Research

Sea level change: Tide Gauges measure only relative sea level change and their records must be corrected for vertical land motion. I am leading work on developing consistently reprocessed GPS coordinate time series and applying them to the sea level problem. Other activities include secular geocentre motion from GPS and polar ice mass contributions to sea level

Glaciology: Geodetic techniques are able to provide important new insights into the dynamics and mass balance of the major ice sheets. I am working on application of GPS for studies of tidal and hydrological interactions with the ice sheets, ice sheet mass balance with GRACE and GOCE, and continuing work from my PhD on the dynamics of the Amery Ice Shelf and its change since the 1960s.

Glacial Isostatic Adjustment: Current efforts relating to GIA are focused on Antarctica, with projects focusing on existing and new GPS measurements of GIA. In 2009-10, we will install 7 new GPS receivers in the southern Antarctic Peninsula region to measure GIA. I am currently Chair of COST Action ES0701, a pan-European project seeking to provide improved constraints on models of GIA and its application to ice mass balance estimates from GRACE.

Tides: Prediction of ocean tide is now possible with an accuracy of a few centimetres over much of the global ocean. The exceptions are the shallow seas and Polar oceans. My focus is on the Polar oceans, directly measuring ocean tides on large ice shelves in Antarctica using GPS (in 2007-8 on the Filchner-Ronne and Larsen C ice shelves) and indirectly through onshore GPS loading displacement measurements. Other tidal work involves investigations into the anelasticity of Earth at tidal periods.

GPS Research: The GPS error spectrum is not well understood and poorly defined signals are evident at >1 mm levels at periods from sub-daily to quasi-secular. Sub-daily signals also propagate to longer periods in 24 h solutions. These bias estimates of geophysical signals - current investigations include propagation of sub-daily signals to longer periods using real and simulated data and signals in long-running short (<1km) baselines.