Ocean currents: Across the Earth
Gulf Stream, Kuroshio, Agulhas: the jets worth tapping
What this tab covers How the resource varies with latitude, climate, terrain and geology: the richest and poorest regions and the leading countries.Wind energy enters the ocean circulation mainly over the Southern Ocean and the northern storm tracks, but the fast currents worth tapping are narrow jets along the western sides of ocean basins, such as the Gulf Stream.
Fast surface currents occur where wind-driven gyres are squeezed against the western boundaries of ocean basins. Elsewhere, wind-driven currents are typically 0.2 m/s or slower and carry only a few W per m2.
Rich and poor regions
| Region | Resource | Level |
|---|---|---|
| Gulf Stream, Florida to North Carolina | Contains the vast majority of the US ocean current resource; 49 TWh/yr technical4 | high |
| Kuroshio (off Japan) and Agulhas (off south-east Africa) | Named by the IPCC as currents with flow fast enough for modern technology; no resource estimate given8 | medium |
| Southern Ocean | Receives about 80% of the wind's work on the general circulation, but remote, deep and stormy2 | medium |
| North Pacific and North Atlantic storm tracks | Main areas of wind energy input to the surface layer after the Southern Ocean3 | medium |
| Most other US coastal waters | Non-tidal currents of about 0.2 m/s or less4 | low |
The places where the wind puts energy into the ocean are not the places where it can be captured. About 80% of the wind's work on the general circulation enters over the Southern Ocean, far from users and in very deep water. The energy that is practical to use is concentrated in a few narrow western boundary currents close to land, of which the Gulf Stream off the south-eastern United States, averaging about 6.4 km/h, is the best studied. The IPCC renewables report names the Kuroshio off Japan and the Agulhas off south-east Africa as other currents fast enough for modern turbines, but gives no resource figures for them.
Sources
- Vertical mixing, energy, and the general circulation of the oceans (Wunsch and Ferrari, Annual Review of Fluid Mechanics 36, 281-314) Annual Reviews (copy hosted by Ifremer), 2004
- Wind energy input to the Ekman layer (Wang and Huang, Journal of Physical Oceanography 34, 1267-1275) American Meteorological Society (copy hosted by Ifremer), 2004
- Marine Energy in the United States: An Overview of Opportunities (Kilcher, Fogarty and Lawson, NREL/TP-5700-78773) National Renewable Energy Laboratory / US DOE, 2021
- Special Report on Renewable Energy Sources and Climate Change Mitigation, Chapter 6: Ocean Energy (Lewis et al.), sections 6.2.1 and 6.2.4 IPCC, 2011