Thermal legacy of a large paleolake in Taylor Valley, East Antarctica, as evidenced by an airborne electromagnetic survey

Krista F Myers,Ross A Virginia,Denys Grombacher,Esben Auken,Peter T Doran,Slawek M Tulaczyk,Nikolaj Foged,Jill A Mikucki,Thue S Bording,Hilary A Dugan,Neil T Foley

doi:10.5194/tc-15-3577-2021

Abstract

Abstract. Previous studies of the lakes of the McMurdo Dry Valleys have attempted to constrain lake level history, and results suggest the lakes have undergone hundreds of meters of lake level change within the last 20 000 years. Past studies have utilized the interpretation of geologic deposits, lake chemistry, and ice sheet history to deduce lake level history; however a substantial amount of disagreement remains between the findings, indicating a need for further investigation using new techniques. This study utilizes a regional airborne resistivity survey to provide novel insight into the paleohydrology of the region. Mean resistivity maps revealed an extensive brine beneath the Lake Fryxell basin, which is interpreted as a legacy groundwater signal from higher lake levels in the past. Resistivity data suggest that active permafrost formation has been ongoing since the onset of lake drainage and that as recently as 1500–4000 years BP, lake levels were over 60 m higher than present. This coincides with a warmer-than-modern paleoclimate throughout the Holocene inferred by the nearby Taylor Dome ice core record. Our results indicate Mid to Late Holocene lake level high stands, which runs counter to previous research finding a colder and drier era with little hydrologic activity throughout the last 5000 years.

Highlights

Lakes provide a refuge to life in some of the more extreme environments on Earth, especially in places with strong seasonality such as polar regions
This study provides a third method for estimating lake level history during the previously unconstrained Mid to Late Holocene (5 ka to present) using a novel application of electrical resistivity data to identify the subsurface thermal legacy of paleolake levels in Taylor Valley (TV)
Lake levels in TV have fluctuated in the past, leaving behind a complex history of overprinted lacustrine deposits and subsurface thermal signatures

Summary

Introduction

Lakes provide a refuge to life in some of the more extreme environments on Earth, especially in places with strong seasonality such as polar regions. The evolution of lake basins is important to survival of local ecosystems, and interpreting the history of lake levels and water availability can provide important insights into long-term ecosystem dynamics. Despite extremely low temperatures and minimal precipitation, the McMurdo Dry Valleys (MDVs; Fig. 1) are the site of a series of closed-basin lakes fed by alpine glacial melt and snowmelt via ephemeral streams as well as by direct subsurface recharge (Toner et al, 2017; Lawrence et al, 2020). Annual lake levels in the MDVs have been recorded since the 1970s, which provides a window into the dynamic climatic and geologic drivers of the MDV hydrologic system (Fountain et al, 2016). The fluctuation in the MDV lakes alters the biological and chemical exchange between surface waters, soils, and groundwater, making it critical for understanding MDV connectivity and ecosystem

Results

Discussion

Conclusion