Marine Climate

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Leeuwin Current

Leeuwin current fig2

Lead Author: 

Ming Feng 1

Co Authors: Nick Caputi 2 and Alan Pearce 3

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What is happening?

Since the mid 1970s, the Leeuwin Current has weakened due to more frequent El Niño events. However, in the past two decades, a strengthening is observed, linked to natural decadal variability not long-term change. Associated with this, there has been a southward range shift in marine biota.

What is expected?

The Leeuwin Current is likely to weaken over the coming century. Despite this, warming will continue to drive southward range shifts in marine biota and there will be more frequent extreme temperature events.

What we are doing about it?

IMOS is monitoring the Leeuwin Current. National Reference Stations at Darwin, Exmouth, Rottnest and Esperance and are providing physical and water quality data. Coastal water temperatures are monitored along the Western Australian coastline by the Department of Fisheries as part of a rock lobster program.

Summary

The long-term trend of the Leeuwin Current (LC) is essentially driven by the variations and changes of Pacific equatorial easterly winds. The LC has experienced a strengthening trend during the past two decades, likely due to natural variability, which has almost reversed the weakening trend during 1960s to early 1990s. Currently, most climate models project a weakening trend of the Pacific trade winds and a reduction of the LC strength in response to greenhouse gas forcing. Whereas changes induced by the greenhouse gas forcing induced changes may be clear in the long-time climate projection (e.g. 2100), for assessment of short-term climate projection (e.g. 2030s), natural decadal climate variations still need to be taken into account.

Whereas the average rising trend in sea level off the WA coast has been ~1.5 mm per year over the past century, there has been an acceleration of the... continued on the full report

El Niño – Southern Oscillation

Elnino-global-sst

Lead Author: 

Neil J. Holbrook 1

Co Authors: Jaclyn N. Brown 2, Julie Davidson 3, Ming Feng 4, Alistair J. Hobday 5, Janice M. Lough 6, Shayne McGregor 7, Scott B. Power 8 and James S. Risbey 9

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Neil Holbrook - El Nino Southern Oscillation (ENSO)


Author: Marine Climate Change 2012
| Time: 20.22 min

What is happening?

While observed El Niño-Southern Oscillation (ENSO) variability is within the broad range of natural variability, the possibility that anthropogenic forcing has influenced ENSO cannot be ruled out.

What is expected?

While the mean climate of the Pacific is expected to change, it is unclear how the amplitude or frequency of ENSO will change (if at all) over the next 100 years.

What we are doing about it?

Investing in Pacific region climate change programs, high quality data collection and monitoring, improving pre-instrumental ENSO reconstructions, process studies to understand mechanisms of variability, and enhancing modelling capabilities.

Summary

El Niño–Southern Oscillation (ENSO) is the dominant mode of year-to-year (interannual) climate variability observed globally (e.g., Philander 1990), and its environmental and socioeconomic impacts are felt worldwide (McPhaden et al. 2006). It is the major source of natural climate variability for Australia (e.g. Nicholls et al. 1997; Power et al. 1998; CSIRO-BoM 2007). ENSO drives changes in rainfall (Ropelewski and Halpert 1987, 1989; Allan et al. 1996; Power et al. 1999), surface air temperature (e.g., Power et al. 1998), river flow (Kahya and Dracup 1993; Merendo 1995; Power et al. 1999), agricultural production (Nicholls 1985; Phillips et al. 1998; Power et al. 1999; Hammer et al. 2000), ecosystems (Holmgren et al. 2001), tropical cyclones (e.g., Nicholls 1984; Solow and Nicholls 1990; McDonnell and Holbrook 2004a,b; Werner and Holbrook 2011; Werner et al. 2011; Callaghan and... continued on the full report

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Marine Environment

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Marine Reptiles

Snake

Lead Author: 

Mariana M.P.B. Fuentes 1

Co Authors: Mark Hamann 2 and Vimoksalehi Lukoschek 3

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What is happening?

Local declines of sea snakes on coral reefs may be the result of changing environmental conditions. Warming beaches are changing long-term sex ratios of hatchling turtles.

What is expected?

Some turtle nesting beaches will produce more females, but the long-term implications for turtle populations are unknown. Turtle nesting beaches will be lost due to sealevel rise and coastal development.

What we are doing about it?

The Australian Government, together with the WA, NT and Qld Governments are currently supporting a project to monitor sand temperatures on key turtle nesting beaches. Monitoring programs focused on crocodiles and nesting turtles are ongoing.

Summary

Few additional observations have been made of impacts from changes in climatic variables on marine reptiles since the first report card in 2009. However, there are a growing number of studies that have started to explore potential impacts of climate change on marine reptiles. Still, most evidence for climate change impacts on sea turtles comes from studies on loggerhead and green turtles in eastern Queensland. There is still low knowledge about vulnerability of crocodiles to climate change. However, there is more confidence that warmer water temperatures will influence behavior and possibly the distribution of the estuarine crocodile. There still is very limited knowledge of how the effects of climate change will impact sea snakes and there are no studies directly investigating this issue. What is clear, however, is that sea snakes at Ashmore Reef have undergone unprecedented local... continued on the full report

Seabirds

Seabirds

Lead Author: 

Lynda E. Chambers 1

Co Authors: Peter Dann 2, Carol Devney 3, Nic Dunlop 4, and Eric J. Woehler 5

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What is happening?

Tropical and subtropical species breeding at Houtman Abrolhos, WA are now experiencing poor breeding success outside of El Niño years linked to warming. Large range extension reported for Bridled Tern in south-west Australia in response to ocean warming.

What is expected?

Warming will impact the timing and breeding success of temperate seabird species. Little penguin breeding is expected to become earlier and more successful to 2030s, but later decline as temperatures warm further. Increases in extreme fire days in southern and eastern Australia will lead to higher risk of injury and death for colonial nesting species, such as penguins.

What we are doing about it?

Implementation of fast-response fire action plans to reduce the risk of fire in seabird colonies close to human settlements or infrastructure. Investigating human adaptation options to increase resilience of conservation dependent seabirds and marine mammals impacted by climate change

Summary

The 2009 Marine Report Card provided a comprehensive summary on the current body of research into the observed and predicted impacts of climate variation and change on seabirds in the Australian region. The vulnerability of a diverse range of Australian seabirds to variation and change in climate was determined and the species and ecosystems that may be more resilient to future climate warming were identified. It was clear from this first review that not all Australian seabirds are affected similarly, with responses varying by species and location, and that considerable data gaps hindered greater synthesis.

For seabirds in the Australian region, climatic and oceanographic variation and change has been associated with changes in distribution, success and timing of breeding, chick growth and survival of adults and immature birds, across many foraging guilds and regions. Since the first... continued on the full report

Temperate Fish

Temperate fish

Lead Author: 

David J Booth 1

Co Authors: Will Figueira 2, Greg Jenkins 3 and Rod Lenanton 4

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What is happening?

Additional evidence and reviews confirm previous reports of southward range extensions for many coastal temperate fishes.

What is expected?

Reduced freshwater flows are likely to have negative effects on estuarine dependent species, such as bream, and adaptation in relation to water flow management may be needed.

What we are doing about it?

There is ongoing experimental and observational work to understand the environmental tolerances and hence adaptive capacity of temperate fishes.

Summary

Since the first report card, little on-the-ground research on range shifts of temperate fishes has been reported. Several reviews of range shifts of Australian coastal fishes (Booth et al 2011 and Madin et al. 2012) have highlighted approaches for collecting and applying the data. Research in Western Australia (e.g. Langlois et al 2010, Cheung et al. 2011) has shown that many species of groundfish and reef fish are distributed latitudinally based on clear water temperature gradients, suggesting that climate-change SST increases/differences will significantly affect ranges. Langlois et al. 2010 conclude that “the old climatically buffered, oligotrophic seascape of south-western Australia has provided a simple system in which the consistent influence of physiological gradients on the abundance and distribution of fish species can be observed".

Little new evidence of effects of any... continued on the full report

Tropical Coastal Fish

Tropicalfish

Lead Author: 

Philip L. Munday 1,2

Co Authors: Alistair J. Cheal 3, Nicholas A. J. Graham 1, Mark Meekan 4, Morgan S Pratchett 1, Marcus Sheaves 2, Hugh Sweatman 3, Shaun K. Wilson 5

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What is happening?

New research suggests that some species have a greater capacity to acclimate to rising temperatures than previously thought; however whether such acclimation capacity is widespread in tropical marine fishes, and whether some critical processes (e.g. reproduction) remain significantly impaired, is unknown.

What is expected?

In addition to effects of habitat degradation, warmer ocean temperatures will cause distribution shifts in some tropical fishes, increasing the geographic ranges of some species and decreasing the ranges of others, including some commercially important species.

What we are doing about it?

Experimental and observational work is underway to investigate the adaptive capacity of tropical fish.

Summary

Climate change is expected to affect populations and communities of tropical marine fishes in many ways, ranging from indirect effects associated with habitat degradation and altered resource availability to direct effects of rapidly changing environmental conditions. In the short-term (up to 2030), the projected impact of climate change on Australia’s tropical coastal and demersal fishes is largely tied to the fate of critical benthic habitats, especially for coral reef environments, which are highly vulnerable to elevated temperature, ocean acidification and more intense storms. There is good evidence and strong consensus that climate-induced coral bleaching affects the community structure and abundance of reef-associated fishes, especially when it leads to the structural collapse of reef habitat. In the longer-term (after 2030), sea level rise and altered rainfall patterns are... continued on the full report

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