Research Themes
Buried Ice Deposits in Antarctica
Cenozoic Vegetation History of Antarctica
East Antarctic Ice Sheet Evolution
Surface Processes & Numerical Modeling
The realization that in-situ and near in-situ ashfall up to 15 million years in age rest directly on the modern Dry Valleys landscape has prompted us to take a closer look at the range of periglacial processes operating in region. As part of this effort, we have deployed meteorological sensors (Onsett HOBO® data loggers) throughout the valleys in order to determine the spatial distribution and magnitude of microclimate variation, and to assess the resultant surface processes/ landforms that are endemic to each microclimate zone.
On the basis of measured variations in summertime atmospheric temperature and relative humidity (RH), soil temperature, average wind speed/direction, and soil moisture, we divide the region into three microclimate zones: a coastal thaw zone (CTZ), in which elevated soil temperatures and seasonally-moist soils foster development of saturated active layers; an inland-mixed zone (IMZ), in which abundant surface water and saturated active layers are restricted to the margins of melting snowbanks, ephemeral streams, and thawed-lake margins; and, a stable-upland zone (SUZ), in which atmospheric and soil temperatures are too cold and dry to permit the development of traditional, saturated active layers.
Equilibrium landforms as those that are endemic to, and in balance with, local microclimate conditions in each zone. Our assemblage of equilibrium landforms in the CTZ includes tafoni, solifluction lobes, thermokarst, ice-wedge polygons, and low-gradient slopes with mature, low-density gullies. In the IMZ, equilibrium landforms include gelifluction lobes, sand-wedge and composite polygons, desert pavements with wind-polished cobbles, and immature, closely spaced gullies. Finally, equilibrium landforms that best characterize the SUZ include sublimation polygons, debris-covered glaciers, pitted surface cobbles, salt-cemented duricrusts, and puzzle rocks.
Of particular interest are the unusual landforms and surface processes endemic to the SUZ, in which environmental conditions are among the most Mars-like on earth (click here for more details on our Mars-Antarctic analog studies). Within the SUZ, we have studied, and modeled, the formation of sublimation polygons, the magnitude of warming that would initiate slope failures (e.g., shallow planar slides that today occur in the CTZ), and the rate of vapor-diffusion from buried-ice surfaces to the atmosphere. For the latter, we have shown that buried-ice deposits in the SUZ sublimate at an average rate of 0.1 mm a-1, with rates reduced to <0.001 mm a-1 if summertime temperatures drop by ~3°.
Salt Geochemistry
Along with our colleague, Dr. Huiming Bao at LSU, we are modeling the origin and transport history of soil-salts in the Dry Valleys. This salt repository offers an opportunity to study atmospheric chemistry (past and present), the origin and transport of ions in soils, the weathering activity of soils, and post depositional soil-leaching processes/ cryoturbation within this unique environment. Our most recent work has focused on the distribution, concentration, and isotopic signature of chloride and sulfate in Dry Valley soils. We test a hypothesis that soil sulfate in the Dry Valleys is a predictable mixture of three major components: sea-salt sulfate, non-sea-salt sulfate, and background sulfate (derived from weathering and volcanic sources) that to a large extent, varies as a function of elevation and distance from the coast. By measuring sulfate’s three stable isotope parameters, i.e., D17O, d18O, and d34S, plus estimating independently the end-member stable isotope parameters for the three components on the basis of published reports and our measured data, we solve explicitly the mixing proportion for each component using a set of three simultaneous linear equations. For Cl studies, one result is that sublimation tills in the SUZ have their Cl input from two boundaries: a till-atmosphere interface at the top and a buried-ice-till interface at the bottom, differing distinctively from basal tills where there is no salt contribution from the bottom.
Selected Publications
(* Student Advisee)
Levy, J.S., Head, J.W., and Marchant, D.R. 2008. The role of thermal contraction crack polygons in cold-desert fluvial systems. Antarctic Science 20(6), 565-579.
Bao, H., Barnes, J.D., Sharp, Z.D., and Marchant, D.R. 2008. Two chloride sources in soils of the McMurdo Dry Valleys, Antarctica. Journal of Geophysical Research, 113 (D3) D03301, doi:10.1029/2007JD008703.
*Swanger, K.M. and Marchant, D.R. 2007. Sensitivity of ice-cemented Antarctic soils to greenhouse-induced thawing: are terrestrial archives at risk? Earth and Planetary Science Letters 259, 347-359.
Levy, J.S., Marchant, D.R., and Head, J.W., III. 2006. Distribution and origin of patterned ground on Mullins Valley debris-covered glacier, Antarctica: the role of ice flow and sublimation. Antarctic Science 18, 385-398.
*Kowalewski, D. E., Marchant, D.R., Levy, J.S., and Head, J.W. III. 2006. Quantifying low rates of summertime sublimation for buried glacier ice in Beacon Valley, Antarctica. Antarctic Science 18, 421-428.
Bao, H., and Marchant, D.R. 2006. Quantifying sulfate components and their variations in soils of the McMurdo Dry Valleys, Antarctica, J. Geophys. Res., 111, D16301, doi:10.1029/2005JD006669.
*Lewis, A.R., Marchant, D.R., Baldwin, S.L, and Webb, L.E. 2006. The age and origin of the Labyrinth, western Dry Valleys, Antarctica: evidence for extensive middle Miocene subglacial floods and freshwater discharge to the Southern Ocean. Geology 34 (7), 513-516.
Marchant, D.R., *Lewis, A., Phillips, W.C., *Moore, E.J., Souchez, R., and Landis, G. P. 2002. Formation of patterned-ground and sublimation till over Miocene glacier ice in Beacon Valley, Antarctica. Geological Society of America Bulletin 114, 718-730.
Summerfield, M.A., Sugden, D.E., Denton, G.H., Marchant, D.R., Cockburn, H.A.P., and Stuart, F.M., 1999. Cosmogenic isotope data support previous evidence of extremely low rates of denudation in the Dry Valleys region, southern Victoria Land, Antarctica. Geological Society of London, Special Publication 162, 255-267.