Studies of relatively small outlet glaciers over a few years show that glacial meltwater can lubricate their beds and that this increases the rate of ice flow, which in turn can lead to increased sea level rise. However, the structure of the meltwater drainage system can evolve into a series of connected channels which drain meltwater more efficiently, precluding the acceleration of ice loss. Until now, the extent to which these processes operate when huge, continental-scale ice sheets melt over hundreds to thousands of years has remained unknown. This paper presents the first evidence of changes in meltwater drainage systems over continental and millennial scales. We show that as the North American ice sheet retreated, from about 13 to 7 thousand years ago, the drainage system evolved into numerous large subglacial channels, resulting in relatively stable ice flow during the demise of this large ice sheet. Ice sheet models do not currently incorporate switches in meltwater drainage systems, which is required for accurate predictions of future ice sheet dynamics and associated sea level rise.
Seismic evidence for a crustal magma reservoir beneath the upper east rift zone of Kilauea volcano, Hawaii Guoqing Lin et al., Division of Marine Geology and Geophysics, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida 33149, USA; email@example.com. Posted online 10 January 2014, http://dx.doi.org/10.1130/G35001.1.
An anomalous body with low Vp (compressional wave velocity), low Vs (shear wave velocity), and high Vp/Vs anomalies is observed at 8-11 km depth beneath the upper east rift zone of Kilauea volcano in Hawaii by simult
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