[Alumnos] HOY 15:00 hs.Charla invitada: Geof. Nadia Fantello

[Secretaría de Ciencia y Técnica]

Hola a todos,

Les recordamos que hoy tendremos la siguiente Charla invitada a las 
15:00 hs. en el Salón Meridiano.

Atentamente,

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Secretaría de Ciencia y Técnica
FCAGLP

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*CHARLA INVITADA: “Estimating trapped gas concentrations as bubbles 
within lake ice using ground-penetrating radar.”*

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(Estimación de gas atrapado en hielo de lagos en forma de burbujas 
empleando georradar)


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*Nadia Fantello*

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University of Wyoming

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Resumen: Freshwater lakes are an important source of atmospheric methane 
(CH4); however, uncertainties associated with quantifying fluxes limit 
the accuracy of climate warming projections. Among emission pathways, 
ebullition (bubbling) is the principal and most challenging to account 
for given its spatial and temporal patchiness. When lakes freeze, many 
methane-rich bubbles escaping from lake-bottom sediments are temporarily 
trapped by downward-growing lake ice. As bubble position is then 
seasonally fixed, we postulate that it should be possible to locate 
bubbles using a geophysical approach sensitive to perturbations in the 
ice-water interface and ice sheet structure generated by bubbles. This 
study utilizes ground-penetrating radar (GPR) to non-invasively quantify 
the amount of ebullition gas present in lake ice. To do this requires an 
appropriate petrophysical transformation that relates radar wave 
velocity and volumetric gas content. We utilized laboratory experiments 
to show that electromagnetic models and volumetric mixing formulas were 
good representation of the gas volume-permittivity relationship. Second, 
by combining two GPR geometries (common and multi- offset) we were able 
to locate bubbles and estimate gas volume with low uncertainty. Finally, 
we found that GPR reflection patterns were associated with different 
previously identified ice-bubble classes. These geophysical results 
coupled with ancillary field measurements and ice-growth models also 
suggest how GPR can contribute to estimates of seasonal and annual 
ebullition fluxes over large spatiotemporal scales within and among 
lakes, thereby helping to reduce uncertainties in upscaled estimate of 
ecosystem methane emissions.

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