Scientist to Gather Greenhouse Gas Emissions from Melting Permafrost

Goddard scientist Emily Wilson poses here with an early version or prototype of her recently miniaturized laser heterodyne radiometer — an instrument for which she received a patent in 2014. Image Credit: NASA

A NASA scientist who has developed a novel suitcase-size instrument to measure column carbon dioxide and methane is taking her recently patented instrument on the road this summer to comprehensively measure emissions of these important greenhouse gases from Alaska’s melting permafrost. 

Emily Wilson, a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, will use her recently patented miniaturized laser heterodyne radiometer (mini-LHR) to carry out a multi-disciplinary field campaign at three sites — each representing a different type of permafrost — near Fairbanks, Alaska, in June. Her team has designed a unique and comprehensive experiment that records permafrost depth and structure, meteorological data, and concentrations of methane and carbon dioxide during the seasonal ground melt.

Multi-Disciplinary Approach

“With the global mean temperature rising, the release of these gases could create an amplified effect,” she said. “These data will allow us to estimate fluctuation of emissions from the melting permafrost.”

Permafrost is permanently frozen soil. Comprising 24 percent of the Northern Hemisphere, permafrost contains old organic carbon deposits — some relicts from the last glaciation — that are locked up beneath the surface. Scientists have observed that more of the permafrost’s upper layer, or the active layer, is melting each summer, creating concern that the thawing could lead to the significant greenhouse-gas emissions.

Further exacerbating the situation is the fact that while methane doesn’t linger as long as carbon dioxide in the atmosphere, it is more potent and effective at absorbing heat, creating a positive feedback, where emissions leads to more warming, which in turn accelerates the thaw.

Highly portable, the mini-LDR is ideal for permafrost studies, Wilson said. Made up of commercially available components, the instrument literally can go anywhere to measure carbon dioxide and methane in the atmospheric column — that is, the levels of these gases in a vertical column extending from the ground to space. Currently, the only ground-based network that measures these two greenhouse gases in the atmospheric column is the Total Carbon Column Observing Network. However, the network has 22 operational sites globally, with limited coverage in the Arctic.

“We’re targeting areas where there is limited coverage,” she said.

To prepare for the campaign, Wilson made her instrument more rugged and more sensitive. She added a satellite communications port to remotely retrieve data, a thermally controlled instrument housing to protect the instrument from changing temperatures, and a solar grid and battery storage system for powering the instrument in remote locations.

Source: Nasa

Viking fortress discovery: Archaeological dating results

Two carbon-14 dating results have removed all doubt regarding the authenticity of the Viking fortress.
Credit: Image courtesy of Aarhus University

In September 2014, archaeologists from the Danish Castle Centre and Aarhus University announced the discovery of a Viking fortress in a field belonging to Vallø Manor, located west of Køge on the east coast of Sealand. This was the first discovery of its kind in Denmark in over 60 years. Since then, archaeologists have been waiting impatiently for the results of the dating of the fortress. Now the first results are available, and they will be presented at a seminar at Aarhus University on 18 November.

"When the discovery was published back in September, we were certain that we had found a Viking ring fortress, but since then there have been intense discussions online and amongst archaeologists about whether we were right. Now we know without doubt that we have found a fortress from the 10th century," says archaeologist Nanna Holm, curator of the Danish Castle Centre.

Two carbon-14 dating results have removed all doubt regarding the authenticity of the Viking fortress. The carbon-14 dating was performed by the AMS 14C Dating Centre at the Department of Physics and Astronomy at Aarhus University in close collaboration with Accium BioSciences' laboratories in Seattle.

"The two samples were both taken from the outermost tree rings of charred logs that were found in the northern gateway of the fortress. The results of the two samples are almost identical: The fortress was built in the period between the year 900 and the beginning of the 11th century," explains Marie Kanstrup, an employee at the AMS 14C Dating Centre at the Department of Physics and Astronomy, Aarhus University.

Dating is important in determining the role of the fortress in the history of the Viking age

Søren Sindbæk, a professor of medieval archaeology at Aarhus University, explains that archaeologists are still working to date the fortress more precisely.
"We would like to determine a specific year. The carbon-14 method can't provide that, but we are working on different methods that can help us date the fortress even more precisely."

Dating the fortress will be an important step towards understanding its role in the history of the Viking age.

"We can't say whether or not it's Harald Bluetooth's fortress yet, but now that we've dated it to the 10th century, the trail is getting hotter. The things we've discovered about the fortress during the excavations all point in the same direction. We already know that there's a good chance that we'll find conclusive evidence next year," says Sindbæk.

A structure meant to symbolise power

Even though the excavations have closed for this year, the finds bode well for future efforts. The archaeologists' investigations have also revealed that the Viking fortress was built right next to the open sea.

"The excavation showed that there was a basin of fresh or brackish water right next to one side of the fortress -- presumably a quite narrow inlet leading out to Køge Bay. When the fortress was built, hundreds of tonnes of the heavy clay subsoil would have had to have been dug out into the sea basin," explains Nanna Holm.

According to Nanna Holm, this work was undertaken for no other reason than to give the fortress an impressive location. The structure was meant to signal power.

The same master builder may be responsible

The excavation has also shown that the construction of the fortress is closely related to other Viking fortresses such as Fyrkat near Hobro, Aggersborg near the Limfjord and Trelleborg near Slagelse. These fortresses were undoubtedly built during the reign of Harald Bluetooth, and still more evidence suggests that Borgring, as the fortress has been named, might have belonged to the same building programme.

"There are a lot of similar details in these structures. And it's been wonderful to see the same things coming to light at Borgring. In addition to the structure of the rampart and the gates, we have also found traces of a street with wood paving running along the inside of the rampart -- just like in Fyrkat, Aggersborg and Trelleborg. The most striking thing, however, is the measurements of the fortress. The rampart of Borgring is 10.6 metres wide. That is exactly the same width as the rampart of Fyrkat. So it's hard to avoid the sense that the same master builder was responsible," says Sindbæk.

Source: Aarhus University