highstand

A highstand refers to a period when sea level is at its highest point relative to the land. This is often associated with interglacial periods, such as the one we are currently in, where melting ice sheets contribute to higher ocean volumes.12

Sea level itself is the position of the air-sea interface used as a reference for elevations and depths. It is constantly affected by tides, atmospheric pressure, and wind. For longer-term measurements, mean sea level is used, which is the average height of the sea surface over time.3

Throughout Earth's history, particularly during the Pleistocene Epoch, sea levels have fluctuated dramatically. During glacial periods, sea levels dropped significantly as water was locked up in ice sheets, exposing vast areas of continental shelves. Conversely, during interglacial periods, melting ice caused sea levels to rise, sometimes reaching levels higher than today. For instance, about 125,000 years ago, sea level was approximately 6 meters (19.6 feet) higher than it is now.31