Why in News
New scientific research published in May 2026 warns that the Atlantic Meridional Overturning Circulation (AMOC) — the ocean’s global heat redistribution engine — could weaken by up to 59% by 2100, more than three times worse than the previous dominant estimate of 15%. The finding has alarmed scientists because even a 15% weakening was projected to cause significant disruptions to the Indian Summer Monsoon. A 59% weakening would be catastrophic for South Asian weather patterns, agriculture, and food security. This comes as the India Meteorological Department (IMD) has already forecast a below-normal 2026 southwest monsoon at 90–95% of the Long Period Average (LPA).
What Is AMOC?
The Atlantic Meridional Overturning Circulation (AMOC) is a large system of ocean currents — sometimes called the “global conveyor belt” — that circulates water throughout the world’s oceans and plays a critical role in regulating Earth’s climate.
How It Works
| Stage | Process |
|---|---|
| 1. Surface flow northward | Warm, salty surface water flows north through the Atlantic toward the Arctic/sub-polar region |
| 2. Cooling and sinking | In the North Atlantic, the water cools, becomes denser, and sinks to the deep ocean |
| 3. Deep water return | Cold, dense deep water flows southward at depth |
| 4. Upwelling | The deep water gradually rises (upwells) in other ocean basins and returns to the surface |
AMOC is driven by thermohaline circulation — differences in temperature (thermo) and salinity (haline) that determine water density. It transports roughly 1.3 petawatts of heat northward — comparable to 1.3 million large power plants.
Why Is AMOC Weakening?
Climate change is destabilising AMOC through two mechanisms:
- Arctic ice melt releases large volumes of freshwater into the North Atlantic. Freshwater is less dense than salt water, preventing the normal sinking of surface water that drives the circulation.
- Warming oceans reduce the temperature differential that drives density-driven circulation.
Satellite data and oceanographic buoy arrays (the RAPID array since 2004) have confirmed AMOC is already at its weakest in at least 1,000 years.
The 59% Weakening Projection
Previous IPCC reports projected AMOC would weaken by approximately 15% by 2100 under high-emissions scenarios. The new 2026 research (peer-reviewed, published in a leading oceanography journal) uses updated ice sheet melting models incorporating Greenland and Antarctic ice loss rates observed since 2019. Their revised projections:
| Scenario | AMOC Change by 2100 |
|---|---|
| Previous (IPCC AR6) high-emissions | ~15% weakening |
| New (2026) high-emissions model | ~59% weakening |
| Tipping point (complete collapse) | Possible if warming exceeds 1.6°C–2°C above pre-industrial |
A complete AMOC collapse (not yet likely in the 21st century but not ruled out) would trigger a rapid drop of 5–10°C in Western Europe while other regions face severe disruptions.
Impact on India’s Monsoon
The Indian Summer Monsoon (June–September) is fundamentally a product of differential heating between the Indian Ocean and the Asian landmass. AMOC’s influence on the monsoon operates through the following pathways:
1. Southward Shift of the Inter-Tropical Convergence Zone (ITCZ)
AMOC carries heat northward; when it weakens, the Northern Hemisphere cools relative to the Southern Hemisphere. This asymmetry pushes the ITCZ southward — pulling the monsoon rain belt away from India.
2. Intensification of La Niña/El Niño Extremes
AMOC weakening disrupts sea surface temperature patterns in the Pacific, making El Niño events more frequent and intense. Strong El Niño years are already correlated with weak Indian monsoons.
3. Reduced Arabian Sea Warming
AMOC influences Atlantic SSTs, which in turn affect Indian Ocean heat content via atmospheric teleconnections. Less heat transport means cooler Arabian Sea SSTs — weakening the low-pressure gradient that drives monsoon winds.
4. Monsoon Variability Increase
Even without a reduction in total monsoon rainfall, AMOC weakening increases year-to-year variability — more droughts and more flood years, less predictable onset and withdrawal.
India’s Vulnerability
| Sector | Exposure to Monsoon Disruption |
|---|---|
| Agriculture | ~55% of crop area is rain-fed; kharif crops (rice, maize, pulses) directly dependent on June–September rains |
| Groundwater | Monsoon recharges 45% of India’s groundwater; 60% of irrigation depends on groundwater |
| Hydropower | River-dependent projects (Bhakra, Hirakud, Tehri) require adequate monsoon inflows |
| Drinking water | 600+ million people in rural India depend on monsoon-fed water bodies |
| GDP | Agriculture contributes ~15–18% of GDP; a 10% monsoon deficit causes ~2% GDP contraction historically |
IMD’s 2026 Monsoon Forecast (Already Concerning)
The IMD forecast for the 2026 Southwest Monsoon season (June–September) is below normal — 90–95% of the Long Period Average (LPA of 87 cm). This is independent of AMOC but adds urgency.
AMOC and India’s Climate Policy Imperatives
India’s NDC (Nationally Determined Contribution) under the Paris Agreement targets net-zero by 2070 and commits to reducing emissions intensity of GDP by 45% from 2005 levels by 2030. However, AMOC weakening is primarily driven by global cumulative emissions — especially from developed nations historically. This creates a climate justice dimension: India bears disproportionate consequences of a phenomenon to which it has historically contributed least.
India is actively pursuing:
- Mission LiFE (Lifestyle for Environment) — behavioural change
- National Action Plan on Climate Change (NAPCC) — 8 national missions including National Water Mission
- State Action Plans on Climate Change (SAPCC) — state-level adaptation
UPSC Relevance
Prelims: AMOC (Atlantic Meridional Overturning Circulation); thermohaline circulation; ITCZ (Inter-Tropical Convergence Zone); RAPID array (ocean monitoring); IMD 2026 monsoon forecast — below normal (90–95% LPA); El Niño–monsoon link; India’s NDC (net-zero 2070); Paris Agreement; NAPCC; Mission LiFE
Mains GS-1: Indian monsoon mechanism; climate change impact on Indian agriculture and water security; thermohaline circulation and global climate regulation
Mains GS-3: Climate change and India’s vulnerability; India’s climate commitments under Paris Agreement; climate justice and historical responsibility; food security; water management; Himalayan glaciers and river systems under climate stress
Essay: “The greatest threats to India’s security in the 21st century will not come from borders but from a destabilising climate.”
Facts Corner — Knowledgepedia
- AMOC: Atlantic Meridional Overturning Circulation; ocean’s thermohaline conveyor belt; redistributes ~1.3 petawatts of heat northward
- New research (May 2026): AMOC could weaken 59% by 2100; vs earlier IPCC estimate of ~15%
- Mechanism: Arctic freshwater from melting ice → reduces salinity → prevents deep water formation → slows circulation
- RAPID Array: Continuous AMOC monitoring array across Atlantic at 26°N; operational since 2004
- ITCZ: Inter-Tropical Convergence Zone; monsoon belt; shifts southward if Northern Hemisphere cools
- India monsoon: June–September (SW monsoon); ~87 cm LPA over 50-year average
- IMD 2026 forecast: Below normal (90–95% of LPA)
- El Niño link: Warm Pacific SSTs suppress Indian monsoon; AMOC weakening intensifies El Niño frequency
- 55% of India’s crop area is rain-fed; 45% of groundwater recharged by monsoon
- India’s NDC: Net-zero by 2070; emissions intensity −45% from 2005 by 2030
- NAPCC: 8 national missions; includes National Water Mission, National Mission for Sustaining Himalayan Ecosystem
- Paris Agreement Article 2: Limit warming to 1.5°C above pre-industrial levels
Sources: Business Today — AMOC and Indian monsoon, Insights on India — AMOC, MIT Climate Portal — AMOC collapse probability
