Measuring Changes in Sea Level Around Antarctica

This study focusses on the wharf mounted tidal gauge at Casey station in the Australian Antarctic Territory. The data collected from the gauge had largely remained unprocessed and survey data to the tidal gauge not collated. The main aim of the project was to process the data and ascertain a sea level record from around Casey station, whilst making corrections in the data for bedrock uplift (glacial isostatic adjustment (GIA)) which can be picked up on the Casey station GNSS receiver that forms part of the Australian Regional GNSS network. The Australian Antarctic Division (AAD) has four stations as a part of Australia’s Antarctic Territory, three of which are on the continent of Antarctica, Casey, Mawson and Davis and one sub-Antarctic station, Macquarie Island. Since approximately 1996 each station has been collecting sea level data via a variety of pressure sensors, which have been upgraded and improved over the years. At Casey pressure and temperature readings from top and bottom wharf mounted sensors are recorded and sent to an instrument cabinet where they are stored on a data logger. A barometer and temperature sensor inside the wharf hut also records data. The barometer is required to measure sea level pressure in order to be able to calculate the height of the water column. This wharf mounted gauge has been recording data since 2008, however minimal processing of data has occurred to date. Raw CSV files provide by the AAD were stitched together with sea water density and water column height above the bottom pressure sensor calculated over a time series using Excel. Data was then processed to eliminate sea level variations due to tidal constituents and high frequency climatic fluctuations (Gharineiat & Deng, 2018) using MATLAB. Data was corrected for GIA, using the figures provided from the Casey Station GNSS receiver. A costal sea level trend was calculated for Casey station over the period of approximately 11 years, and stability of the wharf was investigated, and found to have minimal movement providing assurance on the stability of the tidal gauge. A sea level rise of 4.2 mm/year was calculated, though it was identified that there was a high level of uncertainty associated with this rate, possibly due to too much ‘noise’ in the data. The sea level history obtained from the tidal gauge at Casey station provides useful information, however for any conclusive outcomes to be drawn on whether there has been local sea level rise, a twenty year history would need to be obtained in order to remove the effects of decadal cycles, such as long period lunar effects. This length of data at Casey station is not yet available