Statistical extraction of volcanic sulphate from nonpolar ice cores

• Published in: Journal of Geophysical Research Vol. 117; no. D3; pp. D03306 - n/a
• Main Authors: Moore, J. C., Beaudon, E., Kang, Shichang, Divine, D., Isaksson, E., Pohjola, V. A., van de Wal, R. S. W.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 16.02.2012; American Geophysical Union
• Subjects: Anthropogenic factors; Atmospheric sciences; Cores; Cryosphere; Earth sciences; Earth, ocean, space; Everest; Exact sciences and technology; Geophysics; Ice; ice core studies; Sulfates; Svalbard; Volcanoes; Asia; Eurasia; Arctic region; Himalayas; polar regions; Svalbard; Antarctica; Mount Everest; Antarctic ice sheet; Greenland; models; calcium; geologic sections; eruptions; volcanoes; melting; ice; sulfates; extraction; windows; drill cores; Biogenic factor; ions; Polar region; flow; Anthropogenic factor
• ISSN: 0148-0227; 2169-897X; 2156-2202; 2156-2202; 2169-8996
• DOI: 10.1029/2011JD016592

Ice cores from outside the Greenland and Antarctic ice sheets are difficult to date because of seasonal melting and multiple sources (terrestrial, marine, biogenic and anthropogenic) of sulfates deposited onto the ice. Here we present a method of volcanic sulfate extraction that relies on fitting sulfate profiles to other ion species measured along the cores in moving windows in log space. We verify the method with a well dated section of the Belukha ice core from central Eurasia. There are excellent matches to volcanoes in the preindustrial, and clear extraction of volcanic peaks in the post‐1940 period when a simple method based on calcium as a proxy for terrestrial sulfate fails due to anthropogenic sulfate deposition. We then attempt to use the same statistical scheme to locate volcanic sulfate horizons within three ice cores from Svalbard and a core from Mount Everest. Volcanic sulfate is <5% of the sulfate budget in every core, and differences in eruption signals extracted reflect the large differences in environment between western, northern and central regions of Svalbard. The Lomonosovfonna and Vestfonna cores span about the last 1000 years, with good extraction of volcanic signals, while Holtedahlfonna which extends to about AD1700 appears to lack a clear record. The Mount Everest core allows clean volcanic signal extraction and the core extends back to about AD700, slightly older than a previous flow model has suggested. The method may thus be used to extract historical volcanic records from a more diverse geographical range than hitherto. Key Points Identification of volcanic sulfate from ice core sulfate budget Four new records of volcanism from ice cores outside Greenland and Antarctica New way of dating difficult ice cores from outside polar ice sheets