MARINE HEATWAVES
1. Context
Marine heatwaves (MHWs) in the Arctic show a worrying trend since 2007, marginal seas more vulnerable: Study A marine heatwave occurs when surface water temperatures are higher than 95 per cent of the values from the past 30 years for at least five consecutive days.
2. About marine heat waves
A marine heat wave is an extreme weather event. It occurs when the surface
temperature of a particular region of the sea rises to 3 or 4 degrees Celsius above the
average temperature for at least five days. MHWs can last for weeks, months or
even years.
The impact of marine heat waves on ocean life
- Marine heatwaves (MHWs) have significant and often devastating impacts on ocean life. Despite seemingly minor temperature increases of 3 or 4 degrees Celsius, these events can have catastrophic consequences for marine ecosystems.
- For example, along the Western Australian coast in the summers of 2010 and 2011, MHWs resulted in devastating fish kills, where large numbers of fish and aquatic animals died suddenly and unexpectedly within a short period and were confined to specific areas.
- Moreover, studies have shown that MHWs can lead to the destruction of kelp forests, which play a crucial role in marine ecosystems by providing habitat and food for many marine animals. The increased water temperatures associated with MHWs are detrimental to kelp, which typically thrive in cooler waters.
- Another significant impact of MHWs is coral bleaching, as seen in the tropical Atlantic and Caribbean in 2005.
- During this event, high ocean temperatures caused more than 80 per cent of surveyed corals to bleach, with over 40 per cent ultimately dying.
- Coral bleaching occurs when corals expel the algae living in their tissues, turning them completely white. This phenomenon severely stresses corals, reducing their reproductive capacity and increasing their vulnerability to fatal diseases.
- Since many marine animals rely on coral reefs for survival, damage to corals threatens their existence as well.
- MHWs also contribute to the growth of invasive alien species, which can disrupt marine food webs.
- Additionally, these events force species to alter their behaviour in ways that increase their risk of harm.
- For instance, MHWs have been linked to incidents of whale entanglements in fishing gear, further highlighting the far-reaching consequences of these heatwaves on marine wildlife.
3. How do Marine Heat Waves Impact Humans?
- Marine heatwaves (MHWs) not only affect marine life but also have significant impacts on humans.
- As ocean temperatures rise during MHWs, storms such as hurricanes and tropical cyclones can become more intense.
- Warmer temperatures lead to increased evaporation and heat transfer from the oceans to the air.
- Consequently, storms travelling across warm oceans gather more water vapour and heat, resulting in stronger winds, heavier rainfall, and more flooding when these storms make landfall.
- This heightened intensity of storms can lead to devastating consequences for human communities in affected areas.
- Furthermore, coral reefs, which are adversely affected by MHWs, are not only essential for marine wildlife but also for human populations.
- According to NOAA, approximately half a billion people rely on reefs for food, income, and protection. When MHWs destroy coral reefs, these human populations are also significantly impacted, facing disruptions to their food sources, livelihoods, and coastal protection.
- The socio-economic impacts of MHWs extend to coastal communities as well. For instance, an MHW over the northwest Atlantic Ocean in 2012 caused marine species accustomed to warmer waters to migrate northward and alter their migration patterns earlier than usual.
- This shift affected fisheries targeting these species in the United States, resulting in economic losses and disruptions to local communities.
- As global temperatures continue to rise, MHWs are projected to become more frequent, intense, and prolonged, exacerbating their adverse effects on both marine ecosystems and human societies.
4. Global warming affecting marine heat waves and oceans
- Global warming, driven by the increase in greenhouse gas emissions, is profoundly affecting marine heatwaves (MHWs) and the overall health of oceans. Studies, including one published in the journal Nature in 2018 titled 'Marine heatwaves under global warming,' reveal alarming trends.
- Over recent decades, MHWs have become longer-lasting, more frequent, and more intense due to soaring global temperatures. Between 1982 and 2016, the study found a doubling in the number of MHW days, with projections indicating a further increase by a significant factor under various warming scenarios.
- Crucially, the study attributes 87 per cent of MHWs to human-induced warming, emphasizing the direct link between anthropogenic activities and the intensification of marine heatwaves. This intensification is exacerbated by the oceans' role in absorbing approximately 90 per cent of the additional heat generated by greenhouse gas emissions since the Industrial Revolution.
- As a result, global mean sea surface temperatures have risen by nearly 0.9 degrees Celsius since 1850, with a notable increase of around 0.6 degrees Celsius over the last four decades alone.
- With global air temperatures on the rise, ocean temperatures are also increasing, leading to the escalation of MHWs. Compounding this issue, the onset of El Nino conditions, characterized by abnormal warming of surface waters in the equatorial Pacific Ocean, is further exacerbating heat extremes.
- Scientists warn that El Nino events are likely to intensify extreme heat events and could potentially break temperature records in various regions worldwide.
- The unprecedented impact of concurrent phenomena such as soaring global air and ocean temperatures, increased MHWs, and record-low Antarctic sea ice levels. The uncertainties regarding the future consequences of these trends, emphasise the urgent need for proactive measures to mitigate the escalating risks posed by climate change on marine ecosystems and human societies.
5. The Way Forward
Marine heatwaves are a serious threat to both marine ecosystems and human societies. Understanding the causes and consequences of MHWs is crucial for taking proactive measures to address climate change and protect our oceans and ourselves.
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For Prelims: Marine Heatwaves, Coral Reefs, El Nino, Climate Change,
For Mains:
1. Explain the relationship between global warming and the increasing frequency and intensity of Marine heat waves (MHWs). Assess the potential socio-economic and ecological repercussions of this phenomenon in the Arctic region. (250 words)
2. Discuss the ethical implications of human activities contributing to Marine heat waves (MHWs) and the disproportionate impact they have on vulnerable coastal communities. (250 words)
3. Imagine you are heading a national task force responsible for developing a comprehensive strategy to address Marine heat waves (MHWs). Outline your key priorities and action plan, taking into account scientific evidence, public participation, and sustainable solutions. (250 words)
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Previous Year Questions
1. Consider the following statements: (UPSC 2022)
1. High clouds primarily reflect solar radiation and cool the surface of the Earth.
2. Low clouds have a high absorption of infrared radiation emanating from the Earth's surface and thus cause a warming effect.
Which of the statements given above is/are correct?
A. 1 only B. 2 only C. Both 1 and 2 D. Neither 1 nor 2
2. What are the possible limitations of India in mitigating global warming at present and in the immediate future? (UPSC 2010)
1. Appropriate alternate technologies are not sufficiently available.
2. India cannot invest huge funds in research and development.
3. Many developed countries have already set up their polluting industries in India.
Which of the statements given above is/are correct?
A. 1 and 2 only B. 2 only C. 1 and 3 only D. 1, 2 and 3
Answers: 1-D, 2-A
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Source: The Indian Express
