Abstract: A method for marine wellbore drilling includes pumping drilling fluid through a drill pipe in a wellbore below a bottom of a drilling riser extending from proximate the bottom of the water to a drilling platform on the surface. Drilling fluid returning from the wellbore is discharged from a position proximate the bottom of the drilling riser into a fluid line extending from the position to the platform. Drilling fluid in the fluid line is pumped from a depth in the body of water shallower than the position of discharge of fluid from the riser and at which a column of fluid in the marine drilling riser at an elevation above an intake of a pump in the fluid line exerts a dynamic fluid pressure exceeding fluid pressure at the intake of the pump. The riser fluid level is selected to provide a selected fluid pressure in the wellbore.