An Overview

• The US Scientists have simulated the climate change events that led to the Permian extinction, which wiped out most of the life under the oceans some 250 million years ago.
• The Permian era (298.9 million to 252.2 million years ago) was a time before the dinosaurs ruled the planet. The oceans were 10 degree C warmer than they are now, and oxygen levels were 80% lower.
• During the period, land masses collided to form the arid supercontinent Pangaea. The massive Panthalassic Ocean, which covered much of the Earth, was home to many sponge and coral species, ammonites (tiny shelled organisms), brachiopods (invertebrate animals closely related to starfish), and fusulinid foraminifera (single celled organisms closely associated with modern amoebas). Reptiles began to flourish. Sharks and bony fish thrived.
• Towards the end of the era, a series of volcanic eruptions in the present-day central Siberia region injected massive amounts of greenhouse gases (GHGs) into the atmosphere.
• The uncontrolled GHG emissions triggered climatic changes due to which Roughly 96% of marine species and 70% of land species went extinct. Thus, scientists refer to

this period as the “Great Dying”.

Oceans: A Crucial Asset for Sustainable Future

• Oceans are the planet’s largest ecosystem, accounting for 95% of all space available for life and hosting 90% of the planet’s total species.
• Mountain ranges, hydrothermal vents that resemble terrestrial hot springs, and volcanoes rise from the seafloor. The landscape is dotted with trenches, which go as deep as 11,000 metres (m) and the oceans are home to organisms of all sizes and shapes: from microorganisms to the blue whale.
• The average depth of the oceans is 3,700 m, and 80% of the areas have not been explored at all to study the impact of Climate change.
• The oceans modulate the global climate and control the planetary temperature, and thus the weather events like rain, storms, cyclones, floods and droughts.
• Human lives are intimately tied to the oceans. About 50-80% of the oxygen produced on Earth can be traced back to the sea.
• According to UN data, these saltwater bodies support the livelihoods of 3 billion people.
• The Ocean currents —the continuous movement of water act as conveyor belts, as they transport warm water from the equators to the pole and cooler waters from the poles to the equators. Upwelling currents allow the vertical movement of water, pushing cold, nutrient-rich water from the ocean depths to the surface, which is critical for fisheries.
• The most important role the oceans play is that of a carbon sink as four-fifths of the global carbon cycle is circulated through them. According to the 5th Assessment Report published by the UN Intergovernmental Panel on Climate Change (ipcc) in 2014, the oceans have absorbed more than 90% of the global warming created by humans since the 1970s.
• Thus, without the oceans, the global average temperatures would have jumped by almost 56oC.

Impacts of Climate Change on Oceans

1. a) In Hot Water

• The oceans must have a carrying capacity to keep on doing the job as a carbon and heat sink but over the years, they have been heating up.
• The global sea surface temperature (sst) is roughly 1oC higher than 140 years ago. Changes in ocean temperatures and currents will lead to alterations in climate patterns around the world.
• Ocean heat content has impacted all the six major oceans since 1998. But the most significant warming has been in the southern oceans.
• The analysis shows that human-induced climate change and natural variability were causing heat content to accumulate in the Southern Ocean and the heat could shift to the northern hemisphere in the next decade.
• High ocean temperatures are changing ocean currents, too. They seem to have picked up the pace by 15% per decade from 1990 to 2013. The impacts are more pronounced in the tropical oceans due to surface winds that have intensified since the 1900s.
• The Indian Ocean, in particular, has emerged as the biggest victim of climate change. Sea surface temperatures of the Indian Ocean have risen by an average of 1°C from 1951 to 2015, compared to the global average of about 0.7°C.
• The pattern emerging from the Arabian Sea, the northern part of the Indian Ocean, is

particularly concerning. It used to be cooler than 28°C, but during the last few decades it has warmed up rapidly, with temperature trends crossing 1.2-1.4°C in parts of Arabian Sea since the 1950s and as a result has started to favor cyclones. Between 2001 and 2019, the Arabian Sea recorded a 52% increase in cyclones. Very severe cyclones have increased by 150%.

1. b) Emergence of frequent Marine Heatwaves

• Scientists have noted another new challenge called marine heatwaves, a term coined as recently as 2011. 

• Marine heatwaves are classified as a hazard or natural calamity and these events often accompany El Niño events in the Pacific Ocean.

• This happens when SST exceeds 90% for five days in a row, from the previous SST observations recorded at the same time in the last 30 years. Factors such as increased warming and weak winds contribute to its formation.

• In 2020, some scientists studied the impact of marine heatwaves on the Indian Ocean basin and found SST in the Bay of Bengal (northeastern part of the Indian Ocean) hovered 33-34oC which is the highest ever recorded in open seas across the globe since we started recording temperatures.
• As per NOAA, the western part of the Indian Ocean and the Bay of Bengal were the
• most hit. Eg: The west Indian Ocean recorded over 66 events of heatwaves and north of Bay of Bengal saw 94 events. The duration and frequency of heatwaves increased by 20 days and 1.5-2 events per decade between 1982 and 2019.
• Scientists suspect that Marine heatwaves could be fuelling cyclones as the 2020 Amphan super cyclone took less than 36 hours to go from Category 1 (cyclonic storm) to Category 5 (super cyclone).

1. c) Melting Arctic

• According to the National Snow and Ice Data Center, High Sea surface temperatures are accelerating the melting of the white Arctic region. The extent of the Arctic Sea ice cover for May 2022 was 12.88 million sq km which was 410,000 sq km below the 1981-2010 average.
• In the South Pole, Antarctica does not seem as impacted. Still, the sea ice cover reached a record low in February 2022 and lost an ice shelf with a surface area of 1,100 sq km, roughly the size of Rome.
• The global mean sea level increased by an average of 4.5 millimetres (mm) per year between 2013 and 2021. This was two times higher than the 1993 and 2002 rates.
• The IPCC estimates that the global sea level could rise by 0.6 to 1.1 m by 2100 and 5 m by 2300 under the high emissions scenario.

1. d) The Churning effect

• Scientists observed that if emissions continue to climb and temperatures reach around 4.9°C by the end of this century, close to 40% of marine genera could perish by 2300 and 8% by 2100.
• The global average temperature in the current Anthropocene era is already up by 1.1°C since pre-industrial times. If the world continues on its current path of high ghg emissions, it is expected to rise by 5oC by 2100.
• The ideal oxygen levels in the oceans should lie between 7 and 8 milligrams per litre (mg/l). Regions with oxygen concentrations below 2 mg/l are hypoxic or low oxygen zones and those with less than 0.2 mg/l of oxygen are called anoxic.
• Warming oceans impair water movement, which leads to poor exchange of oxygen between the surface waters and deeper waters which results in oxygen minimum zones and dead zones in the ocean.
• Globally, about 1.15 million sq km of the seafloor is exposed to oxygen concentrations of less than 0.7 mg/l. Eg: The Arabian Sea is the poster child of oxygen minimum zones. It covers 20% of the area, going as deep as 800 m.
• According to IUCN, Ocean oxygen levels are expected to drop by an average 3-4% by 2100 overall due to climate change and increased nutrient discharges.
• The impacts include decreased biodiversity, shifts in species distributions, displacement or reduction in fishery resources and expanding algal blooms driven by the overgrowth of microscopic algae or algae-like bacteria.
• While losing oxygen, the oceans are also turning acidic as they soak up more carbon dioxide (CO2) leading to “Ocean Acidification”.
• As per IPCC report, the open ocean surface pH is now the lowest it has been for at least 26,000 years.
• Species are already traveling poleward at a rate of 59 km per decade on average, as stated by IPCC’s “Climate Change 2022: Impacts, Adaptation and Vulnerability”. Eg: North Atlantic right whale.
• Hence, Climate change is choking the oceans and its inhabitants.

Mining Trouble

• The underwater world without the energy of the sun and oxygen is unique and beyond human imagination. Unfortunately, even before completely discovering and

understanding it, there is a mad rush to exploit the vast resources through deep-sea

Mining.

• Deep-sea mining involves extracting massive polymetallic sulphide ore from hydrothermal vents, ferromanganese crusts from seamounts and polymetallic manganese ore from the sea floor.

• These ores are rich in cobalt, manganese, zinc, and other rare metals needed to build batteries for electric vehicles and renewable energy, smartphones and laptops.

• As of May 2022, the International Seabed Authority (ISA), an intergovernmental body tasked with managing deep-sea mining activities, has allocated 31 contracts to explore deep-sea mineral deposits.
• According to IUCN, more than 1.5 million sq km of International seabed, roughly the size of Mongolia, has been set aside for mineral exploration.
• India formally joined the race on June 16, 2022, when the country approved the “Deep Ocean Mission” to explore the deep ocean for resources and develop deep-sea technologies for sustainable use of ocean resources.
• India plans to create an integrated mining system to extract polymetallic nodules from 6,000 m depth in the central Indian Ocean and the exploration studies of minerals will pave the way for commercial exploitation in the near future.
• Mining has the potential to disturb the fine ecological balance underwater. If the seabed is soft, it will generate a lot of clay into the system, and it will affect the biota, including microorganisms.
• A single polymetallic-nodule mining operation, the most promising technologies for seabed mining, could release 50,000 cubic metres of sediment, broken mineral fines, and seawater per day.
• A hydrothermal vent operation could discharge 22,000 to 38,000 cubic metres of sediment per day. These discharges could circulate in the ocean continuously for up to 30 years.
• Experts from multiple institutions emphatically say that the world should steer away from deep-sea mining till such time as it knows if and how well deep ocean species can adapt to the changes.

Crumbling Ocean Diversity

• Based on depth, the oceans are divided into zones, or for practical purposes, ecological zones.

1. i) Photic Zone: The upper portion (0 to 200 m) is called the photic. Sunlight reaches this zone, allowing photosynthesis to occur. Phytoplanktons like marine microalgae that produce 50% of the world’s oxygen live here.
2. ii) Twilight Zone: Beneath the photic zone is the deep sea extending from 200 m to 1000 m. At this depth, only a small amount of light trickles down. One study estimated that up to about 90% of the world’s total fish density appears here.

• iii) Aphotic Zone: Below 1,000 m is the aphotic zone. The aphotic zone can be broken down into the bathypelagic zone or midnight zone (between 1,000 and 4,000 m), the abyss pelagic or the abyss (between 4,000 and 6,000 m) and the hadopelagic zone or hadal zone is 6,000 m and deeper. This is a dark world inhabited by giant squids, anglerfish and Goblin Shark etc.
• Currently, climate velocity is twice as fast at the surface because of greater surface warming. This implies that deep-sea species are less likely to be at risk from climate change than those at the surface.
• Scientists observed that by 2100, climate velocities in the twilight zone will be 11 times faster than the present rate.
• The warming oceans have also altered the human food plate over the years which suggest that crumbling ocean diversity is a cause of concern and alarming.

Conclusion

• We have already largely transformed the oceans and so climate change needs to be embedded with ocean considerations to address various concerns in terms of conservation and sustainable resource management in the ocean.
• An international treaty to protect the oceans from the impacts of climate change should be negotiated at the earliest else continuous warming will only take the world closer to a situation similar to the Permian extinction.