Context:
Researchers recently found that MHWs deep in oceans may be significantly under-reported.
Marine Heat Waves (MHWs):
- Defined by sea surface temperatures rising 3-4°C above the average for at least 5 days
- Can occur in any season.
- Occurs not just in the surface, but also in deep oceans
- Primarily triggered by temperature changes in the twilight zone
- Causes –
- Surface Heat Flux – Prolonged high-pressure systems that heat the water’s surface.
- Advection – Ocean currents transporting warmer water into a region.
- Winds – Influence the warming intensity during MHWs.
- Climate Modes – Phenomena like El Nino alter MHW likelihood in specific regions.
- Human-Caused Climate Change – 87% of MHWs linked to human-induced warming.
- Duration – Last from weeks to years.
- Impacts – Extreme Weather Events, Increased Ocean Stressors, Fisheries Collapse, Coral Deaths and Socioeconomic Challenges for local communities
Twilight Zone of Ocean:
- Also known as – Mesopelagic Zone or the midwater zone.
- Extending from 200 meters to 1,000 meters
- Light that penetrates to this depth is extremely faint.
- Bioluminescent creatures (visible light produced by the creatures themselves) starts appearing in this zone.
Source: The Indian Express
Previous Year Question
La Nina is suspected to have caused recent floods in Australia. How is La Nina different from EI Nino?
1. La Nina is characterized by unusually cold ocean temperature in equatorial Indian ocean whereas EI Nino is characterized by unusually warm ocean temperature in the equatorial Pacific Ocean.
2. EI Nino has adverse effect on southwest monsoon of India, but La Nina has no effect on monsoon climate.
Which of the statements given above is/are correct?
[UPSC Civil Services Exam – 2012 Prelims]
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer: (d)
