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When melt water leaves an ice sheet, where does it go? 

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Some of it it quickly flows off the surface of the ice toward the ocean

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through underground channels. But some water gets trapped near the top of the ice sheet

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in a region of compacted snow which has not yet 

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been squeezed hard enough to become solid ice. 

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This region is known as firn and it sits between the fresh snow above and the solid ice below. 

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In some places, so much water can accumulate in the firn 

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that it acts as a natural aquifer within an ice sheet or a glacier.

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A new NASA study of the massive Helheim Glacier 

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in eastern Greenland shows that some of the water trapped in the firn

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may be reaching the bedrock of the glacier through giant cracks in the ice

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called crevasses. 

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Helheim is criss-crossed by a series of these large crevasses, 

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and models show that the water flows into these crevasses and descends all the way down to the glacier bed.

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From there, the water has a clear path to the ocean.

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This study is a step toward understanding how firn aquifer water 

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contributes to sea level rise.