It expects students to give a clear description of the mechanism of the oceanic currents. It also expects students to elaborate in detail the impact of oceanic currents on the global weather pattern with examples.
Introduction:
The ocean covers 71 percent of the planet and holds 97 percent of its water, making the ocean a key factor in the storage and transfer of heat energy across the globe. The movement of this heat through ocean currents affects the regulation of global weather pattern.
Body:
Ocean currents are located at the ocean surface and in deep water below 300 meters (984 feet). They can move water horizontally and vertically and occur on both local and global scales.
The ocean has an interconnected current, or circulation, system powered by wind, tides, the Earth’s rotation (Coriolis effect), the sun (solar energy), and water density differences.
The topography and shape of ocean basins and nearby landmasses also influence ocean currents. These forces and physical characteristics affect the size, shape, speed, and direction of ocean currents. Figure 1 represents the ocean currents.
Figure 1: Oceanic Currents
There are 2 types of Ocean Currents: First one’s are Surface Currents also called Wind-Driven Currents and the second one’s are Deep-water Currents also called Thermohaline Currents.
The Surface Currents are a result of the Wind-stress and are modified by Coriolis force.deep-ocean currents are driven by differences in the water’s density, which is controlled by temperature (thermo) and salinity (haline).
Impact on global weather pattern:
Coastal Areas weather: Most of warm currents are found in eastern margin of continent in lower latitude and influencing the coastal climate such as North Atlantic drift in eastern USA, Florida current in gulf of Florida etc. So, Coastal areas will generally have more moderate temperatures than inland areas because of the heat capacity of the ocean.
Fishing grounds: Places where cold currents meet warm currents are characterized by Fog conditions which make navigation difficult. These areas are also characterized by fishing grounds due to abundance of nutrients to support marine life. For instance, In E. Asia meeting of the warm Kuroshio and the cold Oyashio current provides ideal conditions for rich fishing grounds in Japan.
Desiccating effects: Cold current brings the temperature down and creates a desiccating effect and foggy condition in the coastal area through which it passes.
El-Nino and La-Nino: El-Nino is also caused due to periodic changes in cold water current replaced by warm water currents off Peruvian coasts which affects weather pattern of South Asia, Africa, and Oceania.
Global Thermohaline circulation: Ocean currents act as global conveyor belts which transfer heat from one part of the earth to another. They regulate the coastal climate thereby indirectly regulating the vegetation, fauna and the lifestyles of the people.
Great ocean conveyor belt: The global conveyor belt includes both surface and deep ocean currents that circulate the globe in a 1,000-year cycle. The global conveyor belts circulation is the result of two simultaneous processes: warm surface currents carrying less dense water away from the Equator toward the poles, and cold deep ocean currents carrying denser water away from the poles toward the Equator.
The ocean’s global circulation system plays a key role in distributing heat energy, regulating weather and climate, and cycling vital nutrients and gases.
Desert: Cold current are generally found in the western margin of the continents in lower latitudes, usually associated with the desert landforms in these latitudes e.g. California current in western USA, Peru current in western south America etc.
Temperature and Humidity: Warm current increases the temperature and humidity of the coastal area through which it passes, such as the Norwegian current which increase the temperature of the coastal areas of North Sea make the port workable and climate cool and moist.
Here we have seen the impact of ocean currents on the global weather pattern. However, due to global warming induced climate change the flow of ocean currents is affected in some regions. Such as, evidence from Greenland ice cores, showed that the North Atlantic circulation could come to an abrupt halt within the space of a century or two. Fears arose that global warming might trigger such a switch, which could wreak serious harm.
Conclusion:
As we know that climate change is the biggest global challenge from the environmental perspective, the knowledge of Ocean currents and their circulation can help to minimize the negative effect of climate change and will also help to re-establish the balance of the nature.
