Is the sea level rising?

We have all heard about the rising level of our oceans, especially due to global warming, but how do we know that they are rising? Should you take out a picture of you at the beach when you were younger and compare it to last year’s photo? NO! It is a lot more complex than that, but here we are to explain it!

Let’s start by the beginning! Why is the sea level rising? It is rising because there is more water! Is it because there is more rain in certain areas of the world? No. It is mostly due to the ice melting and the amount of water that was stored as ice or snow melts (click here to read our article about glaciers and Frank Sinatra). More melted snow and ice therefore gives us more water as it flows all the way down to our oceans.

What happens to the water? As our planet is getting warmer, our oceans get warmer. What happens to warm water? It expands, therefore it takes more space on our coastlines! This is called thermal expansion. NASA believes that our oceans have risen about 21cm since 1900 and is rising 3.4mm per year since 1993. The estimate total sea level rise between 1900 and 2018 was well below the 3.4mm, it was at 1.56mm/year!

I bet you will be surprised to hear that sea level varies depending on the region! Sea level has risen all over the world but in some regions it has decreased, for example in eastern Japan, in South Africa and far off the coast of Maine (USA). NASA even estimates that the sea surface height change from 1992 to 2019 in these regions may have reached -15cm! Why is that? It actually depends on geographic differences, the temperature of the water, the currents and tides, but also gravity! However these regions are exceptions because water has been going up almost everywhere!

How do we measure that? Without a ruler! We have to look at the bigger picture, literally! We have to go all the way up in space to find the satellites that monitor our sea levels. What do they calculate? First they calculate the distance between the satellite and the ocean. Then they calculate the distance between the satellite and the center of our planet. By doing that they can then calculate the distance between the core of planet Earth and the level of the ocean. If it is increasing, it clearly means that there is more water, therefore that the sea level is rising!

It is rising slowly but surely. It takes many years but it is clear that it will affect populations around the world. It is a real shame to see that due to climate change, some regions are left without freshwater and that others are suffering the rise of warm, salted, water. As we can see, this is due to the melting of our glaciers and ice sheets, as well as the expansion of the ocean waters as they get warmer. What can be done? We need to find a way to avoid the melting of our freshwater stored as ice around the world and avoid the heating of our oceans due to greenhouse gases. Imagine a warm mojito… you don’t want that! You don’t want a warm ocean either…