Summer has been marked by excessive heat waves across the globe. From the UK to the U.S, the effects of climate change are being felt far and wide. While it may be obvious the current heatwave anomoly is directly linked to our changing climate, few realise the key role our oceans play to regulate this process.

Our oceans generate 50% of the oxygen we need, absorb 40% of all carbon dioxide emissions and capture 90% of the excess heat generated by those emissions.  They’re not just the lungs of our planet, but also its largest heat sink, providing a vital buffer against rising temperatures and the effects of climate breakdown. But, the ability to safeguard life underwater and on land is being compromised by two bedevilling human-induced causes – can you guess what they are?

 

Yin and yang: the sun and the ocean as the Earth’s climate moderator

The ocean is our Earth’s natural climate moderator. It regulates weather patterns around the globe,  controlling heat waves, rainfall, floods and droughts. Without the ocean, our Earth would be much hotter than it currently is. It’s the largest heat sink on Earth, meaning it absorbs and stores massive amounts of the sun’s energy.

Ocean currents are like highways that carry this heat and spread it more evenly around the planet. But the interaction between these two natural forces is changing. In the last 200 years, the ocean has absorbed one-fourth of the CO2 produced by human activity and 90% of the excess heat caused by the rising concentration of greenhouse gases (GHG) emissions in our atmosphere.

While the ocean protects humans from the full consequences of our emissions, the excess heat and carbon absorbed deep in the sea is altering marine ecosystems.

 

The current threat to our oceans

As we have increased our reliance on fossil fuels and maintained an upward trajectory of emitting greenhouse gas emissions, the ocean has moderated the effects and spared us from the extreme impacts we would otherwise experience. And while this has served as a vital buffer against the full consequences of our emissions, the impact of rising temperatures is beginning to ripple through our oceans.

The increasing concentration of heat-trapping GHG emissions has jeopardised the ocean’s capacity to act as a heat sink, in turn compromising life both below water and on land. Rising temperatures result in weakened oceanic currents. If the water at the poles isn’t as cold and dense, it simply won’t be able to circulate as well. What’s more, the melting of the Greenland continental ice sheet is pouring fresh water into the salty ocean, altering the density of water masses.

This shift in balance is having an effect throughout the globe. From increasing heat waves in Europe to compromised marine ecosystems, the impact shouldn’t be understated.

Whether it’s for the good or the bad, the oceans and climate change are inextricably linked. And this may – or may not – come as a shock, but so is our uncompromising plastic problem.

Plastic: the last piece of the ocean compromising puzzle

At least half of the Earth’s oxygen comes from the ocean.  The majority of this production is from oceanic plankton – small, microscopic organisms that are invisible to the human eye but serve a massive purpose in the Earth’s ecosystem.

Plankton plays a fundamental role in maintaining the ocean’s heat and carbon sink capacity. But with more plastic smothering plankton, this function is being compromised.

The presence of plastics on the sea surface is a serious problem that is interfering with fundamental biological processes. These processes control the flow of important gases like oxygen between the sea surface and the atmosphere. When there’s a lot of plastics present, the flow of oxygen into the atmosphere – and the flow of CO2 from the atmosphere into the ocean – slows down.

Plastic blocks sunlight from getting to plankton, which in turn prevents the organism from being able to photosynthesise, produce oxygen or store CO2. We might not be able to see plankton, but just because it’s not visible to the human eye doesn’t mean its not important.

We must act

These threats may seem far from home, but the ocean’s influence doesn’t stop at the coastline. If the ocean stores less CO2, absorbs less heat or creates less oxygen, our Earth could be subject to unimaginable changes. We need to think long and hard about the consequences of our actions, and turn that thinking into meaningful action.

A healthy ocean free from plankton smothering plastic has a greater chance of adapting to climate change impacts. In turn, this means we too have a better chance at adapting.

Our oceans are one of our greatest allies in the fight against a changing climate. However, if we carry on this fossil-fuel burning and plastic pollution littering upwards trajectory, this will no longer be the case.