How Do Warm Oceans Affect the Climates?

Our oceans are becoming warmer. The increasing trends of greenhouse gas emissions in the EU and beyond are causing global heating of the environment, which not only affects the air but the water too. But how does this affect the climate in tangible terms?

According to a new study, the fact that oceans are becoming more stable (with warmer water resting more consistently on the surface) could be damaging to the environment in a number of different ways. As well as being less adept at absorbing carbon dioxide from the atmosphere and distributing nutrients among the marine organisms which live within it, a warmer ocean also provides fuel for extreme weather events.

Taken all together, these three outcomes could have disastrous consequences for the planet. A stabler ocean will only become even warmer at a faster pace in the future, leading to an exponentially detrimental situation where both the air and sea suffer from an ever-worsening feedback loop of warming.

Stable stratification

Just as hot air rises, so too does warmer water naturally ascend to the surface of the ocean. The stratification of the ocean in this manner – with warm, less dense water resting above cold, denser water – is a common phenomenon witnessed the world over.

However, this stratification is generally disrupted when the warmer water at the top of the ocean becomes heavier than that beneath it due to an increased salt content. This most commonly occurs when the surface level water evaporates, thus increasing the salt content in the water itself and causing it to sink. This process mixes the warmer water with the colder water beneath to keep surface temperatures cooler and distribute nutrients more evenly.

The recent study, published in the journal Nature Climate Change, found that stabilisation of the ocean’s stratification has increased by 5.3% since 1960. The majority of that stability was witnessed in the upper 200m of the ocean, where warmer temperatures have prevented the natural process of mixing to occur.

Manmade impacts

While a more stable ocean may sound intuitively like a good thing, it’s actually detrimental to the environment on a number of levels. First and foremost, warmer surface water is less effective in absorbing carbon, meaning there will be more of the harmful greenhouse gas in our atmosphere and global warming will be exacerbated.

Secondly, warm waters can accelerate and intensify extreme weather events like tsunamis and typhoons, which can put a strain on already limited water supplies and  cause significant damage to both humans and animals. And finally, marine ecosystems will be impacted due to a less efficient distribution of nutrients in the water itself.

However, the most concerning aspect of a warmer ocean is the spiralling effect it could have in future. Unchecked, these warmer temperatures will only feed into ever greater warming events, starting a chain reaction that will be difficult to keep in check unless decisive action is taken urgently.