Abstract
Abstract. Outlet glaciers that flow through the Transantarctic Mountains (TAM) experienced changes in ice thickness greater than other coastal regions of Antarctica during glacial maxima. As a result, ice-free areas that are currently exposed may have been covered by ice at various points during the Cenozoic, complicating our understanding of ecological succession in TAM soils. Our knowledge of glacial extent on small spatial scales is limited for the TAM, and studies of soil exposure duration and disturbance, in particular, are rare. We collected surface soil samples and, in some places, depth profiles every 5 cm to refusal (up to 30 cm) from 11 ice-free areas along Shackleton Glacier, a major outlet glacier of the East Antarctic Ice Sheet. We explored the relationship between meteoric 10Be and NO3- in these soils as a tool for understanding landscape disturbance and wetting history and as exposure proxies. Concentrations of meteoric 10Be spanned more than an order of magnitude across the region (2.9×108 to 73×108 atoms g−1) and are among the highest measured in polar regions. The concentrations of NO3- were similarly variable and ranged from ∼1 µg g−1 to 15 mg g−1. In examining differences and similarities in the concentrations of 10Be and NO3- with depth, we suggest that much of the southern portion of the Shackleton Glacier region has likely developed under a hyper-arid climate regime with minimal disturbance. Finally, we inferred exposure time using 10Be concentrations. This analysis indicates that the soils we analyzed likely range from recent exposure (following the Last Glacial Maximum) to possibly >6 Myr. We suggest that further testing and interrogation of meteoric 10Be and NO3- concentrations and relationships in soils can provide important information regarding landscape development, soil evolution processes, and inferred exposure durations of surfaces in the TAM.
Highlights
One of the most intriguing questions in biogeography concerns the relationship between the evolution of terrestrial organisms and landscape disturbance, in Antarctica
During the Last Glacial Maximum (LGM), the East Antarctic Ice Sheet (EAIS) expanded along its margins, and some of the greatest increases in height occurred at outlet glaciers which flow through exposed peaks of the Transantarctic Mountains (TAM) and drain into the Ross and Weddell seas (Anderson et al, 2002; Golledge et al, 2012; Mackintosh et al, 2014)
All three profiles are ice-cemented at the bottom and are shallow compared those collected from the McMurdo Dry Valleys (Dickinson et al, 2012; Schiller et al, 2009; Valletta et al, 2015), though they are comparable to profiles collected at Roberts Massif by Graham et al (1997)
Summary
One of the most intriguing questions in biogeography concerns the relationship between the evolution of terrestrial organisms and landscape disturbance (e.g., glacial overriding, soil wetting), in Antarctica. The sampling methodology was designed to capture a range of soils which have low salt concentrations due to recent exposure from glacial retreat following the Last Glacial Maximum (LGM) and soils that were likely exposed since at least the last glacial period These data include some of the only meteoric 10Be and NO−3 concentration data from the CTAM (Claridge and Campbell, 1968b, 1977; Graham et al, 1997; Lyons et al, 2016), inform knowledge of landscape disturbance and wetting history, may potentially be used to infer soil exposure duration, and are useful in understanding Antarctic terrestrial biogeography. Many of the currently exposed TAM soils were overrun by ice during the LGM, and some may have only recently been exposed
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