Sea-Level Changes
Oceanography EN, Physical Geography, UPSC Notes

Sea-Level Changes | UPSC

Sea-level changes refer to fluctuations in the mean sea level caused by eustatic factors (changes in ocean water volume due to ice melt and thermal expansion) and tectonic factors (isostatic, epeirogenic, and orogenic movements). This guide covers all mechanisms of sea-level change, short-term fluctuations driven by density, pressure, currents, and wind, the impact of sea-level fall on landforms and coral reefs, and the latest IPCC AR6 projections for global and India-specific sea-level rise.

Theories of Origin of Coral Reefs UPSC
Oceanography EN, Physical Geography, UPSC Notes

Theories of Origin of Coral Reefs | UPSC

Various theories have been proposed to explain how coral reefs formed, from Darwin’s Subsidence Theory (1842) to Daly’s Glacial Control Theory (1915). This guide covers all four major theories — Darwin, Murray, Daly, and Davis — with evidence for and against each, plus the modern integrated view that combines tectonic subsidence, sea-level changes, and biological growth patterns.

elnino
Oceanography EN, Physical Geography, UPSC Notes

El-Nino, La-Nina, ENSO, El Nino Modoki | UPSC Oceanography

El Nino and La Nina are opposite phases of the El Nino-Southern Oscillation (ENSO) cycle — a recurring climatic pattern involving temperature changes in the tropical Pacific Ocean. This guide covers Walker Circulation, Southern Oscillation Index, Indian Ocean Dipole (IOD), El Nino Modoki, Madden-Julian Oscillation (MJO), and how each phenomenon impacts the Indian monsoon, global weather patterns, and cyclone formation.

ocean resources
Oceanography EN, Physical Geography, UPSC Notes

Ocean Resources: Biotic and Abiotic | UPSC Oceanography

Ocean resources are classified into biotic (plankton, nekton, benthos) and abiotic (minerals, energy). The ocean provides food, fuel, minerals, renewable energy, and supports global trade. This guide covers mineral reserves from seawater to deep-sea floor, energy sources like OTEC, wave, tidal, and offshore wind, the Blue Economy concept, and India’s Sagarmala project and Deep Ocean Mission.

temperature distribution of oceans
Oceanography EN, Physical Geography, UPSC Notes

Vertical & Horizontal Temperature Distribution of Oceans | UPSC

Ocean temperature varies from latitude to latitude and from the surface to the bottom. The ocean is divided into three vertical zones — the surface (mixed) zone, the thermocline, and the deep zone. This guide covers all factors affecting ocean temperature including latitude, winds, currents, evaporation, and density, as well as the horizontal distribution of temperature across different oceans and latitudes.

Salinity of ocean water
Oceanography EN, Physical Geography, UPSC Notes

Salinity of Ocean Water | UPSC

Salinity of ocean water refers to the total dissolved salt content in seawater, expressed in parts per thousand (ppt). The average ocean salinity is 35.2 ppt. This guide covers factors affecting salinity including evaporation, freshwater input, and ocean currents, along with horizontal distribution across all oceans and seas, vertical distribution, the halocline, and the complete salt budget cycle.

Ocean Currents
Oceanography EN, Physical Geography, UPSC Notes

Ocean Currents | UPSC

Ocean currents are continuous movements of ocean water in a specific direction, driven by planetary winds, temperature, salinity, gravity, and the Coriolis force. This guide covers warm and cold currents, types based on depth and temperature, primary and secondary forces, gyres, Sargasso Sea, upwelling, the role of cold currents in desert formation, and the process of Atlantification in the Arctic.

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