Question.
With suitable examples explain the factors causing sea level changes.
उपयुक्त उदाहरणों सहित समुद्र-स्तर में परिवर्तन लाने वाले कारकों की व्याख्या कीजिए।
( UPSC Geography Optional Paper 2 2024, 10 Marks)
Answer.
The rising or lowering of sea level for a longer period[ not like tides] is called sea-level changes. It can be influenced by a variety of natural and human-induced factors. These factors can lead to either an increase or a decrease in sea levels.
The following are some main factors that cause sea level changes:
Thermal Expansion (Water Expansion):
Due to global warming and climate change, ocean water warms up. Warm water expands, increasing the volume of water in the oceans, which leads to a rise in sea levels.
Example: During the 20th century, global warming caused about 30% of the sea level to rise.
Melting of Ice Sheets and Glaciers:
Due to global warming, land-based ice, such as glaciers and ice sheets melt, leading to water flow from melting ice to ocean water, contributing to rising sea levels.
Example: The glaciers in the Himalayas, the Alps, and the Andes are retreating rapidly due to rising temperatures. For instance, between 1992 and 2017, Antarctica lost approximately 2.7 trillion tons of ice, contributing significantly to rising sea levels.
Land Subsidence (Sinking of Land):
Sea levels can appear to rise in areas where the land itself is sinking. This can occur due to natural geological processes, or human activities such as groundwater extraction, mining, or oil drilling.
Example: In Jakarta, excessive groundwater pumping has led to the land sinking by as much as 10 cm per year.
Isostatic Rebound (Land Rising):
In parts of Scandinavia and Canada, the land is still rising due to isostatic rebound ( ice sheet melting). This is causing the relative sea level to fall in these regions, despite global sea levels rising.
Conclusion:
Sea level changes are the result of a complex interaction between natural processes and human activities. Factors like thermal expansion, the melting of ice, land subsidence, and Isostatic Rebound all contribute to either rising or falling sea levels. Understanding these factors is critical for predicting future sea level trends and mitigating the impacts of climate change on coastal communities.
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