Past sea level

Past sea level is the height of the ocean surface at earlier times, reconstructed from geological, biological, and archaeological evidence. It reflects changes in ocean volume and the elevation of the seafloor and land.

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Relative sea level: The height of the sea surface relative to the adjacent land at a particular place and time. Most geological indicators record this local relationship, not ocean height alone.
Glacio-eustasy: Global sea-level change caused by water moving between the oceans and continental ice sheets. Growth and melting of ice sheets transfer large amounts of water into or out of the ocean.
Last Glacial Maximum: The interval when global ice sheets reached their greatest extent during the most recent glaciation, about 26,000 to 19,000 years ago. Its low sea level exposed continental shelves and provides a major benchmark for reconstructions.
Marine Isotope Stage 5e: The warm interval about 129,000 to 116,000 years ago, also called the Last Interglacial. Coastal deposits from this interval constrain sea levels during a climate warmer than the preindustrial climate.
Glacial isostatic adjustment: The continuing deformation of Earth and redistribution of gravity as ice sheets grow or melt. Its spatially varying effects must be modeled to infer global sea level from local records.
Sea-level datum: A reference surface or elevation used to measure heights, often based on observed tidal levels. Reconstructions need a consistent reference for comparing elevations across sites and periods.
Thermal expansion: An increase in a substance’s volume as its temperature rises. Warmer ocean water occupies more volume and raises sea level without adding water.
Holocene sea-level rise: The rise in global mean sea level following the last glacial period, continuing through the Holocene. Its changing rates reveal how deglaciation and later ocean processes shaped modern coasts.
Barbados coral terraces: Elevated fossil coral reefs on Barbados that record former sea-level positions and subsequent land uplift. Their dated corals provide a classic record of Last Interglacial sea level.
Indicative meaning: The relationship between a sea-level indicator’s measured position and the water level it represents. Uncertainty in that relationship can dominate estimates from biological and sedimentary evidence.