Nav: Home

New insight from Great Barrier Reef coral provides correction factor to climate records

June 18, 2019

CHAMPAIGN, Ill. -- Newly developed geological techniques help uncover the most accurate and high-resolution climate records to date, according to a new study. The research finds that the standard practice of using modern and fossil coral to measure sea-surface temperatures may not be as straightforward as originally thought. By combining high-resolution microscopic techniques and geochemical modeling, researchers are using the formational history of Porites coral skeletons to fine-tune the records used to make global climate predictions.

The new findings are reported in the journal Frontiers in Marine Science.

For over 500 million years, corals have been passively keeping track of changing sea-surface temperature by recording the ratio of calcium to strontium and oxygen isotopes within their skeletons, the researchers said. The coral skeletons - which are made of calcium carbonate mineral - grow layers like tree rings that have increased amounts of strontium and the lighter isotope of oxygen during the warmer season. Climate scientists take advantage of this process to track sea surface temperature through time.

However, this climate-tracking technique is not without its flaws, said University of Illinois geology and microbiology professor Bruce Fouke, who led the new research.

"We can ground truth coral-based sea-surface temperature records against records made using temperature probes," Fouke said, "Remarkably, the coral records are accurate most of the time, but there are instances where measurements have been off by as much as nine degrees Celsius, and this needs to be rectified."

To grow their skeletons, coral polyps deposit aragonite. However, the mineral also crystalizes from seawater, the researchers said, and that can cause problems when analyzing the original coral skeleton chemistry. As seawater flows through the porous coral structure, it deposits newly crystalized aragonite on top of skeletons. That new aragonite, which may record a different sea-surface temperature, alters original skeletal chemistry through a process called diagenesis, Fouke said.

"It is difficult to tell the diagenetic aragonite from the original coral skeleton without using high-powered microscopes," said Kyle Fouke, a Bucknell University undergraduate student, Carl R. Woese Institute for Genomic Biology affiliate and co-author of the study. "It is also challenging to know exactly when the diagenetic alteration took place - days or decades after the skeletons were formed. Unless you are using the newest microscopy techniques to help select your samples, you could be collecting and measuring a mix of the two very different temperature records."

To test this, the team collected drill cores from the skeletons of living Porites coral heads at 10 to 100 feet water depth on the Great Barrier Reef off the coast of Australia. These large coral heads reach nearly 10 feet in diameter, and some have been growing for hundreds of years.

"Based on our analyses, we see that the older portions of the coral heads growing in deeper seawater contain a higher concentration of diagenetic aragonite," Kyle Fouke said.

"Using a broad array of light, electron and X-ray microscopy techniques - made available under the direction of study co-author Mayandi Sivaguru, an associate director at the Carl R. Woese Institute for Genomic Biology Microscopy Core at the U. of I. - we were able to clearly differentiate between the original skeleton and diagenetic aragonite, when present," said Lauren Todorov, a molecular and cellular biology undergraduate student and study co-author.

Using these techniques, the team uncovered a multitude of different aragonite crystallization histories, ranging from seasonal variations in skeletal growth to smaller-scale processes that could be occurring on daily - even hourly - cycles.

By taking the extra steps to sort out the relative timing between the skeletal and diagenetic aragonite crystallization, the team integrated its data with chemical-mixing models for calcium, strontium and oxygen isotopes from geochemical studies of Porites from Papua New Guinea. From this, the team created the first reliable and reproducible correction factor that determines the magnitude of error that diagenetic alteration can place on sea-surface temperature measurements.

"Additionally, because this has been achieved using the carbonate mineral aragonite, which is ubiquitous among marine life, this same correction factor can be used with other sea creatures that secrete carbonate skeletons and shells," Bruce Fouke said.

Sea-surface temperature records derived from coral skeleton chemistry are the gold standard for accurate climate reconstructions and future predictions, the researchers said, and this new insight only further strengthens this tool.
-end-
The NASA Astrobiology Institute, Office of Naval Research and the Australian Research Council supported this study.

Editor's notes:

To reach Bruce Fouke, call 217-244-5431; email fouke@illinois.edu.

The paper "Correction factors for 18O-derived global sea surface temperature reconstructions from diagenetically altered intervals of coral skeletal density banding" is available online and from the U. of I. News Bureau. DOI: 3389/fmars.2019.00306

University of Illinois at Urbana-Champaign, News Bureau

Related Climate Articles:

Climate action goes digital
More transparent and accessible to everyone: information and communication technologies bring opportunities for transforming traditional climate diplomacy.
Sub-national 'climate clubs' could offer key to combating climate change
'Climate clubs' offering membership for sub-national states, in addition to just countries, could speed up progress towards a globally harmonized climate change policy, which in turn offers a way to achieve stronger climate policies in all countries.
Review of Chinese atmospheric science research over the past 70 years: Climate and climate change
Over the past 70 years since the foundation of the People's Republic of China, Chinese scientists have made great contributions to various fields in the research of atmospheric sciences, which attracted worldwide attention.
How aerosols affect our climate
Greenhouse gases may get more attention, but aerosols -- from car exhaust to volcanic eruptions -- also have a major impact on the Earth's climate.
Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.
How trees could save the climate
Around 0.9 billion hectares of land worldwide would be suitable for reforestation, which could ultimately capture two thirds of human-made carbon emissions.
Climate undermined by lobbying
For all the evidence that the benefits of reducing greenhouse gases outweigh the costs of regulation, disturbingly few domestic climate change policies have been enacted around the world so far.
Climate education for kids increases climate concerns for parents
A new study from North Carolina State University finds that educating children about climate change increases their parents' concerns about climate change.
Inclusion of a crop model in a climate model to promote climate modeling
A new crop-climate model provides a good tool to investigate the relationship between crop development and climate change for global change studies.
Natural climate solutions are not enough
To stabilize the Earth's climate for people and ecosystems, it is imperative to ramp up natural climate solutions and, at the same time, accelerate mitigation efforts across the energy and industrial sectors, according to a new policy perspective published today in Science.
More Climate News and Climate Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Making Amends
What makes a true apology? What does it mean to make amends for past mistakes? This hour, TED speakers explore how repairing the wrongs of the past is the first step toward healing for the future. Guests include historian and preservationist Brent Leggs, law professor Martha Minow, librarian Dawn Wacek, and playwright V (formerly Eve Ensler).
Now Playing: Science for the People

#565 The Great Wide Indoors
We're all spending a bit more time indoors this summer than we probably figured. But did you ever stop to think about why the places we live and work as designed the way they are? And how they could be designed better? We're talking with Emily Anthes about her new book "The Great Indoors: The Surprising Science of how Buildings Shape our Behavior, Health and Happiness".
Now Playing: Radiolab

The Third. A TED Talk.
Jad gives a TED talk about his life as a journalist and how Radiolab has evolved over the years. Here's how TED described it:How do you end a story? Host of Radiolab Jad Abumrad tells how his search for an answer led him home to the mountains of Tennessee, where he met an unexpected teacher: Dolly Parton.Jad Nicholas Abumrad is a Lebanese-American radio host, composer and producer. He is the founder of the syndicated public radio program Radiolab, which is broadcast on over 600 radio stations nationwide and is downloaded more than 120 million times a year as a podcast. He also created More Perfect, a podcast that tells the stories behind the Supreme Court's most famous decisions. And most recently, Dolly Parton's America, a nine-episode podcast exploring the life and times of the iconic country music star. Abumrad has received three Peabody Awards and was named a MacArthur Fellow in 2011.