Revealing the secrets of permafrost
Submitted by minh on 22 February 2012
This is how we spend about two months of each year before returning to our warm European laboratories to analyse our data. What are we doing and why do we do it?
What is permafrost?
When winter arrives and the temperatures drop, ice forms on puddles or ponds. When the temperature stays below 0 °C for long enough, even the ground freezes. In some cases, the ground can remain continuously frozen for more than two years; we call this permafrost.
In theory, detecting permafrost is relatively easy: simply insert a thermometer into the ground and take regular measurements over two years. However, obtaining accurate and representative data is more complicated. This is because the ground’s most superficial layer is directly affected by solar radiation and weather conditions, so unlike the permafrost below, it thaws in the warm season.
After several years of data logging, we can determine whether permafrost exists and what its thermal evolution was: how the ground temperature changed over the monitored period at different depths.
What can we learn from permafrost?
Why do we and other scientists want to know if the ground is frozen below the surface? Permafrost can be important in daily life, as well as telling us about the past and future climate on Earth; it can even teach us about other planets.
By measuring the temperature near the surface, we can see if the active layer is becoming thicker – as the permafrost below thaws – or thinner. This tells us how the climate is changing, as the thickness depends not only on air temperature, but also on factors such as snow cover. By monitoring the thickness of the active layer at different sites on Earth, we can investigate the influence of global warming on ground temperatures.
Permafrost not only tells us about our current climate, but can also reveal our past climate. If a piece of rock warms up during the day, it will start to cool down the following night. However, it will remain warm for some time – especially deep in the rock, far from the surface where heat is being lost. Measuring temperatures at different depths inside the piece of rock can tell us about the rock’s previous thermal conditions. We can do the same in permafrost – the deeper we dig, the further we are travelling into the past.
Recently, scientists have discovered that changes in the active layer not only indicate climate change but can actually contribute to it. In the northern hemisphere, permafrost soils contain huge amounts of frozen organic matter. As global warming causes the active layer to thicken, this organic matter is exposed to decomposition by micro-organisms, releasing carbon dioxide and methane – important greenhouse gases – into the atmosphere, increasing the rate of global warming.
Permafrost can also have a direct impact on humans, in areas where houses, roads and railways have been built on permafrost.
Studying permafrost in Antarctica
For over two decades, our team has been conducting long-term permafrost research on different sites on Livingston and Deception Islands in the Antarctic Peninsula region. We measure the ground temperature both near the surface and inside boreholes as deep as 25 metres. We monitor the temperature in the ground, compare it with air and surface temperatures, and study the factors that affect ground temperature: from wind speed to rock properties such as thermal conductivity, porosity and humidity. We also measure the thickness of the active layer every year in the thaw season. Some of the boreholes have been monitored continuously for up to 25 years; others were drilled in the past six years.
What do our data reveal? The main result is that although some areas that were previously permafrost are now unfrozen all year round, most of the ground on Livingston and Deception Islands is approximately as frozen as it was 10 years ago, despite global warming (Figure 8). These local differences are determined by the properties of the soil and rocks: material with higher thermal conductivity, for example, thaws more quickly. Over the next few decades, therefore, we expect permafrost with lower thermal conductivity to succumb to global warming, too. We hope to wrap up warm and return to Antarctica regularly to find out.
Figure 8: Patterns in freezing and thawing at three different depths in the Incinerador borehole (230 cm deep) on Livingston Island, between 2000 and 2010. Currently, we do not have enough spatial and temporal information to conclude that the permafrost in the Antarctic Peninsula is affected by global warming. In the Incinerador borehole, there is a slight positive trend in the thawing index, but the freezing index shows no change – overall, the permafrost is still stable. Images courtesy of Miguel Ramos
w1 – The US Public Broadcasting Service has developed an activity to make your own permafrost in class, build a house on it and observe the consequences of thawing. See: www.pbs.org/edens/denali/permawht.htm
w2 – The International Permafrost Association co-ordinates international co-operation among scientists and engineers working on permafrost. See: www.ipa-permafrost.org
The US National Snow and Ice Data Center runs an educational website on frozen ground, including many activities and resources on permafrost. See: http://nsidc.org/frozenground
The Scientific Committee on Antarctic Research offers a wealth of teaching resources on the Antarctic for students of all ages, in different languages, including dressing an Antarctic scientist in appropriate clothing. See: www.scar.org/about/capacitybuilding/antarcticeducation
The United States Antarctic Museum has made lists of educational opportunities for teachers to experience the Antarctic and of resources for their students. See: www.usap.gov/usapgov/educationalResources.cfm?m=5
To find some wonderful pictures of Antarctica to use in your lessons, visit: www.coolantarctica.com
To learn about one school teacher’s trip to the Antarctic, see:
It is more than 25 years since a hole in the ozone layer was discovered over Antarctica. To find out what caused it and what the current situation is, see:
If you found this article useful, why not browse the full series of climate-change-related articles in Science in School? See: www.scienceinschool.org/climatechange
Miguel Ángel de Pablo is an assistant professor of geology at the Universidad de Alcalá in Madrid, Spain. He is a geologist and has a great deal of experience working on the geology of Mars, where the surface remains frozen. He joined the Antarctic research team in 2007 to study terrestrial permafrost in an effort to understand the Martian geological processes related to frozen terrains.
Miguel Ramos is an associate professor of physics at the Universidad de Alcalá, and leads the university research into Antarctic permafrost. He has spent 25 years working on Antarctica, studying the effect of climate on the thermal evolution of the South Shetland Islands.
Gonçalo Vieira is an assistant professor of geographical studies at the Universidad de Lisboa in Lisbon, Portugal. He is a geographer and the head of a Portuguese team working on permafrost and other periglacial processes, mainly in Antarctica. He has collaborated with Miguel Ramos since 2002.
Antonio Molina is a PhD student in the department of planetology and habitability at the Centro de Astrobiología CSIC / INTA in Madrid, Spain. He is a young researcher who has been studying Martian processes and the terrestrial analogues, especially those related to frozen soils, since 2009. He has participated in one Antarctic campaign as a member of the Antarctic research team of the Universidad de Alcalá.
Many people know what permafrost is: frozen ground. But if researchers spend decades studying permafrost, there must be a lot more to know than just this simple information.
This article describes what permafrost is, how it can be researched, what can be learned from this research, and why the information revealed is valuable. Additionally, it contains information that could be used in the secondary-school science classroom for teaching many subjects and topics, including biology (e.g. ecology), environmental science (e.g. climate change), physics and chemistry (e.g. water and material properties), geology (e.g. rock properties) and meteorology (e.g. wind and temperature).
For lower-secondary-school students (ages 13-15), the article would be a good source of information about what permafrost is, how it is studied and what kind of important information it reveals. For upper-secondary-school students (ages 16-19), the article would also be helpful in understanding how everything that happens on the planet has direct or indirect implications that go far beyond what anyone can first imagine. For example, students will realise that global warming can negatively affect human land use and development.
The article would be most appropriate for study in the countries of northern Europe as well as countries with very high mountains, as these countries are the ones that have permafrost. Nevertheless, because climate change, which affects and is affected by permafrost, is a global problem, this article can provide valuable information in any classroom, anywhere in the world.
Michalis Hadjimarcou, Cyprus