Rip Currents Have Least Friction

Abstract

Surface gravity waves continually come to the beach but rarely go back to sea. They bring excess mass to shore which must be returned offshore. Rip currents do that job because there is less overall friction in the nearshore region than there is in the only other imagined circulation, a two-layer scheme, which has in fact never been seen. An argument is presented to support this proposal. If correct, rip currents join a group of geophysical flow phenomena that persist, probably because there is zero friction associated with them, which include surface gravity waves, tornadoes and hurricanes, individually promoted recently.