Measuring changing sea levels as a response to climate change represents a challenging problem. Current sea level rise estimates are at the 1-2 mm/yr level, hence extremely accurate measurement is required to observe any change. Satellite altimeters are the tool of choice to measure sea level change due to their global coverage - they measure over the same spot roughly every ten days.
Calibration of the satellite altimeters is vital to ensure the measurements of sea level are accurate and are not drifting over time. As part of a global effort, this project involved undertaking a series of calibration measurements in Bass Strait, approximately 40km north west of Burnie.
The aim of the calibration study was to measure the absolute bias of the satellite altimeter - this was done using a range of instrumentation placed along the coastline and out at sea. The main equipment included two GPS equipped buoys which measure sea surface height every 1 second. The buoys are custom made out of flower pots - purely because the antennas were a perfect fit in the flower pot container. Results from the GPS buoys are accurate at the 1-2 cm level - some kilometers out to sea.
Results from the study revealed some puzzling anomalies associated with the newest altimeter - Jason-1. These results were confirmed from other calibration sites operated by NASA and the French Space Agency, CNES. In light of the results, other scientists using the altimeter data can modify exactly how the data is used to achieve the highest possible accuracy.
The project was undertaken at the School of Geography and Environmental Studies in collaboration with CSIRO Marine Research.
For more information on this particular project, follow the links below.
Subject link: PhD
Staff link: Christopher Watson