Sea Level Variability in Coastal Marine Systems

Sea level along coastlines fluctuates on a multitude of temporal and spatial scales, driven by long-term trends, seasonal cycles, meteorological events and oceanographic processes. Gradual changes arise from global climate warming, leading to thermal expansion of seawater and melting of land ice, while regional patterns are modulated by changes in atmospheric circulation, ocean currents, coastal geomorphology and land movements. Superimposed on these trends are seasonal oscillations linked to wind regimes, river discharge and gravitational effects of tides. Extreme events such as storm surges and tidal amplification can produce sudden and locally severe inundations. Accurate characterisation of these variations is essential for coastal planning, ecosystem management and the protection of human settlements. Measurement techniques range from in situ tide gauges to satellite altimetry and numerical modelling, each offering complementary insights into the physics of sea level change and variability. As sea level rise accelerates, understanding both mean and extreme fluctuations in coastal marine systems underpins adaptation strategies and informs the design of resilient infrastructure.

Research from Nature Portfolio

Recent studies have advanced the decomposition of surface currents to reveal how pressure-driven and wind-driven components shape sea level variability. By separating geostrophic and ageostrophic currents, researchers have identified two dominant circulation regimes corresponding to spring and winter climatologies in enclosed basins. Machine learning tools applied to wind vectors and sea level anomaly fields now enable robust recognition of these regimes, clarifying how shifts in atmospheric forcing translate into changes in coastal sea surface height. This integrated approach quantifies the relative influence of dynamic topography and wind-driven flows on seasonal and interannual sea level patterns, offering improved predictive capability for regional coastal management.

Sea Level Variability in Coastal Marine Systems publication trend

The graph below shows the total number of articles in sea level variability in coastal marine systems across all publications each year (not limited to Nature Index journals).

Technical terms

Sea level anomaly: Deviation of the instantaneous sea surface height from its long-term mean, often used to highlight transient events.

Dynamic topography: Elevation of the sea surface above the geoid due to horizontal pressure gradients and ocean currents.

Geostrophic current: Oceanic flow that results from a balance between the horizontal pressure gradient force and the Coriolis effect.

Ageostrophic current: Component of flow not in geostrophic balance, driven by wind stress, friction or acceleration.

Storm surge: Temporary rise in coastal water level caused by low atmospheric pressure and strong onshore winds during storm events.

Bayesian hierarchical modelling: Statistical approach that pools information across multiple sites or datasets, accounting for site-specific and shared uncertainties.

References

1. Sea surface circulation in the Baltic Sea: decomposed components and pattern recognition. Scientific Reports (2024).
2. Bayesian hierarchical modelling of sea-level extremes in the Finnish coastal region. Natural Hazards and Earth System Science (2023).
3. The Impact of Serial Cyclone Clustering on Extremely High Sea Levels in the Baltic Sea. Geophysical Research Letters (2024).
4. Determination of Accurate Dynamic Topography for the Baltic Sea Using Satellite Altimetry and a Marine Geoid Model. Remote Sensing (2023).