Weather and climate touch all aspects of Australian life. The ocean drives the climate system, and the impacts of ocean variability and ocean change will affect our society across generations. Improving our understanding is fundamental to better decision-making by governments, industries and communities into the future.
In State of the Climate report, long-term trends in Australia’s climate are discussed. This is the third biennial State of the Climate report. As with the earlier reports, the report focuses primarily on climate observations and monitoring carried out by the Bureau of Meteorology and CSIRO in the Australian region, as well as on future climate scenarios.
Key points for the ocean are:
- Sea-surface temperatures in the Australian region have warmed by 0.9°C since 1900.
- The Earth is gaining heat, most of which is going into the oceans.
- Global mean sea level increased throughout the 20th century and in 2012 was 225 mm higher than in 1880.
- Rates of sea-level rise vary around the Australian region, with higher sea-level rise observed in the north and rates similar to the global average observed in the south and east.
- Ocean acidity levels have increased since the 1800s due to increased CO2 absorption from the atmosphere.
Observations provided by Australia’s Integrated Marine Observing System (IMOS) contribute to the report findings in four key sections:
Sea-surface temperature: remotely sensed sea surface temperature (SST) data are important inputs to climate models, and there is a need for high quality in-situ SST observations to improve validation of satellite SST and ocean models. IMOS provides streams of high quality, near real-time (within 24 hours), SST observations from 14 vessels in previously un-validated regions around Australia such as coastal areas and the Southern Ocean.
Ocean heat content: ocean heat and salinity to a depth of 2,000 metres below the surface are observed by the global Argo float array. IMOS deploys 30 floats per annum through Argo Australia, which along with other national and international deployments has resulted in 10% of the global array of 3,800 floats delivering a continuous data stream for the Australian region.
Sea level: satellites monitoring the height of the ocean (called altimeters) are the tool of choice for studying sea level rise. Precise measurement from space pushes these satellite systems to their limits and some high quality measurements from within the ocean are required. State-of-the-art GPS buoys maintained by IMOS provide the only altimeter calibration and validation sites in the Southern Hemisphere.
Ocean acidification: ocean acidity is measured in units of pH, and is monitored globally via a number of platforms including a network of repeat hydrographic surveys, time-series stations, floats and glider observations, and volunteer observing ships. IMOS maintains three acidification time-series stations around Australia (Kangaroo Island, Yongala and Maria Island) as well as measurements from volunteer observing ships, and data from these stations is contributing to the new Global Ocean Acidification Observing Network (GOA-ON).
For further information and to download the full report:
Bureau of Meteorology www.bom.gov.au/state-of-the-climate/