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Lead (sea Ice)
A lead (, rhymes with "reed") is a large fracture within an expanse of sea ice, defining a linear area of open water that can be used for navigation purposes. Leads vary in width from meters to hundreds of meters. As is the case for polynyas (another sea ice feature involving open water), leads allow the direct interaction between the atmosphere and the ocean, and are important for Arctic sea ice ecology. Additionally it has been lately found that ice leads contribute significantly to the amount of mercury deposited onto surface and leaked into the ocean. If the air is cold enough (typically in the winter), the water within a lead quickly refreezes, such that in many cases, leads are partly or entirely covered by a thin layer of new ice.Weeks, W. F. (2010) ''On sea ice'' (Chap. 11). University of Alaska Press, Fairbanks, 664 p. Differences between leads and polynyas Unlike polynyas, which tend to occur, and remain, at a given location, leads are transient features that can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lead (sea Ice) Drawing
Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate hardness, soft and malleable, and also has a relatively low melting point. When freshly cut, lead is a shiny gray with a hint of blue. It tarnishes to a dull gray color when exposed to air. Lead has the highest atomic number of any stable nuclide, stable element and three of its isotopes are endpoints of major nuclear decay chains of heavier elements. Lead is toxic, even in small amounts, especially to children. Lead is a relatively unreactive post-transition metal. Its weak metallic character is illustrated by its amphoteric nature; lead and lead oxides react with acids and base (chemistry), bases, and it tends to form covalent bonds. Compounds of lead are usually found in the +2 oxidation state rather than the +4 state common with lighte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chukchi Sea
Chukchi Sea ( rus, Чуко́тское мо́ре, r=Chukotskoye more, p=tɕʊˈkotskəjə ˈmorʲɪ), sometimes referred to as the Chuuk Sea, Chukotsk Sea or the Sea of Chukotsk, is a marginal sea of the Arctic Ocean. It is bounded on the west by the Long Strait, off Wrangel Island, and in the east by Point Barrow, Alaska, beyond which lies the Beaufort Sea. The Bering Strait forms its southernmost limit and connects it to the Bering Sea and the Pacific Ocean. The principal port on the Chukchi Sea is Uelen in Russia. The International Date Line crosses the Chukchi Sea from northwest to southeast. It is displaced eastwards to avoid Wrangel Island as well as the Chukotka Autonomous Okrug on the Russian mainland. Geography The sea has an approximate area of and is only navigable about four months of the year. The main geological feature of the Chukchi Sea bottom is the Hope Basin, which is bound to the northeast by the Herald Arch. Depths less than occupy 56% of the total a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sea Ice
Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oceans. Much of the world's sea ice is enclosed within the polar ice packs in the Earth's polar regions: the Arctic ice pack of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean. Polar packs undergo a significant yearly cycling in surface extent, a natural process upon which depends the Arctic ecology, including the ocean's ecosystems. Due to the action of winds, currents and temperature fluctuations, sea ice is very dynamic, leading to a wide variety of ice types and features. Sea ice may be contrasted with icebergs, which are chunks of ice shelves or glaciers that calve into the ocean. Depending on location, sea ice expanses may also incorporate icebergs. General features and dynamics Sea ice does not simply grow a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polynya
A polynya () is an area of open water surrounded by sea ice. It is now used as a geographical term for an area of unfrozen seawater within otherwise contiguous pack ice or fast ice. It is a loanword from the Russian полынья (), which refers to a natural ice hole and was adopted in the 19th century by polar explorers to describe navigable portions of the sea. There are two main types of polynyas: coastal polynyas, which can be found year-round near the Antarctic and Arctic coasts and are mainly created by strong winds pushing the ice away from the coast, and mid-sea or open-ocean polynyas, which may be found more sporadically in the middle of ice pack in certain locations, especially around Antarctica. These locations are generally preconditioned by certain oceanic dynamics. One of the most famous mid-sea polynyas is the Weddell Polynya, also known as the Maud Rise Polynya, which occurs in the Lazarev Sea over the Maud Rise seamount. It was first spotted in September 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arctic Sea Ice Ecology And History
The Arctic sea ice covers less area in the summer than in the winter. The multi-year (i.e. perennial) sea ice covers nearly all of the central deep basins. The Arctic sea ice and its related biota are unique, and the year-round persistence of the ice has allowed the development of ice endemic species, meaning species not found anywhere else. There are differing scientific opinions about how long perennial sea ice has existed in the Arctic. Estimates range from 700,000 to 4 million years. Endemic species The specialized, sympagic (i.e. ice-associated) community within the sea ice is found in the tiny (mostly <1mm diameter) liquid filled network of pores and brine channels or at the ice-water interface. The organisms living within the sea ice are consequently small (<1mm), and dominated by , and unicellular plants and animals. |
Sea Ice
Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oceans. Much of the world's sea ice is enclosed within the polar ice packs in the Earth's polar regions: the Arctic ice pack of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean. Polar packs undergo a significant yearly cycling in surface extent, a natural process upon which depends the Arctic ecology, including the ocean's ecosystems. Due to the action of winds, currents and temperature fluctuations, sea ice is very dynamic, leading to a wide variety of ice types and features. Sea ice may be contrasted with icebergs, which are chunks of ice shelves or glaciers that calve into the ocean. Depending on location, sea ice expanses may also incorporate icebergs. General features and dynamics Sea ice does not simply grow a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synoptic Scale Meteorology
The synoptic scale in meteorology (also known as large scale or cyclonic scale) is a horizontal length scale of the order of 1000 kilometers (about 620 miles) or more. This corresponds to a horizontal scale typical of mid-latitude depressions (e.g., extratropical cyclones). Most high- and low-pressure areas seen on weather maps (such as surface weather analyses) are synoptic-scale systems, driven by the location of Rossby waves in their respective hemisphere. Low-pressure areas and their related frontal zones occur on the leading edge of a trough within the Rossby wave pattern, while high-pressure areas form on the back edge of the trough. Most precipitation areas occur near frontal zones. The word ''synoptic'' is derived from the Greek word ('), meaning ''seen together''. The Navier–Stokes equations applied to atmospheric motion can be simplified by scale analysis in the synoptic scale. It can be shown that the main terms in horizontal equations are Coriolis force and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fast Ice
Fast ice (also called ''land-fast ice'', ''landfast ice'', and ''shore-fast ice'') is sea ice that is "fastened" to the coastline, to the sea floor along shoals or to grounded icebergs.Leppäranta, M. 2011. The Drift of Sea Ice. Berlin: Springer-Verlag. Fast ice may either grow in place from the sea water or by freezing pieces of drifting ice to the shore or other anchor sites.Kovacs, A.and M. Mellor. 1974. "Sea ice morphology and ice as a geologic agent in the Southern Beaufort Sea." pp. 113-164, in: ''The Coast and Shelf of the Beaufort Sea'', J.C. Reed and J.E. Sater (Eds.), Arlington, Va.: U.S.A. Unlike drift (or pack) ice, fast ice does not move with currents and winds. The width (and the presence) of this ice zone is usually seasonal and depends on ice thickness, topography of the sea floor and islands. It ranges from a few meters to several hundred kilometers. Seaward expansion is a function of a number of factors, notably water depth, shoreline protection, time of ye ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drift Ice
Drift ice, also called brash ice, is sea ice that is not attached to the shoreline or any other fixed object (shoals, grounded icebergs, etc.).Leppäranta, M. 2011. The Drift of Sea Ice. Berlin: Springer-Verlag. Unlike fast ice, which is "fastened" to a fixed object, drift ice is carried along by winds and sea currents, hence its name. When drift ice is driven together into a large single mass (>70% coverage), it is called pack ice. Wind and currents can pile up that ice to form ridges up to tens of metres in thickness. These represent a challenge for icebreakers and offshore structures operating in cold oceans and seas. Drift ice consists of ice floes, individual pieces of sea ice or more across. Floes are classified according to size: ''small'' – to ; ''medium'' – to ; ''big'' – to ; ''vast'' – to ; and ''giant'' – more than . Drift ice affects: * Security of navigation * Climatic impact (see Polar ice packs) * Geological impact * Biosphere influence (see ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pressure Ridge (ice)
A pressure ridge, when consisting of ice, is a linear pile-up of sea ice fragments formed in pack ice by accumulation in the convergence between floes. Such a pressure ridge develops in an ice cover as a result of a stress regime established within the plane of the ice. Within sea ice expanses, pressure ridges originate from the interaction between floes,A ''floe'' is any individual piece of sea ice larger than . as they collide with each other.http://nsidc.org/cryosphere/seaice/index.html .Weeks, W. F. (2010) ''On sea ice''. University of Alaska Press, Fairbanks, 664 p. Currents and winds are the main driving forces, but the latter are particularly effective when they have a predominant direction. Pressure ridges are made up of angular ice blocks of various sizes that pile up on the floes. The part of the ridge that is above the water surface is known as the ''sail''; that below it as the ''keel''.These terms also apply for any floating ice feature, such as icebergs. Pressure ri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Finger Rafting
Finger rafting develops in an ice cover as a result of a compression regime established within the plane of the ice. As two expanses of sea ice converge toward another, one of them slides smoothly on top of the other (it is overthrusted) along a given distance, resulting in a local increase in ice thickness. The term ''finger rafting'' refers to the systematic alternation of interlocking overthrusts and underthrusts involved in this process. Such a pattern derives its name from its resemblance to the interlocking of fingers. The process ''Rafting'', also called ''telescoped ice'', is most noticeable when it involves new and young ice, but also occurs in ice of all thicknesses.Weeks, W. F. (2010) ''On sea ice'' (Chap. 12). University of Alaska Press, Fairbanks, 664 p. The process of finger rafting as such is commonly observed inside a lead, once a thin layer of ice (at the nilas stage) has formed. Although this ice is typically very weak (it is unable to support its own wei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frazil Ice
Frazil ice is a collection of loose, randomly oriented ice crystals millimeter and sub-millimeter in size, with various shapes, e.g. elliptical disks, dendrites, needles and of an irregular nature. Frazil ice forms during the winter in open-water reaches of rivers as well as in lakes and reservoirs, where and when the water is in a turbulent state, which is, in turn, induced by the action of waves and currents. Turbulence causes the water column to become supercooled, as the heat exchange between the air and the water is such that the water temperature drops below its freezing point (in order of a few tenths of °C or less). The vertical mixing associated with that turbulence provides enough energy to overcome the crystals' buoyancy, thus keeping them from floating at the surface. Frazil ice also forms in oceans, where windy conditions, wave regimes and cold air also favor the establishment of a supercooled layer. Frazil ice can be found on the downwind side of leads, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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