Stochastic Simulations of Bed Topography Constrain Geothermal Heat Flow and Subglacial Drainage Near Dome Fuji, East Antarctica

Topographic variability beneath ice sheets regulates ice flow, basal melting, refreezing processes, and meltwater drainage. The preservation of old ice layers and basal ice stratigraphy is sensitive to these subglacial processes, and Dome Fuji, inland East Antarctica, is one of the few regions where 1.5-Ma old ice can be preserved for investigating a major climatic change that occurred in the mid-Pleistocene. We used stochastic simulation methods and radar data to generate an ensemble of simulated bed topography with the continuous and realistic roughness necessary to assess basal conditions. Ensemble analysis reveals the magnitude and spatial distribution of topographic uncertainty, facilitating uncertainty-constrained assessments of subglacial drainage and topographic adjustments to geothermal heat flow (GHF). We find that topographic variability can lead to widespread local GHF variations of +/- 20% of the background value, which aggregate to raise the regional value and suggest previously underestimated distributions and rates of basal melting. We also find that survey profile spacing has an increasing influence on topographic uncertainty for rougher bed, deriving an empirical relationship that could guide future survey planning based on uncertainty tolerance. The landscape beneath ice sheets affects ice flow, melt and refreeze at the base, subglacial drainage of meltwater, and the presence of very old ice near the base, which can be used for climate reconstruction. Dome Fuji, inland East Antarctica, is one of the few candidate sites for drilling an ice core that covers a major climatic change around 1 million years ago. Using ice thickness measurements from airborne and ground-based radar surveys with spacings of 0.25-10 km, we simulated values between measurements to produce 100 possible continuous grids of the landscape beneath Dome Fuji. For each result, we estimate the impact of valleys and ridges on geothermal heat distribution and predict subglacial water flow directions and lakes that store basal meltwater beneath the ice sheet. Averaged results show where processes are most likely to occur while also indicating uncertainty. We find that landscape variability beneath the ice sheet could increase the distribution and rates of deep ice melting. The uncertainty analysis we applied could also be used to assist the planning of future surveys aiming to map the landscape beneath thick ice in this region and elsewhere in Antarctica and Greenland. Stochastic simulations yield uncertainty-constrained analyses of subglacial drainage and topography-adjusted geothermal heat flow (GHF)Order-of-magnitude rougher bed than previous work shows widespread local GHF variability, impacting regional-mean and bed conditionsNew empirical relationship derived to implement bed-elevation uncertainty into radar survey planning for varying bed roughness

Automated summary

The topographic variability beneath ice sheets plays a crucial role in regulating ice flow, basal melting, refreezing processes, and meltwater drainage. A study conducted in Dome Fuji, inland East Antarctica, reveals that the landscape variability beneath the ice sheet could have a significant impact on the distribution and rates of basal melting. It also emphasizes the importance of considering topographic uncertainty when planning future surveys to map the landscape beneath thick ice in this region and elsewhere in Antarctica and Greenland.