Being the "expert" you claim, would expect you have the answer.
North polar has significant bodies of water scattered about within, such that warm ocean currents can reach within and limit thickness and extent of ice on water surface, plus accumulation on most coastal areas. Most of the permanent and thicker ice, is on Greenland which is large enough to produce the effect similar to Antarctica. The major central portion of North polar circle is ocean and ice often is only a few feet thick, why we've seen photos of submarines breaking through.
Southern polar has the huge land mass of the Antarctic continent centered within the major portion of the circle, 'warm' water flow is only around the outer edges. Land masses retain cold more than water does, hence ice melts less frequently, and slower, making accumulations in thickness more easily attained.
Ice core samples from both Greenland and Antarctica show extensive ages spanning more than centuries, going into millennial ranges. The ice layers going into scores to hundreds of feet thickness.
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