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Introduction

In recent decades, the tropical Indian Ocean has experienced a rapid and concerning increase in ocean warming. The rise in Sea Surface Temperature (SST) has been measured at approximately 1oC between 1951 and 2015, with a rate of 0.15°C/decade. Shedding light on this issue, a recent study conducted by the Indian Institute of Tropical Meteorology (IITM), an autonomous institute under the Ministry of Earth Sciences, has focused on marine heat waves. The study reveals that the western Indian Ocean witnessed a significant surge with 66 Marine Heat Wave events, while the Bay of Bengal experienced 94 events during the period of 1982-2018. This represents a four-fold increase in marine heat waves in the western Indian Ocean and a two-to-three fold increase in the North Bay of Bengal. Notably, the year 2021 witnessed six marine heat waves in the western Indian Ocean over 52 days, along with four marine heat waves in the North Bay of Bengal over 32 days. Although these heat waves did not break previous records, they were still well above normal. This article aims to delve into the consequences of ocean warming and explore the urgent need for mitigation and adaptation measures.

Ocean Warming: A Cause for Concern

Oceans play a pivotal role in Earth's climate system, absorbing the majority of solar radiation. However, the consequences of global warming have impacted our oceans significantly. Rising ocean temperatures pose various problems with far-reaching ramifications:

• Rising Sea Levels: As water heats up, it expands and occupies more space. Consequently, warming oceans contribute to a rise in sea levels. Scientists predict that this effect alone could lead to a 30cm (12 inches) increase in sea levels by the end of this century. Many large cities worldwide, constructed on reclaimed land, sit within this critical margin. For instance, cities like Mumbai and Sydney are vulnerable to the threats posed by rising sea levels. Moreover, melting polar ice sheets, accelerated by warming oceans, further exacerbate the rise in sea levels. The combination of melting ice and expanding water could result in a meter rise in sea levels by 2100, potentially displacing hundreds of millions of people and creating climate refugees.
• Extreme Weather Amplification: Warmer oceans intensify and prolong tropical storms, making cyclones more destructive due to unusually warm ocean temperatures. Coastal regions already grappling with rising seas will face heightened flooding and increased vulnerability. Additionally, warming temperatures lead to changing rainfall patterns, redistributing water vapor in the atmosphere. Some areas will experience more rainfall, while others become drier, disrupting ecosystems and amplifying the risks associated with extreme weather events.
• Threat to Ocean Life: Ocean warming's impact on marine life is profound, with various threats emerging:
  • De-oxygenation: Thermal expansion resulting from warming oceans depletes oxygen levels. Regions such as Japan, Taiwan, and the Baltic Sea have witnessed significant fish die-offs due to oxygen depletion.
  • Coral Bleaching: Coral reefs, highly sensitive to warmer seas, face significant dangers. The Great Barrier Reef alone experienced the death of half its corals between 2016 and 2017 due to ocean heat waves. The impact extends globally, affecting nearly three-quarters of the world's coral reefs. As oceans continue to warm, coral die-offs are expected to become increasingly frequent.
  • Disrupted Ecosystems: Increased flooding caused by ocean warming washes excessive nutrients into the sea, leading to plankton blooms. This, in turn, starves certain areas of oxygen, making it difficult for fish to survive. Such disruptions jeopardize marine ecosystems and threaten the balance of oceanic life.
• Food Security Concerns: Warmer oceans force fish species to migrate to cooler areas, potentially resulting in food shortages in regions where waters are becoming too warm to support fish populations. According to the Food and Agriculture Organization of the United Nations, marine and freshwater capture fisheries, along with aquaculture, provide approximately 15% of animal protein to 4.3 billion people. Tropical regions face severe food security risks due to ocean warming's impact on fisheries.
• Melting Sea Ice: Warming oceans contribute to the accelerated melting of sea ice. While melting sea ice doesn't directly affect sea levels since it already floats on the ocean's surface, its disappearance diminishes the planet's ability to reflect solar heat back into space. Consequently, the overall warming of the planet is amplified. This poses significant challenges for Arctic communities, such as the Inuit in Canada, whose cultural practices depend on sea ice for sustenance and survival.
• Emerging Threats: Ocean warming also triggers secondary threats that affect both the environment and human health:
  • Disease Prevalence: Increasing ocean temperatures can facilitate the prevalence of diseases and mutations, potentially leading to the emergence of more superbugs.

Way Forward: Combating Ocean Warming

Given the severity and breadth of the consequences arising from ocean warming, urgent action is imperative. Here are some key steps that must be taken:

• Limiting Greenhouse Gas Emissions: Immediate efforts are required to achieve the mitigation targets set by the Paris Agreement. The global average temperature increase must be held well below 2°C above pre-industrial levels to mitigate the impact of ocean warming.
• Protecting Marine and Coastal Ecosystems: Implementing well-managed protected areas is crucial to conserve and protect ecologically significant marine habitats. Regulation of human activities within these habitats and preventing environmental degradation is vital.
• Restoring Marine and Coastal Ecosystems: Efforts should focus on restoring damaged ecosystems. Measures can include constructing artificial structures like rock pools to provide surrogate habitats for organisms or implementing assisted breeding techniques to enhance species' resilience to warmer temperatures.
• Enhancing Human Adaptation: Governments must introduce policies to ensure sustainable limits in fisheries production. This can be achieved through measures such as setting precautionary catch limits and eliminating subsidies that contribute to overfishing. Additionally, the establishment of coastal setback zones, restricting certain types of development along shorelines, can mitigate damage caused by coastal flooding and erosion. Investing in new monitoring tools for forecasting and controlling marine disease outbreaks is also crucial.
• Strengthening Scientific Research: Increased investment in scientific research is necessary to effectively measure and monitor ocean warming and its impacts. Precise data on the scale, nature, and consequences of ocean warming will facilitate the design and implementation of appropriate mitigation and adaptation strategies.

Conclusion

The health of our oceans, encompassing their temperature, chemistry, currents, and diverse life forms, is fundamental to sustaining life on Earth. Over three billion people rely on marine and coastal biodiversity for their livelihoods. Consequently, ocean health should be viewed as a global issue, demanding concerted efforts from all nations. The Sustainable Development Goal 14, which aims to conserve and sustainably use oceans, seas, and marine resources, serves as a guiding principle in addressing this urgent matter. By embracing mitigation and adaptation measures, we can fortify our resilience against the devastating consequences of ocean warming and ensure a sustainable future for our planet.