Useful terms:
- Glacier - a large accumulation of ice (and snow) that is able to move (very slowly) downslope purely due to the forces of gravity and its own mass.
- Ice sheet - a sheet of ice that covers a land mass and is greater than 50,000km wide.
- Ice shelf - a permanent floating sheet of ice that is connected to a land mass.
- Ice Cap - a mass of ice that is less that 50,000km wide and is often found at high altitudes. Can sometimes feed into glaciers.
- Icebergs - pieces of ice that were formed on land, but have become detached (the action of calving) and now float in expanses of open water.
- Sea ice - ice which forms when ocean water freezes.
Ice at the land surface
In the past the climate has been much colder and ice coverage extended far beyond where it does today. These periods of time have been aptly named 'ice ages', of which there have been 5 in the earth's history. The most recent ice age started 100,000 years ago and came to an end around 10,000 years ago. The map below shows ice coverage at the height of the last ice age, where much of Northern Europe, including Scotland and Northern England, were covered in ice. Ice ages were periods of extensive glacial activity and their impact on the landscape through various geomorphic processes can still be seen today.
In the past the climate has been much colder and ice coverage extended far beyond where it does today. These periods of time have been aptly named 'ice ages', of which there have been 5 in the earth's history. The most recent ice age started 100,000 years ago and came to an end around 10,000 years ago. The map below shows ice coverage at the height of the last ice age, where much of Northern Europe, including Scotland and Northern England, were covered in ice. Ice ages were periods of extensive glacial activity and their impact on the landscape through various geomorphic processes can still be seen today.
Current ice coverage
Cold environments are less extensive today, but can still be found distributed across the globe, with ice sheets located in Greenland and Antarctica, glaciers located in the Alps, Himalayas and Andes mountain ranges, and ice caps in places such as Iceland. That Antarctic ice sheet is the largest mass of ice on the planet and holds 70% of the world's freshwater. If it was to entirely melt sea levels would rise upwards of 60m.
The map below shows the global distribution of glaciers in blue and ice sheets in white.
The map below shows the global distribution of glaciers in blue and ice sheets in white.
Current trends
Although some glaciers are increasing in size, the ongoing overall trend is in the reduction of global ice coverage. Over the past 30 years it has become increasingly common for large ice shelves to rapidly disintegrate with some retreating by as much as 90%. While the break up of ice shelves is not uncommon, it usually takes between months and years for it to calve into icebergs, more recently it is taking a matter of weeks and in some cases days. The collapses are most likely linked to climate change and warming air and water temperatures. While there is a direct link to an increased melt rate on the surface of ice shelves, the reduction of sea ice is also thought to have had an impact. Sea ice acts as a barrier around the ice shelves, protecting them from the worst ocean conditions, and its reduction has led to shelves being more vulnerable to damaging wave impacts.
Although some glaciers are increasing in size, the ongoing overall trend is in the reduction of global ice coverage. Over the past 30 years it has become increasingly common for large ice shelves to rapidly disintegrate with some retreating by as much as 90%. While the break up of ice shelves is not uncommon, it usually takes between months and years for it to calve into icebergs, more recently it is taking a matter of weeks and in some cases days. The collapses are most likely linked to climate change and warming air and water temperatures. While there is a direct link to an increased melt rate on the surface of ice shelves, the reduction of sea ice is also thought to have had an impact. Sea ice acts as a barrier around the ice shelves, protecting them from the worst ocean conditions, and its reduction has led to shelves being more vulnerable to damaging wave impacts.