Mercury Pollution Found in Deepest Part of Ocean
Two separate studies presented at the Goldschmidt geochemistry conference this week found mercury in fish and crustaceans living 11,000 meters (approximately 36,000 feet) under the sea in the Mariana Trench.
"This is a surprise," Dr. Ruoyu Sun, a scientist from Tianjin University in China who led one of the research teams, said in a Goldschmidt Conference press release published by Phys.org.
Scientists have long known that mercury, which is poisonous to both humans and animals, enters the ocean and the animals within it, concentrating in higher amounts as it works its way up the food web through a process called bioaccumulation. Swordfish, for example, contain 40 times the amount of mercury that salmon do. This means that humans who eat lots of fish are at risk from mercury poisoning, Newsweek pointed out. This can cause neurological and heart damage, and is especially dangerous for developing fetuses.
However, scientists previously thought that this process was mostly taking place in the upper ocean. Then Sun's team found methylmercury, a toxic form of the metal that easily accumulates in animals, in the ocean's deepest trench.
"Previous research had concluded that methlymercury was mostly produced in the top few hundred metres of the ocean. This would have limited mercury bioaccumulation by ensuring that fish which forage deeper than this would have had limited opportunity to ingest the methylmercury. With this work, we now believe that isn't true," Sun said in the press release.
Sun's team uncovered their results by sending deep-sea lander vehicles in 2016 and 2017 to the Mariana and Yap trenches — "amongst the most remote and inaccessible locations on Earth," Sun said in the press release."
They collected deep-sea animals like amphiopods and snailfish at 7,000 to 11,000 meters (approximately 23,000 to 36,000 feet) and sediments at 5,500 to 9,200 meters (approximately 18,000 to 30,000 feet), according to an abstract. They found mercury in all the animals and could tell it came from the upper ocean because of its "isotopic fingerprint," or chemical signature. The results showed human mercury emissions are "much more pervasive across deep oceans than was previously thought," the abstract concluded.
A separate study led by Dr. Joel Blum of the University of Michigan found similar results in the Mariana Trench and in the Kermadec trench near New Zealand.
"The key finding is that mercury released by humans and deposited from the atmosphere to the surface of the oceans is being transported to the most remote and deepest environments in the ocean," Blum told Newsweek.
While some mercury could have come from natural sources like volcanic eruptions, humans emit almost three times more mercury than nature does through processes like burning fossil fuels or mining metals.
"We know that mercury is introduced into the environment from a variety of natural sources such as volcanic eruptions and forest fires. However, human activities, such as coal and petroleum burning, mining, and manufacturing, are mainly responsible for mercury deposition to marine environments," University of Hawaii professor Ken Rubin, who was not involved in the research, said in the press release. "We are now learning from these two studies that the effects of this deposition have spread throughout the ocean into the deep sea and the animals that live there, which is yet another indicator of the profound impact of modern human activities on the planet."
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The speed and scale of the response to COVID-19 by governments, businesses and individuals seems to provide hope that we can react to the climate change crisis in a similarly decisive manner - but history tells us that humans do not react to slow-moving and distant threats.
A Game of Jenga<p>Think of it as a game of Jenga and the planet's climate system as the tower. For generations, we have been slowly removing blocks. But at some point, we will remove a pivotal block, such as the collapse of one of the major global ocean circulation systems, for example the Atlantic Meridional Overturning Circulation (AMOC), that will cause all or part of the global climate system to fall into a planetary emergency.</p><p>But worse still, it could cause runaway damage: Where the tipping points form a domino-like cascade, where breaching one triggers breaches of others, creating an unstoppable shift to a radically and swiftly changing climate.</p><p>One of the most concerning tipping points is mass methane release. Methane can be found in deep freeze storage within permafrost and at the bottom of the deepest oceans in the form of methane hydrates. But rising sea and air temperatures are beginning to thaw these stores of methane.</p><p>This would release a powerful greenhouse gas into the atmosphere, 30-times more potent than carbon dioxide as a global warming agent. This would drastically increase temperatures and rush us towards the breach of other tipping points.</p><p>This could include the acceleration of ice thaw on all three of the globe's large, land-based ice sheets – Greenland, West Antarctica and the Wilkes Basin in East Antarctica. The potential collapse of the West Antarctic ice sheet is seen as a key tipping point, as its loss could eventually <a href="https://science.sciencemag.org/content/324/5929/901" target="_blank">raise global sea levels by 3.3 meters</a> with important regional variations.</p><p>More than that, we would be on the irreversible path to full land-ice melt, causing sea levels to rise by up to 30 meters, roughly at the rate of two meters per century, or maybe faster. Just look at the raised beaches around the world, at the last high stand of global sea level, at the end of the Pleistocene period around 120,0000 years ago, to see the evidence of such a warm world, which was just 2°C warmer than the present day.</p>
Cutting Off Circulation<p>As well as devastating low-lying and coastal areas around the world, melting polar ice could set off another tipping point: a disablement to the AMOC.</p><p>This circulation system drives a northward flow of warm, salty water on the upper layers of the ocean from the tropics to the northeast Atlantic region, and a southward flow of cold water deep in the ocean.</p><p>The ocean conveyor belt has a major effect on the climate, seasonal cycles and temperature in western and northern Europe. It means the region is warmer than other areas of similar latitude.</p><p>But melting ice from the Greenland ice sheet could threaten the AMOC system. It would dilute the salty sea water in the north Atlantic, making the water lighter and less able or unable to sink. This would slow the engine that drives this ocean circulation.</p><p><a href="https://www.carbonbrief.org/atlantic-conveyor-belt-has-slowed-15-per-cent-since-mid-twentieth-century" target="_blank">Recent research</a> suggests the AMOC has already weakened by around 15% since the middle of the 20th century. If this continues, it could have a major impact on the climate of the northern hemisphere, but particularly Europe. It may even lead to the <a href="https://ore.exeter.ac.uk/repository/handle/10871/39731?show=full" target="_blank" rel="noopener noreferrer">cessation of arable farming</a> in the UK, for instance.</p><p>It may also reduce rainfall over the Amazon basin, impact the monsoon systems in Asia and, by bringing warm waters into the Southern Ocean, further destabilize ice in Antarctica and accelerate global sea level rise.</p>
The Atlantic Meridional Overturning Circulation has a major effect on the climate. Praetorius (2018)
Is it Time to Declare a Climate Emergency?<p>At what stage, and at what rise in global temperatures, will these tipping points be reached? No one is entirely sure. It may take centuries, millennia or it could be imminent.</p><p>But as COVID-19 taught us, we need to prepare for the expected. We were aware of the risk of a pandemic. We also knew that we were not sufficiently prepared. But we didn't act in a meaningful manner. Thankfully, we have been able to fast-track the production of vaccines to combat COVID-19. But there is no vaccine for climate change once we have passed these tipping points.</p><p><a href="https://www.weforum.org/reports/the-global-risks-report-2021" target="_blank">We need to act now on our climate</a>. Act like these tipping points are imminent. And stop thinking of climate change as a slow-moving, long-term threat that enables us to kick the problem down the road and let future generations deal with it. We must take immediate action to reduce global warming and fulfill our commitments to the <a href="https://www.ipcc.ch/sr15/" target="_blank" rel="noopener noreferrer">Paris Agreement</a>, and build resilience with these tipping points in mind.</p><p>We need to plan now to mitigate greenhouse gas emissions, but we also need to plan for the impacts, such as the ability to feed everyone on the planet, develop plans to manage flood risk, as well as manage the social and geopolitical impacts of human migrations that will be a consequence of fight or flight decisions.</p><p>Breaching these tipping points would be cataclysmic and potentially far more devastating than COVID-19. Some may not enjoy hearing these messages, or consider them to be in the realm of science fiction. But if it injects a sense of urgency to make us respond to climate change like we have done to the pandemic, then we must talk more about what has happened before and will happen again.</p><p>Otherwise we will continue playing Jenga with our planet. And ultimately, there will only be one loser – us.</p>
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