It’s hard to deny that over the past hundred years or so, humans have made a bit of a mess of the planet; air pollution, deforestation, and (of particular interest in the news right now) the vast quantities of plastic that are we are throwing away, and that are carried by ocean currents to the far corners of the earth! Sadly, though, if you think that our effect on the oceans is limited to the pollution that we throw into them, then you would be wrong.

In a recent paper, climate scientists have warned that global warming is causing serious disruption to ocean currents, and that our climate problems may be about to get a whole lot worse.

With 71% of its surface covered by water, our ‘Blue Planet’ is aptly named. In fact, without the ocean, the remaining 29% of the planet would be completely uninhabitable. Mankind have a lot to answer for regarding our treatment of the planet, and the oceans have been incredibly forgiving of our behaviour, soaking up and storing half of the CO2 that we produce, as well as vast quantities of heat. In fact, the ocean is a key regulator of our planet, transporting and distributing heat around the globe, and keeping the land at a liveable temperature.

A out of earth view of our planet submerged in water
It’s a watery world. Source: pixabay

So how does the ocean regulate land temperatures so effectively?
When you make yourself a mug of coffee in the morning (or afternoon, evening, 2am. Hey, I’m a student too– no judgement!), you know that in the few seconds that you spend stirring your drink, your spoon gets burning hot. Take the spoon out, and it will cool down just as quickly. The coffee on the other hand will stay warm for much longer (luckily for you)! What you have just observed is thermodynamics at work!

Essentially, liquids are able to hold vast amounts of heat compared to solids, and so they heat up and cool down more slowly. The exact same principle works with our oceans and land masses. The ocean stays a steady, constant temperature, reacting extremely slowly to external temperature changes, and protecting the land against extreme temperatures by giving it heat in winter, and taking heat away in summer. In fact, one of the reasons that the UK has such mild (some would say ‘boring’) weather, is that we are a tiny island surrounded by a huge ocean that protects us from extremes of temperature.

As well as buffering against extreme temperatures, there are a huge number of ocean currents that transport heat around the planet, moving heat from hot land masses at the equator to the colder ones at the poles. One particular group of currents, the AMOC (the Atlantic Meridional Overturning Circulation) is especially active in heat transport. This vast system of currents covers much of the Atlantic ocean, and even includes the Gulf stream.

It works a bit like a conveyer belt. Warm surface water from the tropics is carried up towards the North Pole, where it cools, grows denser, and sinks before travelling back down south again. This system moves vast amounts of heat from the tropics up towards the North Pole, where it is then transferred into the atmosphere.

Without the ocean, the remaining 29% of the planet would be completely uninhabitable.

In the 2004 disaster movie ‘The Day after Tomorrow’, Hollywood director Roland Emmerich takes a stab at imagining what would happen if the AMOC suddenly shut down. Cue flash floods, hurricanes, and an impromptu Ice Age… Perfect movie material.

But is this idea really as crazy as it seems?
In short, yes. Humans would have to work pretty hard to completely shut down one of the largest systems of ocean currents on the planet. However, that is not to say that we aren’t having an impact on it.

As global temperatures rise, and the ice caps at the North Pole continue to melt, a huge amount of fresh water from the North Pole is moving down into the Atlantic. This addition of cold, low-density water is effectively causing a backlog, slowing down the entire conveyer belt. AMOC is now the weakest that it has been in 1,600 years, 15% slower than it was just 50 years ago! This slow down means that less heat will be transferred up North, and temperatures will get more extreme.

A stark contrasting scene with lush green land on the left and bleak desert on the right of the same tree.
Drastic Changes. Source Pixabay

The US should be prepared for hotter weather, whilst back in the UK, winters are set to get colder. On top of mere temperature changes, the hydrological cycle across the entire Northern Hemisphere will be start to shift, causing god-knows-what further knock on effects.

So buckle up Britain! Our boring weather is set to get a lot more interesting. If you want to learn more about climate change and the effects it is having on our world read this article where Tamara Moule asks whether Hurricane Harvey was a one-off disaster, or piece in a greater Climate-Change puzzle?


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