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Down To Earth Magazine July 2022, PART 1: ”Climate Change Impact On Oceans” | Important Terms

Down To Earth Magazine is a fortnightly magazine focusing on politics of environment and development, published in New Delhi, India.

UPSC Previous years’ questions on Development, Environment, Health and Disaster Management give us a clear idea about the increased importance of Down To Earth Magazine.

Down To Earth Magazine is one of the most important and indispensable source for UPSC Civil Services Exam Preparation. Keeping this in mind, here, we come with ”Gist Of Down To Earth Magazine” which covers important environmental current affairs articles in smooth pointed form, keeping in mind the demand of UPSC aspirants.


Climate Change Impact On Oceans: Introduction


  • Ocean Warming Continues through 2021 despite La Niña Conditions.
  • In the past three decades, the top 2,000 metres of the oceans have warmed up due to global warming.
  • A record 235 zettajoules heat was absorbed by the upper 2,000 metres of the ocean in 2021.
  • 90% of the excess heat generated by greenhouse gases is absorbed by the 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.
  • Changes in sea surface temperature can alter marine ecosystems in several ways. For example, variations in ocean temperature can affect what species of plants, animals, and microbes are present in a location, alter migration and breeding patterns, threaten sensitive ocean life such as corals, and change the frequency and intensity of harmful algal blooms such as “red tide.


Marine heatwaves


  • A term coined as recently as 2011. This happens when SST exceeds 90 per cent for five days in a row, from the previous SST observations recorded at the same time in the last 30 years.
  • The world has taken notice of its impacts on biodiversity, and the ripple effects on the economy.
  • Marine heatwaves are classified as a hazard or natural calamity and these events often accompany El Niño events in the Pacific Ocean.
  • Factors such as increased warming and weak winds contribute to its formation.
  • Scientists have found that the western part of the Indian Ocean and the Bay of Bengal were the most hit.


Melting Of the Arctic Region


  • High SSTs 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. This was 410,000 sq km below the 1981-2010 average, according to the National Snow and Ice Data Center, the US agency for polar and cryospheric research.
  • In the South Pole, Antarctica does not seem as impacted. Still, the sea ice cover reached a record low in February 2022. The sea ice cover was 1.92 million sq km, which is 190,000 sq km below the previously held record on March 3, 2017.


A rise in Global Mean Sea Level


  • 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.


Oxygen Minimum Zones and Dead Zones in the Ocean


  • 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.
  • 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.
  • Globally, about 1.15 million sq km of the seafloor is exposed to oxygen concentrations of less than 0.7 mg/l. There’s evidence that the oxygen minimum zones are getting bigger globally due to global warming.
  • The Arabian Sea is the poster child of oxygen minimum zones. It covers 20 per cent of the area, going as deep as 800 m.


Ocean Acidification


  • While losing oxygen, the oceans are also turning acidic as they soak up more carbon dioxide (CO2).
  • The term “ocean acidification” was first coined in 2003 after researchers suspected that acidic waters could take a toll on coral reefs and other organisms whose skeletons or shells are made of calcium carbonate.
  • Acidification corrodes calcium.
  • When CO2 is absorbed by seawater, a series of chemical reactions occur, eventually releasing hydrogen ions into the water.
  • Before the preindustrial era, the ocean pH was 8.2. It is now 8.1. The pH scale is logarithmic, and a 0.1-unit reduction corresponds to a 30 per cent increase in acidity.
  • If we continue on our current trajectory, the pH could further drop to around 7.8, suggest estimates. The open ocean surface pH is now the lowest it has been for at least 26,000 years, according to IPCC.


Impact Of Climate Change on the Indian Ocean


  • The Indian Ocean, in particular, has emerged as the biggest victim of climate change.
  • SST of the Indian Ocean has risen by an average of 1°C from 1951 to 2015, compared to the global average of about 0.7°C.
  • Its average SST has touched 28.08°C, according to a 2014 study published in the Journal of Climate.
  • But the warming is not the same everywhere. From 1901 to 2012, the western Indian Ocean warmed up by 1.28°C against an increase of 0.78°C recorded in other parts of the Indian Ocean.
  • 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 the Arabian Sea since the 1950s. Now its temperatures are often above 28°C, and it has started to favour cyclones.
  • Between 2001 and 2019, the Arabian Sea recorded a 52 per cent increase in cyclones. Very severe cyclones have increased by 150 per cent.


Climate Change Impact On Oceans: Conclusion


The 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 5o C by 2100.

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