Daan Beelen, Lesli Joy Wood

Mapping sediment deposition and erosion by thermohaline ocean bottom currents is important for the development of ocean infrastructure, future geo resources and understanding the sedimentology of contourites and abyssal dunefields. However, only a limited percentage (estimated 20%) of the ocean floor has been mapped directly through seismic or sonar imaging. To better delineate where zones of bottom current deposition and erosion exist, we develop a prediction from numerical model solutions and sedimentological measurements of the ocean floor. This is achieved by integrating three types of data, which include: 1) Bottom current shear stress from a model run of the HYCOM numerical ocean model (Chassignet et al., 2019). 2) Sedimentation rates from ocean lithospheric age (Müller et al. 2008) and sediment thickness from the GlobSed Model (Straume et al., 2019). 3) The measured extents of bottom current deposits from sonar observations (the contourite atlas by Claus et al., 2017). Shear stresses and sedimentation rates inside and outside the mapped extents of bottom current deposits allow us to quantify the conditions that are conducive for bottom current deposition. These conditions are then extrapolated and displayed on a 1/12° arcsecond resolution map of the world’s oceans, and validated through comparison with known mapped systems. Based on our prediction, around 12% of the ocean has significant deposition by bottom currents while only 1% has erosion. Most bottom current activity occurs where thermohaline currents impinge upon the ocean floor like on continental slopes or on some areas of the abyssal plain. Deposition and erosion also occur where constriction of ocean bottom currents takes place as in straits and seaways. Inland basins (i.e., seas) and continental shelves are mostly-disconnected from global-ocean thermohaline bottom current conveyers and therefore have limited bottom current deposition and erosion. Mid ocean ridges also have little bottom current deposition due which is due to low sediment supply.