Systems and methods are disclosed for sealing a high pressure fluid cavity from a low pressure fluid cavity in a rotating machine such as a gas turbine engine. The cavities are at least partially disposed between a rotatable shaft and a sump housing radially displaced from the rotatable shaft. A seal assembly comprises an air riding carbon seal ring and a circumferential ceramic runner. The carbon seal ring is sealingly engaged with the sump housing and has a radially inward facing seal surface. The circumferential ceramic runner is carried by the shaft and has a radially outward facing seal surface extending axially along the shaft. The radially inward facing seal surface of the air riding carbon seal ring sealingly engages the radially outward facing seal surface of the ceramic runner during rotation of the rotatable shaft at a predetermined range of rotational speeds.