The United Nations declared 2021-2030 as the UN Decade of Ocean Science for Sustainable Development. The global ocean system covers 71 per cent of the planet. Yet, it is the most unexplored and least understood component of our planet and the climate system. Ocean exploration has a long history going as far back as 5000 BC when coastal communities turned to the waters for food and later to ocean exploration around 600 BC to the colonial exploration in the 14th and 15th centuries which has continued since the 19th century in the form of scientific exploration. Regardless of this long history of exploration, as of June 2024, only about 26 per cent of the seafloor has been mapped. The impact of the ocean on climate and civilization is still an ongoing topic of research, as we understand only five per cent of this vast frontier. Recently, there has been a push towards deep sea exploration and mining to explore the deeper chasms of the oceans. India announced its idea of the Deep Ocean Mission in 2023 aimed at harnessing the resources of the deep ocean with the country’s economic zones.

How much do we know about the oceans?

What we do know with certainty about the ocean is its importance as a source of food, navigational routes and its importance in maintaining a habitable planet. For example, the existence of the Gulf Stream is crucial for maintaining survivable temperatures across most of Europe, especially during winter. At the same time, the Antarctic Circumpolar Current (ACC) has been key in keeping the white continent at temperatures as low as -40?C. Additionally, we are just learning of the importance of the global conveyor belt in the recycling of nutrients and other gasses between the surface and abyssal layers of the ocean. It was only in the 1980s that scientists discovered that oceans contribute to about 50 per cent of the oxygen on our planet. The threat of colonization and industrialization has destroyed vast areas of the ocean. Since the Industrial Revolution, humanity has largely focused on treating every part of the planet as a resource for making human life and existence “easier”. The oceans have been treated as an endless source of food and commercial fishing has led to a massive decline in the number of fishes across the global ocean systems.

Ocean pollution: A problem no one talks about

The oceans have been used as a dumping ground for trash, which is seen clearly as the Great Pacific Garbage Patch (there have been garbage patches discovered in the Atlantic Ocean as well), chemical waste, medical waste (used bandages, needles, chemicals, Covid masks etc.) as well as releasing of toxic waste such as the cooling waters from Fukushima nuclear plant. Of this, plastic waste constitutes 80 per cent of the waste dumped in the ocean. The UNESCO Ocean Literacy portal mentions that about eight to 10 million metric tonnes of plastic is dumped in the ocean every year. This plastic gets transported through ocean currents, where ocean turbulence and sunlight break it down into microplastics.

A recent study has reported that the deep sea is a permanent reservoir of plastic. Recent research has also revealed that microplastics have been found in samples of drinking water, soil, air, and snow and the human body (including the fetus and the bloodstream). In this marine environment, plastic and microplastics have wreaked havoc and pose danger to the marine life that calls the ocean, its home. There has been documentation that ghost nets (discarded from commercial fishing) pose a choking hazard to marine life. There have also been records of beached marine mammals dying due to stomach blockages from ingesting plastic. The International Union for Conservation of Nature suggests that 17 per cent of the species affected by marine plastic are on their Red List of Threatened Species. The UNESCO Ocean literacy portal also mentions that 100 per cent of all plastic ever produced still exists on the planet. Another source of threat for marine flora and fauna is oil spills which leach toxins before the surface of the ocean and pose a threat to the marine ecosystem. It was also reported in studies in 2019 that humans ingest plastic regularly.

Ocean and climate change

Another added stress to this fragile ecosystem has been ocean warming. Since the industrial revolution of the 1800’s, human activities have released carbon dioxide into the atmosphere leading to an enhanced greenhouse effect. As of May 2024, the amount of carbon dioxide recorded in the atmosphere at the Mauna Loa Observatory, Hawaii was at 426.90ppm. According to current research, oceans absorb approximately 25 per cent of the carbon dioxide released into the atmosphere and about 90 per cent of heat. This sinking of carbon dioxide into the oceans comes at the cost of ocean acidification. Increased absorption of carbon dioxide has led to vast regions of the ocean turning acidic which has caused bleaching of coral reefs across the world. The efficiency of ocean absorption also depends on ocean temperatures among other factors. Ocean temperatures have been steadily rising in the past decade. This has an impact on multiple levels such as, on the global ocean current system, not to mention it causes heat stress to marine flora and fauna, reducing the efficiency of carbon dioxide absorption.

The rise in temperatures of the ocean surface and subsurface has also resulted in the acceleration of extreme weather events such as an increase in the frequency and intensity of tropical cyclones and marine heatwaves. Tropical cyclones are driven by moist energy from warm oceans, so an increase in ocean temperatures is directly linked to the increased frequency and intensity of tropical cyclones. The latest cyclone, Hurricane Beryl, has intensified into a category 5 storm by undergoing rapid intensification and has formed unusually early in 2024, causing massive devastation as it ravages through the Caribbean region. The last cyclone in the Bay of Bengal was cyclone Remal ravaged parts of West Bengal during elections this year. Marine heat waves occur due to an anomalous increase in ocean temperatures over a long period. They are defined by their duration and intensity. Studies show that marine heatwaves have increased by 50 per cent over the last decade and this has serious implications for the survival of the endangered marine species and the marine food chain. For example, a massive marine heat wave of 2014 in the northeast Pacific resulted in a mass die-off of seabirds and mammals in the region. All these extreme weather patterns along with the rise in sea level pose the risk of coastal erosion, loss of livelihood and an existential threat for islands that are vulnerable to extreme sea level rise. In the context of India, rising sea levels and natural disasters such as tropical cyclones, and other events have made the Indian subcontinent one of the most vulnerable regions on the planet.

Tackling the crisis

Oceans have long been a mysterious frontier on our planet, still largely unexplored and challenging to understand. However, our understanding of the oceans is precarious to begin with and is changing at an unprecedented scale and intensity. Most of the climate mitigation efforts are aimed at providing technological solutions. One such proposed mitigation effort has been ocean carbon capture and removal technology which aims at reducing the impact of excess carbon absorption by the oceans. Sustainable mitigation, conservation policies, and environmental efforts should prioritize the preservation of marine ecosystems and the coastal communities that depend on them for generations. Relying solely on technological advancements overlooks the fundamental issue of unchecked consumption by a few, which lies at the heart of climate disruption.

A massive win for ocean conservation was the historical UN Global Ocean treaty called the High Seas Treaty which took a decade of negotiations and has been signed by 91 countries. Advocacy groups have been working tirelessly to formulate legislation for banning destructive fishing practices and also towards ocean cleanup (such as 4ocean). On individual levels, there need to be concerted efforts such as reducing the usage of single-use plastics and consuming ocean bounties more responsibly. Our planet is called the Pale Blue Dot owing to the presence of oceans, and it requires more focus on conservation efforts to protect all life on this aquaplanet.

(Aditi Deshpande (she/they) is an Assistant Professor at the Department of Atmospheric and Space Sciences in Savitribai Phule Pune University)