Investigating the behavior of mid-Archean tides and potential implications for biogeochemical cycling

A variety of different controls have been proposed for Precambrian marine productivity ranging from environmental factors such as temperature to the flux rate of nutrients (e.g., phosphorus) derived from the continents. In addition to other first-order differences in the Earth system such as a less luminous young Sun, the Earth and Moon were substantially closer together, which would have resulted in a greater tidal forcing. The potential biogeochemical implications of this enhanced forcing have been little explored. Here we use idealized bathymetries and continental configurations to examine mid-Archean ocean tides. We find that, even in the absence of realistic coastal geometries, mid-Archean tidal velocities, sea-surface height, and mixing equaled or exceeded modern values, and that there would have been higher frequency of extreme values. We use a modern tidal model with accurate coastal geometry (HYbrid Coordinate Ocean Model; HYCOM) to scale the idealized results. We propose that mid-Archean water parcel velocities would have been at least 4.5 times greater than at present, that sea-surface height would have been at least 2.5 times greater than at present, and that tidal mixing fronts would have been more common. Each of these factors would result in greater flux and distribution of nutrients, both due to exposure of the sea beds/nascent continents and enhanced onshore-offshore transport, potentially strongly influencing marine productivity even in the absence of substantial permanently exposed subaerial continental landmass.