Shokr / Sinha Sea Ice

Physics and Remote Sensing
1. Auflage 2015
ISBN: 978-1-119-02796-6
Verlag: John Wiley & Sons
Format: EPUB
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)

E-Book, Englisch, 600 Seiten, E-Book

Reihe: Geophysical Monograph Series

Sea Ice: Physics and Remote Sensing addresses experiences acquired mainly in Canada by researchers in the fields of ice physics and growth history in relation to its polycrystalline structure as well as ice parameters retrieval from remote sensing observations, The volume describes processes operating at the macro- and microscale (e,g,, brine entrapment in sea ice, crystallographic texture of ice types, brine drainage mechanisms, etc,), The information is supported by high-quality photographs of ice thin-sections prepared from cores of different ice types, all obtained by leading experts during field experiments in the 1970s through the 1990s, using photographic cameras and scanning microscopy, In addition, this volume presents techniques to retrieve a suite of sea ice parameters (e,g, ice type, concentration, extent, thickness, surface temperature, surface deformation, etc,) from space-borne and airborne sensor data, The breadth of the material on this subject is designed to appeal to researchers and users of remote sensing data who want to develop quick familiarity with the capabilities of this technology or detailed knowledge about major techniques for retrieval of key ice parameters, Volume highlights include: Detailed crystallographic classification of natural sea ice, the key information from which information about ice growth conditions can be inferred, Many examples are presented with material to support qualitative and quantitative interpretation of the data, Methods developed for revealing microstructural characteristics of sea ice and performing forensic investigations, Data sets on radiative properties and satellite observations of sea ice, its snow cover, and surrounding open water, Methods of retrieval of ice surface features and geophysical parameters from remote sensing observations with a focus on critical issues such as the suitability of different sensors for different tasks and data synergism, Sea Ice: Physics and Remote Sensing is intended for a variety of sea ice audiences interested in different aspects of ice related to physics, geophysics, remote sensing, operational monitoring, mechanics, and cryospheric sciences,

Mohammed Elsayed Shokr is a research scientist in Science and Technology Branch at Environment Canada, He is also affiliated with IEEE Geoscience and Remote Sensing Society (Institute of Electrical and Electronics Engineers) and the CASI Canadian Remote Sensing Society (Canadian Aeronautics and Space Institute), His research interests include studying sea ice physical and electrical properties which have greater implications in operational monitoring and climate studies, He also uses remote sensing techniques for sea ice modelling, Nirmal Sinha is an Engineer at the NRC Institute for Aerospace Research in Ottawa, Ontario, His research focuses on high temperature materials, like ceramics and advanced alloys that are used inside jet engines or gas turbine engines, This involves applying theories and experimental techniques about how snow and ice behaves around its melting point, to aerospace materials such as titanium-based and nickel-based 'superalloys',

Autoren/Hrsg.

Shokr, Mohammed

Sinha, Nirmal

Sinha, Nirmal K.

Leseproben

1
Introduction
1.1. BACKGROUND
Our world is divided into five regions according to the position of the Sun throughout the year: a tropical region around the equator, two temperate regions and two polar regions. On two equinoxes, March 21 and September 23, the Sun is directly overhead the equator and the Sun’s rays reach both the North and the South Poles. On June 21 (the summer solstice), the Sun is directly overhead the Tropic of Cancer (about 23.5°N) in the northern temperate region, and on December 22 (the winter solstice) it is positioned directly overhead the Tropic of Capricorn (about 23.5°S) in the southern temperate region. In the two polar regions, mostly relevant to the material in this book, the Sun never sets in their summer and never rises in their winter. The Arctic region (or zone) containing the north polar region with latitudes greater than “about” 66.6°N and the Antarctic region (or zone) containing the south polar region having latitudes greater than “about” 66.6°S are the primary cryospheric regions of the world. Although the latitudes of the Arctic and the Antarctic circles depend on Earth’s axial tilt, which fluctuates slightly with time (about 2° over a 40,000?year period), the variations in the boundaries of the polar region are very small and negligible. The secondary cryospheric regions are the Alps, Andes, Himalaya, Rockies, etc. Among the secondary cryospheric regions, the Himalayan belt covers and affects the largest effective area of human habitation. Climate change has been affecting all the cryospheric regions of the world, and the effects can be directly observed and quantified using air- and space-borne remote sensing as well as land-based instruments. Remotely sensed images of the land- and ocean-based snow and ice information are paramount in understanding the state of health of Earth for sustainability of life. Other methods such as ice core analysis of ice caps and ice shelves are also used. After all, snow is the messenger of the sky and the environment. Sea ice covers most of the oceanic surface of the primary cryospheric area of the global surface. The world of sea ice encompasses the polar region, particularly the Arctic basin and a belt around the continent of Antarctica. Out of the 71% of Earth’s surface that is covered by ocean about 7%–15% is covered by sea ice at certain times (more in the winter and less in the summer). That is equivalent to 5%–10% of Earth’s surface. Sea ice area in the Arctic varies between a minimum of about 4 million km2 in September to a maximum of about 15 million km2 in March. The corresponding figures for the Antarctic are 3 million and 18 million km2 in February and September, respectively. Sea ice can develop very smooth or very rough surfaces. It can be soft or hard, a bare surface or snow covered, stagnant (fastened to the shoreline) or mobile pack ice, and stiff and silent or crushing with loud noise. It exhibits seasonal variations to which life in the polar regions is closely adapted. In the Arctic region, sea ice starts its growth in September/October and reaches its maximum in March when it covers the entire Arctic basin. This trend is reversed during the summer, and the ice extent reaches its minimum in September. In the Antarctic the annual fluctuations range between a minimum in February to a maximum in September when ice extends to latitudes between 55° and 65°S. For a limited time during the summer months, certain areas of the polar waters in the Arctic zone are used extensively by ships (ice strengthened or escorted by icebreakers) where the floating bodies of new and old sea ice and icebergs can prove hazardous. The expected reduction of sea ice extent, the reduction of the navigationally hazardous old ice, and the increase in the duration of summer melting season will certainly increase marine activities in these areas. No doubt, the Arctic waters, particularly the legendary Northwest Passage that passes through the Canadian Arctic Archipelago and the Beaufort Sea, will be used more in the future for shipping goods between Asia, North America, and Europe. Average sea ice covered area in either the Arctic or the Antarctic is about the same (about 15 million km2) during the winter. However, because the mean thickness of sea ice is 3 and 1.5?m in the Arctic and the Antarctic, respectively, the maximum volume of the sea ice cover in the Arctic (about 0.045 million km3) is nearly twice that of the Antarctic. In summer, ice extent shrinks significantly to about 50% of the winter coverage in the Arctic. Nearly 90% of the sea ice coverage disappears by the end of the summer in the Antarctic. Ice that melts completely during the summer is called “seasonal ice” or “annual ice.” If the ice melts only partially, then the part that survives until the next winter and growth season is called “perennial ice.” This can be second-year or multiyear ice depending on how many summers the ice has survived. As a major component of the cryosphere, sea ice influences the global ocean and atmosphere in a profound manner. Its continuous interaction with the underlying oceans and the overlaying atmosphere leaves major impacts on weather, climate, and ocean current systems. Moreover, ice in one form or the other plays a significant role in the daily life of communities inhabiting the cold regions of Earth. Sea ice in particular influences the coastal areas in most of the circumpolar nations of the Northern Hemisphere. It affects to a lesser extent a few countries in the Southern Hemisphere. Of all the countries of the world, Canada has the longest coastline and has the largest reservoir of freshwater lakes and rivers with floating ice in them annually at least for half of the year. Except for Alaska, practically all the areas north of the 49°N in North America belong to Canada. While sea ice plays a major role in areas above 60° (north or south) it does not affect areas below that latitude except in the Hudson Bay, Labrador Sea, and the Gulf of St. Lawrence in Canada and to a relatively lesser extent in the Baltic Sea, Gulfs of Bothnia and Fin in Europe, the Sea of Okhotsk, north of Japan, and Bohai Bay in China. Above about 35°N in Eurasia and North America, most of the streams, rivers, and lakes (Black Sea, Sea of Azo, and Caspean Sea in Eurasia and the Great Lakes, to name a few among thousands, in North America) have some ice cover each winter. In fact, severity of winters in North America is often measured in terms of ice coverage of the five Great Lakes (Lake Superior, Lake Michigan, Lake Huron, Lake Erie, and Lake Ontario). In spite of the fact that sea ice covers vast areas of sea surface of Earth, most of the people of the primary cryospheric regions of the world have not seen it or are even aware of it. That is because most people, even within the cold regions of Earth, live far from the areas affected by sea ice. Other than a few thousand multinational scientific observers and a few annual visitors, nobody lives in the south polar zone (beyond the Antarctic Circle). Only a few small communities of the Falkland Islands and Argentina consider the Antarctic region their home. On the other hand, beyond the Arctic Circle in circumpolar areas of Alaska, Canada, Norway, and Russia, perhaps a few million people live. This is incomparable to the nearly 1500 million people living in Afghanistan, Bangladesh, China, India, Nepal, Pakistan, and Tibet who are indirectly affected by the Himalayan cryosphere, but sea ice does not exists in that region. It is not uncommon for people who live away from the circumpolar boundaries to be confused between sea ice and icebergs. Yet, general awareness about sea ice has been growing as public information about the decline of sea ice in the Arctic with its positive economic impacts and negative environmental impacts is spreading. This book, though not oriented to serve as a popular science document, provides scientific information with explanations that may hopefully expand the domain of interest in sea ice and attract a number of young scientists to pursue studies about its physical aspects as well as its detection using spaceborne remote sensing technologies. The Arctic basin consists of primarily the Canadian and the Eurasian subbasins [for details on these two basins, see Chapter 3 in Weeks, 2010]. It is extremely difficult to obtain sea ice data in these areas because of the remote locations and extreme climate conditions in which ice exists. This situation also applies, perhaps to a lesser extent to ice-rich areas north of Russia because of year-round marine activities in Barents Sea, Kara Sea, Laptev Sea, and East Siberian Sea. Until the beginning of the twentieth century information about sea ice was mainly gathered and used by the local people who lived in the sub-Arctic regions. Later, increasing information was obtained from ship sighting and harbor icing records, but the purpose remained to assist the very limited marine operations. However, since the end of World War II in 1945 and the beginning of the Cold War, there had been a significant increase in human activity in both the polar regions and in particular the Arctic. Numerous weather stations equipped to gather scientific information and military bases with airports and radar lines were constructed in Canada, Alaska, and Greenland. Although some of the supplies for the construction and maintenance of these bases were transported by aircraft, ice-strengthened ships escorted by icebreakers were extensively used during the...