Sea-Level Variability and Extremes

Sea Level Variability and Extremes

In the next five years, we aim to take significant steps in the advancement of our knowledge concerning global and regional sea-level variability and extremes

The Challenge

Mean sea level has risen at approximately 1.8mm per year over the last 55 years according to observations from 177 coastal tide gauges with near global coverage. However, since 1992, near-global satellite observations using laser altimetry suggest that global sea level is rising at a rate closer to 3mm per year.

The effects of climatic change caused by both human activity and natural variability in the Earth-Ocean system are causing these changes in sea level across the global oceans by a combination of thermal expansion and the addition of mass to the ocean through ice melting. Ocean volume change is associated with the expansion of the ocean as it warms up.  Change in the mass of the ocean is mainly due to melting of glaciers and ice sheets with some contributions from water stored in continental reservoirs or groundwater extraction.

Our Research

Sea level varies on a wide range of time scales, from hours (tides and storm surges) to millions of years (ocean basin changes). The NOC looks at the causes of changes in sea level over all time scales with a strong focus on climate and climatic change processes. Our research uses sea level data from tide gauges and satellite altimetry as well as computer models to predict how sea level will change globally and regionally over the next few decades to centuries. The NOC also uses a variety of techniques to study vertical land movement since this also affects the interpretation of tide gauge data. This involves the analysis of geological records through to modern measurements using the Global Positioning System and other geodetic techniques.

How this provides a benefit to society

By 2050 it is expected that around five billion people will live in coastal areas, and so will be at increased risk from coastal flooding linked to rising sea levels and storm surges. Against this backdrop it is vital to improve predictions of regional sea level change to inform future coastal planning and to develop more reliable flood forecasting systems.

The NOC has made significant contributions towards understanding the causes and contributing factors to sea level change through the analysis of historic data and the collection of new scientific data and the production of new global sea level models. By improving predictions of regional sea level change, NOC’s world-class science can be used to inform future coastal planning and develop more reliable flood forecasting systems thus protecting billions of people.