Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Weather extremes are growing trend in Northern Australia, corals show

09.02.2011
The extreme rain events that have caused flooding across northern Australia may become an increasingly familiar occurrence, new research suggests. The study uses the growth patterns in near-shore corals to determine which summers brought more rain than others, creating a centuries-long rainfall record for northern Australia.

“This reconstruction provides a new insight into rainfall in northeast Queensland,” says Janice Lough, climate scientist of the Australian Institute of Marine Science (AIMS) in Townsville, Queensland, who authored the study. “These coral samples, which date from 1639 to 1981, suggest that the summer of 1973-1974 was the wettest in 300 years. This summer is now being compared with that record-setting one.”

Eastern Australia is recovering from a fierce cyclone that struck last week, adding to damage from serious flooding. The flooding began in November following record rainfall, and has slowly spread to the south along the coast.

Lough’s research indicates the country might be in for more weather extremes. Following a period of relatively low precipitation and rainfall variability from the mid-18th to mid-19th centuries, average rainfall for the region has significantly increased and become more variable since the late 19th century, with wet and dry extremes becoming more frequent, she says. Her new findings have been accepted for publication in Paleoceanography, a journal of the American Geophysical Union.

To create the rainfall record, Lough selected cores from her institute’s archive that had been taken from long-lived, massive Porites coral found along Australia’s Great Barrier Reef. The 17 samples had been collected from reefs located up to 30 kilometers (about 19 miles) away from Queensland’s northeastern shore.

Porites form large dome-shaped colonies that can be up to 8 meters (26 feet) in height and hundreds of years old. The coral colonies secrete underlying calcium-carbonate skeletons in annual bands of dense and less dense material. The coral bands can be counted like tree rings to calculate the colony’s age. The oldest core Lough analyzed dates back to 1639; the other coral cores analyzed for the study date back to the 17th to 19th centuries.

Northern Australian rainfall is seasonal, occurring almost exclusively during the summer. It is also highly variable year-to-year. The rain flushes degraded plant matter and a mix of compounds called humic acids into the ocean, particularly near the coast. During wet summers, more humic acid gets absorbed by the coral and stored in its skeleton. When slices of the coral are analyzed under ultraviolet light, the growth bands with more humic acid luminesce more (giving off more light) than the bands of coral growth from drier years, which allows researchers to create a record of rainfall. (The corals stimulated by ultraviolet light emit light through both fluorescence and phosphorescence; the term luminescence includes both sources of light.)

Lough used a custom-built luminometer to measure the intensity of the luminescence, which she translated into relative rainfall for each yearly band preserved in the coral. The annual records from the multiple coral cores were then calibrated against the instrumental rainfall record of the 20th century and used to reconstruct summer rainfall records back to the start of the coral colonies’ growth.

The records show that the frequency of extreme events has changed over the centuries, and is currently at a peak. During the earliest part of the reconstructed record, from about 1685 to 1784, wet years occurred on average every 12 years, and very dry years every nine. From 1785 to 1884, the frequency dropped: very wet years occurred about every 25 years, and very dry years every 14 years. However, between 1885 and 1981, the extremes increased dramatically in frequency, with very dry years taking place every 7.5 years on average, and very wet years about once every three years.

As a second part of the study, Lough compares the coral records with other proxy climate records from the paleoclimatology database of the National Oceanic and Atmospheric Administration, a U.S. agency. The level of agreement between the different records was mixed, but the increase in rainfall variability since the late 19th century is evident in two independently-derived proxy records of a recurrent tropical climate pattern known as the El Niño-Southern Oscillation.

A record of Australia’s past climate is particularly valuable, Lough says, as there is an overall lack of data on long-term climate variability in the tropics and the southern hemisphere. Such data is needed to place the current variability of the region’s climate in an historical context. The records derived from the Great Barrier Reef corals support predictions that tropical rainfall variability will increase in a warming world. AIMS researchers are currently analyzing coral cores from other tropical coral reefs of Australia to further study long-term rainfall and climate patterns.

Title:
“Great Barrier Reef coral luminescence reveals rainfall variability over northeastern Australia since the 17th century”
Author:
Janice Lough, Senior Principal Research Scientist, Australian Institute of Marine Science, Queensland, Australia.
Contact information for the author:
Phone: 61 07 47534248, E-mail: j.lough@aims.gov.au

Kathleen O’Neil | American Geophysical Union
Further information:
http://www.agu.org

More articles from Earth Sciences:

nachricht Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

nachricht Modeling magma to find copper
13.01.2017 | Université de Genève

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Water - as the underlying driver of the Earth’s carbon cycle

17.01.2017 | Earth Sciences

Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

17.01.2017 | Materials Sciences

Smart homes will “LISTEN” to your voice

17.01.2017 | Architecture and Construction

VideoLinks
B2B-VideoLinks
More VideoLinks >>>