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Geostrophic current
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<p>A geostrophic current is an <a href="/facts/Oceanic_current/vfwdGwPY">oceanic current</a> in which the <a href="/facts/Pressure_gradient/v7BmlAAS">pressure gradient</a> force is balanced by the <a href="/facts/Coriolis_effect/SqCyUY6d">Coriolis effect</a>. The direction of geostrophic flow is parallel to the <a href="/facts/Isobar_(meteorology)/35Qten5r">isobars</a>, with the high pressure to the right of the flow in the <a href="/facts/Northern_Hemisphere/EFwyqL25">Northern Hemisphere</a>, and the high pressure to the left in the <a href="/facts/Southern_Hemisphere/QfJ4z9L5">Southern Hemisphere</a>. The concept is familiar from <a href="/facts/Weather_map/rlRyVys2">weather maps</a>, whose isobars show the direction of <a href="/facts/Geostrophic_wind/WyPS2KPJ">geostrophic winds</a>. Geostrophic flows may be <a href="/facts/Barotropic/QQp41uUH">barotropic</a> or <a href="/facts/Baroclinity/kW8Anrsg">baroclinic</a>. A geostrophic current may also be thought of as a rotating shallow water wave with a frequency of zero. </p><p>The principle of <i><a href="/facts/Geostrophy/WyPS2KPJ">geostrophy</a></i> or <i>geostrophic balance</i> is useful to oceanographers because it allows them to infer <a href="/facts/Ocean_current/vfwdGwPY">ocean currents</a> from measurements of the <a href="/facts/Sea_surface_height/mEsQ4ERT">sea surface height</a> (by combined <a href="/facts/Satellite_altimetry/r9AAcApl">satellite altimetry</a> and <a href="/facts/Gravimetry/kPrbm8wx">gravimetry</a>) or from vertical profiles of <a href="/facts/Seawater_density/fRBJjbws">seawater density</a> taken by ships or autonomous buoys. The major currents of the world's <a href="/facts/Ocean/8W8lYgjD">oceans</a> including the <a href="/facts/Gulf_Stream/hJCFM34w">Gulf Stream</a>, the <a href="/facts/Kuroshio_Current/WJP7fLQf">Kuroshio Current</a>, the <a href="/facts/Agulhas_Current/fDvP6BBE">Agulhas Current</a>, and the <a href="/facts/Antarctic_Circumpolar_Current/ahv1m7k3">Antarctic Circumpolar Current</a>, are approximately in geostrophic balance and examples of geostrophic currents. </p>