Zeeniveaus

Zeeniveaus is the Dutch term for sea levels, describing the height of the ocean surface relative to a reference frame such as the geoid and the land. The concept covers both the global average level and regional variations. Global mean sea level (GMSL) is estimated from satellite altimetry and long-running tide gauges and serves as a baseline for climate-related changes.

Since the late 19th century, GMSL has risen, with an accelerating trend in recent decades. The rise is caused mainly by two processes: thermal expansion of seawater as it warms and the added water from melting glaciers and ice sheets. Regional sea level can differ from the global average due to variations in ocean currents, wind patterns, atmospheric pressure, and vertical land motion (subsidence or uplift).

Measurement relies on a combination of autonomous tide gauges along coastlines and ocean-observing satellites (for example, TOPEX/Poseidon, Jason series, and newer missions). These tools monitor changes over time, allowing scientists to attribute causes and project future levels, with regional projections varying based on local factors.

Impacts of rising zeeniveaus include increased coastal flooding, higher storm surge risk, erosion, and saltwater intrusion into aquifers and ecosystems. Adaptation strategies encompass coastal defenses, careful land-use planning, and, in some places, managed retreat.