6.2
Melting of Arctic Glaciers and ice-caps and its impact on sea level
Did you know?
Glaciers can move very quickly?
Global sea level would rise seven meters if the Greenland Ice Sheet melted and 58 meters if the Antarctic Ice Sheet would melt (don't worry too much, it will not happen for thousands of years)?
Watch the Greenland ice sheet melting. Also, watch two animations showing how glaciers respond to climate change and how glaciers formed modern landscapes.
Did you know that when more water was locked in ice sheets during the glacial maximum of the Ice Age (the part of the last ice age with the largest ice sheets more than 20 000 years ago), sea level was 125 m lower and people and animals walked between continents (what is now Alaska and Russia across the Bering land bridge, see Introduction p 24, in Stories of Arctic Science, 2015.
During the Last Glacial Maximum, there were large tundra ecosystems with mammoths, wholly rhinoceroses and extensive land areas with a lot of soil carbon. These are now under the sea.
Many mega cities are located near the coast line just above sea level and are vulnerable to even small increases in sea level rise (look at where sea level rise will be a problem — Climate Central)
Many coastal areas in developing countries have important low lying agricultural land vulnerable to sea level rise and the farmers have limited possibilities to relocate.
The retreating margin of the Greelnad Ice Sheet revealing ice-polished rock. Photo: Terry Callaghan
The melting Greenland Ice Sheet now has rivers, torrents and waterfalls on it! | Photo: Terry Callaghan
Glaciers "drain" the Ice on the ice sheet ending in the sea or incresingly, inland on the way to the sea. | Photo: Terry Callaghan
The Jacobshavn Isbrae is the world's most productive glacier producing an enormous number of gigantic icebergs. It was probably an iceberg from this glacier that sank the Titanic! | Photo: Terry Callaghan
Get Active!
What causes the sea level to rise?
You will need:
Experiment 1a
Does melting sea ice lead to sea level rise?
Instructions
Take the metal dish and half fill it with water.
Put ice cubes in the water.
Using the magic marker pen, draw a line on the side of the pet dish to show the level of the water. This line represents the sea level.
Allow the ice cubes to melt completely, without heating the water!
Check the 'sea level'. Has it gone up?
Experiment 1b
Does melting land ice lead to sea level rise?
Instructions
Fill the same metal dish/pan half full.
Using the magic marker pen, mark the level of the 'sea'.
Put ice cubes on the rim.
Allow them to fully melt without heating the water!
Check the 'sea level'. Has it gone up?
NB: If you can't find a metal dish with a flat rim, allow the ice cubes to melt through your fingers. It will have the same effect!
Experiment 1c
Do warmer oceans lead to rising sea levels?
Instructions
Fill the metal dish/pan three quarters full.
Heat it with a hot water bottle / heat-pack. If you are using a pan you can heat it on a stove but you must be accompanied by an adult.
What happens to the water?
The science behind the results
What causes the sea level to rise?

Climate change raises the level of the sea. Increasing global and Arctic temperatures cause the sea level to go up for two reasons:
1
Hotter air melts ice on the land, such as glaciers and the Greenland Ice Sheet. The hotter the air is, the more ice melts and the faster it melts. The melted ice turns into flowing water and runs off the land into the sea, adding more water to the ocean.
2
Water expands (takes more space) as it gets warmer. When we cook food in a pan, we don't fill the pan to the top as the water overflows when it gets hot. In the same way, warm seawater takes up more space in the ocean basin, causing the sea level to rise (go up).
Sea ice that melts does not cause the sea level to go up. This is because sea ice is just frozen sea water and if it melts when it is already in the water then the volume (amount) of water stays the same, and the sea level stays the same.
From our experiments we know that:
  • 1a) Melting sea ice does not lead to sea level rise. In the first part of the experiment, the water level (sea level) did not go up.
  • 1b) Melting ice on land does cause sea level rise. In the second part of the experiment, the water level (sea level) went up.
  • 1c) Warmer Arctic seas increase sea level. In the final part of the experiment, the water level (sea level) went up or even spilt out over the edge of the metal dish.
Why does this matter?
Even a small increase in sea levels could affect tens of millions of people living along the coast across the globe, and the landscapes around them. Higher sea levels would flood some low-lying areas, forcing people to abandon their homes and move to another area and low-lying islands could be completely covered by water. As seawater goes inland it can cause freshwater fish, birds, and plants to lose their habitats. Higher sea levels also mean that storm surges – the rise in seawater level during a storm – will be bigger and happen more often, reaching farther inland and causing more frequent and unpredictable flooding.