Browsing by Author "Tedesco, Marco"

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Biogeophysical properties of an expansive Antarctic supraglacial stream
(2017) SanClements, M. D.; Michael, D.; Smith, Heidi J.; Foreman, Christine M.; Tedesco, Marco; Chin, Yu-Ping
Supraglacial streams are important hydrologic features in glaciated environments as they are conduits for the transport of aeolian debris, meltwater, solutes and microbial communities. We characterized the basic geomorphology, hydrology and biogeochemistry of the Cotton Glacier supraglacial stream located in the McMurdo Dry Valleys of Antarctica. The distinctive geomorphology of the stream is driven by accumulated aeolian sediment from the Transantarctic Mountains, while solar radiation and summer temperatures govern melt in the system. The hydrologic functioning of the Cotton Glacier stream is largely controlled by the formation of ice dams that lead to vastly different annual flow regimes and extreme flushing events. Stream water is chemically dilute and lacks a detectable humic signature. However, the fluorescent signature of dissolved organic matter (DOM) in the stream does demonstrate an extremely transitory red-shifted signal found only in near-stream sediment leachates and during the initial flushing of the system at the onset of flow. This suggests that episodic physical flushing drives pulses of DOM with variable quality in this stream. This is the first description of a large Antarctic supraglacial stream and our results provide evidence that the hydrology and geomorphology of supraglacial streams drive resident microbial community composition and biogeochemical cycling
Comparative analysis of morphological, mineralogical and spectral properties of cryoconite in Jakobshavn Isbræ, Greenland, and Canada Glacier, Antarctica
(2013-07) Tedesco, Marco; Foreman, Christine M.; Anton, J.; Steiner, N.; Schwartzman, T.
We report the results of a comparative analysis focusing on grain size, mineralogical composition and spectral reflectance values (400â€“2500 nm) of cryoconite samples collected from Jakobshavn IsbrÃ¦, 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 IsbrÃ¦ 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.