Sea levels rising
Let's dive into the subject of rising sea levels, one of the well-known consequences of climate change. In this article, we explore the causes and consequences of this phenomenon, which is starting to look more and more like our reality.
Rising sea water levels threatens 300 million people
Source: Barbado today
Causes of sea levels rising
The melting of ice in the icy regions of Greenland and West Antarctica is accelerating significantly as a result of global warming. The Greenland ice sheet alone contains enough ice to raise sea levels by six to seven metres," explains glaciologist Heïdi Sevestre.
Today, the large masses of ice in the glaciers and ice caps are no longer replenishing themselves properly. Normally, these huge ice formations partially melt during the summer, but regain their solidity when winter temperatures return.
As a result of global warming, there is less snowfall, shorter winters and earlier springs. The ice is not reconstituting itself in the same way as before. This creates an imbalance between melting and recharging of snow, leading to a rise in sea level.
Scientists also believe that meltwater from upstream and seawater from downstream are seeping under the Greenland ice caps, accelerating the glaciers' slide towards the sea. In other words, when freshwater penetrates the base of the ice caps, it melts them, weakens them and causes them to slide into the ocean.
Another factor is thermal expansion. When water heats up, it expands, causing sea levels to rise. Around half of the rise in sea level over the last 25 years is due to the heat absorbed by the oceans, which therefore occupy more space.
This visual shows the causes of rising sea levels: temperature is rising,
causing glaciers to melt and water to expand, leading to rising sea levels.
Source : Surfrider
Consequences
Melting ice and rising sea levels have major consequences for our planet.
For example, ice-free summers in the Arctic will lead to an increase in extreme weather phenomena such as heat waves, forest fires and floods.
Rising sea levels will intensify weather phenomena such as storm surges, coastal erosion and hurricanes, causing major damage. Flooding will become more frequent, more widespread and more severe, especially in very low-lying areas where there is a risk of constant flooding.
In addition, as coastal erosion intensifies, the danger of flooding and submersive waves along the coast increases.
Rising sea levels will also lead to the intrusion of salt water into the land, affecting groundwater reserves (sources of drinking water) and water resources for irrigation.
Research shows that sea level rise is accelerating and could reach one metre by 2050. Reducing greenhouse gas emissions can help limit this rise, but adaptation measures are needed to deal with the inevitable consequences of rising sea levels.
In social terms, hundreds of millions of people living in coastal communities are threatened by rising sea levels. If this trend continues, these populations will be forced to move to higher ground, leading to demographic problems linked to forced migration due to climate change.
In France
In France, one coastal home in 10 is threatened by rising sea levels. The area most at risk will be the mouth of the Seine, the Atlantic coast and, to a lesser extent, the Mediterranean coast.
Among the major cities most at risk between 2020 and 2050 are Le Havre (by far the most threatened), Caen, Bordeaux, Arcachon, Deauville, Bayonne, Toulon and Sète.
As a result of global warming, four out of ten French people (42%) have already thought about changing where they live in May 2023.
A few figures
Greenland is losing more than six times as much ice today as it did forty years ago, and it is the ice mass that contributes most to the rise in sea levels.
Over the 20th century, global sea levels rose by 18 cm (between 1870 and 2000). The current annual rise is around 3 millimetres.
In France, by 2100, sea levels could rise by an average of 20 to 43 cm (optimistic scenario) or 23 to 51 cm (pessimistic scenario).
Many islands affected
40% of the world's population resides less than 100 km from a coastline, and 10% of the world's population live in coastal areas less than 10 metres above sea level. Many Pacific islands are at risk, as most of these volcanic islands are only a few metres above sea level.
Scientists expect most of the islands of Tuvalu to become uninhabitable by the end of the century. Countries such as Tuvalu, Kiribati and the Marshall Islands are already experiencing rising sea levels, with floods sweeping salt water onto farmland and inundating sources of drinking water.
Mrs Mottley, President of Barbados, declared in 2021 that a global heat rise of two degrees Celsius would be a "death sentence" for islands and coastal communities. She called for the nations of the world to "redouble their efforts" to change the situation, and said that failure to provide sufficient funding to small island nations, which are on the forefront of climate change, would be worth "lives"...
Key points
📌 The melting of glaciers and ice caps, as well as the thermal expansion of the oceans, all contribute to rising sea levels. These phenomenas are exacerbated by global warming.
📌 The summer sea ice could disappear from the Arctic as soon as 2030, ten years earlier than predicted by the IPCC (even in a low greenhouse gas emissions scenario).
📌 The Greenland ice cap has sufficient ice to raise sea levels by six to seven metres," explains the glaciologist Heïdi Sevestre.
📌 In France, by 2100, sea levels might increase on average by 20 to 43 cm (optimistic scenario) or 23 to 51 cm (pessimistic scenario).
📌 Rising sea levels have major effects, including
- an increase in storm surges and coastal erosion
- flooding will become more frequent and severe, particularly in low-lying areas
- salt water intrusion into the land will affect groundwater reserves.
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