Physics
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.c13a0558w&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #C13A-0558
Physics
0726 Ice Sheets, 0758 Remote Sensing, 0776 Glaciology (1621, 1827, 1863), 5462 Polar Regions, 6225 Mars
Scientific paper
Circumpolar layered deposits on Mars consist almost entirely of water ice (Ih), but the roles of surface mass fluxes and possible ice flow in shaping those deposits remains a fundamental, open question. Topography of the layered deposits is dominated by arcuate, v-shaped troughs (with wall slopes of roughly 10 degrees) separated by smooth, low-slope topography (slopes less than roughly 1 degree). In the north, smooth, inter- trough topography is relatively common on a flat-bedded lobe known as Gemina Lingula, which bounds Chasma Boreale on the south and east. Based on prior work in Antarctica, we have applied an inverse method to interpret inter-trough topography. We found strong evidence for past ice flow on Gemina Lingula, prior to formation of the troughs, based on observations of ice-mass geometry normalized by characteristic dimensions. Solution of the inverse problem with normalized topography yields estimates of the ice-flow-law exponent, but does not yield information on absolute time-scales. Here we analyze un-normalized topography to estimate a new dynamical parameter, which relates absolute surface mass flux rates at the time of flow to near-basal temperatures. Surface mass flux rates and ice mass geometry in turn determine the time-scale of equilibration to variations in climatic forcing, for given temperatures. We find a strong, spatially coherent variation in the dynamical parameter over an area spanning roughly 400 km on Gemina Lingula. From this, we quantify the spatial variation in equilibration time-scales on Gemina Lingula, under several temperature scenarios based on variations in Martian orbital parameters over the past 5 million years.
Byrne Shane
Koutnik Michelle R.
Murray Christopher B.
Pathare Asmin V.
Waddington Edwin D.
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