Matsuoka, K., Frank Pattyn, Denis Callens, Howard Conway: Radar characterization of the basal interface across the grounding zone of an ice-rise promontory in East Antarctica, Ann. Glaciol., in press.

Satellite image of "FranKenny" ice rise (peninsula of grounded ice sticked out to the shelf ice area) and adjacent ice shelf and open ocean. The white line show the transect that we studied.

Boundaries of two objects or groups are always full of complexity.  Most of Antarctic ice meets ocean at the downstream end.   The proximity of the ice floating point frequently referred as grounding zone, because there is several-kilometer-long zone where ice is partially grounded (or floating).  Theoretical studies showed that dynamics of upstream ice is sensitive to the characteristics of the grounding zone.  In this study, we examined the grounded-ice peninsula and adjacent ice shelf in order to examine how the basal interface of the ice varies from the grounded ice to floating ice. Read the rest of this entry »

Matsuoka, K.: Pitfalls in radar diagnosis of ice-sheet bed conditions: lessons from englacial attenuation models, Geophys. Res. Lett., 38, L05505, doi:10.1029/2010GL046205. [Link to the full paper]

This figure shows ice thickness dependence of the radar power returned from the bed. The slope of fitted lines (line, red, blue, and green) varies in terms of the ice thickness range, showing non-rigorous aspect of the traditional method.

As medical doctors see the inside of our body using X-rays, glaciologists use super-powerful cell phones to peer inside and bottom of thousand-meter-thick ice.  When the echo from the bed is stronger, it is in general interpreted that the bed is wetter.  In this way, we delineate wet bed, where less basal drag is applied to the ice so the ice flows faster than the dry-bed area.  This paper rises a question on this widely-accepted view how to interpret the radar data.

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Langley, K., J. Kohler, K. Matsuoka, A. Sinisalo, T. Scambos, T. Neumann, A. Muto, J-G. Winther, and M. Albert: Recovery Lakes, East Antarctica: radar assessment of sub-glacial water extent, Geophys. Res. Lett, 38, L05501, doi:10.1029/2010GL046094. [Link to the full paper]

The color of stripes show the radar reflectivity at the lower interface of the ice sheet. White curves highlight the shore of subglacial lakes proposed by a previous research

Recovery Lakes are subglacial lakes in East Antarctica.  Four extremely smooth and flat ice surface identified with satellite images are thought an expression of giant subglacial lakes, but no direct evidence showing the lakes were not known.  The Norwegian-US traverse during the International Polar Year (IPY) made extensive radar measurements in this area.  In this paper, we present a suite of evidence to discuss the current conditions of these hypothetical subglacial lakes.

Dr. Matsuoka participated in the analysis of the radar data.  In particular, he contributed to extract effects of the overburden ice on strength of radar signals back from the ice-bottom interface.  The radar signals from bed are affected by the bed properties as well as overburden ice during the round trip to the bed.

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