指有丝分裂前期结束后，在中期前段这一时期，在核膜即将破裂时，于核两极四周出现的一种透明带。极帽呈圆锥型，轮廓不清晰，外观上显有如核中渗出的状态，在沿核两极的长轴上，显出微弱的复折射性。这一时期特称为极帽期（polar cap stage）。
如果这种变暖发生，两极的冰帽将开始融化，从而使海平面上升数米，并严重淹没沿海城市。
If this warming up took place, the ice caps in the poles would begin to melt, thus raising sea level several metres and severely flooding coastal cities.
他会警告负责极区的部长，如果再不下措施抑制温室气体的排放，则北极的冰帽将在五年内完全消失。
He is expected to warn ministers in polar regions that the arctic ice cap may totally disappear in as little as five years if nothing is done to curb greenhouse emissions.
今年，姗姗的爸爸成为了飞两极冰帽的航班上的飞行员。
This year, Shanshan's dad was a pilot on flights over the Polar Cap.
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