Marine Climate

Page 1 of 2 pages  1 2 > 

East Australian Current

Lead Author: 

Ken Ridgway 1

Co Authors: Katy Hill 2

Download this report in PDF format: Click here

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

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

Download this report in PDF format: Click here

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

Lead Author: 

Janice M. Lough 1

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

Download this report in PDF format: Click here

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

Lead Author: 

John A. Church 1

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

Download this report in PDF format: Click here

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

Page 1 of 2 pages  1 2 > 

Marine Environment

Page 1 of 4 pages  1 2 3 4 > 

Zooplankton

Lead Author: 

Anthony J. Richardson 1

Co Authors: David McKinnon 2, and Kerrie M. Swadling 3

Download this report in PDF format: Click here

What is happening?

Decline of cold-water zooplankton and increase in warm-water species with warming off eastern Tasmania from the 1970s to the present. Reduced calcification of pteropod snail shells over the past 40 years in northeast and north-west Australia.

What is expected?

Range shifts toward higher latitudes, earlier zooplankton blooms with warming, changes in nutrient enrichment and thus zooplankton abundance, and reduction in pteropod and foram abundance due to acidification will reorganize foodwebs in time and space and impact fish, seabirds and marine mammals.

What we are doing about it?

Australia is now better placed to track and respond to changes in zooplankton abundance, distribution and timing through the IMOS AusCPR (Australian Continuous Plankton Recorder) survey and National Reference Stations program.

Summary

Zooplankton are (generally) microscopic animals that float and have limited ability to swim against currents. Zooplankton play many important roles in marine systems, including directly and indirectly feeding most fish, turtles, seabirds, mammals, and bottom-dwelling animals, shaping the pace of climate change, and producing oil and natural gas deposits by their death and decomposition. In the first Report Card in 2009, there were no published impacts of climate change on Australian zooplankton, but now we have two studies. Between the early 1970s and 2000-2009 off eastern Tasmania, abundances of key cold-water zooplankton species have declined and warm-water species have increased. The second study suggested thinning and increased porosity of shells of two pteropod snails in NW and NE Australia over the past 40 years as ocean pH declined. These changes are likely to be the first of... continued on the full report

Seagrass

Lead Author: 

Rod Connolly

Download this report in PDF format: Click here

What is happening?

A southern range extension of 300 km into Moreton Bay (Qld), of the tropical seagrass Halophila minor consistent with warming and a strengthening East Australian Current.

What is expected?

Declines in seagrass abundance and extent due to sea-level rise and increased storminess. Warming temperatures increase extinction risk for temperate species already considered Vulnerable or Near Threatened under IUCN guidelines. Decline and loss of some species of intertidal seagrass in northern Australia with warmer air temperatures.

What we are doing about it?

Ongoing monitoring and research into the impacts of climate change on seagrass beds, including quantitative modelling at local scales. Investigations into the role of seagrass beds as carbon sinks for CO2 mitigation.

Summary

Seagrasses in Australia are extensive and diverse, and function as ecosystem engineers. They oxygenate the water column, regulate nutrients, stabilise sediments, protect shorelines by restricting water movement, provide food for finfish, shellfish and mega herbivores including green turtles and dugongs, and support commercially and recreationally important fisheries species.

As plants living in shallow coastal waters, the critical factors for seagrass growth are light, temperature, CO2, nutrients and suitable substrate, all of which are affected by climate change. Seagrasses are therefore vulnerable to a changing climate, and will be sentinels for the changing marine ecosystems of Australian coastal waters.

Seagrass habitat continues to be at risk from the direct impacts of human activities along the coastline. Two temperate seagrass species found only in Australia were recently... continued on the full report

Macroalgae and Temperate Rocky Reefs

Lead Author: 

Thomas Wernberg 1

Co Authors: Dan A. Smale 1,7, Adriana Vergés 2,3, Alexandra H. Campbell 2,3, Bayden D. Russell 4, Melinda A. Coleman 5, Scott D. Ling 6, Peter D. Steinberg 2,3, Craig R. Johnson 6, Gary A. Kendrick 1 and Sean D. Connell 4

Download this report in PDF format: Click here

What is happening?

A recent analysis of herbarium records back to the 1940s suggests temperate seaweeds on both east and west coasts of Australia have retreated south 10-50 km per decade as waters have warmed. A recent extreme warming event (marine heatwave) in Western Australia caused substantial changes to seaweed habitats, including a reduction in large habitatforming species. In eastern Tasmania, a substantial decline in algal habitat is associated with southward expansion of a grazing sea urchin aided by the strengthening of the East Australian Current and warmer temperatures.

What is expected?

Warming will reduce the resilience of macroalgal habitats to other stressors such as pollution. Temperate species will contract their ranges southwards and tropical species expand their ranges further south. Many temperate species, found only in Australia, are at risk of extinction in the next 50-100 years. Extreme events (storms, heat waves, etc) will increase in frequency and magnitude and drive shifts in species’ distributions and interactions.

What we are doing about it?

IMOS Autonomous Underwater Vehicle Facility will provide long-term monitoring of water properties and temperate reefs at key locations in Qld, NSW, Tas and WA. Several research projects focusing on climate change and temperate macroalgae are under way. These focus both on establishing the range of impacts as well as the mechanistic relationships which drive impacts of climate change.

Summary

Australia’s temperate macroalgal (seaweed) flora is one of the most species rich and endemic in the world, and it supports similarly unique invertebrate and fish life. Climate change is a threat to this biodiversity, particularly because there are limited refuges south of the Australian continent.

The previous assessment (2009) concluded that there is clear evidence that organisms on temperate rocky reefs are vulnerable to the direct and indirect impacts of climate change, and that observed responses to date are consistent with effects of increasing ocean temperature, often in combination with additional stressors such as fishing, eutrophication and invasive species.

Since the first report card, more examples of possible impacts of climate change on temperate marine macroalgae and associated organisms have emerged. The range of impacts remains largely as previously reported, but... continued on the full report

Phytoplankton

Lead Author: 

Gustaaf Hallegraeff 1

Co Authors: John Beardall 2, Steve Brett 3, Martina Doblin 4, Peter Thompson 5

Download this report in PDF format: Click here

Professor Gustaaf Hallegraeff - Institute for Marine and Antarctic Studies - University of Tasmania


Author: Marine Climate Change 2012
| Time: 6.95 min

What is happening?

The red-tide dinoflagellate Noctiluca scintillans has expanded its range into southern Tasmanian waters and beyond since 1994, associated with warming water and enhanced transport by the East Australian current.

What is expected?

Changes in timing of seasonal phytoplankton blooms may impact marine food webs.

What we are doing about it?

Establishment of IMOS National Reference Stations and AusCPR (Australian Continuous Plankton Recorder) tows are enhancing Australia-wide phytoplankton and biogeochemical data collections for monitoring responses.

Summary

Prediction of the impact of global climate change on marine phytoplankton is fraught with uncertainties. A range of environmental changes will influence phytoplankton, including warming, enhanced stratification, alteration of ocean currents, intensification or weakening of local nutrient upwelling, heavy precipitation, and storm events causing changes in land runoff and micronutrient availability. Further, elevated CO2 could directly reduce calcification through ocean acidification, but also stimulate photosynthesis or other biogeochemical processes such as N-fixation. Phytoplankton responses are likely to be species- or even strain-specific. Complex factor interactions exist and simulated ecophysiological laboratory experiments rarely allow for sufficient acclimation or take into account physiological plasticity and genetic strain diversity. In the absence of multi-decadal Australian... continued on the full report

Page 1 of 4 pages  1 2 3 4 > 

Untitled Document