<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=windows-1252">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<p>Hola a todos,<br>
<br>
Les recordamos que hoy tendremos la siguiente Charla invitada a
las 15:00 hs. en el Salón Meridiano. <br>
</p>
<p>Atentamente,<br>
</p>
<p> --<br>
Secretaría de Ciencia y Técnica<br>
FCAGLP</p>
<p>---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------</p>
<p>
<meta charset="utf-8">
<b style="font-weight:normal;"
id="docs-internal-guid-73c9d288-ccf5-2f1b-e962-8e9413a64df2"><br>
<p dir="ltr"
style="line-height:1.44;margin-top:0pt;margin-bottom:7pt;text-align:
justify;"><span style="font-size:14pt;font-family:Verdana;color:#000000;background-color:transparent;font-weight:700;font-style:normal;font-variant:normal;text-decoration:underline;vertical-align:baseline;white-space:pre-wrap;">CHARLA INVITADA: “Estimating trapped gas concentrations as bubbles within lake ice using ground-penetrating radar.”</span></p>
<p dir="ltr"
style="line-height:1.44;margin-top:0pt;margin-bottom:7pt;text-align:
justify;"><span style="font-size:14pt;font-family:Verdana;color:#000000;background-color:transparent;font-weight:700;font-style:normal;font-variant:normal;text-decoration:underline;vertical-align:baseline;white-space:pre-wrap;">(Estimación de gas atrapado en hielo de lagos en forma de burbujas empleando georradar)</span></p>
<p dir="ltr"
style="line-height:1.44;margin-top:0pt;margin-bottom:7pt;text-align:
justify;"><br>
<b style="font-weight:normal;"
id="docs-internal-guid-73c9d288-ccf5-2f1b-e962-8e9413a64df2">
<p dir="ltr"
style="line-height:1.2;margin-top:0pt;margin-bottom:0pt;text-align:
justify;"><span style="font-size:14pt;font-family:Verdana;color:#000000;background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap;">Nadia Fantello</span></p>
<p dir="ltr"
style="line-height:1.2;margin-top:0pt;margin-bottom:0pt;text-align:
justify;"><span style="font-size:14pt;font-family:Verdana;color:#000000;background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap;">University of Wyoming</span></p>
</b></p>
<br>
<p dir="ltr"
style="line-height:1.728;margin-top:0pt;margin-bottom:7pt;text-align:
justify;"><span style="font-size:12pt;font-family:Verdana;color:#000000;background-color:transparent;font-weight:700;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap;">Resumen</span><span style="font-size:12pt;font-family:Verdana;color:#000000;background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap;">: 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. </span></p>
</b><br class="Apple-interchange-newline">
</p>
</body>
</html>