, morphologies and elemental compositions of particulates. But such investigations have been rare because most of the previous studies were carried out using melted samples. We observed particulates in glacial ice samples retrieved by the North Greenland Eemian Ice Drilling (NEEM), using an optical microscope and a cryo-scanning electron microscope (OM and cryo-SEM). These methods allow for in-situ observations of particulates in ice. Particulates in ice sections up to 10 x 5 cm2 were mapped with the OM, and the locations were analyzed. Several areas (ca. 1 x 1 cm2) were selected from the ice sections, and observed with the cryo-SEM. Elemental compositions of particulates were analyzed using an energy dispersive X-ray spectrometer (EDS) equipped on the cryo-SEM. In samples taken from within and outside of cloudy bands around 1548 m depth (ca. 19.2 kyr BP), particulates existed both within grains and at grain boundaries. In cloudy bands, most particulates aligned in a direction perpendicular to the core-axis, while particulates in samples outside cloudy bands showed weaker alignments. The cryo-SEM observations showed that the mode diameter was 3.1 - 4.2 μm. But more than half of the particulates were aggregates of smaller particulates whose mode diameter was 0.65 - 0.88 μm. The EDS analyses showed that most particulates contained silicon, aluminum, sodium, and magnesium. We also found particulates containing calcium, iron, sulfur, and chlorine. We are on the way of analyzing the mechanisms that formed aligned particulates. We also plan to analyze the variations of elemental compositions in different climatic stages.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.C41C1759S
- Keywords:
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- 3337 Global climate models;
- ATMOSPHERIC PROCESSESDE: 0724 Ice cores;
- CRYOSPHEREDE: 1621 Cryospheric change;
- GLOBAL CHANGEDE: 4901 Abrupt/rapid climate change;
- PALEOCEANOGRAPHY