Glaciers fix time. Glacial ice can range in age from several hundred years to several hundreds of thousands of years. The ice contains little bubbles, preserving the atmosphere from the date of their formation, and revealing what the climate was like at the time. From this information past climatic periods can be reconstructed, showing how and why climate changed, and giving a lead to how it might change into the future. For the last century, with few exceptions, glaciers around the world have been retreating, consistent with the increase in global mean air temperature associated with the production of climate-influencing gases. 

The Greenlandic icebergs are photographed at the UNESCO heritage site at Disko Bay, near Ilulissat, some 300 km north of the Arctic Circle. They are carved from the Eqip Sermia glacier. The visual experience is akin to that of a continually reshaping landscape, like a vast chessboard of moving ice-pieces.

The Jökulsárlón  icebergs in Iceland are carved from the he Hvannadalshnúkur  Glacier. These icebergs present faces of solidity, dignity and power, but this belies their increasing vulnerability. Over the last century these glaciers have been in retreat, a phenomenon linked with increases in atmospheric CO2 and air, sea and land temperatures. These vast storehouses of fresh water are being released into sea at an increasing rate, raising the prospect of worldwide rising water levels. Some scientists predict that climate change may be approaching a "tipping point" resulting in a gradual, if inevitable, removal of the north polar ice sheet.