Joint Inversion for Surface Accumulation Rate and Geothermal Heat Flow From Ice‐Penetrating Radar Observations at Dome A, East Antarctica. Part II: Ice Sheet State and Geophysical Analysis.

Dome A is the summit of the East Antarctic Ice Sheet, underlain by the rugged Gamburtsev Subglacial Mountains. The rugged basal topography produces a complex hydrological system featuring basal melt, water transport and storage, and freeze‐on. In a companion study, we used an inverse model to infer the spatial distributions of geothermal heat flow (GHF) and accumulation rate that best fit a variety of observational constraints. Here, we present and analyze the best‐fit state of the ice sheet in detail. Our modeled result agrees well with the observed water bodies and freeze‐on structures, while also predicting a significant amount of unobserved water and suggesting a change in stratigraphic interpretation that reduces the volume of the freeze‐on units. Our modeled stratigraphy agrees well with observations, and we predict that there will be two distinct patches of ice up to 1.5 Ma suitable for ice coring underneath the divide. Past divide migration could have interrupted stratigraphic continuity at the old ice patches, but various indirect lines of evidence suggest that the divide has been stable for about the last one and a half glacial cycles, which is an encouraging but not definitive sign for stability in the longer term. Finally, our GHF estimate is higher than previous estimates for this region, but consistent with possible heterogeneity in crustal heat production. Plain Language Summary: In a companion study, we combined a model with observations to figure out the best‐fit maps of geothermal heat flow and snowfall rate in the highest and coldest part of Antarctica, Dome A. In this study, we analyze the best‐fit model in detail. The observations show liquid water moving around underneath the ice sheet and traveling from melting regions to freezing regions. Our model does a good job of matching those observations, while also suggesting new locations where water underneath the ice may be found and also suggesting that the volume of refrozen ice may be smaller than previously believed. Our model predicts that ice up to one and a half million years old, which would be very useful for ice core science, might be found intact and in order within a narrow region underneath the ice ridge. If the ice ridge has moved over time then our model might be wrong about the old ice, but several indirect lines of evidence suggest that it hasn't moved much. Our best‐fit map of geothermal heat flow is hotter than previous estimates, which emphasizes the fact that even old cold areas of Earth's crust can have local areas that are hotter. Key Points: Our model matches the observed water and freeze‐on locations, predicts new areas to look for water, and estimates freeze‐on volumeOur model predicts that two distinct patches of ice up to 1.5 Ma suitable for coring may be found under the divideOur geothermal heat flow estimate is higher than most previous estimates, reflecting known variability in crustal heat production [ABSTRACT FROM AUTHOR]

Copyright of Journal of Geophysical Research. Earth Surface is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)