What factors control the direction of surface currents in the ocean? What is the Coriolis effect, and how does it affect oceanic circulation? Explain thermohaline circulation.

The Coriolis effect plays a pivotal role in shaping the movement of ocean currents. It's an invisible force that arises because the Earth rotates. As air and water move across the planet's surface, they appear to curve — to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This is not due to any physical force acting on the ocean water itself, but rather a result of the Earth moving underneath it.

For instance, when a current flows northward from the equator, the Earth's rotation causes it to veer to the right. This effect is crucial for understanding weather patterns, ocean currents, and the overall climate system. Think of it as being similar to trying to walk in a straight line on a spinning merry-go-round; you'd have to adjust your path to maintain the direction you want to go. Now imagine that on a planetary scale, and you've got a sense of the Coriolis effect's impact on ocean circulation.

Thermohaline circulation, often dubbed as the 'global conveyor belt', is a complex oceanic engine driven by differences in water temperature and salinity. This intricate system contributes massively to regulating the Earth’s climate by transporting heat around the globe.

When water gets colder and saltier, it becomes denser and sinks, creating deep ocean currents. Conversely, warm water is less dense and stays near the surface. Thermohaline circulation ensures that the deep ocean interacts with the warmer, more sunlit surface waters, allowing the oceans to store and release heat over time.

This grand-scale circulation is like a continuously operating escalator — moving salt and warm water across the globe, influencing climate patterns, marine life habitats, and nutrient distribution in the ocean. Without it, our climate would be drastically different, potentially more extreme and less stable.

Surface currents are essentially rivers flowing within the ocean, and they are influenced by various factors that guide their pathways. Wind is a primary driver, pushing the water's surface and creating current flows that mirror the prevailing wind patterns. Coastlines act as barriers redirecting these currents, while temperature and salinity work together to alter the density of the water, impacting how water masses move and mix.

These currents play a key role in distributing heat around the planet, which is essential for moderating the Earth's climate. They also transport nutrients and help sustain marine ecosystems by bringing food to organisms that inhabit these waters. Moreover, surface currents affect human activities by influencing navigation routes, fishing locations, and even the climate of coastal regions.

Ocean gyres are mammoth circular current systems that exist in the Earth's oceans. Created by the Coriolis effect and influenced by the position of continents, there are five main gyres, each associated with different ocean basins.

The North Atlantic Gyre, for instance, is a well-known current system that includes the Gulf Stream. These gyres move warm and cold waters across great distances, affecting weather patterns, marine ecosystems, and the global climate.

Gyres also have a significant impact on marine debris distribution, as the circulating motion tends to trap and concentrate floating materials like plastics. This can lead to environmental issues, such as the creation of 'garbage patches' within these gyres. Even though they are a natural part of the Earth's oceanic system, understanding and monitoring gyres is important for environmental management and protecting marine life.