Underwater Radionuclide Heatwaves with 3-degree Celsius Radioactivity Decay Dispersed and Spread fastest in North Pacific, and it flowing in Black Stream headed to US Coastal. Future – Everyday Marine Heatwaves is at hand

Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the components of pollution, can be either foreign substances/energies or naturally occurring contaminants.

Although environmental pollution can be caused by natural events, the word pollution generally implies that the contaminants have a human source, such as manufacturing, extractive industries, poor waste management, transportation or agriculture. Pollution is often classed as point source (coming from a highly concentrated specific site, such as a factory, mine, construction site), or nonpoint source pollution (coming from widespread distributed sources, such as microplastics or agricultural runoff).

The United Nations considers pollution to be the "presence of substances and heat in environmental media (air, water, land) whose nature, location, or quantity produces undesirable environmental effects."
 

Radioactive Decay from Radionuclides Emitted Heat Energy

Radioactive contamination is the deposition of, or presence of radioactive substances on surfaces or within solids, liquids, or gases (including the human body), where their presence is unintended or undesirable. The International System of Units (SI) unit of radioactive activity is the becquerel (Bq). One Bq is defined as one transformation (or decay or disintegration) per second.

Such contamination presents a hazard because the radioactive decay of the contaminants produces ionizing radiation (namely alpha, beta, gamma rays and free neutrons). The degree of hazard is determined by the concentration of the contaminants, the energy of the radiation being emitted, the type of radiation, and the proximity of the contamination to organs of the body. It is important to be clear that the contamination gives rise to the radiation hazard, and the terms "radiation" and "contamination" are not interchangeable. The effects of ionizing radiation are often measured in units of gray for mechanical or sievert for damage to tissue.

High levels of contamination may pose major risks to people and the environment. People can be exposed to potentially lethal radiation levels, both externally and internally, from the spread of contamination following an accident (or a deliberate initiation) involving large quantities of radioactive material.

Radionuclides are produced as an unavoidable result of nuclear fission and nuclear explosions. The process of nuclear fission creates a wide range of fission products, most of which are radionuclides. Further radionuclides are created from irradiation of the nuclear fuel (creating a range of actinides) and of the surrounding structures, yielding activation products. This complex mixture of radionuclides with different chemistries and radioactivity makes handling nuclear waste and dealing with nuclear fallout particularly problematic.

A radionuclide is a nuclide that is unstable and known to undergo radioactive decay into a different nuclide, which may be another radionuclide. Radiation emitted by radionuclides is almost always ionizing radiation because it is energetic enough to liberate an electron from another atom. Different isotopes emit different types and levels of radiation, which last for different periods of time. Radionuclides that find their way into the environment may cause harmful effects as radioactive contamination.

 
The Point Source of Radioactive Pollution in effect

The sources of radioactive pollution can be classified into two groups: natural and man-made. Following an atmospheric nuclear weapon discharge or a nuclear reactor containment breach, the air, soil, people, plants, water and animals in the vicinity will become contaminated by nuclear fuel and fission products. Cases of widespread radioactive contamination include the Bikini Atoll, the Rocky Flats Plant in Colorado, the area near the Fukushima Daiichi nuclear disaster, the area near the Chernobyl disaster, and the area near the Mayak disaster.

Many people have argued that an expansion of nuclear power would help combat climate change. A 2025 study found that each nuclear reactor closure in the United States between 1993 and 2022 increased state-level per-capita carbon emissions between 6% and 8%. Others have argued that it is one way to reduce emissions, but it comes with its own problems, such as risks related to severe nuclear accidents, attacks on nuclear sites, and nuclear terrorism. Some activists also believe that there are better ways of dealing with climate change than investing in nuclear power, including the improved energy efficiency and greater reliance on decentralized and renewable energy sources.

A release of radioactive materials followed the 2011 Japanese tsunami which damaged the Fukushima I Nuclear Power Plant, resulting in hydrogen gas explosions and partial meltdowns. The Fukushima disaster was classified a Level 7 event. The large-scale release of radioactivity resulted in people being evacuated from a 20 km exclusion zone set up around the power plant, similar to the 30 km radius Chernobyl Exclusion Zone still in effect.

In 2011, an earthquake and tsunami caused a loss of electric power at the Fukushima Daiichi nuclear power plant in Japan (via severing the connection to the external grid and destroying the backup diesel generators). The decay heat could not be removed, and the reactor cores of units 1, 2 and 3 overheated, the nuclear fuel melted, and the containments were breached. Radioactive materials were released from the plant to the atmosphere and to the ocean.

The nuclear power industry has improved the safety and performance of reactors, and has proposed new safer (but generally untested) reactor designs but there is no guarantee that the reactors will be designed, built and operated correctly. Mistakes do occur and the designers of reactors at Fukushima in Japan did not anticipate that a tsunami generated by an earthquake would disable the backup systems that were supposed to stabilize the reactor after the earthquake.

Scientists suspected that radioactive elements continued to leak into the ocean. High levels of caesium-134 were found in local fish, despite the isotope's comparatively shorter half-life. Meanwhile, radiation levels in the nearby sea water did not fall as expected.

The UNSCEAR report in 2020 determined "direct releases in the first three months amounting to about 10 to 20 PBq [petabecquerel, 10¹⁵ Bq] of iodine-131 and about 3 to 6 PBq of caesium-137". About 82 percent having flowed into the sea before 8 April 2011.

 
Ocean Temperature and its crucial role in Global Climate System

There are many effects of climate change on oceans. One of the most important is an increase in ocean temperatures. More frequent marine heatwaves are linked to this. The rising temperature contributes to a rise in sea levels due to the expansion of water as it warms and the melting of ice sheets on land. Other effects on oceans include sea ice decline, reducing pH values and oxygen levels, as well as increased ocean stratification. All this can lead to changes of ocean currents. Such currents transport massive amounts of water, gases, pollutants and heat to different parts of the world, and from the surface into the deep ocean, for example by moving contaminants from the surface into the deep ocean. All this has impacts on the global climate system.

The various layers of the oceans have different temperatures. For example, the water is colder towards the bottom of the ocean. This temperature stratification will increase as the ocean surface warms due to rising air temperatures. Connected to this is a decline in mixing of the ocean layers, so that warm water stabilizes near the surface. A reduction of cold, deep water circulation follows. The reduced vertical mixing makes it harder for the ocean to absorb heat. So a larger share of future warming goes into the atmosphere and land. One result is an increase in the amount of energy available for tropical cyclones and other storms. Another result is a decrease in nutrients for fish in the upper ocean layers.

The ocean temperature plays a crucial role in the global climate system, ocean currents and for marine habitats. It varies depending on depth, geographical location and season.

The ocean temperature also depends on the amount of solar radiation falling on its surface. In the tropics, with the Sun nearly overhead, the temperature of the surface layers can rise to over 30 °C (86 °F). Near the poles the temperature in equilibrium with the sea ice is about −2 °C (28 °F).

Ocean warming is projected to push the tropical Indian Ocean into a basin-wide near-permanent heatwave state by the end of the 21st century, where marine heatwaves are projected to increase from 20 days per year (1970–2000) to 220–250 days per year. Similarly, in the western North Pacific region, model projections show the mean duration of marine heatwave events rising from about 11 days (1982–2014) to about 138 days per event, and annual marine heatwave days rising to about 270 days by 2100 under high emissions.

A study published in 2025 projected that rising ocean temperatures, together with other climate-driven stressors, will more than double cumulative impacts on marine ecosystems by mid-century. It particularly affects in the Arctic, Antarctic, tropical regions, and coastal areas where biodiversity and human reliance are highest.

While marine heatwaves have mostly been studied at the sea surface, they can also occur at depth, including at the sea floor. It is clear that the oceans are warming as a result of climate change and this rate of warming is increasing. The upper ocean (above 700 m) is warming fastest, but the warming trend extends throughout the ocean. In 2022, the global ocean was the hottest ever recorded by humans.

Unlike heatwaves on land, marine heatwaves can extend over vast areas, persist for weeks to months to years, and extend to subsurface levels. Regional climate patterns including interdecadal oscillations like El Niño Southern Oscillation (ENSO) have also contributed to marine heatwave events such as "The Blob" in the Northeastern Pacific.

Repeated marine heatwaves in the Northeast Pacific led to dramatic changes in animal abundances, predator-prey relationships, and energy flux throughout the ecosystem. Marine heatwave events were expected to increased risk factors and health impacts affect coastal and inland communities as global average temperature and extreme heat events increase. These events had drastic, long-term impacts.