Abstract
AbstractWe report the results of a comparative analysis focusing on grain size, mineralogical composition and spectral reflectance values (400-2500 nm) of cryoconite samples collected from Jakobshavn Isbræ, West Greenland, and Canada Glacier, McMurdo Dry Valleys, Antarctica. The samples from the Greenland site were composed of small particles clumped into larger rounded agglomerates, while those from the site in Antarctica contained fragments of different sizes and shapes. Mineralogical analysis indicates that the samples from Jakobshavn Isbræ contained a higher percentage of quartz and albite, whereas those from Canada Glacier contained a higher percentage of amphibole, augite and biotite. Spectral measurements confirmed the primary role of organic material in reducing the reflectance over the measured spectrum. The reflectance of the samples from the Antarctic site remained low after the removal of organic matter because of the higher concentration of minerals with low reflectance. The reflectance of dried cryoconite samples in the visible region was relatively low (e.g. between ∼0.1 and ∼0.4) favouring increased absorbed solar radiation. Despite high reflectance values in the shortwave infrared region, the effect of the presence of cryoconite is negligible at infrared wavelengths where ice reflectance is low.
Highlights
Cryoconites are mini-entombed ecosystems existing on the surface of glaciers worldwide, composed of mineral sediments, biota and organic material (e.g. Wharton and others, 1981, 1985; Takeuchi and others, 2000; Fountain and others, 2004; Foreman and others, 2007; Bøggild and others, 2010)
We report results concerning spectral, physical and mineralogical properties of cryoconite samples collected over Jakobshavn Isbræ, West Greenland, and Canada Glacier, McMurdo Dry Valleys, Antarctica, during the boreal and austral summers of 2010
We have reported results from a comparative analysis of Jakobshavn Isbræ and Canada Glacier cryoconite samples aimed at quantifying and understanding the mineralogical, morphological and spectral differences and analogies between samples collected at the two sites
Summary
Cryoconites are mini-entombed ecosystems existing on the surface of glaciers worldwide, composed of mineral sediments, biota and organic material (e.g. Wharton and others, 1981, 1985; Takeuchi and others, 2000; Fountain and others, 2004; Foreman and others, 2007; Bøggild and others, 2010). Cryoconite is distinct from other forms of glacier cover (e.g. moraine and loess) in that it contains a variable percentage of organic components that are specific to the location and altitude and can be of extraglacial or englacial origin. Extraglacial cryoconite can originate from rockfall onto the ice surface (Reznichenko and others, 2010) or from transport driven by circulation systems (e.g. Bøggild and others, 2010). Cryoconite of englacial origin comes from the release of debris trapped within glaciers as melting occurs, and may consist of debris that was originally sourced subglacially or extraglacially (Nansen and H., 1891; Odell, 1925; Reznichenko and others, 2010; Wientjes and others, 2011). There are reports of Arctic cryoconite containing soot from forest fires (Kim and others, 2005), cosmic debris (Pillinger and others, 1993; Kurat and others, 1994) and anthropogenic particulates (Pfirman and others, 1995; Meese and others, 1997; Bossew and others, 2006, 2007; Tieber and others, 2009)
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