Antarctic Research

Current Projects

See "Habitability of Mars analog low-temperature brines in the Dry Valleys, Antarctica" on the Mars page.

Past Projects

Fluctuations of the West Antarctic Ice-Sheet in relation to Lake History in Taylor Valley, Antarctica, since the Last Glacial Maximum

Prentice, M. L.; Arcone, S. A.; Sletten, R. S.; Toner, J. D. (graduate student)

Abstract: During the Last Glacial Maximum (LGM), the West Antarctic Ice Sheet (WAIS) expanded and abutted the Trans-Antarctic Mountains near the McMurdo Dry Valleys (MDVs). Several researchers have proposed that this ice mass dammed enormous proglacial lakes (up to 400 m deep) in the MDVs. The formation of these lakes has implications for the maximum extent of the WAIS during the LGM, and the timing of its retreat. A better understanding of the WAIS response to post-LGM warming informs our understanding of current deglaciation tends in the face of global temperature increases. To investigate the past history of lakes in the MDV, we measured the soil chemistry. The basic idea is that the soil chemistry will be impacted by past inundation with lake waters, and can be used to determine their extent. This effort was complimented by sediment coring and Ground Penetrating Radar (GPR) work by M. Prentice. There is also unpublished work done by J. D. Toner on Optically Stimulated Luminescence (OSL) age of sediments in Taylor Valley.

Key results from this project include:

• Paleolake extents: We used the soil chemistry to determine the extent of paleolakes in Taylor Valley. Lakes have several effects on soils. During inundation, they leach soils of soluble salts. In addition, at the lake margins salts accumulate in soils as water wicks upwards and evaporates near the surface. By considering these two processes, we found that paleolakes in Taylor were much less extensive than previously thought, and had a complex history determined by the WAIS retreat and the presence of major valley constrictions and thresholds. These results are presented in "Soluble salt accumulations in Taylor Valley, Antarctica: Implications for paleolakes and Ross Sea Ice Sheet dynamics".
• New understanding of soil chemistry: We found that the soil chemistry was strongly influenced by salt leaching and reactions involving exchangeable cations. Exchangeable cations are positively charged ions found adsorbed onto negatively charged sites on soil surfaces. We found the reactions involving exchangeable cations were responsible for the regional formation of high pH (>10) soils, and the formation of CaCl₂-rich solutions. The formation of CaCl₂-rich solutions in this way could explain the unusual chemistry of Don Juan Pond. These results are explored in "The formation of Ca-Cl-rich groundwaters in the Dry Valleys of Antarctica: Field measurements and modeling of reactive transport".
• New age constraints on post-LGM events: Previous studies have dated the sequence of paleolake events following the retreat of glacial ice and lakes from Taylor Valley using radiocarbon (¹⁴C) dating of stream deposits that have been interpreted as lake deltas. However, there is uncertainty as to whether the deposits actually are deltas, and ¹⁴C dating in Antarctica is problematic due to reservoir effects, leading to ages overestimates by as much as 10 Ka. First, using GPR, we found that almost all of these deposits were stream deposits, not deltas. Then, we applied OSL dating and found a persistent reservoir effect of about 5-7 Ka in the ¹⁴C ages. This lead to a new interpretation of the post-LGM history in Taylor Valley. These results are discussed in "Using Salt Accumulations and Luminescence Dating to Study the Glacial History of Taylor Valley, Antarctica".