|
Ice Divide
An ice divide is the boundary on an ice sheet, ice cap or glacier separating opposite flow directions of ice, analogous to a water divide. Ice divides are important for geochronological investigations that use ice cores, since such coring is typically made at highest point of an ice sheet dome to avoid disturbances arising from horizontal ice movement. Ice divides are used for looking at how the atmosphere varied over time. Coring at dome peaks increases precision of reconstructions as it is the place where horizontal motion is at its least. The Raymond Effect operates at ice divides, creating anticlines in the radar-detected isochrones, allowing greater capture of older ice when coring. Analysis of ice cores relies on the downward motion of ice, trapping changes of atmospheric gases through time into its layers. Scientist locate ice divides and take ice cores from them, which are typically long cylindrical poles of ice, and analyse them to find chemical elements that the snow and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ice Sheet
In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacier, glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are the Antarctic ice sheet and the Greenland ice sheet. Ice sheets are bigger than ice shelf, ice shelves or alpine glaciers. Masses of ice covering less than 50,000 km2 are termed an ice cap. An ice cap will typically feed a series of glaciers around its periphery. Although the surface is cold, the base of an ice sheet is generally warmer due to Geothermal activity, geothermal heat. In places, melting occurs and the melt-water lubricates the ice sheet so that it flows more rapidly. This process produces fast-flowing channels in the ice sheet — these are ice streams. Even stable ice sheets are continually in motion as the ice gradually flows outward from the central plateau, which is the tallest point of the ice sheet, and towards the margins. The ice sheet slope is low around the plate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Greenhouse Effect
The greenhouse effect occurs when greenhouse gases in a planet's atmosphere insulate the planet from losing heat to space, raising its surface temperature. Surface heating can happen from an internal heat source (as in the case of Jupiter) or come from an external source, such as its host star. In the case of Earth, the Sun emits shortwave radiation (sunlight) that passes through greenhouse gases to heat the Earth's surface. In response, the Earth's surface emits outgoing longwave radiation, longwave radiation that is mostly Absorption (electromagnetic radiation), absorbed by greenhouse gases. The absorption of longwave radiation prevents it from reaching space, reducing the rate at which the Earth can cool off. Without the greenhouse effect, the Earth's average surface temperature would be as cold as . This is of course much less than the 20th century average of about . In addition to naturally present greenhouse gases, burning of fossil fuels has greenhouse gas emissions, in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
West Antarctic Ice Sheet
The West Antarctic Ice Sheet (WAIS) is the segment of the Antarctic ice sheet, continental ice sheet that covers West Antarctica, the portion of Antarctica on the side of the Transantarctic Mountains that lies in the Western Hemisphere. It is classified as a marine-based ice sheet, meaning that its bed lies well below sea level and its edges flow into floating ice shelves. The WAIS is bounded by the Ross Ice Shelf, the Ronne Ice Shelf, and outlet glaciers that drain into the Amundsen Sea. As a smaller part of Antarctica, WAIS is also more strongly affected by climate change. There has been warming over the ice sheet since the 1950s, and a substantial retreat of its coastal glaciers since at least the 1990s. Estimates suggest it added around to the global sea level rise between 1992 and 2017, and has been losing ice in the 2010s at a rate equivalent to of annual sea level rise. While some of its losses are offset by the growth of the East Antarctic ice sheet, Antarctica as a whol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Climate
Climate is the long-term weather pattern in a region, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorological variables that are commonly measured are temperature, humidity, atmospheric pressure, wind, and precipitation. In a broader sense, climate is the state of the components of the climate system, including the atmosphere, hydrosphere, cryosphere, lithosphere and biosphere and the interactions between them. The climate of a location is affected by its latitude, longitude, terrain, altitude, land use and nearby water bodies and their currents. Climates can be classified according to the average and typical variables, most commonly temperature and precipitation. The most widely used classification scheme is the Köppen climate classification. The Thornthwaite system, in use since 1948, incorporates evapotranspiration along ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antarctic Ice Sheet
The Antarctic ice sheet is a continental glacier covering 98% of the Antarctic continent, with an area of and an average thickness of over . It is the largest of Earth's two current ice sheets, containing of ice, which is equivalent to 61% of all fresh water on Earth. Its surface is nearly continuous, and the only ice-free areas on the continent are the dry valleys, nunataks of the Antarctic mountain ranges, and sparse coastal bedrock. However, it is often subdivided into the East Antarctic ice sheet (EAIS), West Antarctic ice sheet (WAIS), and Antarctic Peninsula (AP), due to the large differences in topography, ice flow, and glacier mass balance between the three regions. Because the East Antarctic ice sheet is over 10 times larger than the West Antarctic ice sheet and located at a higher elevation, it is less vulnerable to climate change than the WAIS. In the 20th century, EAIS had been one of the only places on Earth which displayed limited cooling instead of warming, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Ice Core Laboratory
The National Science Foundation Ice Core Facility (NSF-ICF), known as the National Ice Core Laboratory (NICL) before 2018, is the primary repository for ice cores collected by the United States. The facility is located at the Denver Federal Center in Lakewood, Colorado, and is managed by the United States Geological Survey (USGS). Funding for the facility comes from the National Science Foundation Office of Polar Programs, while scientific research is managed by the University of New Hampshire. NSF-ICF currently houses ~22,000 m of ice cores collected from Greenland and Antarctica, including the GISP2, Siple Dome, and portions of the Vostok cores. It is the lead facility for management of the West Antarctic Ice Sheet (WAIS) Divide ice core. In addition to providing a large storage facility, maintained at -35 ° C, NSF-ICF also has one of the largest sub-zero research and sample preparation spaces in the world. NSF-ICF is responsible for distributing samples of ice cores in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
WAIS Divide
The WAIS Divide is the ice flow divide on the West Antarctic Ice Sheet (WAIS) which is a linear boundary that separates the region where the ice flows to the Ross Sea, from the region where the ice flows to the Weddell Sea. It is similar to a continental hydrographic divide. Ice core project The WAIS Divide ice core project (West Antarctic Ice Sheet Divide ice core project) investigated past climate changes, ice sheet dynamics and cryobiology. The project was completed by the United States Antarctic Program (USAP) and was funded by the National Science Foundation (NSF). The focus of the project was to develop records spanning the last ~ 80,000 years of the concentration of greenhouse gases in the atmosphere and Antarctic climate, and to do this with the highest possible time resolution. The project is best known for producing records of atmospheric carbon dioxide and methane with high time resolution and dating accuracy. This was accomplished by collecting and analyzing an ice co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Greenhouse Gas
Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. Unlike other gases, greenhouse gases absorb the radiations that a planet emits, resulting in the greenhouse effect. The Earth is warmed by sunlight, causing its surface to radiate heat, which is then mostly absorbed by greenhouse gases. Without greenhouse gases in the atmosphere, the average temperature of Earth's surface would be about , rather than the present average of .Le Treut, H., R. Somerville, U. Cubasch, Y. Ding, C. Mauritzen, A. Mokssit, T. Peterson and M. Prather, 2007:Chapter 1: Historical Overview of Climate Change. In:Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. olomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.) Cambridge University Press, Cambridge, United Kingdom and New Y ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ground-penetrating Radar
Ground-penetrating radar (GPR) is a geophysical method that uses radar pulses to image the subsurface. It is a non-intrusive method of surveying the sub-surface to investigate underground utilities such as concrete, asphalt, metals, pipes, cables or masonry. This nondestructive method uses electromagnetic radiation in the microwave band ( UHF/ VHF frequencies) of the radio spectrum, and detects the reflected signals from subsurface structures. GPR can have applications in a variety of media, including rock, soil, ice, fresh water, pavements and structures. In the right conditions, practitioners can use GPR to detect subsurface objects, changes in material properties, and voids and cracks. GPR uses high-frequency (usually polarized) radio waves, usually in the range 10 MHz to 2.6 GHz. A GPR transmitter and antenna emits electromagnetic energy into the ground. When the energy encounters a buried object or a boundary between materials having different permittivities, it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ice Cap
In glaciology, an ice cap is a mass of ice that covers less than of land area (usually covering a highland area). Larger ice masses covering more than are termed ice sheets. Description By definition, ice caps are not constrained by topographical features (i.e., they must lie over the top of mountains). By contrast, ice masses of similar size that ''are'' constrained by topographical features are known as ice fields. The ''dome'' of an ice cap is usually centred on the highest point of a massif. Ice flows away from this high point (the ice divide) towards the ice cap's periphery. Ice caps significantly affect the geomorphology of the area they occupy. Plastic moulding, gouging and other glacial erosional features become present upon the glacier's retreat. Many lakes, such as the Great Lakes in North America, as well as numerous valleys have been formed by glacial action over hundreds of thousands of years. The Antarctic and Greenland contain 99% of the ice volume on earth, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anticline
In structural geology, an anticline is a type of Fold (geology), fold that is an arch-like shape and has its oldest Bed (geology), beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex curve, convex up in which the hinge or crest is the location where the curvature is greatest, and the limbs are the sides of the fold that Strike and dip, dip away from the hinge. Anticlines can be recognized and differentiated from antiforms by a sequence of rock layers that become progressively older toward the center of the fold. Therefore, if age relationships between various Stratum, rock strata are unknown, the term antiform should be used. The progressing age of the rock strata towards the core and uplifted center, are the trademark indications for evidence of anticlines on a geological map. These formations occur because anticlinal ridges typically develop above thrust faults during crustal deformations. The uplifted core of the fold cau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Raymond Effect
Raymond Effect is a flow effect in ice sheets, occurring at flow divides, which gives rise to disturbances in the stratigraphy, showing unusual arches or anticlines called ''Raymond Arches''. The stratigraphy is detected by radio-echo sounding. The Raymond Effect arises from the unusual flow properties of ice, as its viscosity decreases with stress. It is of importance because it provides field evidence for the flow properties of ice. In addition, it permits dating of changes in ice flow and the establishment of changes in ice thickness. The effect was first predicted by Charles F. Raymond. Raymond Arches and the Raymond Effect have been observed at numerous other ice divides e.g. Siple Dome, Fletcher Ice Rise, Berkner Island, Roosevelt Island, and Korff Ice Rise. Ice viscosity Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it correspon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
