OVERVIEW
The total amount of water on Earth is not increasing, but the volume of liquid filling the ocean basins is growing, raising the sea levels and increasing the amount of fresh water that flows into the oceans.
The additional volume of seawater comes from two places:
(1) the melting of ice sheets and glaciers on land adds water to the sea
(2) less obvious cause of sea level rise, has to do with water expanding as it heats up, so the more thermal energy the ocean absorbs, the more space its water needs.
The more the water heats up, the more the atmosphere heats up and starts a vicious circle.
Water has the ability to absorb a lot of heat, a property known as heat capacity. As a result, when air temperature increases, so does ocean temperature.
Global sea level is currently rising due to thermal expansion of the oceans and melting glaciers, each representing about half of the observed sea level rise and each caused by recent increases in global average temperature. Since 1961-2003, sea level has increased due to thermal expansion and melting of glaciers (from small glaciers, ice caps and ice sheets) at a rate of 1.11 millimetres (0.04 inches) per year. Between 1993 and 2003, the contribution to sea level rise increased for both sources to 2.79 millimetres (0.11 inches) per year. Thus, not only does the sea level rise, but also faster than in the past.
Why is that?
Scientists have discovered that since the beginning of the industrial revolution, the concentration of carbon dioxide in the atmosphere has increased by 39%. Most of the CO2 is generated by the production of energy from fossil fuels that we use to support our lifestyle. This is significant for our climate because carbon dioxide is the most important gas to control the Earth’s atmospheric temperature through the greenhouse effect. Without a greenhouse effect, the Earth’s temperature would be much colder than it is now, but an increase in CO2 traps heat in the atmosphere, leading to temperature increases that have been recorded.
It’s not just freshwater rivers and lakes that are at risk – our aquifers, or natural underground water storage, are at risk of filling with salt water as the ocean encroaches on the land above them. When sea levels rise as rapidly as they have been, even a small increase can have devastating effects on coastal habitats farther inland, it can cause destructive erosion, wetland flooding, aquifer and agricultural soil contamination with salt, and lost habitat for fish, birds, and plants. Already, flooding in low-lying coastal areas is forcing people to migrate to higher ground, and millions more are vulnerable from flood risk and other climate change effects.
Learn more by reading the FULL SCIENTIFIC BACKGROUND
Use the INFO-GRAPHIC to present the topic to your class
Select one of the following Class activities:
- Water consumption
- Water Cycle – Song
- Play with Water