Spatial, seasonal and climatic drivers of suspended sediment atop Great Bahama Bank

Suspension is the key mechanism by which fine-grained sediment (<= 125 mu m) is winnowed and transported across shallow-water carbonate platforms into adjacent deep waters. Unlike sliding and saltation, which deliver sedimentary structures via bedload, the sedimentological signature of suspended sediment is more cryptic. This study focuses on suspended sediment, and its drivers - wind, waves and tides - to better constrain the processes responsible for the transport of fine-grained sediments. By building forward from remote sensing algorithms developed for deep-waters, sediment suspension in the shallow water column can be mapped from satellite. By applying machine learning to Moderate Resolution Imaging Spectroradiometer data for Great Bahama Bank, this study demonstrates how the drivers of sediment suspension change over 18 years across this 100 000 km2 carbonate platform. Through time, both seasonal patterns of suspension, as well as those induced by El Nino-Southern Oscillation and, more subtly, the Atlantic Meridional Overturning Circulation were tracked. El Nino-Southern Oscillation modulates wind-induced currents, while Atlantic Meridional Overturning Circulation affects local sea level. Across space, this study shows how the eastern margin of Great Bahama Bank, which is traditionally considered to be wind-dominated, primarily owes its suspended sediment to tidal currents focused between islands. Sediment suspension across the leeward margin of Great Bahama Bank, meanwhile, can be attributed to wind-induced currents and waves. The authors consider this work a step towards delivering a quantitative, reproducible, process-based understanding of sediment suspension atop carbonate platforms using Earth observation data.

Automated summary

This study focuses on exploring the drivers of suspended sediment, including wind, waves, and tides, to understand the transport processes of fine-grained sediments. By analyzing satellite data, the study demonstrates how these drivers vary over time and space in the Great Bahama Bank carbonate platform. The results show the importance of tidal currents and wind-induced currents and waves in sediment suspension. This work contributes to a better understanding of sediment suspension on carbonate platforms using Earth observation data.