Inclusions in ice layers formed by melting and refreezing processes in a Greenland ice core

• Published in: Journal of glaciology Vol. 69; no. 276; pp. 790 - 802
• Main Authors: Kawakami, Kaoru, Iizuka, Yoshinori, Matoba, Sumito, Aoki, Teruo, Ando, Takuto
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.08.2023
• Subjects: Analytical methods; Brines; Chemical composition; Cores; Firn; Glaciation; Global sea level; Grain boundaries; Greenland ice sheet; Ice; Ice and climate; ice chemistry; ice core; Ice cores; Ice formation; Ice sheet melting; Ice sheets; Inclusions; Melting; Meltwater; Methods; Microscopy; Sea level changes; Sea level rise; Snow; Sodium sulfate; Spectroscopy; Warm climates; Arctic region; Antarctica; Greenland; Ice and climate; ice chemistry; ice core
• ISSN: 0022-1430; 1727-5652
• DOI: 10.1017/jog.2022.101

In recent decades, surface melting on the inland Greenland ice sheet has increased, leading to significant meltwater-refreezing in the snow and firn. Increased knowledge of the physical and chemical characteristics of these melt features (i.e., ice layers) is needed to help estimate future global sea-level rise. Here, using a combination of microscopy and spectroscopy, we investigate the size, shape, location, and chemical compositions of inclusions in 12 ice layers of the SIGMA-A ice core in the northwestern Greenland ice sheet (78°03′06″N, 67°37′42″W, 1490 m a.s.l.). In the ice layers, we found inclusions exceeding 30 μm diameter that could only be formed by melting–refreezing, which we classify into columnar-, particle-, and rod-like inclusions. We propose that the smaller columnar- and particle-like inclusions of solid Na2SO4⋅10H2O and CaSO4⋅2H2O form first, within the ice grains, followed by the larger rod-like inclusions of brines with mainly Na+ and Cl− in grain boundaries. Our results suggest a new proxy that may help identify past warm climates in deeper ice cores in Greenland and for studying future ice sheet melting behavior.