The linear rate, usually in millimetres per year, fitted to monthly mean sea levels at a tide station over several decades after removing the seasonal cycle. It is relative because the gauge sits on land that may sink or rise, so it measures what coastal residents actually experience. Trends vary from strongly positive on subsiding deltas to negative where land is rebounding after ice loss.
Relative sea level trend here is 3.9 millimetres a year, more than half of it from subsidence.
Trends from short records are dominated by year-to-year noise and the nodal cycle; a few decades of data are needed before the number means much.
Also heard as
- sea level trend
- relative sea level rise
- RSLR
Related terms
Vertical land motion
Sinking or rising of the ground at a tide station, which changes the sea level trend the gauge records.
MSL
Mean Sea Level: the plain average of a station's hourly water levels across the tidal datum epoch.
Tidal datum epoch
The fixed 19-year period over which water levels are averaged to compute official tidal datums.
High tide flooding
Shallow coastal flooding that happens when ordinary high tides exceed a local flood threshold, often without a storm.