Climate Change and Oceans
- March 20, 2023
- Posted by: OptimizeIAS Team
- Category: DPN Topics
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Climate Change and Oceans
Subject : Environment
Section: Climate change
Impact of Climate Change on Oceans:
Sea Surface Temperature (SST)
- Sea surface temperature the temperature of the water at the ocean surface is an important physical attribute of the world’s oceans.
- The surface temperature of the world’s oceans varies mainly with latitude, with the warmest waters generally near the equator and the coldest waters in the Arctic and Antarctic regions.
- As the oceans absorb more heat, sea surface temperature increases, and the ocean circulation patterns that transport warm and cold water around the globe change.
Melting Of the Polar Region
- Wintertime Arctic sea ice continues to dip to new lows as the oceans warm.
- Meanwhile, Antarctica is shrinking underwater, as submerged ice is rapidly melting, according to recent studies.
- The effects of this warming on iconic species such as polar bears are well-documented. Under the surface, though, the problem is no less urgent.
- Dwindling sea ice results in the loss of vital habitat for seals, walruses, penguins, whales and other megafauna.
- Sea ice is a critical habitat for Antarctic krill, the food source for many seabirds and mammals in the Southern Ocean. As sea ice has receded in recent years, Antarctic krill populations have dropped, resulting in declines in the species that depend on the krill.
Rise in sea level
- When land-based polar ice melts, it finds its way to the sea. But when water warms, it expands to take up more space a major yet unheralded cause of sea-level rise.
- With sea-level rise accelerating at a rate of about one-eighth of an inch per year, the effects on humanity are plain:
- Higher ocean temperatures are melting polar ice and glaciers from the Greenland and Antarctic sheets at a rapid rate, resulting in an unprecedented rise of sea levels that has the potential to displace more than 680 million people living across low-lying coastal communities, according to a 2019 UN report.
- Recent research revealed that several major coastal cities could be almost entirely underwater due to sea level rise by the middle of the century, including Ho Chi Minh City, Vietnam; Shanghai, China; and Mumbai, India.
Marine heatwaves
- Marine heatwaves have doubled in frequency, and have become longer-lasting, more intense and extensive. The IPCC says that human influence has been the main driver of the ocean heat increase observed since the 1970s.
- The majority of heatwaves took place between 2006 and 2015, causing widespread coral bleaching and reef degradation. In 2021, nearly 60 percent of the world’s ocean surface experienced at least one spell of marine heatwaves.
Warming oceans alter currents
- Climate change affects ocean temperatures as well as wind patterns taken together, these can alter oceanic currents.
- The impacts of changes in ocean currents on humanity could be severe, as currents play a major role in maintaining Earth’s climate. For example, Europe’s relatively mild climate is maintained in part by the large Atlantic current called the Gulf Stream, which is experiencing an “unprecedented slowdown.” Changing these currents will have major implications worldwide for the climate, including changes in rainfall, with more rain in some areas and much less in others and fluctuating air temperatures.
Ocean Acidification
- Burning of fossil fuels that increases greenhouse gas levels in the atmosphere, is also altering the chemical composition of seawater by making it more acidic. The ocean absorbs 30 percent of the carbon dioxide in the atmosphere and when that carbon dissolves into the water, it forms carbonic acid.
- Acidification can dissolve the calcium carbonate shells of marine species such as corals, scallops, lobsters and crabs, and some microscopic plankton that are a foundation of the food web throughout the ocean. These shell-forming organisms provide critical habitats and food sources for other marine life. Increased acidification can also limit the ability of certain fish to detect predators, disrupting the entire marine food chain.
Dead Zones
- Warming oceans impair water movement, which leads to poor exchange of oxygen between the surface waters and deeper waters. This results in oxygen minimum zones and dead zones in the ocean.
- The ideal oxygen levels in the oceans should lie between 7 and 8 milligrams per litre (mg/l). Marine organisms start to leave their homes when the levels drop to 4 mg/l
Loss of marine biodiversity
- Rising temperatures increase the risk of irreversible loss of marine and coastal ecosystems. Today, widespread changes have been observed, including damage to coral reefs and mangroves that support ocean life, and migration of species to higher latitudes and altitudes where the water could be cooler.
- Latest estimates from the UN Educational, Scientific and Cultural Organization warn that more than half of the world’s marine species may stand on the brink of extinction by 2100.
- At 1.1°C increase in temperature today, an estimated 60 percent of the world’s marine ecosystems have already been degraded or are being used unsustainably. A warming of 1.5°C threatens to destroy 70 to 90 percent of coral reefs, and a 2°C increase means a nearly 100 percent loss – a point of no return.
Role of Oceans in reducing Climate Change:
- Oceans are the largest heat sink on the planet: The ocean generates 50 percent of the oxygen we need, absorbs 25 percent of all carbon dioxide emissions and captures 90 percent of the excess heat generated by these emissions. It is not just ‘the lungs of the planet’ but also it is largest ‘carbon sink’ – a vital buffer against the impacts of climate change. The ocean is central to reducing global greenhouse gas emissions and stabilizing the Earth’s climate.
- Mitigating role of Marine Ecosystems:
- Ocean habitats such as seagrasses and mangroves, along with their associated food webs, can sequester carbon dioxide from the atmosphere at rates up to four times higher than terrestrial forests Their ability to capture and store carbon make mangroves highly valuable in the fight against climate change.
- Mangroves also support healthy fisheries, improve water quality, and provide coastal protection against floods and storms.
- Coral reefs are among the most ecologically and economically valuable ecosystems on our planet. Covering less than 0.1 percent of the world’s ocean, they support over 25 percent of marine biodiversity and serve up to a billion people with coastal protection, fisheries, sources of medicine, recreational benefits, and tourism revenues.
- Marine protected areas – areas of the ocean set aside for long-term conservation aims – offer one of the best options to maintain the ocean’s health. Today marine protected areas cover 6.35 percent of the ocean – almost ten times as much as in 2000.
- Oceans are incredible source of renewable energy
- Off-shore wind power is generated by the airflow through wind turbines that mechanically turn electric generators.
- Wind power could cover more than one third of global power needs, becoming the world’s foremost energy source
- Ocean energy systems use the kinetic and thermal energy of seawater – waves or currents for instance – to produce electricity or hea
- These energy sources don’t emit carbon dioxide or other greenhouse gases that contribute to global warming.
- The prospects of green shipping
- Approximately 80 percent of world trade is transported by maritime shipping – which accounts for nearly 3 percent of global greenhouse gas emissions. Reducing the CO2 emissions of ships to zero by 2050 is crucial in the fight against climate change. This means moving away from traditional fossil fuels to new zero-emission energy sources, such as hydrogen, ammonia, methanol, or wind.
- Green shipping corridors – maritime routes between two ports that support zero-emissions technologies for ships – are one way to accelerate the decarbonization of the shipping sector.