Geodetic Oceanography, Polar Oceanography, and Sea Level

POL contribution to Oceans 2025 Theme 1: Climate, Ocean Circulation, and Sea Level.

Global sea level is expected to rise over the 21st century by between 20 and 60 cm, enough to produce large changes in the frequency of extreme flooding events unless expensive changes are made to coastal defences. In order to make informed decisions, good predictions of sea level change are needed, not just globally, but locally.

Global mean sea level is affected by warming of the ocean, which causes it to expand. It is also affected by melting of ice caps and glaciers, and changes to the amount of water stored on land, which lead to changes in the mass of water in the oceans.

In addition, regional sea level is affected by changes in the earth's gravitational field, which causes (and is in part caused by) redistribution of the water in the oceans and on land. It is also affected by ocean dynamics: the currents driven by changing atmospheric forces and sources and sinks of heat and freshwater lead to changes in sea level of up to a metre. The other side of this is that measurements of sea level and ocean bottom pressure can tell us a great deal about the ocean circulation and its important role in heat transport, which is particularly important for those of us to the northwest of the Atlantic. The most dramatic changes in both sea level and climate are expected around the Arctic Ocean.

Finally, it is not only sea level which matters for flooding, but also land level, and it is just as important to monitor and understand changes in land level in order to make useful predictions for the future.

In this theme, we use historical and recent measurements of sea level from tide gauges and satellites together with ocean and earth models and measurements, to understand past and present changes in sea level and land level, and to help produce better predictions of future change. As well as sea level changes, we use geodetic information from GPS and gravity measurements to monitor and understand land movement, satellite gravity measurements to monitor how mass moves around the earth and to help interpret the ocean dynamics associated with sea level, and ocean bottom pressure measurements to cleanly distinguish the effects of mass transport from changes in density in the ocean.

This theme at POL is divided into three Work Packages:

The Ocean Adjustment Process (work package 1.7)
This focuses on the role of ocean dynamics in determining patterns of regional sea level change, and on what can be learnt about the ocean circulation from geodetic measurements - [More].

Arctic Ocean Climate Change (work package 1.8)
This focuses in more detail on the rapidly-changing Arctic region - [More].

Sea Level and Vertical Land Movement (work package 1.9)
This focuses on the interlinked questions of how mass is moving from land to ocean, and the changes in the earth's gravity field and level of the land - [More].

Team members

Dr Rory Bingham
Mr David Blackman
Prof Chris W. Hughes
Prof John Huthnance
Dr Svetlana Jevrejeva
Mr Dave Jones
Mr Danny McLaughlin
Dr Dominik Michel
Dr Miguel Angel Morales Maqueda
Dr Clare Postlethwaite
Dr Vladimir Stepanov
Dr Mark Tamisiea
Dr Graham Tattersall
Dr Simon Williams
Dr Chris Wilson
Prof Philip Woodworth