4 More of the ice that covers the Arctic Ocean in winter is now melting in summer This photograph was taken in August 2012 The orange line shows how much more ice there was at the end of summer in 2005 Meltdown The Arctic and Antarctic are so cold that masses of thick ice called ice caps cover the sea and the land all year round People used to take the ice caps for granted but now they are beginning to melt This book looks at what will happen as each ice cap disappears This will affect the whole Earth and people everywhere 4 Ice caps shrink in spring and summer as some of the ice melts but they refreeze in winter For thousands of years the overall size of the ice caps has remained much the same However since 2000 things have begun to change dramatically When do ice caps melt the most
Very high mountains such as Mount Cook in New Zealand remain covered by snow all year round even in summer Now these mountain ice caps are shrinking too Nearly 70 percent of the world’s freshwater is held in land ice If all of it melted the level of the oceans would rise by a staggering 230 feet 70 m swamping coastlines The Antarctic ice cap is the biggest in the world It consists of frozen freshwater and covers nearly 8 7 million square miles 14 million sq km It is up to 2 5 miles 4 km thick Almost the whole of the island of Greenland is covered with land ice up to 2 miles 3 km thick The ice cap that covers the Arctic Ocean consists of frozen seawater This sea ice covers between 5 6 and 7 5 million square miles 9 and 12 million sq km and is up to 13 feet 4 m thick Is it true Many people did not believe scientists when they first said that the Earth is getting warmer and that the ice caps would melt Today measurements show that more and more ice is melting each summer Worse still it is melting faster than the scientists predicted 5 Number Crunching
6 When ice melts it reveals dark water and land Dark surfaces absorb much more of the Sun’s heat than white snow and ice Why is the Ice Melting Polar ice is melting because the air at the surface of the Earth is getting warmer This is called global warming The pace of warming varies around the world but the Arctic is warming six times faster than the average increase in temperature This is not the first time that the ice caps have melted For example 100 million years ago when the dinosaurs lived the world’s climate was about 36º Fahrenheit 2º C warmer than it is now The current global warming is different however It is happening much faster and the scientific evidence shows that it is humans who are causing it 6 Have the ice caps melted before
7 Heat trap The Earth is becoming warmer because more of the Sun’s heat is being trapped in the atmosphere It is trapped by gases particularly carbon dioxide and methane which are known as greenhouse gases Every year people produce billions of tons of greenhouse gases when they burn fossil fuels coal oil and natural gas They burn them for example to generate electricity and to run cars aircraft and other vehicles 7 An aircraft can travel a long way very fast However aircraft burn vast quantities of fuel and so create massive amounts of carbon dioxide and other greenhouse gases which all contribute to global warming What happens next If we do not stop burning fossil fuels the temperature of the Earth will continue to rise In that case the first ice cap to melt will be the Arctic ice sheet Ice is white and reflects the Sun’s heat When the Arctic sea ice melts the dark water below absorbs the Sun’s heat and warms up The warmer sea melts more ice The land around the Arctic Ocean is called the permafrost because it is permanently frozen Now the permafrost is beginning to melt
