Significant dissipation of tidal energy in the deep ocean inferred from satellite altimeter data

Abstract

How and where the ocean tides dissipate their energy are long-standing questions¹ that have consequences ranging from the history of the Moon² to the mixing of the oceans³. Historically, the principal sink of tidal energy has been thought to be bottom friction in shallow seas^4,5. There has long been suggestive evidence^6,7, however, that tidal dissipation also occurs in the open ocean through the scattering by ocean-bottom topography of surface tides into internal waves, but estimates of the magnitude of this possible sink have varied widely^3,8,9,10,11. Here we use satellite altimeter data from Topex/Poseidon to map empirically the tidal energy dissipation. We show that approximately 10¹² watts—that is, 1 TW, representing 25–30% of the total dissipation—occurs in the deep ocean, generally near areas of rough topography. Of the estimated 2 TW of mixing energy required to maintain the large-scale thermohaline circulation of the ocean¹², one-half could therefore be provided by the tides, with the other half coming from action¹³ on the surface of the ocean.