Zeestromen

Zeestromen, the Dutch term for sea currents, are large-scale movements of seawater that transport heat, nutrients, and biomass across the oceans. They occur on global, regional, and local scales and influence climate, weather, and marine ecosystems. Currents can persist for years or decades and vary with season and climate state.

Surface currents are primarily wind-driven. The interaction between prevailing winds and the Coriolis effect generates geostrophic flows that follow major wind belts. Ekman transport moves water 90 degrees to wind direction, initiating persistent patterns such as gyres in major oceans. Deep currents arise from differences in water density (thermohaline circulation) and can move vast volumes of water slowly, connecting basins and distributing heat and carbon.

Other processes include upwelling, where deep, nutrient-rich water rises to the surface, supporting productive ecosystems; downwelling; and tidal currents produced by the gravitational effects of the Moon and Sun. Notable currents include the Gulf Stream and Kuroshio in the upper ocean, the Antarctic Circumpolar Current around Antarctica, and the North Atlantic Deep Water formation that drives the global overturning circulation.

Measurements rely on satellite altimetry, drifting buoys, moored instruments, and ships' CTD profiles. Climate models use observed currents to simulate heat transport and predict changes under global warming. They influence weather patterns, marine biodiversity, and human activities such as shipping and fisheries.

Zeestromen exhibit substantial natural variability and may respond to climate modes like ENSO and the North Atlantic Oscillation. Ongoing research aims to improve understanding of regional responses, potential shifts in current strength, and implications for regional climates and coastal systems.