Final answer:
The statement is true; the massive weight of the Antarctic ice sheet, which averages up to a mile thick, pushes portions of the continent below sea level. The existence of subglacial basins like the Wilkes Subglacial Basin confirms this. The ice sheet also contains about 70% of the Earth's fresh water, indicating its significance in global sea level regulation.
Step-by-step explanation:
The statement that the Antarctic ice sheet holds the underlying rock below sea level is indeed true. The Antarctic ice sheet is a massive expanse of ice covering about 98% of the continent of Antarctica. This ice sheet is quite deep, averaging up to a mile in thickness and extending in some areas up to nearly three miles deep. Due to the weight and volume of the ice, portions of the continent are pushed below sea level. The presence of subglacial basins, such as the Aurora Subglacial Basin, the Recovery Subglacial Basin, and the Wilkes Subglacial Basin, demonstrate that the landscape below the ice includes areas that are below sea level. These basins were identified using geological and geophysical methods and are further corroborated by marine sediment cores taken from the ocean floor near the continent.
The vast size of the Antarctic ice sheet is also significant in terms of global water storage, holding approximately 70% of the Earth's fresh water. This fact underscores the importance of the ice sheet relative to global sea levels. If the ice was to melt due to climate change, it would lead to a considerable rise in sea levels, affecting low-lying regions globally. Aspects such as subglacial lakes, including Lake Vostok which lies two miles beneath the ice sheet, show that there are significant features sheltered by the ice that are substantial both scientifically and in terms of water storage. The ice sheet's influence on the underlying rock and topography is a critical aspect of Antarctic geography that has implications for understanding past and future climate conditions.