Global wind patterns and the oceans

1. Major Ocean Currents

  • Table 7.1: Major Ocean Currents

    • Gulf Stream

    • North Atlantic Drift

    • Labrador Current

    • West Greenland Drift

    • East Greenland Drift

    • Canary Current

    • North Equatorial Current

    • North Equatorial Countercurrent

    • South Equatorial Current

    • South Equatorial Countercurrent

    • Equatorial Countercurrent

    • Kuroshio Current

    • North Pacific Drift

    • Alaska Current

    • Oyashio Current

    • California Current

    • Peru or Humboldt Current

    • Brazil Current

    • Falkland Current

    • Benguela Current

    • Agulhas Current

    • West Wind Drift

2. Ocean Currents and Wind Patterns

  • Wind Stress

    • Wind exerts a force (known as wind stress) on the ocean.

    • Currents in the upper ocean are primarily driven by wind.

    • Generally flow in the same direction as prevailing winds.

  • Movement of Heat

    • Poleward currents carry warm water; equatorward currents carry cold water.

    • Ocean currents aid in the transfer of heat from the tropics to polar regions, influencing climate.

    • Winter temperature contrasts between Gulf Stream and North America's interior lead to jet streams.

3. Ocean Temperature Dynamics

  • Current Sea-Surface Temperatures

    • Recorded sea surface temperature (SST) analysis shows temperature variances across the Pacific Ocean.

  • Upwelling

    • Cold water, rich in nutrients, upwells along the Pacific coast, particularly in Northern California during summer.

    • Upwelling is driven by the prevailing north winds.

4. Mechanism of Upwelling

  • Alongshore Winds

    • Wind stress pushes surface waters south; the Coriolis effect redirects surface flows offshore.

    • Cold subsurface water rises to replace the moving surface water, leading to nutrient-rich upwelling.

    • Fog may form from cooling of the overlying air due to the cold water.

5. Equatorial Upwelling

  • Temperature Profiles

    • Warm surface waters are separated from icy-cold deep waters by a thermocline.

    • Thermocline depth varies between Pacific regions, deeper in the western and shallower in the eastern Pacific.

  • Easterly Winds Effects

    • These winds push ocean surfaces, necessitating upwelling of cold water to compensate for diverging surface currents.

    • Results in decreased SST along the equator when winds are easterly.

    • Westerly winds lead to downwelling and warmer SST with no upwelling.

6. El Niño/Southern Oscillation (ENSO)

  • Normal Conditions

    • Warmest water and low pressure typical in the western Pacific, during which good fishing flourishes off Peru due to cold upwelling.

  • El Niño Events

    • Characterized by warming of central equatorial Pacific, disruption of wind patterns, and reduced upwelling leading to ecological changes and warmer waters.

    • Influences global climates and causes shifts in storm tracks.

  • La Niña Events

    • Intensified east winds resulting in heightened upwelling, cooler equatorial waters, and enhanced fishing conditions.

7. ENSO Monitoring and Prediction

  • Temperature Monitoring

    • Use of NOAA’s TAO buoy array and satellite measurements for tracking ocean temperatures and atmospheric conditions.

    • Capacities exist to forecast El Niño conditions with significant accuracy, up to a year in advance.