Ocean temperature
Current Tasmanian ocean temperatures
In Tasmania, water temperatures vary from an average of 12 degrees Celsius in late winter, to an average of 18 degrees Celsius in late summer, with greater fluctuations in sheltered coastal areas and estuaries. Every month since 1944, temperature, salinity, nutrients and, more recently, phytoplankton/zooplankton data have been collected at Maria Island off the east coast of Tasmania. This project was recently extended as part of the Integrated Marine Observing System (IMOS) (http://imos.org.au) so temperature, salinity, oxygen levels, turbidity and fluorescence (to give a measure of productivity otherwise known as chlorophyll a) are automatically measured by water quality meters every 10 minutes.
Meet Dr Katty Hill, the Scientific Officer for the Integrated Marine Observing System (IMOS) at the University of Tasmania in Hobart. She has been collecting and compiling data about the causes of the changes in the strength of the East Australian Current (EAC), and its affect on water temperatures around Tasmania.
Katy has analysed 50 years of temperature data collected at the Maria Island research station. The results show that the observed warming at Maria Island are three times the global average, at 2.28 degrees Celsius per century (with a large 1 degree rise Celsius between 1944 and 1998). In Tasmania this is primarily caused by the increased extension and strength of the East Australian Current (EAC) bringing warmer water from the north.
Katy Hill working on a ship in the Southern Ocean, South of Africa taking measurements of the ocean.
Sea surface temperatures at Maria Island for 50 years showing the upward trend of sea temperatures.
Projected temperatures
A temperature rise of a few degrees does not really sound like a lot; it actually sounds quite nice, especially if you have ever been swimming in the chilly Tasmanian sea. However, in reality, a rise of even one degree Celsius is expected to have significant impact upon the biological systems of the ocean, which are highly evolved and conditioned to current temperatures.
Meet DR Alistair Hobday a researcher at the CSIRO Climate Adaptation Flagship, Marine and Atmospheric Research division. Alistair uses modelling to project changes in the ocean temperatures around Tasmania, and in particular the impact of the EAC.
Dr Alistair Hobday diving on holidays, not just for research.
Alistair has provided Redmap with a set of six images which compares the present extent of the EAC during summer and winter with the projected conditions of 2030 and 2070. The scenarios used to develop these images are 'high emission scenarios (CSIRO call them A1FI projections) projecting what may happen if emissions were to increase into the future.
Projections of the effects of climate change on Tasmanian marine temperatures and the extent of the EAC
Present conditions:
In recent years, average summer temperatures in the waters off Tasmania's east coast barely reach the low 20s. The southern extent of the warmest EAC waters is restricted to Bass Strait, Flinders Island and the north coast. During winter waters are less than 15 degrees Celsius.
2030 projected conditions:
By 2030, waters off eastern Tasmania are projected to be warmer, due in part to local warming as well as an extension south of the warm EAC; projections show some impact of the EAC along most of the east coast during summer. Summer temperatures may reach the mid 20s, and extend to the north-east coast. During winter, waters are also projected to warm but the influence of the EAC is minor. Due to local warming and the effect of the EAC, the east coast of Tasmania is expected to reach temperatures equivalent to those currently experienced by eastern Victoria.
2070 projected conditions:
By 2070 there are significant changes predicted in the extent of the EAC, with projections showing that the entire east coast will experience temperatures in the low to mid 20s in summer. Winter temperatures will be higher and the EAC will persist for longer in southern waters. Due to underlying warming and the effect of the EAC, the east coast is expected to reach temperatures equivalent to those currently experienced by southern New South Wales by 2070.
You too can research the temperatures of the ocean like Katy and compare your findings to actual temperature data collected from Tasmanian locations. Just follow this link to the instructions and worksheets to measure ocean temperature in northern, southern, north-eastern and western Tasmania.
Do you want to know more about increasing temperature and its effect on our oceans? Check out these links:
Tasmanian ocean temperature data collected every 10 minutes can be seen in real time online. To see this data go to http://imos.aodn.org.au and click on the real time tab.
Southern Tasmanian Temperature, salinity, conductivity readings are provided on this site by real time wireless sensors for the latest information go to http://www.marine.csiro.au/wfowsn/wfowsn.jsp
The CSIRO Marine Research Remote Sensing facility provides Sea Surface Temperature images (from the USA’s National Oceanographic and Atmospheric Administration satellites). Just click your mouse over an area to find out the temperature: http://www.marine.csiro.au/~lband/web_point/
Source information for temperature:
A special thanks to Katy Hill, Alistair Hobday and Mike Porteus for their significant contributions including images and content to the Temperature Page.
G.J. Edgar, N.S. Barrett and D.J.(1999) Graddon A Classification of Tasmanian Estuaries and Assessment of their Conservation Significance using Ecological and Physical Attributes, Population and Land Use. Technical Report No. 2, Tasmanian Aquaculture and Fisheries Institute.
Hill K. L, S. R. Rintoul, R. Coleman, and K. R. Ridgway, Wind-forced low frequency variability of the East Australian Current, Geophysical Research Letters, 35, L08602, doi:10.1029/2007GL032912, 2008.
Pecl G, Frusher S, Gardner C, Haward M, Hobday A, Jennings S, Nursey-Bray M, Punt A, Revill H, van Putten I (2009). The east coast Tasmanian rock lobster fishery – vulnerability to climate change impacts and adaptation response options. Report to the Department of Climate Change, Australia.
