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Why the Oceans

The ocean is far more than the home to a dazzling variety of plants and animals or an important source of food to us. It also plays a crucial role in the regulation of our climate and stores vast amounts of the excess heat that has accumulated in the Earth system since pre-industrial times. It also takes up a significant portion of anthropogenic CO2, removing it from the atmosphere and preventing additional warming.

All these services from the ocean become increasingly important under climate change – while, at the same time, being more and more at peril.

 

A century of change, everywhere, and an urgent call for action

The recently published 6th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) clearly states that human-made climate change is rapid, widespread, and intensifying. And it is affecting many critical aspects and functions of the oceans.

Nowadays, CO2 concentrations are higher than over the past 2 million years – or, in the words of renowned climate scientist, Erich Fischer, “higher than ever in the history of humankind”. Global warming of 1.5 or 2°C – the upper limit defined in the Paris Agreement – will be exceeded during the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur. But even then, there are many changes due to past and future greenhouse gas emissions that will remain irreversible for centuries to millennia, especially in the ocean. Examples include the thawing of the big ice sheets, global sea level rise, and ocean warming, acidification, and deoxygenation.

Climate change impacts the ocean at various levels. There is ocean warming, which over the past century progressed faster than at any other time since the end of the last deglacial transition (around 11,000 years ago). In addition to gradual ocean warming, there is also an increase in extreme temperature events, so-called marine heatwaves. These have doubled in frequency since the 1980s and are projected to become even more frequent, longer, and intense in the future. This has adverse effects on many marine organisms, especially highly temperature-sensitive corals. Beyond coral bleaching, marine heatwaves can also cause changes in primary production, shifts in species compositions and distributions, toxic algal blooms, and declines in fisheries catch.

Ocean acidification is compounding the effects of ocean warming. pH levels in the open ocean as low as now are unusual in the last 2 million years, and their reduction is projected to continue. This is another hard blow to corals, and harms other calcifying wildlife as well, including important phytoplankton species, bryozoans, crustaceans like crabs, molluscs such as squids or oysters, and echinoderms such as starfish.

On top of this, there is ocean deoxygenation, a decrease in the oxygen content of the upper ocean caused by ocean warming, stratification, and eutrophication. In its most extreme state, ocean deoxygenation can cause so-called “dead zones”, regions with too little oxygen to sustain life. These areas are projected to expand in the future.

In some cases, entire ocean currents are projected to be altered by global warming. One example is the Atlantic Meridional Overturning Circulation (AMOC) – the mighty current that transports warm water from the Caribbean to Europe – which is projected to weaken over the 21st century. And while there is medium confidence that there will not be an abrupt collapse of the AMOC within this century, such a major climate tipping point cannot be ruled out completely.

A visible and more known effect is the thawing of the enormous ice sheets in Greenland and Antarctica, which contributes to sea level rise (together with the thermal expansion of warmer sea water). Over the next 2,000 years, global mean sea level is projected to rise about 2-3m if warming is limited to 1.5°C, 2-6m if limited to 2°C, and 19-22m with 5°C warming.

Additionally, under continued warming, the Arctic will be practically ice-free during summer for the first time before 2050 – a state that might become the new normal by 2100 under high greenhouse gas emissions. This might have major impacts on species that depend on sea ice for their survival, feeding, or breeding, such as whales, polar bears, and seals.

Many of these impacts will pose major challenges to marine organisms and ecosystems around the globe and may push some of them to or beyond their capacity to adapt or acclimate. This may not only doom certain species but might even devastate entire stretches of vastly important oceanic ecosystems and hotspots of marine life such as coral reefs.

Under these prospects, it becomes more important and more urgent than ever to safeguard our oceans. They are literally our biggest ally in the race against climate change, and we need to preserve their health, biodiversity, and resilience as well as the services they provide, so they can continue to aid climate change mitigation.

 

What needs to be done?

Reading the report makes it clear that we’re headed towards uncharted territory. Never before has humanity faced a world with oceans simultaneously warming, acidifying, deoxygenating, and deteriorating as fast and as they do now. But even though all this sounds dooming, there is still hope. We are not simply at mercy of climate change – quite the contrary, we are causing and driving it. Our actions determine in which direction we are headed, and at what speed. We still have the power to slow climate change, weaken the amplitude of its impacts, and turn the tide on relevant aspects. And although we have already committed some processes to worrying trajectories for hundreds, maybe even thousands of years – other consequences can still be alleviated or avoided, sometimes even reversed – if we react with fast, decisive, and persistent reductions in greenhouse gas emissions immediately.

The climate we experience in the future depends on our actions now. Or, as oceanographer Sylvia Earle phrases it: “Our actions over the next 10 years will determine the state of the ocean for the next 10,000 years”. This new Assessment report is an urgent wake-up call – one we must heed before it’s too late.

 

Immediate action for our oceans

To take up that responsibility and protect our oceans, OceanCare calls for an immediate ban on hydrocarbon exploration and a phase-out of hydrocarbon exploitation worldwide. This would represent a significant step towards the urgently needed decarbonization of our economies, and additionally reduce another source of stress and danger to marine wildlife.

OceanCare also calls on the International Maritime Organisation (IMO) to introduce a binding speed reduction for the maritime transport sector. This is a proven and easily implementable, fast yielding, and highly effective way to reduce carbon emissions from a major sector of economy – and, as a side-effect, also greatly reduces noise emissions, another stressor for marine wildlife. The European Union and its Member States should be at the forefront of promoting this operational measure and impose it wherever possible in its waters.

Alongside these direct climate actions, OceanCare focuses on reducing additional stressors impacting marine wildlife and ecosystems such as pollution, overfishing, habitat degradation, entanglements, ship strikes, and whaling. This may not directly mitigate climate change’s deleterious effects on our oceans, but it will likely help to build resilience within ecosystems and animal populations – and our hope that they will be able to adapt or acclimate to future changes and continue to give life to our invaluable ally and life support system, the oceans.