By comparison, the study says, ice breaking off and melting from Greenland’s ice sheet contributes 28 per cent of the world’s ice to the oceans, and the Antarctic ice sheet a further 12 per cent.
The accelerating contribution of glaciers and ice caps is due in part to rapid changes in the flow of tidewater glaciers that discharge icebergs directly into the ocean, the researchers say.
When the glacier with its "toe in the water" thins, they says, a larger fraction of its weight is supported by water and it slides faster and sends more ice into the ocean.
Alaska’s Columbia Glacier, which drops 3cukm into Prince William sound, had shrunk about 14.5km since 1980 and was expected to shrink the same amount in the next two decades, said geologist and co-author of the study Robert Anderson.
The melting of the ice sheets of Greenland and the Antarctic is not expected to catch up with that of glaciers and ice caps untilthe end of the century, the study says.
The researchers estimate the accelerated melting of glaciers and ice caps will add 10.2cm-24.1cm to the sea level rise globally by 2100. The figures do not include the expansion of the oceans as they get warmer, which could double the levels.
A 30cm rise in the sea level causes a shoreline retreat of 30m or more, they say, and about 100million people live within about 1m of sea level.