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Approximately 22 Gt of siliciclastic sediment are delivered to the coastal ocean each year across the Earth’s latitude-controlled climate zones. Latitude effects are seen as controls on physical and biogeochemical weathering and thus sediment production; latitude effects also influence precipitation and wind patterns and impact sediment transport through, for example, river-water density and thus through the particle settling velocities of the suspended load. Glacial transport of sediment, including subglacial processes, meltwater, and iceberg rafting, dominates polar regions (10% of land surfaces). Subpolar regions (21% of the global land surface) include many nonglacial environments receiving low intensity rainfall and with low levels of sediment production (physical weathering) and fluvial transport. Their coastal regions are dominated by storm waves modulated by seasonal sea ice. Temperate regions (14%) are zones of moderate sediment production and fluvial transport, regional pockets of eolian transport, and coastal zones highly influenced by storm waves under the westerlies. The subtropical regions (18%) experience high rates of sediment production, moderate rates of precipitation, high rates of eolian transport via the trade winds (North Africa accounts for the majority of the global dust flux), and coastal zones heavily influenced by both swells and storm waves. The tropical region comprises the largest land mass (37%), with very high rates of precipitation (via the InterTropical Convergence Zone [ITCZ]) and sediment production (from biogeochemical weathering), high rates of fluvial clay and silt and sand transport, moderate levels of eolian transport, and swell-dominated coasts. Preservation of woody debris in the tropics is much smaller than in other climatic zones. Tropical river basins can produce and transport 2.5 times more sediment than a similar scale basin located in a temperate region and 12 times more sediment than a similar scale Arctic basin. Both eolian and glacial transport rates were an order of magnitude larger under ice age conditions, and such conditions repeatedly occurred during the past several million years.

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