WARMING OF INDIAN OCEAN

According to the Indian Institute of Tropical Meteorology (IITM), between 1950-2020, the Indian Ocean had become warmer by 1.2°C and climate models expect it to heat up a further 1.7°C–3.8°C from 2020–2100.

Key Highlights:

• Projected Increase in Frequency:

• Marine heatwaves, currently averaging 20 days per year, are forecasted to surge dramatically, potentially escalating tenfold to 220–250 days annually.
• The tropical Indian Ocean, in particular, faces the ominous prospect of transitioning into a near-permanent state of heatwave conditions, posing grave consequences for marine ecosystems and biodiversity.

• Ecological Impact:

• The intensification of marine heatwaves precipitates widespread habitat degradation, characterized by phenomena such as coral bleaching, seagrass loss, and the deterioration of kelp forests.
• These ecological disruptions reverberate throughout the marine food web, exerting detrimental effects on fisheries and jeopardizing the livelihoods of coastal communities reliant on marine resources.

• Escalating Heat Content:

• The heat content of the Indian Ocean, measured from the surface to a depth of 2,000 meters, is currently escalating at an alarming rate of 4.5 zetta-joules per decade.
• Projections suggest a staggering acceleration to 16–22 zetta-joules per decade in the future, underscoring the magnitude of anthropogenic-driven ocean warming and its implications for climate dynamics.

• Thermal Expansion and Sea-Level Rise:

• Rising ocean temperatures engender thermal expansion, causing seawater volume to swell—a phenomenon known as thermal expansion.
• This process accounts for over half of the observed sealevel rise in the Indian Ocean, surpassing the contributions from glacial and sea-ice melting.
• Consequently, coastal regions face heightened vulnerability to inundation and erosion, exacerbating risks associated with sea-level rise.

 • Shifts in Dipole Events:

• Climate models project notable alterations in the frequency and intensity of dipole events—an atmospheric phenomenon characterized by temperature differentials between the western and eastern Indian Ocean.
• While extreme dipole events are anticipated to surge by 66%, moderate events are projected to decline by 52% by the century's end, accentuating the variability and unpredictability of regional climate patterns.

Definition and Measurement:

• A marine heatwave denotes a prolonged period of anomalously high ocean temperatures, delineated by its duration and intensity.
• Scientists typically gauge ocean temperature using sea surface temperature (SST), with deviations from the average SST termed as temperature anomalies. w The threshold for defining a marine heatwave varies globally, but as a general guideline, an SST anomaly of 1 degree Celsius (approximately 2 degrees Fahrenheit) may signify a marine heatwave, while anomalies of 2-3 degrees Celsius (or about 4-6 degrees Fahrenheit) are indicative of more extreme heatwave events.

• Scope and Duration:

• Marine heatwaves can occur year-round and span expansive distances across the Ocean, ranging from 500 to 2000 kilometers (or 300 to 600 miles).
• These warm periods, characterized by elevated SSTs, exert far-reaching impacts on marine ecosystems, biodiversity, and climate dynamics.

• Environmental Implications:

• The proliferation of marine heatwaves poses significant ecological and environmental challenges, precipitating widespread coral bleaching, marine species displacement, and alterations in oceanic circulation patterns.
• Moreover, marine heatwaves can exacerbate the frequency and intensity of extreme weather events, such as hurricanes and typhoons, further destabilizing coastal ecosystems and communities

Impacts of Ocean Warming on Climate and Ecosystems:

• Monsoon Season Vulnerability:

• Ocean warming poses significant implications for the southwest monsoon season, which supplies approximately 70% of India's annual rainfall.
• Elevated sea surface temperatures can disrupt atmospheric circulation patterns, potentially altering precipitation patterns and intensifying the variability of monsoon rainfall.

• Heightened Risk of Extreme Weather Events:

• The escalation of ocean temperatures may exacerbate the frequency and intensity of extreme weather phenomena, including tropical cyclones and floods.
• Rising sea levels, stemming from thermal expansion, further compound the risks associated with coastal inundation and erosion, amplifying vulnerabilities for coastal communities and infrastructure.

• Impact on Indian Ocean Dipole (IOD):

• Ocean warming is anticipated to influence the behavior of the Indian Ocean Dipole (IOD), a climate phenomenon characterized by temperature differentials across the Indian Ocean.
• Changes in IOD phases can exert pronounced effects on regional climate patterns, influencing monsoon rainfall dynamics across India and South Asia.

Ocean Acidification:

• The projected decrease in ocean pH levels, from approximately 8.1 to 7.7 by the century's end, underscores the phenomenon of ocean acidification.
• This shift in acidity levels can have detrimental consequences for marine ecosystems, as many marine organisms exhibit sensitivity to changes in ocean acidity.
• Disruptions in pH balance may disrupt marine food webs, coral reef health, and biodiversity, jeopardizing the resilience of coastal ecosystems. Addressing the Challenges of Marine Heatwaves: Strategies for Mitigation:

 • Mitigating Ocean Warming:

To mitigate the impacts of Marine Heatwaves (MHWs), concerted efforts are required to slow down ocean warming.

• Governments must prioritize the implementation of measures aimed at reducing fossil fuel-based emissions, in alignment with the objectives outlined in the Paris Agreement.
• Additionally, investment in nature-based solutions, guided by the IUCN Global Standard for Nature-based Solutions, can bolster ecosystem resilience and mitigate the impacts of MHWs.

• Enhancing Research and Monitoring:

• Building research capacity is essential for monitoring MHWs, understanding their impacts, and predicting future heatwave events.
• Research initiatives should strive to establish a temperature baseline considering species' thermal limits, and integrate physical and biological data to enhance predictive capabilities and identify vulnerable biodiversity.
• Establishing global networks, such as the Marine Heatwave International Group, facilitates collaboration and enables the implementation of comprehensive research programs.

• Multi-Stakeholder Engagement:

• Effective responses to MHWs necessitate the collective action of diverse stakeholders, including policymakers, researchers, the private sector (e.g., fisheries, aquaculture, ecotourism), conservationists, and civil society.
• Local management agencies play a crucial role in raising awareness among stakeholders and implementing forecast systems to facilitate a coordinated response to MHW events.

 • Building Regional Ocean Resilience:

• National and sub-national governments are urged to design and implement measures aimed at protecting communities and enhancing regional ocean resilience.
• Initiatives may include the establishment and conservation of marine protected areas to serve as sanctuaries for vulnerable species, as well as the implementation of catch management regulations to mitigate economic losses associated with MHWs.