28 July 2009

Changing climate means fewer shipwrecks

Cosmos Online
Climate change has led to a decline in severe storms along Australia's notorious Shipwreck Coast – a graveyard for hundreds of ships during the 19th and 20th centuries.
Falls of Halladale

The Falls of Halladale (pictured here run aground near Peterborough, Victoria in 1918) is one of over 700 vessels wrecked along Australia's Shipwreck Coast. Credit: Wikimedia

SYDNEY: Climate change has led to a decline in severe storms along Australia’s notorious Shipwreck Coast – a graveyard for hundreds of ships during the 19th and 20th centuries.

The Australian National Shipwrecks Database has a record of more than 700 vessels that have been sunk along the Shipwreck Coast, along the southwest of the state of Victoria, over the past 200 years.

These were often caused by fierce storms rolling in from the Southern Ocean, says a new study.

Fierce storms

According to the research, published in the Australian Meteorological and Oceanographic Journal, these storm-related shipwrecks have declined over the past century.

While this is in part due to improved ship construction, forecasting and navigation, researchers wondered if it is also less stormy along the Victorian coastline today than in the 19th century.

A team from Monash University and the Australian Bureau of Meteorology, both in Melbourne, used historic data to look at storm conditions along the Victorian coastline from 1865 to 2006.

They examined weather records taken at the Cape Otway lighthouse at 9am and 3pm every day since 1865. According to Lisa Alexander, study co-author and Monash University climate scientist, large differences in pressure observations between the two daily recordings indicates stormy weather.

Far fewer severe storms

The researchers found the number of severe storms at Cape Otway has decreased by 40% since the mid 19th century.

“By thoroughly checking the climate record we have identified 836 severe storms at Cape Otway between 1865 and 2006,” said Alexander. “At the end of the 19th century there was an average of seven severe storms per year, causing a lot of damage. Currently there are approximately four per year.”

Furthermore, the researchers used the National Shipwreck Database to see if recorded shipwrecks were linked with storm events recorded at Cape Otway.

“Some of the recorded shipwrecks say the ship disappeared without a trace, so now, in some cases, we can say there was a severe storm at that time so it’s likely [the storm was responsible]” she said.

Barry Brook, director of the University of Adelaide’s Research Institute for Climate Change and Sustainability, said that the study has convincingly shown a downtrend in severe storm events over the last 150 years.

“The Australian coastline is less hazardous as a result,” said Brook. “It’s good news if you’re a yachty and want to avoid being cast against the rocks but bad news if you’re in agriculture.”

More research needed

That’s because the study also shows that a reduction in severe storms is linked with a reduction in low-pressure systems that bring rain to southern Australia, he said.

“This is one bit of work that confirms changes in storm tracks and storms in the Southern Hemisphere and especially in the southern parts of Australia,” said Carsten Fredericksen an expert in climate variability at the Bureau of Meteorology, who was not involved in the study.

“There has been a shift in climate and as a result a change in storm tracks. It is most likely global warming that caused the change in climate but more work needs to be done to properly make this attribution,” added Fredericksen.


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