Surface currents in the oceans are primarily caused by a combination of factors, including temperature differences, wind action, and the Coriolis effect. These factors interact to create the complex patterns of ocean circulation that we observe.

1. Temperature Differences:
- Temperature differences play a significant role in driving surface currents in the oceans. Warm water tends to rise and flow towards cooler regions, while cold water sinks and flows towards warmer regions.
- The movement of water due to temperature differences is known as thermohaline circulation. This circulation is driven by the density differences caused by variations in temperature and salinity.
- For example, in the Atlantic Ocean, the Gulf Stream is a warm surface current that flows from the Gulf of Mexico to the North Atlantic. This current is driven by the temperature difference between the warm waters of the Gulf of Mexico and the cooler waters of the North Atlantic.

2. Wind Action:
- Wind action is another important factor that influences surface currents. Winds generate friction on the surface of the ocean, which in turn creates movement in the water.
- The direction and strength of the winds determine the direction and speed of the surface currents. Strong and persistent winds can create powerful currents that can transport large amounts of water over long distances.
- For instance, the trade winds in the tropics blow from east to west, creating the Equatorial Counter Currents. These currents flow against the prevailing currents and have a significant impact on the circulation patterns in the tropical regions.

3. Coriolis Effect:
- The Coriolis effect is a result of the Earth's rotation and influences the direction of surface currents.
- As the Earth rotates, objects moving over its surface appear to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
- This deflection of moving objects, including water currents, is known as the Coriolis effect. The Coriolis effect causes surface currents to move in a curved path rather than a straight line.
- The Coriolis effect is particularly important in shaping the major ocean currents, such as the Gulf Stream and the Kuroshio Current.

In conclusion, surface currents in the oceans are primarily caused by temperature differences, wind action, and the Coriolis effect. These factors work together to create the intricate patterns of ocean circulation that play a vital role in regulating climate and transporting heat around the globe.