THE LITTLE BOOK on Permafrost the LITTLE BOOK on PERMAFROST About the Book
Total Page：16
File Type：pdf, Size：1020Kb
THE LITTLE BOOK ON Permafrost THE LITTLE BOOK ON PERMAFROST About the book INTRODUCTION This e-learning material was created within the “PAGE21 – Permafrost in the Arctic and its Global Effects in the 21st Century“ project. The project is an EU Seventh Framework Programme funded large scale integrating collaborative project, aiming to understand the interactions between the global climate system and the frozen ground. The multidisciplinary nature of the science and the wide range of countries covered in the PAGE21 project combine to provide a wealth of opportunities for disseminating information. One of the tasks within the project was to create materials for education and training and that way ensure that the vast amount of knowledge entailed in the project consortium will be distributed to the widest possible audience for the benefit of community as a whole. This e-learning material “Little book on Permafrost” was created by the PAGE21 participant Arctic Portal in Iceland with the support of the PAGE21 project office as well as the project coordination team at Alfred Wegener Institute, Potsdam, Germany. 1 The PAGE21 project e-learning material “Little book on permafrost” was developed in close cooperation with Prof. Dr. Kenji Yoshikawa from the Water and Environmental Research Center Institute of Northern Engineering at the University of Alaska Fairbanks. The texts in this e-learning material are mostly based on Prof. Dr. Yoshikawa’s “Permafrost in Our Time” publication, an overview of an extensive permafrost temperature project that Prof. Dr. Yoshikawa has led in Alaskan schools, which came out in March 2013. This book is created under a Creative Commons license. It can be freely used for educational purposes. Permafrost lain area in Ny Alesund, northern part of Svalbard. Photo: Hjalti Hreinsson 2 Chapter 1 What is Permafrost This chapter introduces permafrost, explains how it is defined and familiarizes the reader with the major permafrost areas of the world. Chapter 1 What is permafrost? CHAPTER OVERVIEW Permafrost is defined as ground that remains continuously at or below 0° degrees 1. What is permafrost of Celsius for at least two consecutive years. 2. Polygons Permafrost is formed when the ground cools down in winter and produces a frozen 3. Pingo layer below the surface that then remains frozen throughout the following summer, or longer. 4. Where can permafrost be found? Permafrost does not have to contain water or ice. As long as the temperature of the ground stays at or below freezing point year after year, it is still considered permafrost, even if the ground is completely dry. This is because permafrost is defined by temperature. The active layer is the soil near the ground surface that thaws each summer, but freezes again during the winter. The ground temperature can fluctuate between 20 and 30°C between summer and winter. Deep in the ground, however, soil temperature changes little from season to season. At 2–20m depth, depending on soil material, there is no seasonal change in temperature at all. It means that there is the same temperature all year around. Deeper ground does not respond to heat coming from the atmosphere as quickly as the ground surface. In the middle of winter in February, ground surface is getting very cold, but that cold hasn’t yet reached deeper underground. In April, 4 though, it is the coldest time of the year at 1m depth. Sunshine is frequent in April in the North, and snow has melted in many areas. But only 1m below ground, it is the coldest time of the year and pipes to and from houses may freeze unless they’re heated. The thickness of permafrost depends on local climatic conditions, vegetation cover, soil type and soil moisture content. It is also impacted by the heat from the Earth’s center. Permafrost thickness can vary a lot being anywhere from 1 meter to 1600 meters in depth. The deepest permafrost areas are in Siberia. The earth´s core temperature is similar to the temperature of the sun’s surface or approximately 5500°C. Earth´s average ground surface temperature, on the other hand, depends on where on earth it is measured. Permafrost can be found where the average air temperature on the surface of the earth is around or below 0°C (32°F). FACT! Earth’s average temperature is about 17°C, a temperature most humans feel comfortable in. The temperature range we live in is not Houses in Svalbard are most often built on poles. Poles are run wide compared to temperature variations in the universe. People deep into the ground and houses built on top. It prevents flooding can live in a range of only −50°C to 50°C (range 100°C), and that’s and sinking, resulted by permafrost. Storage can be used with clothing for cold temperatures. For the naked condition, the underneath the houses, commonly used for bikes etc. temperature range we can live in is only 10° to 35°C. Photo: Hjalti Hreinsson 5 Infograph: What is permafrost? Illustration: Arctic Portal 6 Pipes in Svalbard are above ground because of permafrost. Bridges are for people and snowmobiles. Photo: Hjalti Hreinsson Permafrost preserves bodies and therefore the cemetery in Longyerbyen has been for over 70 years. People who are ill are transferred to mainland Norway. Bodies of deceased people are also moved and not buried in Svalbard. Several graves fill the small cemetery, many of them miners who died in accidents and some who died as a result of the Spanish flu. The latest burial was conducted in the 1930´s. Photo: Hjalti Hreinsson Houses in Longyearbyen, Svalbard. Poles are in front of the houses and storage areas can be seen underneath. Photo: Hjalti Hreinsson 7 Polygons The polygons are formed due to the periodical freeze and thaw of the permafrost. When the climate gets colder in the fall, the active layer slowly starts to freeze. In winter, during very low temperatures, the frozen soil fractures forming cracks on the ground. In spring when the ground starts to melt again the cracks fill with melting snow and water. This water stays in the cracks forming ice wedges in the permafrost when the soil again starts to freeze in the fall. The ice wedges are only a few millimeters at first, but with time, when the active layer frequently freezes and thaws again the ice wedges get larger and form ice wedge polygons on the ground. Both pictures show permafrost polygons. The picture on the right shows how polygons can also form underwater. Photos: Julia Boike 8 Infograph: Permafrost polygons Illustration: Arctic Portal 9 Infograph: Pingo Illustration: Arctic Portal Pingo is a small hill formed out of ice. When the pingo hill melts, the ground collapses and water runs into the centre forming a volcano crater-like pond. 10 Where can permafrost be found? Arctic Permafrost can be found in all regions in the Arctic. Alaska Permafrost is thickest in the northernmost part of Alaska, but it is found to some extent beneath nearly 85 percent of Alaska. On the Arctic coastal plain it extends as much as over 600m (2000 feet) below the surface and is found virtually everywhere. Southward its thickness gradually decreases and it becomes Permafrost ground. Photo: GettyImages more and more discontinuous, broken by taliks, pockets of unfrozen ground. Near Anchorage, permafrost is found only in Institute of University of Alaska Fairbanks. Depths of these isolated patches, and in Southeast Alaska it is found only high in boreholes are typically 60 to 80m, and measurements are usually the mountains. taken annually. Since the early 1990´s, permafrost temperatures in Much of the permafrost in Alaska is tens of thousands of years Alaska have changed noticeably. Generally, the increases in old. River erosion and gold mining have revealed the remains of permafrost temperature are more profound at coastal Arctic sites now-extinct animals from the last great ice age 100,000 to 10,000 (from 1.5 to 3.0°C) and less profound in interior Alaska (from 0.5 years ago, when animals such as woolly mammoths, mastodons, to 1.5°C). lions, and saber-toothed cats roamed what is now Alaska. Canada In Alaska, permafrost observatories, equipped with boreholes, The Canadian Arctic Archipelago, located in the northern were established in the 1970s and 1980s along the Trans-Alaskan extremity of North America, covers approximately 1,424,500 km2 Pipeline as well as at other locations in Alaska by the Geophysical (550,000 sq.mi). It consists of 36.563 islands, and covers a large 11 Map: Permafrost Extent 12 part of Northern Canada – most of Nunavut and part of the Northwest Territories. It is one of the coldest permafrost temperature regions in Northern Hemisphere, going down to -14°C. Retrogressive thaw slumps, which develop due to the thawing of ice-rich permafrost on slopes, are commonly seen at Western part of Canadian Arctic. These huge thaw slumps trigger massive sediment export from the permafrost and a lot of suspended solid discharges to the ocean. Siberia – Russia Siberia contributes the most to the world’s permafrost proportion. The thickest permafrost in the world is found in Siberia (over 1000m). Subsea permafrost is also widely present in the offshore of the Siberian Arctic Coast. Northern Siberian coastal Islands (Novosibirsk Islands) are one of the coldest permafrost areas in Siberia. Interestingly, Oymyakon, one of the coldest places in Northern hemisphere with -72ºC record minimum temperature, does not have the coldest permafrost temperature, because of very hot summer temperature. Permafrost research site in Ny Alesund, Svalbard. Photo: Hjalti Hreinsson 13 Scandinavia Permafrost can be found in most places in Svalbard and its temperature ranges from -2 to -6°C.