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250 Words15 Marks
Q.How do ocean currents and water masses differ in their impacts on marine life and coastal environment? Give suitable examples? (Answer in 250 words)
UPSC Mains 2019•Geography
Model Answer
View this Question In PYQ RealmSyllabus Point
- Important Geophysical Phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc., geographical features and their location-changes in critical geographical features (including water-bodies and ice-caps) and in flora and fauna and the effects of such changes.
Approach
- Introduction (30-40 words): Define and distinguish ocean currents and water masses.
- Body (170-180 words):
- Explain the impacts of ocean currents on marine life and coastal environments with examples.
- Discuss the impacts of water masses (upwelling/downwelling) with examples.
- Conclusion (30-40 words): Summarize how climate change is disrupting these ocean systems.
Introduction
Ocean currents are continuous, directed movements of seawater generated by forces such as wind and temperature differences (e.g., the warm Gulf Stream and the cold Labrador Current). In contrast, water masses are large, homogeneous bodies of water characterized by distinct temperature and salinity profiles, often driving vertical movements like downwelling in the Norwegian Sea.
Body
Impacts of Ocean Currents
- On Marine Life:
- Nutrient Distribution: Currents act as global conveyor belts, distributing oxygen and nutrients vital for marine life.
- Plankton Transport: They carry plankton across vast distances. For instance, the Gulf Stream transports plankton from the Gulf of Mexico to the Grand Banks, creating rich fishing grounds.
- Mixing Zones: The convergence of warm and cold currents (e.g., Kuroshio and Kurile currents near Japan) creates nutrient-rich zones supporting diverse marine life.
- Disruptive Currents: Anomalous currents like El Niño can devastate local ecosystems by destroying plankton populations off the coast of Peru.
- On Coastal Environments:
- Heat Regulation: Currents maintain global thermal balance by transferring tropical heat to polar regions and vice versa.
- Climate Modification: Warm currents moderate coastal climates (e.g., the North Atlantic Drift keeps Western Europe temperate).
- Desertification: Cold currents stabilize the air, suppressing rainfall and forming coastal deserts (e.g., the Benguela Current's role in the Namib Desert).
- Fog Formation: The meeting of warm and cold currents generates dense fog, as seen near Newfoundland (Gulf Stream and Labrador Current).
Impacts of Water Masses
- Downwelling of Water Masses:
- Carries oxygen-rich surface waters to deep-sea organisms.
- However, because it sinks surface nutrients, downwelling zones generally exhibit low marine productivity.
- Upwelling of Water Masses:
- Brings cold, nutrient-dense deep waters to the surface.
- This fertilizes surface waters, supporting massive fish populations (e.g., the Peruvian upwelling zone is one of the world's most productive fisheries).
Conclusion
Anthropogenic climate change is slowing down ocean circulation by melting glaciers and altering salinity. Preserving these delicate systems by mitigating global warming is critical to protecting marine biodiversity and coastal climates.