Marine Climate

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East Australian Current

Tasmania eac

Lead Author: 

Ken Ridgway 1

Co Authors: Katy Hill 2

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What is happening?

The intensification of flow and accelerated warming observed in the EAC is also seen in other Southern Hemisphere western boundary current systems, driven by the strengthening and contraction south of Southern Hemisphere westerlies (wind), although regional responses mean rates of warming differ among systems. A range of species, including plankton, fish and invertebrates, are now found further south because of enhanced transport of larvae and juveniles in the stronger EAC and the high rate of regional warming.

What is expected?

EAC flow will increase off southeast Australia with a compensating decrease off north-east Australia.

What we are doing about it?

New observations established as part of IMOS are beginning to provide an integrated view of the EAC. Long-term monitoring at Maria Island (Tas),and Port Hacking (NSW), are being sustained and enhanced as part of a network of National Reference Stations; a new station has also been established at North Stradbroke Island (Qld). IMOS is also supporting the Ships of Opportunity XBT network (provides temperature profiles every 25 km along ship tracks) in the Tasman Sea, which captures key limbs of the EAC system; and is delivering these data in real time.

Summary

The East Australian Current (EAC) is a complex and highly energetic western boundary system in the south-western Pacific off eastern Australia. The EAC forms part of the western boundary of the South Pacific Gyre and the linking element between the Pacific and Indian Ocean gyres.

The EAC is similar to other western boundary currents and is dominated by a series of mesoscale eddies which produce highly variable patterns of current strength and direction. Seasonal, interannual and particularly strong decadal changes are observed in the EAC which tend to mask the underlying long-term trends related to greenhouse gas (GHG) forcing.

Observations from a long-term coastal station off Tasmania show that the EAC has strengthened and extended further southward over the past 60 years. The south Tasman Sea region has become both warmer and saltier with mean trends of 2.28°C/century and... continued on the full report

Ocean acidification

Carbonic-acid-3d-vdw

Lead Author: 

William R. Howard 1

Co Authors: Merinda Nash 2, Ken Anthony 3, Katherine Schmutter 4, Helen Bostock 5, Donald Bromhead 6, Maria Byrne 7, Kim Currie 5, Guillermo Diaz-Pulido 8, Stephen Eggins 9, Michael Ellwood 9, Bradley Eyre 10, Ralf Haese 11, Gustaaf Hallegraeff 12, Katy Hill 13, Catriona Hurd 14, Cliff Law 5, Andrew Lenton 15, Richard Matear 15, Ben McNeil 16, Malcolm McCulloch 17, Marius N. Müller 12, Philip Munday 18, Bradley Opdyke 9, John M. Pandolfi 19, Russell Richards 20, Donna Roberts 21, Bayden D. Russell 22, Abigail M. Smith 23, Bronte Tilbrook 15, Anya Waite 17, Jane Williamson 24

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Dr Donna Roberts and Dr Will Howard


Author: Marine Climate Change 2012
Ocean Acidification - Carbon dioxide dissolving in the oceans has lowered pH by 0.1 units since 1750, representing a 30% increase in hydrogen ion (acid) concentration | Time: 12.42 min

What is happening?

Most conclusions about biological responses to ocean acidification in Australian waters come from laboratory manipulations rather than observations. However, reduced calcification observed in Southern Ocean zooplankton suggest ocean acidification is already impacting biological systems.

What is expected?

Great Barrier Reef corals and coralline algae will continue to experience reduced calcification rates. Benthic calcifiers, such as molluscs and deep-water corals in Antarctic and southern Australian waters, will show reduced calcification and/or increased dissolution.

What we are doing about it?

Research is underway to improve the methods and equipment used for high-precision carbonate chemistry measurements. Monitoring of carbon chemistry in the open ocean and some shallow coastal systems, including the Great Barrier Reef, has already commenced. Research is underway to investigate effects of ocean acidification on whole coral ecosystems in the Great Barrier Reef.

Summary

Increasing atmospheric CO2 concentration is causing increased absorption of CO2 by the world’s oceans, in turn driving a decline in seawater pH and changes in ocean carbonate chemistry that are collectively referred to as ocean acidification. Evidence is accumulating to suggest ocean acidification may directly or indirectly affect many marine organisms and ecosystems, some of which may also hold significant social and economic value to the Australian community.

This report aims to provide a brief overview of the current state of scientific knowledge regarding the process of ocean acidification; current and future projected levels of ocean acidification; and, observed and projected impacts of current and future predicted levels of ocean acidification on marine organisms and ecosystems in the region. This report also briefly discusses potential social and economic implications, policy... continued on the full report

Temperature

Temperature

Lead Author: 

Janice M. Lough 1

Co Authors: Alex Sen Gupta 2 and Alistair J. Hobday 3

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What is happening?

Ocean temperatures around Australia have warmed by 0.68oC since 1910-1929, with south-west and south-eastern waters warming fastest. The rate of temperature rise in Australian waters has accelerated since the mid-20th century; from 0.08oC/decade in 1910-2011 to 0.11oC/decade from 1950-2011.

What is expected?

New results based on a relatively high scenario for greenhouse gas emissions (RCP8.5) indicate greatest warming in south-east (>3oC) and north-west waters (~2.5oC) by the end of this century.

What we are doing about it?

Investing in regional monitoring as part of the Integrated Marine Ocean Observing System (IMOS) to measure changes in ocean temperatures. Developing ocean models to project changes in coming decades. Ongoing development of seasonal forecasting models and applications to support timely adaptation responses by marine users.

Summary

Sea surface temperature (SST) surrounding Australia has undergone significant warming since the early 20th century. Average SST for the most recent 20-year period (1992-2011) was 0.68oC warmer than the period 1910-1929. This significant change in regionally-averaged SST is of similar magnitude to the warming of Australian air temperature (+0.74oC) and to globally-averaged land and sea temperatures (+0.71oC) between the same two periods. Australian region SST for every decade from 1921-1930 through 2001-2010 has been warmer than the preceding decade. The rate of globally-averaged temperature rise has accelerated since the mid-20th century; similarly, for Australian waters the rate of warming was 0.08oC/decade from 1910-2011 and 0.11oC/decade from 1950-2011. Since the first Report Card in 2009, the then warmest year (1998) for Australian region SST has been superseded by that in 2010. 15... continued on the full report

Sea level

Coast

Lead Author: 

John A. Church 1

Co Authors: Neil J. White 1, John R. Hunter 2 and Kathleen L. McInnes 1

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What is sea level rise?


Author: GreenCrossAustralia
John Church, CSIRO Fellow Centre for Australian Weather and Climate Change explains sea level rise. | Time: 4.15 min

What is happening?

Sea levels are rising around Australia, with fastest rates currently in northern Australia. New analyses of sedimentary records from the east coast of Tasmania confirm slow sea-level change over 1000s of years until the early 20th century, when there was a significant acceleration in the rate of sea-level rise. High sea-level events on annual to decadal timescales have increased by a factor of three during the 20th century.

What is expected?

Sea level will continue to rise during the 21st century and beyond, and result in inundation of low-lying coastal regions and coastal recession.

What we are doing about it?

Satellite altimeters and the Australian Baseline Sea Level Monitoring Array have provided a comprehensive picture of sea level around the Australian coastline since the early 1990s. Adaptation planning will be informed by national and regional assessments of coastal inundation and recession due to future changes in sea level and wave climate.

Summary

Many Australians live near the coast but coastal regions and their valuable ecosystems are threatened by rising sea levels. Globally, sea level is now rising after several centuries of relatively stable values. The rate of rise increased from the 19th to the 20th century and during the 20th century. The average of global-averaged sea-level rise during the 20th century was about 1.7 mm yr-1. The current rate (1993 to present) is about 3.1 ± 0.4 mm yr-1. Sea levels are rising around Australia and the frequency of extreme high sea-level events that occur on annual to decadal timescales has increased by a factor of about three during the 20th century. Sea-level rise is a result of expansion of the oceans as they warm and the addition of mass to the ocean from glaciers and ice caps, and the ice sheets of Greenland and Antarctica. Sea level will continue to rise during the 21st century and... continued on the full report

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Marine Environment

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Tidal Wetlands

Tidal wetlands

Lead Author: 

Catherine E Lovelock 1

Co Authors: Greg Skilleter 2, Neil Saintilan 3

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What is happening?

The red mangrove Rhizophora stylosa is expanding within its range at its southern limits; the expansion is still to be attributed to climate change however knowledge of thermal limits suggests warming plays a role.

What is expected?

Increasing levels of atmospheric CO2 will increase tidal wetland productivity over the coming century. Sea-level rise will affect tidal wetlands, however spatial variation in sea-level rise, large and variable tidal ranges, and data gaps for large portions of the Australian coastline reduce our confidence in predictions for some regions.

What we are doing about it?

Systems to monitor surface height have been deployed in Moreton Bay, south-east Qld and in tidal wetlands in southern Australia The network will provide greater knowledge of possible thresholds of sea-level rise that exceed the adaptive capacity of coastal mangrove and saltmarsh ecosystems to keep pace.

Summary

Climate change is likely to have a strong impact on mangroves, salt marshes and other tidal wetlands. Their position in the intertidal exposes them to a multitude of ocean and atmospheric climate change drivers which leads to high vulnerability to climate change. Tidal wetlands are extremely sensitive to sea level rise. For example, too much flooding and mangroves will “drown”, too little and their productivity will be reduced and they may be replaced with salt marsh or cyanobacterial communities. The strong regulation of productivity and species composition by soil salinity and humidity (influenced by rainfall, river flows and groundwater) in tidal wetlands also makes these ecosystems highly sensitive to changes in rainfall. At the southern edge of their distribution mangroves are likely to often be limited by minimum temperatures and thus rises in air and sea temperatures is... continued on the full report

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