The evolution of sea level

Rising sea levels are one of the most visible and worrying indicators of global climate change. This phenomenon not only threatens coastal communities, but also has profound implications for ecosystems, the economy and global geopolitics.

Causes of Sea Level Rise

1. Melting of Glaciers and Ice Caps

One of the main causes of rising sea levels is the melting of glaciers and ice caps. As global temperatures rise, glaciers in Greenland, Antarctica and other regions of the world are melting, releasing large amounts of fresh water into the oceans.

Example:

• GreenlandGreenland is estimated to have lost around 3.8 trillion tonnes of ice between 1992 and 2018, contributing approximately 10.6 mm to global sea level rise.

2. Thermal Expansion of Sea Water

Global warming also causes thermal expansion of seawater. When water warms, it expands. This phenomenon, although less obvious than ice melting, is a significant contribution to sea level rise.

Relevant Data:

• Thermal expansion has contributed to approximately 50% of the observed sea level rise in recent decades.

3. Loss of land ice

In addition to glacier melt, ice loss in land-based regions such as the Arctic is also adding water to the oceans. This loss of permafrost and other land-based ice deposits further increases sea levels.

Impacts of Sea Level Rise

1. Coastal Flooding

Coastal communities are the most vulnerable to rising sea levels. More frequent and severe flooding can destroy infrastructure, homes and natural resources.

Example:

• Venice ItalyIn November 2019, Venice experienced its worst flooding in 50 years, with water levels reaching 1.87 metres, causing significant damage to its historical and cultural heritage.

2. Coastal erosion

Rising sea levels accelerate coastal erosion, leading to the loss of land and habitat crucial to many species.

Relevant Data:

• It is estimated that by 2050, millions of people could be displaced due to coastal erosion and rising sea levels.

3. Saltwater Intrusion

Salt water can infiltrate freshwater supplies and agricultural soils, affecting agriculture and drinking water sources.

Example:

• Mekong Delta, Vietnam:Saltwater intrusion has affected agricultural productivity, especially in rice cultivation, which is vital to the local economy.

Future Sea Level Projections

Scientific projections indicate that sea level will continue to rise throughout the 21st century and beyond, with variations depending on greenhouse gas emissions and other climatic factors.

1. IPCC projections

The Intergovernmental Panel on Climate Change (IPCC) projects several scenarios of sea level rise:

Scenarios:

• Low emissions scenario (RCP2.6): An increase of approximately 0.28 to 0.61 meters by 2100.
• High emissions scenario (RCP8.5): An increase of approximately 0.63 to 1.01 meters by 2100.

2. Uncertainty Factors

There are uncertain factors that may influence these projections, such as the speed of ice melting in Greenland and Antarctica, and the adaptive capacity of ecosystems and human communities.