Frequency, magnitude, and characteristics of aeolian sediment transport: McMurdo Dry Valleys, Antarctica

Abstract

[1] Due, in part, to the challenging environment of Earth's high-latitude regions, available information on cold climate effects on aeolian processes in these areas remains limited. Data from these areas, however, provide insight into the physics of sediment transport by wind and the controls on erosive winds in proximity to ice caps and topographic influences. This study presents a 2 year record of meteorological, saltation activity, horizontal saltation flux, and particle size distribution data from four sites in the McMurdo Dry Valleys of Antarctica, 2008 to 2010. Saltation measurements revealed daily and seasonal patterns with spring and summer sediment transport events occurring between 09:00 and 24:00 hours due to thermally generated winds. Fall and winter events occur at any time of day with the strongest associated with foehn winds. Threshold wind speed at 4.2 m in all seasons for all locations was %10 m s À1 . Saltation occurred in the temperature range À40 C to +5 C. Westerly winds in the fall/winter and easterly winds in spring/summer are associated with the majority of transport events. The sand in transport is mainly 250 to 500 mm in diameter and poorly sorted. The integrated saltation flux varies over three orders of magnitude among the sites, with the lowest mean flux recorded in the Taylor Valley (2.9 kg m À1 day À1) and the highest in the eastern Victoria Valley (2271 kg m À1 day À1 ) for 24 hours of continuous saltation. The percentage of time saltation active at these locations annually is %2%, %4%, and %13%, respectively, for the Victoria, Taylor, and Wright Valleys.

Aeolian Material Transport and Its Role in Landscape Connectivity in the McMurdo Dry Valleys, Antarctica

“…Meanwhile, aeolian material collected 100 cm above the surface had the highest aeolian flux in the Lake Bonney basin and <1 g·m −2 ·year −1 in the Lake Hoare basin (Lancaster, ). The material collected at 30 cm is predominately sand sized and is likely dominated by saltation, which helps to account for these noted transport variations (Deuerling et al, ; Gillies et al, ; Lancaster et al, ). Physical obstacles in the landscape of Taylor Valley, such as the Nussbaum and Bonney Riegels (~700 and 200 m above sea level, respectively), likely impede aeolian transport, which also affect fluxes (Fountain et al, ; Šabacká et al, ).…”

Antarctica's Dry Valleys: A potential source of soluble iron to the Southern Ocean?

“…The relatively low dust emission rates in Antarctica are overall not surprising if we consider that the mean annual wind speeds are moderate (about 5 m s −1 ) [e.g., Doran et al , ], and the saltation events in this area occur at low temperatures in the range of −40°C to +5°C [ Gillies et al , ]. Other studies have shown that in the Taylor Valley, maximum wind speeds of 30 m s −1 are reported [e.g., Doran et al , ]; however, Gillies et al [] found that maximum wind speeds did not exceed 25 m s −1 . Although soils in Antarctica are generally cemented by ice and sometimes covered by a crust [ Doran et al , ], a warming of +0.5°C h −1 in spring and summer was observed as a precursor to initiate saltation [ Gillies et al , ].…”

“…Other studies have shown that in the Taylor Valley, maximum wind speeds of 30 m s −1 are reported [e.g., Doran et al , ]; however, Gillies et al [] found that maximum wind speeds did not exceed 25 m s −1 . Although soils in Antarctica are generally cemented by ice and sometimes covered by a crust [ Doran et al , ], a warming of +0.5°C h −1 in spring and summer was observed as a precursor to initiate saltation [ Gillies et al , ]. However, during the winter months, wind gusts can often exceed 37 m s −1 [e.g., Nylen et al , ], and the occurrence of a dry and ice‐free top part of the soil profile associated with hyperaridity may favor saltation and aeolian transport [ Gillies et al , ].…”

Changes in the saltation flux following a step‐change in macro‐roughness

“…Observations of the change in mean grain size as a function of height show complex patterns including a decrease in mean grain size with height (Williams, ; Li et al ., ) while other available data reveal instances of an increase in mean grain size with height (Williams, ; Xing, ; Speirs et al ., ; Gillies et al ., ). Additionally, it has often been observed that at some distance above the surface the grain size trend can reverse (Williams, ; Xing, ; Farrell et al ., ; Zhang et al ., ), which may be indicative of a change in transport system dynamics (Andreotti, ).…”

“…Understanding how large roughness elements affect sand transport is important as there are many natural surfaces where sand transport occurs among large roughness elements including vegetation or sediment mounds covered in vegetation, for example nebkhas (Wolfe and Nickling, ; Al‐Awadhi, ; Gillies et al ., ), or varying amounts of solid roughness elements composed of rocks (Gillies et al ., , ; Lancaster et al ., ). Arrays of large roughness elements that have been manufactured have been tested to evaluate their effectiveness to serve as a method to reduce sand transport and the associated dust emissions, for example, at the Keeler Dunes, Keeler, CA (Gillies et al ., ).…”