Improved interpretation of volcanic traces in ice

Storms, cold, poor harvests — the year 1816 was a “year without a summer” in European history. The reason was the eruption of the Indonesian volcano Tambora a year earlier. It had thrown huge amounts of sulfur compounds into the stratosphere (at altitudes of 15-50 km) where they spread around the entire globe and significantly weakened solar radiation for several years afterwards. Such intense volcanic eruptions are quite common in Earth’s history. To better understand their impact on the climate and the atmosphere, scientists try to reconstruct those eruptions accurately. Important archives of information are ice cores from Greenland and Antarctica because the sulfur particles ejected from the volcano fall back to the surface. A portion of that fallout is trapped in the ice of the polar regions and can be analyzed even thousands of years afterwards. The former aerosol contamination of the atmosphere is derived from it using a simple ratio calculation.

But this method has its limitations. “Volcanic aerosols in the stratosphere absorb infrared radiation, thereby heating up the stratosphere, and changing the wind conditions subsequently,” said Dr. Matthew Toohey, atmospheric scientist at GEOMAR Helmholtz Centre for Ocean Research Kiel. Using an atmospheric model, he has now tested the effects of this phenomenon. “We have found that the deposition of sulfur compounds in the Antarctic after very large volcanic eruptions in the tropics may be lower than previously thought,” the atmospheric researcher summarizes the findings of the study which has just been published in the current issue of the international Journal of Geophysical Research – Atmosphere.

For the study, Dr. Toohey and his colleagues from GEOMAR and the Max Planck Institute for Meteorology in Hamburg have used an aerosol-climate model to track 70 different eruption scenarios while analyzing the distribution of the sulfur particles. It was based on real volcanic eruptions during the past 200,000 years in Central America, which had been investigated in the framework of the Collaborative Research Project 574. “In our calculations, we could clearly see the differences in distribution and deposition between the northern and southern hemispheres,” explains co-author and director of the working group, Dr. Kirstin Krüger. The spatial deposition of sulfur particles in the bipolar ice cores, as calculated in the model, agrees well with the actually measured deposits of large volcanic eruptions, such as Pinatubo in 1991 or even of Tambora of 1815.

“If we know how volcanic sulfur particles affect the atmospheric winds, we can have a much improved interpretation of the traces of volcanic activities in the ice cores,” says Dr. Toohey. For one, there are better estimates of the strength of an outbreak. And secondly, the previously undetermined traces of volcanic eruptions that could not be assigned to any particular event or volcano eruption, can now be clearly traced to their origin.

“In any case, the results of our model study give a clear indication that the bipolar variability of sulfate deposits must be taken into consideration if the traces of large volcanic eruptions are to be deduced from ice cores,” says Dr. Krüger, “Several research groups that deal with this issue have already contacted us to verify their data through our model results.”

Earthworms could help scientists ‘dig’ into past climates

A team of UK researchers believe earthworms could provide a window into past climates, allowing scientists to piece together the prevailing weather conditions thousands of years ago.

A laboratory study by researchers from the Universities of Reading and York has demonstrated that balls of calcium carbonate (small lumps of chalk-like material) excreted by the earthworm Lumbricus terrestris – commonly known as lobworms or nightcrawlers – maintain a memory of the temperature at which they were formed.

This, say the researchers, in an article in the journal Geochimica et Cosmochimica Acta, means that calcite granules, commonly recorded at sites of archaeological interest, have the potential to reveal important information about past climates which could be used to enhance and benchmark climate change models.

The study, which also involved English Heritage’s Centre for Archaeology, was funded by the Natural Environment Research Council (NERC).
Lead author Dr Emma Versteegh from the Department of Geography and Environmental Science at the University of Reading, said: “These chalk balls will allow us to reconstruct temperatures for specific time intervals in which they were formed. Reconstructions like this are interesting for archaeologists, because they give a climatic context to their finds. More importantly, climate proxies are the only means we have to study climate beyond the instrumental record, which only goes back about 150 year

“This knowledge about past climates is of vital importance for developing and benchmarking climate models that make predictions for the future. Many different proxies already exist, but no proxy is perfect, or is available in every location, so it is good to have many different ones.”

The proof of concept study involved keeping modern-day Lumbricus terrestris at different temperatures, then carrying out isotopic testing on the calcite granules excreted. This successfully demonstrated that the granules remembered the temperature at which they were formed.

Principal Investigator Professor Mark Hodson from the University of York’s Environment Department, and formerly of the University of Reading, said: “There are many conflicting theories about why earthworms produce calcite granules, but until now, the small lumps of chalk-like material found in earthworm poo have been seen as little more than a biological curiosity. However, our research shows they may well have an important role to play, offering a window into past climates.”

The researchers are now gathering samples from archaeological sites dating back thousands of years in preparation for isotopic testing.
Dr Stuart Black, from the University of Reading’s Department of Archaeology, added: “We believe this new method of delving into past climates has distinct advantages over other biological proxies. For example, we believe it will work for the full seasonal range of temperatures, whereas methods such as tree rings, do not “record” during winter. In addition, because the chalk balls are found in direct context with archaeological finds, they will reveal temperatures at the same location. At present, links are often attempted with climate proxies many hundreds or even thousands of miles away.”

Study reveals ancient jigsaw puzzle of past supercontinent

A new study published today in the journal Gondwana Research, has revealed the past position of the Australian, Antarctic and Indian tectonic plates, demonstrating how they formed the supercontinent Gondwana 165 million years ago.

Researchers from Royal Holloway University, The Australian National University and Geoscience Australia, have helped clear up previous uncertainties on how the plates evolved and where they should be positioned when drawing up a picture of the past.

Dr Lloyd White from the Department of Earth Sciences at Royal Holloway University said: “The Earth’s tectonic plates move around through time. As these movements occur over many millions of years, it has previously been difficult to produce accurate maps of where the continents were in the past.

“We used a computer program to move geological maps of Australia, India and Antarctica back through time and built a ‘jigsaw puzzle’ of the supercontinent Gondwana. During the process, we found that many existing studies had positioned the plates in the wrong place because the geological units did not align on each plate.”

The researchers adopted an old technique used by people who discovered the theories of continental drift and plate tectonics, but which had largely been ignored by many modern scientists.

“It was a simple technique, matching the geological boundaries on each plate. The geological units formed before the continents broke apart, so we used their position to put this ancient jigsaw puzzle back together again,” Dr White added.

“It is important that we know where the plates existed many millions of years ago, and how they broke apart, as the regions where plates break are often where we find major oil and gas deposits, such as those that are found along Australia’s southern margin.”

After millennia of mining, copper nowhere near ‘peak’

New research shows that existing copper resources can sustain increasing world-wide demand for at least a century, meaning social and environmental concerns could be the most important restrictions on future copper production.

Researchers from Monash University have conducted the most systematic and robust compilation and analysis of worldwide copper resources to date. Contrary to predictions estimating that supplies of this important metal would run out in around 30 years, the research has found there are plenty of resources within the reach of current technologies.

The database, published in two peer-reviewed papers, was compiled by Dr Gavin Mudd and Zhehan Weng from Environmental Engineering and Dr Simon Jowitt from the School of Geosciences. It is based on mineral resource estimates from mining companies and includes information vital for carbon and energy-use modelling, such as the ore grade of the deposits.

Dr Jowitt said the database could change the industry’s understanding of copper availability.

“Although our estimates are much larger than any previously available, they’re a minimum. In fact, figures for resources at some mining projects have already doubled or more since we completed the database,” Dr Jowitt said.

“Further, the unprecedented level of detail we’ve presented will likely improve industry practice with respect to mineral resource reporting and allow more informed geological exploration.”

Dr Mudd said the vast volumes of available copper meant the mining picture was far more complex than merely stating there were ‘x’ years of supply left.

“Workers’ rights, mining impacts on cultural lands, issues of benefit sharing and the potential for environmental degradation are already affecting the viability of copper production and will increasingly come into play,” Dr Mudd said.

Despite examples like the Ok Tedi mine in Papua New Guinea, where mining has continued despite widespread environmental degradation that has affected thousands of residents, non-economic factors have constrained some mining operations and the researchers believe this will become increasingly important in the near future. An example is the Pebble copper-gold project in Alaska, which after more than a decade still doesn’t have the necessary approvals due to the environmental and cultural concerns of nearby residents.

“Pressingly, we need to acknowledge that with existing copper resources we’re not just going to be dealing with the production of a few million tonnes of tailings from mining a century ago; we are now dealing with a few billion tonnes or tens of billions of tonnes of mine waste produced during modern mining,” Dr Mudd said.

The researchers will now undertake detailed modelling of the life cycles and greenhouse gas impacts of potential copper production, and better assessment of future environmental impacts of mining.

They will also create similar databases for other metals, such as nickel, uranium, rare earths, cobalt and others, in order to paint a comprehensive picture of worldwide mineral availability.