The distribution of geothermal flux in West Antarctica

• Main Author: Quartini, Enrica
• Other Authors: Blankenship, Donald D., Young, Duncan A., Dalziel, Ian W.D., Lavier, Luc, Schroeder, Dustin M., Wilson, Clark R.
• Format: Thesis
• Language: English
• Published: 2018
• Subjects: West Antarctica; Aerogeophysics; Subglacial volcanism; Ice penetrating radar; Aeromagnetics; Geothermal heat flux; Antarctic; West Antarctic Ice Sheet; Byrd; Siple; Marie Byrd Land; Thwaites Glacier; Siple Coast; Antarc*; Antarctica; Ice Sheet
• Online Access: https://hdl.handle.net/2152/85063; https://doi.org/10.26153/tsw/12033

The West Antarctic Ice Sheet (WAIS) contains the equivalent of ∼3.3 m of global sea level rise and is the largest ice sheet on Earth grounded almost entirely below sea level. This is a potentially unstable configuration that makes WAIS prone to rapid collapse during interglacial periods, a condition known as marine instability. One poorly understood but possibly dominant process in past and future collapses of WAIS is its coupling with the underlying West Antarctic Rift System (WARS), a Jurassic through Cenozoic region of intracontinental extension characterized by active volcanism. WARS’ topographic range, complex tectonic history, and volcanism exert a large influence on the distribution of elevated geothermal flux, a critical but poorly constrained ice sheet boundary condition for the collapse-prone marine- based WAIS. Examples of elevated geothermal flux have been observed throughout the West Antarctic Rift System (WARS). Uncertainties remain however on the timing, evolution, and extent of both the WARS and its volcanism. In this dissertation I analyze magnetic anomalies in the context of other aerogeophysical data in central West Antarctic Rift System (WARS) in order to evaluate the distribution of potential hotspots in the region. I identify three different regions with distinct magnetic character and correlate each region to specific stages of tectonic and magmatic activity in WARS. My interpretation supports both the hypothesis that Marie Byrd Land was tectonically and magmatically reactivated multiple times during the Jurassic and Cenozoic and that a hotspot was emplaced there later in the Cenozoic. I also use the approach described by Schroeder et al. (2014a) to investigate the distribution of elevated and possibly transient geothermal flux along Marie Byrd Land and the Siple Coast of West Antarctica. I employ a vast archive of radar sounding datasets in West Antarctica and use coherent phase sensitive radar to constrain the geometry of subglacial water systems (Schroeder et al., 2013). Under constrained conditions, the amplitude of radar returns can be used with a subglacial water routing model to infer basal melt (Schroeder et al., 2014a). This technique is based on the assumption that the brightness of radar reflectors is proportional to the areal coverage by water at the ice-bed interface. The assumption is valid in the case of subglacial distributed canals, which have been proved to be the current sub-glacial water system dominating the Thwaites Glacier catchment in West Antarctica (Schroeder et al., 2013). Once a ground water transportation system has been selected, the technique uses the bed topography and ice surface elevation to calculate the hydraulic head in a region, which gives information on the subglacial water flow direction and the extent of the upstream catchment. Both of these quantities are used to estimate the total water flow in the region. If the amount of water detected from the radar amplitude analysis exceeds the estimates of total water flow, then an additional source of basal melting, such as geothermal flux, needs to be invoked. Comparing the results with previous assessments of water production due to basal friction (Joughin et al., 2009), the amount of water melt produced by geothermal flux can be estimated. Geological Sciences