Relationship between meteoric 10Be and NO3− concentrations in soils along Shackleton Glacier, Antarctica

• Published in: Earth Surface Dynamics
• Main Authors: Diaz, Melisa A., Corbett, Lee B., Bierman, Paul R., Adams, Byron J., Wall, Diana H., Hogg, Ian D., Fierer, Noah, Lyons, W. Berry
• Format: Text
• Language: English
• Published: 2021
• Subjects: Antarctic; East Antarctic Ice Sheet; Shackleton; Shackleton Glacier; Transantarctic Mountains; Antarc*; Antarctica; Ice Sheet
• Online Access: https://doi.org/10.5194/esurf-9-1363-2021; https://esurf.copernicus.org/articles/9/1363/2021/

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 10 Be and <math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="a33a7d42b70ca1fe513ac92c5832eec2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="esurf-9-1363-2021-ie00004.svg" width="25pt" height="16pt" src="esurf-9-1363-2021-ie00004.png"/></svg:svg> in these soils as a tool for understanding landscape disturbance and wetting history and as exposure proxies. Concentrations of meteoric 10 Be spanned more than an order of magnitude across the region ( 2.9×10 8 to 73×10 8 atoms g −1 ) and are among the highest measured in polar regions. The concentrations of <math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="eb51cd45ba2a21283d090226a04e61ba"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="esurf-9-1363-2021-ie00005.svg" width="25pt" height="16pt" src="esurf-9-1363-2021-ie00005.png"/></svg:svg> were similarly variable and ranged from ∼1 µ g g −1 to 15 mg g −1 . In examining differences and similarities in the concentrations of 10 Be and <math xmlns="http://www.w3.org/1998/Math/MathML" id="M17" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="822fcc3376206f5298bc14405cca7022"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="esurf-9-1363-2021-ie00006.svg" width="25pt" height="16pt" src="esurf-9-1363-2021-ie00006.png"/></svg:svg> 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 10 Be 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 10 Be and <math xmlns="http://www.w3.org/1998/Math/MathML" id="M21" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="8a28d0a06c83cc478fcb3953dfc5e6ea"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="esurf-9-1363-2021-ie00007.svg" width="25pt" height="16pt" src="esurf-9-1363-2021-ie00007.png"/></svg:svg> concentrations and relationships in soils can provide important information regarding landscape development, soil evolution processes, and inferred exposure durations of surfaces in the TAM.