The causes of an Ice Age are not clear. One theory is that the Earth’s tilt and its orbit of the Sun have changed. An orbit that took our planet further from the Sun would result in a cooler climate.
An ice age is a time where a significant amount of the Earth’s water is locked up on land in continental glaciers.
During the last ice age, which finished about 12,000 years ago, enormous ice masses covered huge swathes of land now inhabited by millions of people.
Canada and the northern USA were completely covered in ice, as was the whole of northern Europe and northern Asia.
At the moment the Earth is in an interglacial period – a short warmer period between glacial (or ice age) periods.
The Earth has been alternating between long ice ages and shorter interglacial periods for around 2.6 million years.
For the last million years or so these have been happening roughly every 100,000 years – around 90,000 years of ice age followed by a roughly 10,000 year interglacial warm period.
Causes:
Ice ages don’t just come out of nowhere – it takes thousands of years for an ice age to begin.
An ice age is triggered when summer temperatures in the northern hemisphere fail to rise above freezing for years. This means that winter snowfall doesn’t melt, but instead builds up, compresses and over time starts to compact, or glaciate, into ice sheets.
Over thousands of years these ice sheets start to build up – it seems to be in northern Canada when that first happens – and then they spread out across the northern hemisphere.
“It’s a long term trend over thousands of years to colder summers,” Dr Steven Phipps, an ice sheet modeller, said.
Dr Phipps is also a climate system modeller and palaeoclimatologist with the University of Tasmania.
The onset of an ice age is related to the Milankovitch cycles – where regular changes in the Earth’s tilt and orbit combine to affect which areas on Earth get more or less solar radiation.
When all these factors align so the northern hemisphere gets less solar radiation in summer, an ice age can be started.
Picture Credit : Google