Ocean Worlds (2019) 6027.pdf

OCEAN- INTERACTIONS IN THE MCMURDO SOUND: LESSONS FOR DEEP ICE ON OCEAN WORLDS? B. E. Schmidt1, J. D. Lawrence1, M. R. Meister1, D. J. G. Dichek1, C. D. Ramey1, B. Hurwitz1, A. M. Spears1, A. D. Mullen1, F. E. Bryson1, J. J. Buffo1, J. B. Glass1, A. M. Stockton1, 1Georgia Institute of Technol- ogy ([email protected])

Introduction: Without in situ information about the (Ross Ice Shelf and Europa Underwater probe, PI B. E. conditions of the ice-ocean interface on other planets, Schmidt). terrestrial analogs will provide the menu of options from The Icefin ROV was developed at Georgia Institute which to choose as we cobble together the best physical of Technology to enable subglacial and borehole-based processes to consider in modeling these new worlds and science operations, making the deep polar ocean under interpreting data from them. As part of an ongoing de- ice more accessible. Icefin is 110 kg, 4 m long, and 0.24 velopment of under-ice exploration technology geared m in diameter with approximately 2 km maximum at enabling planetary science research as well as access- range. Modular payloads include a CTD (conductivity, ing previously unknown regions of the Antarctic, we temperature, pressure), dissolved oxygen sensor, sonar, have had the opportunity to observe ocean interactions and imaging systems among other sensors to enable on a variety of scales from shallow accretionary envi- physical observations in challenging subglacial envi- ronments powered by a long-range ice-pump circulation ronments [1]. in large ice shelf cavities (see abstract J. Lawrence et al, Local-scale ice-ocean interactions: In each of this meeting), to ocean-sea ice interactions that provide these environments, we find a host of different scale fea- constraints on how ice formation at the interface may tures related to ocean influence from thin brine channels operate on other worlds (see abstract by Buffo et al, this were sea ice formed water carves the surface of the glac- meeting), to places where the ocean is actively altering ier, to small cupped textures at shallow depths to large the base of deep draft ice. Here, we focus on the latter— scale undulations near the base of the . In par- where a combination of visual and sonar data of charac- ticular, we observed changing scales in the erosion of teristic melt-induced textures and in situ oceanographic the base of the Erebus Glacier Tongue from near its data capture the dynamic interaction between water and grounding line to 5km downstream, allowing us to ob- ice. While glaciers themselves are not analogs for Eu- serve how these interactions change with time and ropa or other ocean words per se, the scale of these in- depth, and providing a window into the rates at which teractions allows us to begin to capture the rates associ- these interactions occur. Similarities between the fea- ated with melting due to both temperature and pressure. tures observed at shallow depths for all three glaciers Observations: Here, we present direct observations may suggest the importance of turbulent flow. from Evans Ice Wall (~50m depth), We present several examples and preliminary inter- (~150m depth) and Erebus Glacier Tongue (~300m pretations of these new data as new constraints on how deep draft), near McMurdo Station, to link to think about the interaction of large and small scale the physical ocean state with the ice texture induced by thermohaline circulation on planetary ices. the interactions. Between October and December 2018, References: [1] Meister, M., et al. (2018) OCEANS we operated the ROV Icefin for over 75 hours during 22 2018 MTS/IEEE 10.1109/OCEANS.2018.8604725 dives as part of the NASA-funded RISE UP program