Our oceans, which cover about 70% of the Earth’s surface, have a reciprocal relationship with global climate and weather patterns. While oceans tend to influence regional and weather conditions around the world, changes in the climate can also have profound impacts on the oceans. This cycle, albeit a relatively simple one, is actually a lot more complex than one could imagine. So, how does climate change affect the ocean? 

How Does Climate Change Affect the Ocean?

Generally speaking, oceans are dynamic in nature. This massive carbon sink plays crucial and regulatory roles in the Earth’s climate. Oceans are known to absorb most of the solar energy reaching the Earth, and warming of the oceans is generally slower than the atmosphere, resulting in moderate coastal weather with few hot and cold extremes. However, these conditions have begun to change in recent years.

Oceans absorb almost 90% of the extra energy from greenhouse gas effects, and this has resulted in ocean warming at depths of 1,000 metres. This in turn, has led to consequences such as enhanced ocean warming and stratification – where seawater naturally forms stratified layers with lighter waters near the surface and denser waters at greater depth – variability in ocean regimes, and modification of ocean habitats and ecosystems. A 2019 Intergovernmental Panel on Climate Change (IPCC) report revealed that in response to climate change and the concurrent greenhouse warming, coral bleaching and ocean warming events such as marine heat waves are likely to increase, putting a greater strain on the global oceans. 

Furthermore, atmospheric warming has led to the melting of glaciers and land ice, causing rising sea levels, which have led to erosion, saltwater intrusion and destruction of coastal habitats and shorelines. The increase in anthropogenic greenhouse gas emissions have also resulted in extreme El Niño events such as sea surface warming, changing ocean circulation patterns and precipitation frequencies. On the other hand, La Niña events have also seen a build-up in recent years, and tend to have complex impacts on weather patterns particularly in the Pacific Ocean. Both El Niño and La Niña events are part of the El Niño Southern Oscillation (ENSO), where the former brings warming effects while the latter brings significant cooling or changes in winter seasons in the Pacific regions.

Carbon dioxide emissions tend to acidify oceans making aquatic species and marine habitats more vulnerable to declines and damage. This ocean acidification aggravates physiological stresses and reduces growth and survival rates of several marine species.

So why is this important?

The global oceans and coastlines provide significant ecosystem services such as marine habitats, carbon sequestration, oxygen production, as well as food and income generation. Salt marshes and mangroves which comprise the coastal ecosystems are key players in carbon sequestration processes. Due to continual deforestation activities taking place in many parts of the globe, the subsequent degradation of these ecosystems releases approximately 1 billion tons of carbon dioxide annually – contributing to 20% of global carbon emissions.

The impacts of rising ocean temperatures and ocean acidification are already observable in the current environment. With increasing amounts of atmospheric greenhouse gases, coral reefs are at great risk, and this consequently adds strain to food production, coastline protection and other services provided by coral reef ecosystems. In addition, plastic pollution is also known to contribute to ocean warming and threatens marine life. The cumulative impacts of deforestation, agricultural runoff, overexploitation of marine resources, overfishing and more also weaken marine ecosystems of the world.

To surmise, greenhouse warming has complex and perhaps, severe impacts on the ocean than on land. However, it is important to note here, that the biosphere in general, needs to be protected from the consequences of global warming.

What is Currently Being Done? 

So, what comes next after learning how climate change can affect the ocean? We take action. The worldwide population depends on the oceans and marine ecosystems. The protection, management and conservation of the hydrosphere therefore is important to support the provision of carbon sequestration and other services on which people depend. Studying the oceans is vital to understand anthropogenic climate change. Many organisations such as The World Climate Research Programme (WCRP), World Meteorological Organization (WMO) and many others are actively researching the oceans to better comprehend the ocean-atmosphere linkages and relationships. The WMO in particular also collaborates with the Food and Agriculture Organisation to understand the impacts of climate change on marine productivity and fisheries.  

Countries have also started developing policies and implementing sustainable practices which can conserve the oceans and protect fisheries and marine habitats. An example is Marine Protected Areas (MPAs), which protect marine habitats, including regulating human activities and thereby maintaining climate change resilience. Certain strategies like REDD+ (Reducing Emissions from Deforestation and Forest Degradation) and Nationally Determined Contributions (NDCs) under the Paris Agreement, enable MPAs with sustainable tools to preserve marine ecologies.

On a larger scale, G7 nations have pledged in May 2021 to protect 30% of global land and at least 30% of the global ocean by 2030. While this is certainly a start, there may be some concerns on how this progress would be measured in the coming years. For example, one publication highlights certain key findings that need to be viewed in parallel with the 30 x 30 initiative. While 30% of the land on Earth is classified as areas of particular importance for biodiversity protection, in order to reverse the extinction crisis, there needs to be an additional 20% of land that needs to be conserved. To supplement this, another publication states that conservation of 30 percent of the land would reduce the extinction crisis by half; this may not meet the standards set by the Global Biodiversity Framework (GBF). Moreover, the 30 x 30 plan isn’t universal i.e. it may not be multi-purpose due to the varying biological wealth and natural habitats that exist in various countries. Based on the ecological wealth of countries, some may need to contribute more to the initiative, while others, say the developing nations could find it easier to achieve the optimal goal. Hence, this warrants a deep dive into the workings of the 30 x 30 strategy.

The goal is to adopt proper implementation of global strategies that can ensure marine and coastal protection and the conservation of the global oceans in general. With decades of increasing greenhouse emissions, the climate has been responding in many ways to ensure a healthy environment. But there exists a tipping point, which if crossed, will warrant effective countermeasures. 

More than hundred countries across the globe responsible for a majority of these emissions, have made national climate commitments and pledges to curb their impacts on the environment. Building upon the first ever UNFCCC Ocean – Climate Dialogue, notable campaigner and US special climate envoy John Kerry said, “When the world talks about the climate crisis, the ocean crisis must be front and centre in that conversation. One way to ensure that happens will be to establish an ongoing forum for ocean issues here in Glasgow in the COP26 decision text”. Many marine scientists and conservationists considered the incorporation of the oceans in the UN Climate Regime as a “win”. 

With the Paris Agreement, the recent COP26 summit in Glasgow among others, we can definitely say that we are off to a good start. However, much of this progress would require continual updates and revisions to make sure we are on track. By taking certain issues head-on and using nature-based solutions, we can certainly ensure a secure and resilient ecosystem for the years to come. 

If you liked learning how climate change can affect the ocean, you might also like: 10 Plastic Pollution in the Ocean Facts You Need to Know