Just as the relentless movement of water in rivers and streams can smooth the jagged edges of rocks over time, ocean currents can smooth ice fragments into round shapes.

奔流不息的河水，随着时间流逝，能够将边缘锋利的石头打磨光滑，与此类似，洋流也可以将冰块的边缘打磨圆润。

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It is an extremely complex measurement, because there are so many factors at work: shifting ocean currents, the dynamics and movement of large ice shelves, and the varying temperature and saltiness of water at different places.

WSJ: Polar Ice Sheets Melt at Faster Pace