冻结核和凝华核总称为冰核，冰晶本身就是冰核。冰核不要求能溶解于水，但要求其分子结构与冰晶类似，便于水分子在核面上按一定的规则排列成为冰晶。水汽能在冰晶表面上直接凝华，使冰晶不断增大，过冷却水滴与冰晶接触一般也会立刻冻结，所以冰晶本身就是冰核。
近代的探险队已经从绿色冰山和冰核中带回了一些冰块样本，这些样本呈垂直的圆柱状，是沿着南极洲大陆的冰川冰架从极深的位置中取出的。
Recent expeditions have taken ice samples from green icebergs and ice cores—vertical, cylindrical ice samples reaching down to great depths—from the glacial ice shelves along the Antarctic continent.
研究人员从格陵兰冰核中遗留的冰泡上能够测出这个变化。
Researchers can measure that change in the bubbles of ice left behind in ice cores in Greenland.
所以，在这里挖出的冰核都能像树木年轮那样按季节数出年份来。
The ice cores pulled up at WAIS will be dated by counting back these seasonal layers as if they were tree rings.
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