How do glaciers affect global sea level and the amount of exposed continental land?

In the context of paleogeography, the growth and retreat of glaciers are primary drivers of eustatic sea-level changes, which significantly alter the amount of exposed continental land.12

Impact on Sea Level

The world's oceans serve as the ultimate source of water for glacial ice. When global climates cool, water that would otherwise remain in the ocean basins is locked up as ice on land, causing global sea levels to drop. Conversely, as glaciers retreat during warmer interglacial periods, this meltwater returns to the oceans, resulting in a rise in sea level.324

Impact on Exposed Land

These fluctuations directly dictate the extent of exposed continental shelves. During periods of maximum glaciation, such as the last glacial maximum 18,000 years ago, sea levels were significantly lower—often by more than 100 metres—which exposed vast areas of the continental margins. This exposure created new land bridges, such as the one that once connected Siberia to Alaska, facilitating the migration of animals and early humans. When sea levels rise, these coastal environments become submerged, moving shorelines landward and flooding previously dry continental areas.415