Publication Date

2020

Document Type

Dissertation/Thesis

First Advisor

Dodd, Justin P.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Earth, Atmosphere and Environment

Abstract

Submarine groundwater discharge (SGD) at a continental scale is one of the least constrained components of the hydrologic cycle and may represent a significant flux of iron and silica waters to the global ocean. Quantifying SGD along the Antarctic margin is complicated by complex subglacial and subsurface hydrogeology and limited observational data. Airborne transient electromagnetic (AEM) surveys have identified extensive high-salinity subsurface brines in the McMurdo Dry Valleys (MDV) that are hydrologically connected to surface features in the MDV (e.g. Taylor Glacier, saline lakes) and are potentially a significant source of SGD to McMurdo Sound. A 2D numerical model was developed using TOUGH2 to determine the transport time of brines from the MDV to the marine sediments in McMurdo Sound. A salinity of 45.3 g/L was used as an initial brine composition based on chlorine concentrations in Taylor Valley soils. An estimated 65 to 95% of surface water in the MDV is lost via sublimation/evaporation, therefore, modern infiltration rates were estimated at 5% of the initial surface water volume (meltwater and precipitation). Infiltration rates of 5%, 25%, 50% and 100% were also modeled as a proxy for brine flux under different climatic regimes where variable mean annual air temperature, precipitation, and meltwater contribution could increase or decrease the amount of water that reaches the subsurface. At present day infiltration rates, the transport of brines from the MDV to McMurdo Sound occurs at timescales of >50 ky; however, infiltration rates of >50% of the total surface water volume can transport brines from up valley to the coastal sediments in as short as 10 ky. While this model does not capture all components of a warmer or wetter climate in the MDV, these results provide the first estimate of the timescales and brine contribution to SGD in the nearshore environment of the MDV. During warmer than present periods of Earth history (e.g. the Pliocene, future), SGD may represent a significant source of terrestrial brines to McMurdo Sound on sub-orbital timescales. Mixing of the SGD brines with marine bottom waters may represent a potentially unknown, yet significant, component of the land-ice-ocean system, and may complicate the interpretation of nearshore marine paleoenvironmental proxies.

Extent

87 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

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