Oceanography is a foundational physical geography topic. Prelims tests: names of major currents (Gulf Stream, Kuroshio, Labrador, Humboldt/Peru), causes of tides (spring vs. neap), ocean resources (polymetallic nodules, gas hydrates), and UNCLOS zones (EEZ, continental shelf). Mains demands: (a) role of ocean currents in global climate (thermohaline circulation, ENSO), (b) tidal energy potential in India, (c) ocean resources and the Blue Economy, (d) IOD and monsoon linkage. The Indian Ocean focus distinguishes Indian UPSC from generic oceanography.
Gulf Stream, Kuroshio, N. Atlantic Drift, Brazil Current — flow from tropics to poles
Cold currents
Labrador, Humboldt (Peru), Benguela, Canary — flow from poles to tropics
Major Current Systems (Gyres):
Ocean
Gyre
Warm Currents
Cold Currents
N. Atlantic
Clockwise
Gulf Stream, N. Atlantic Drift
Canary
S. Atlantic
Anti-Clockwise
Brazil Current
Benguela
N. Pacific
Clockwise
Kuroshio, N. Pacific Drift
California
S. Pacific
Anti-Clockwise
E. Australian Current
Humboldt (Peru)
Indian Ocean
Seasonal (monsoon-driven)
Agulhas, Somali (summer)
W. Australian
Thermohaline Circulation (Global Conveyor Belt):
Deep water forms in N. Atlantic (Labrador Sea, Greenland) — cold, salty water sinks
Travels south → Southern Ocean → Indian/Pacific → upwells
Timescale: ~1000 years for complete cycle
Threat: Global warming → freshwater pulse from Greenland melting → could slow/stop circulation → drastic climate shift
Tides:
Type
Cause
Frequency
Spring tide
Sun + Moon aligned (full/new moon)
Highest high, lowest low
Neap tide
Sun + Moon perpendicular (quarter moon)
Smallest range
Diurnal
One high, one low per day
Gulf of Mexico
Semi-diurnal
Two highs, two lows per day
Most of world
Mixed
Two unequal highs/lows
West Coast USA
Tidal range: Bay of Fundy (Canada) — 16m (highest); Gulf of Khambhat (India) — 11m
Tidal energy: Potential in Gulf of Khambhat, Gulf of Kutch, Sundarbans (India)
Tidal bore: Hooghly River, Amazon (Pororoca), Qiantang (China)
Ocean Resources:
Resource
Location
Potential
Polymetallic nodules
Central Indian Ocean Basin
Mn, Ni, Cu, Co — India has exploration rights
Gas hydrates
Krishna-Godavari, Mahanadi, Andaman
Methane-rich; ~1,894 trillion m³ (India estimate)
Polymetallic sulphides
Mid-ocean ridges
Cu, Zn, Au
Cobalt crusts
Seamounts
Co, Pt, Ni
UNCLOS (United Nations Convention on the Law of the Sea, 1982):
Zone
Distance from Baseline
Rights
Territorial sea
12 nm
Full sovereignty
Contiguous zone
24 nm
Enforce customs, immigration
Exclusive Economic Zone (EEZ)
200 nm
Exploration, exploitation of resources
Continental Shelf
Up to 350 nm
Extended shelf submission
High Seas
Beyond EEZ
Common heritage of mankind
Blue Economy — India's Context:
7,517 km coastline; 2.3 million sq km EEZ
SAGAR (Security and Growth for All in the Region) — India's maritime vision
Deep Ocean Mission (2021) — ₹4,000+ cr — submersible to 6,000m depth
Port-led development — Sagarmala Project
Fisheries: 4th largest in the world — Blue Revolution
Key Facts
Fact
Detail
Total ocean area
~361 million sq km (71% of Earth)
Deepest point
Mariana Trench (~11,000m)
Largest current
Antarctic Circumpolar Current
Highest tide range
Bay of Fundy (16m)
India's EEZ
2.3 million sq km
UNCLOS ratification
India ratified 1995
PYQ Table
Year
Question
Type
2023
"Discuss the role of ocean currents in influencing the climate of coastal regions."
Mains
2022
"Explain the concept of 'Blue Economy' and its significance for India."
Mains
2021
Consider the following about thermohaline circulation...
Prelims
2020
"How do tides influence human activities in coastal areas?"
Mains
2019
Consider the following pairs (current - ocean)...
Prelims
2018
"What are ocean resources? Discuss India's potential in deep-sea mining."
Mains
Statement Elimination Guide
Statement
Truth Value
Why?
"The Gulf Stream is a cold current"
False
It is a warm current, flowing from Gulf of Mexico to NW Europe
"Spring tides occur only in spring season"
False
They occur every full moon and new moon — any season
"India's EEZ is about 2 million sq km"
Roughly True
2.3 million sq km
"UNCLOS was adopted in 1982"
True
Adopted 1982; came into force 1994
"The Humboldt Current flows along the west coast of Africa"
False
It flows along South America's west coast (Peru/Chile)
Current Affairs Hook
2023-24: India's Deep Ocean Mission — MATSYA 6000 submersible trials (June 2024). ISA (International Seabed Authority) — India signed two contracts for polymetallic nodules (Central Indian Ocean Basin, 2002) and polymetallic sulphides (2016). The Blue Economy 2.0 was announced in the 2024 Interim Budget. IMD — Indian Ocean Dipole (IOD) monitoring for monsoon prediction. Sea-level rise — IPCC AR6 shows Indian Ocean rising ~3.7mm/year, threatening coastal cities (Mumbai, Chennai, Kolkata). The Great Pacific Garbage Patch highlights the plastic pollution crisis. Coral bleaching in Lakshadweep (2024) due to marine heatwave.
Interlinkages
→ Indian Monsoon (GS-I): Indian Ocean currents, IOD, and monsoon linkage