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84-573: The lake is threatened by salt water contamination from disappearing sea ice , as well as oil drilling in Alpine, Alaska and by ConocoPhilipps Willow project . Its name comes from the Iñupiaq language Tasiqpak , recorded by Rochfort Maguire as Tasok-poh in 1854, and reported to mean "big lagoon", "big enclosed coastal water" or "big coastal lake". It is also known as Lake Teshekpuk,Tasekpuk Lake,Tasirkpuk Lake,Tasyukpun and Tasiqpak. Teshekpuk Lake

168-430: A beach with a light swell, ice eggs up to the size of a football can be created. Nilas designates a sea ice crust up to 10 centimetres (3.9 in) in thickness. It bends without breaking around waves and swells. Nilas can be further subdivided into dark nilas – up to 5 cm (2.0 in) in thickness and very dark and light nilas – over 5 cm (2.0 in) in thickness and lighter in color. Young ice

252-445: A certain point such a disc shape becomes unstable and the growing isolated crystals take on a hexagonal, stellar form, with long fragile arms stretching out over the surface. These crystals also have their c-axis vertical. The dendritic arms are very fragile and soon break off, leaving a mixture of discs and arm fragments. With any kind of turbulence in the water, these fragments break up further into random-shaped small crystals which form

336-462: A mile and salt water has contaminated freshwater lakes. Migratory birds, caribou and other wildlife populations have lost habitat, and the sparse human infrastructure along the coastline has been damaged. According to Stan Senner, executive director of Audubon Alaska, "The area (Teshekpuk Lake) is one of the most important areas in the entire Arctic, and I don't just mean in Arctic Alaska...It

420-402: A more unified bureau mission and recognized the value of the remaining public lands by declaring that these lands would remain in public ownership. The law directed that these lands be managed with a view toward "multiple use" defined as "management of the public lands and their various resource values so that they are utilized in the combination that will best meet the present and future needs of

504-569: A much more reliable measure of long-term changes in sea ice. In comparison to the extended record, the sea-ice extent in the polar region by September 2007 was only half the recorded mass that had been estimated to exist within the 1950–1970 period. Arctic sea ice extent ice hit an all-time low in September 2012, when the ice was determined to cover only 24% of the Arctic Ocean, offsetting the previous low of 29% in 2007. Predictions of when

588-547: 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. Sea ice does not simply grow and melt. During its lifespan, it

672-614: A pilot project on the Pryor Mountains Wild Horse Range known as the Adopt-A-Horse initiative. The program took advantage of provisions in the WFRHBA to allow private "qualified" individuals to "adopt" as many horses as they wanted if they could show that they could provide adequate care for the animals. At the time, title to the horses remained permanently with the federal government. The pilot project

756-633: A process called congelation growth. This growth process yields first-year ice. In rough water, fresh sea ice is formed by the cooling of the ocean as heat is lost into the atmosphere. The uppermost layer of the ocean is supercooled to slightly below the freezing point, at which time tiny ice platelets (frazil ice) form. With time, this process leads to a mushy surface layer, known as grease ice . Frazil ice formation may also be started by snowfall , rather than supercooling. Waves and wind then act to compress these ice particles into larger plates, of several meters in diameter, called pancake ice . These float on

840-513: A regular and recurring presence on a vast amount of public lands, roads and recreation sites. They focus on the protection of natural and cultural resources, other BLM employees and visitors. Given the many locations of BLM public lands, these rangers use canines, helicopters, snowmobiles, dirt bikes and boats to perform their duties. By contrast BLM special agents are criminal investigators who plan and conduct investigations concerning possible violations of criminal and administrative provisions of

924-479: A standard protocol for studying the output of coupled atmosphere-ocean general circulation models. The coupling takes place at the atmosphere-ocean interface where the sea ice may occur. In addition to global modeling, various regional models deal with sea ice. Regional models are employed for seasonal forecasting experiments and for process studies . Sea ice is part of the Earth's biosphere . When sea water freezes,

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1008-442: A state of shear . Sea ice deformation results from the interaction between ice floes, as they are driven against each other. The result may be of three types of features: 1) Rafted ice , when one piece is overriding another; 2) Pressure ridges , a line of broken ice forced downward (to make up the keel ) and upward (to make the sail ); and 3) Hummock , a hillock of broken ice that forms an uneven surface. A shear ridge

1092-421: A suspension of increasing density in the surface water, an ice type called frazil or grease ice . In quiet conditions the frazil crystals soon freeze together to form a continuous thin sheet of young ice; in its early stages, when it is still transparent – that is the ice called nilas . Once nilas has formed, a quite different growth process occurs, in which water freezes on to the bottom of the existing ice sheet,

1176-608: Is a 22 miles (35 km) wide lake on the Alaska North Slope within the National Petroleum Reserve-Alaska . It is South of Pitt Point, 12 miles (19 km) east of Harrison Bay , 80 miles (130 km) east of Point Barrow . Teshekpuk Lake is the largest lake in Arctic Alaska, and the largest thermokarst lake in the world. The Teshekpuk Lake region is considered one of the most productive, diverse, and sensitive wetland ecosystems in

1260-422: Is a general term used for recently frozen sea water that does not yet make up solid ice. It may consist of frazil ice (plates or spicules of ice suspended in water), slush (water saturated snow), or shuga (spongy white ice lumps a few centimeters across). Other terms, such as grease ice and pancake ice , are used for ice crystal accumulations under the action of wind and waves. When sea ice begins to form on

1344-464: Is a pressure ridge that formed under shear – it tends to be more linear than a ridge induced only by compression. A new ridge is a recent feature – it is sharp-crested, with its side sloping at an angle exceeding 40 degrees. In contrast, a weathered ridge is one with a rounded crest and with sides sloping at less than 40 degrees. Stamukhi are yet another type of pile-up but these are grounded and are therefore relatively stationary. They result from

1428-447: Is a significant source of errors in sea-ice thickness retrieval using radar and laser satellite altimetry, resulting in uncertainties of 0.3–0.4 m. Changes in sea ice conditions are best demonstrated by the rate of melting over time. A composite record of Arctic ice demonstrates that the floes' retreat began around 1900, experiencing more rapid melting beginning within the past 50 years. Satellite study of sea ice began in 1979 and became

1512-465: Is a transition stage between nilas and first-year ice and ranges in thickness from 10 cm (3.9 in) to 30 cm (12 in), Young ice can be further subdivided into grey ice – 10 cm (3.9 in) to 15 cm (5.9 in) in thickness and grey-white ice – 15 cm (5.9 in) to 30 cm (12 in) in thickness. Young ice is not as flexible as nilas, but tends to break under wave action. Under compression, it will either raft (at

1596-829: Is called landfast ice, or more often, fast ice (as in fastened ). Alternatively and unlike fast ice, drift ice occurs further offshore in very wide areas and encompasses ice that is free to move with currents and winds. The physical boundary between fast ice and drift ice is the fast ice boundary . The drift ice zone may be further divided into a shear zone , a marginal ice zone and a central pack . Drift ice consists of floes , individual pieces of sea ice 20 metres (66 ft) or more across. There are names for various floe sizes: small – 20 to 100 m (66 to 328 ft); medium – 100 to 500 m (330 to 1,640 ft); big – 500 to 2,000 m (1,600 to 6,600 ft); vast – 2 to 10 kilometres (1.2 to 6.2 mi); and giant – more than 10 km (6.2 mi). The term pack ice

1680-620: Is less dense than water, it floats on the ocean's surface (as does fresh water ice). 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,

1764-602: Is not protected by a national park or monument designation. The BLM's May 30, 2019 statement proposed an additional 183,668 acres on "lands managed by the Canyon Country, Color Country, Green River, and West Desert districts" that would be listed for the quarterly oil and gas lease sale on September 10, 2019. In their May 2019, September lease offerings, the BLM said that they had "245 million acres of public land located primarily in 12 Western states, including Alaska" and across

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1848-673: Is part of the East Asian–Australasian Flyway site network. While the lake covers just 18 percent of the National Petroleum Reserve-Alaska , it hosts more than 40 percent of all aquatic birds visiting the Alaska North Slope . In 1963, the Teshekpuk Lake research station was established. In 2007, the observatory was reestablished with research projects funded by National Science Foundation , U.S. Geological Survey , Bureau of Land Management, European Space Agency, and European Union. It studies impacts of climate change on

1932-585: Is particularly common around Antarctica . Russian scientist Vladimir Vize (1886–1954) devoted his life to study the Arctic ice pack and developed the Scientific Prediction of Ice Conditions Theory , for which he was widely acclaimed in academic circles. He applied this theory in the field in the Kara Sea , which led to the discovery of Vize Island . The annual freeze and melt cycle is set by

2016-401: Is sea ice that has survived at least one melting season ( i.e. one summer). For this reason, this ice is generally thicker than first-year sea ice. Old ice is commonly divided into two types: second-year ice , which has survived one melting season and multiyear ice , which has survived more than one. (In some sources, old ice is more than two years old.) Multi-year ice is much more common in

2100-482: Is simply the most important goose-molting area in the Arctic." On January 11, 2006, the U.S. Department of the Interior (DOI) approved oil and gas drilling on approximately 500,000 acres (2,000 km) of land in and around Teshekpuk Lake. Up to 90,000 geese congregate in this area in summer to undergo wing molt, and up to 46,000 caribou use the area for both calving and migration. Some environmental groups contested

2184-637: Is the SIG Sauer P320 chambered in 9mm which is replacing the SIG Sauer P226 /P229 both chambered in .40 S&W. The BLM manages free-roaming horses and burros on public lands in ten western states. Though they are feral , the agency is obligated to protect them under the Wild and Free-Roaming Horses and Burros Act of 1971 (WFRHBA). As the horses have few natural predators, populations have grown substantially. WFRHBA as enacted provides for

2268-540: Is the agency's largest ever purchase in the state. In 2024 the Department of the Interior has begun to advance a new rule according to which the Bureau of Land Management can distribute restoration leases and mitigation leases exactly in the same way as it distributes new leases for oil and gas drilling. The designed land will be used for nature conservation including use of indigenous knowledge. Established in 2000,

2352-518: Is the main driving force, along with ocean currents. The Coriolis force and sea ice surface tilt have also been invoked. These driving forces induce a state of stress within the drift ice zone. An ice floe converging toward another and pushing against it will generate a state of compression at the boundary between both. The ice cover may also undergo a state of tension , resulting in divergence and fissure opening. If two floes drift sideways past each other while remaining in contact, this will create

2436-426: Is used either as a synonym to drift ice , or to designate drift ice zone in which the floes are densely packed. The overall sea ice cover is termed the ice canopy from the perspective of submarine navigation. Another classification used by scientists to describe sea ice is based on age, that is, on its development stages. These stages are: new ice , nilas , young ice , first-year and old . New ice

2520-448: Is very dynamic. Due to the combined action of winds, currents, water temperature and air temperature fluctuations, sea ice expanses typically undergo a significant amount of deformation. Sea ice is classified according to whether or not it is able to drift and according to its age. Sea ice can be classified according to whether or not it is attached (or frozen) to the shoreline (or between shoals or to grounded icebergs ). If attached, it

2604-502: The Arctic than it is in the Antarctic . The thickness of old sea ice typically ranges from 2 to 4 m. The reason for this is that sea ice in the south drifts into warmer waters where it melts. In the Arctic, much of the sea ice is land-locked. While fast ice is relatively stable (because it is attached to the shoreline or the seabed), drift (or pack) ice undergoes relatively complex deformation processes that ultimately give rise to sea ice's typically wide variety of landscapes. Wind

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2688-472: The Department of the Interior . It took several years for this new agency to integrate and reorganize. In the end, the Bureau of Land Management became less focused on land disposal and more focused on the long term management and preservation of the land. The agency achieved its current form by combining offices in the western states and creating a corresponding office for lands both east of and alongside

2772-708: The Grand Staircase–Escalante National Monument in southern Utah, the first of now 20 national monuments established on BLM lands and managed by the agency. The establishment of Grand Staircase–Escalante foreshadowed later creation of the BLM's National Landscape Conservation System in 2000. Use of the Antiquities Act authority, to the extent it effectively scuttled a coal mine to have been operated by Andalex Resources , delighted recreation and conservation enthusiasts but set up larger confrontations with state and local authorities. Under

2856-565: The Homestead Act of 1862 . Most BLM public lands are located in these 12 western states: Alaska , Arizona , California , Colorado , Idaho , Montana , Nevada , New Mexico , Oregon , Utah , Washington and Wyoming . The mission of the BLM is "to sustain the health, diversity, and productivity of the public lands for the use and enjoyment of present and future generations." Originally BLM holdings were described as "land nobody wanted" because homesteaders had passed them by. All

2940-788: The Land Ordinance of 1785 and the Northwest Ordinance of 1787. These laws provided for the survey and settlement of the lands that the original Thirteen Colonies ceded to the federal government after the American Revolution . As additional lands were acquired by the United States from Spain , France and other countries, the United States Congress directed that they be explored, surveyed, and made available for settlement. During

3024-702: The Mississippi River . As a matter of course, the BLM's emphasis fell on activities in the western states as most of the mining, land sales, and federally owned areas are located west of the Mississippi. BLM personnel on the ground have typically been oriented toward local interests, while bureau management in Washington are led by presidential guidance. By means of the Federal Land Policy and Management Act of 1976, Congress created

3108-603: The National Landscape Conservation System is overseen by the BLM. The National Landscape Conservation System lands constitute just about 12% of the lands managed by the BLM. Congress passed Title II of the Omnibus Public Land Management Act of 2009 (Public Law 111-11) to make the system a permanent part of the public lands protection system in the United States. By designating these areas for conservation,

3192-729: The United States General Land Office as part of the Department of the Treasury to oversee the disposition of these federal lands. By the early 1800s, promised bounty land claims were finally fulfilled. In the 19th century, other bounty land and homestead laws were enacted to dispose of federal land. Several different types of patents existed. These include cash entry, credit, homestead, Indian, military warrants, mineral certificates, private land claims, railroads, state selections, swamps, town sites, and town lots. A system of local land offices spread throughout

3276-529: The ice dynamics and the thermodynamical properties (see Sea ice emissivity modelling , Sea ice growth processes and Sea ice thickness ). There are many sea ice model computer codes available for doing this, including the CICE numerical suite . Many global climate models (GCMs) have sea ice implemented in their numerical simulation scheme in order to capture the ice–albedo feedback correctly. Examples include: The Coupled Model Intercomparison Project offers

3360-448: The ocean surface and collide with one another, forming upturned edges. In time, the pancake ice plates may themselves be rafted over one another or frozen together into a more solid ice cover, known as consolidated pancake ice. Such ice has a very rough appearance on top and bottom. If sufficient snow falls on sea ice to depress the freeboard below sea level, sea water will flow in and a layer of ice will form of mixed snow/sea water. This

3444-571: The American people." Since the Reagan administration in the 1980s, Republicans have often given priority to local control and to grazing, mining and petroleum production, while Democrats have more often emphasized environmental concerns even when granting mining and drilling leases. In September 1996, then President Bill Clinton used his authority under the Antiquities Act to establish

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3528-503: The BLM and other statutes under the United States Code. Special agents are normally plain clothes officers who carry concealed firearms and other defensive equipment, make arrests, carry out complex criminal investigations, present cases for prosecution to local United States Attorneys and prepare investigative reports. Criminal investigators occasionally conduct internal and civil claim investigations. The current sidearm

3612-605: The BLM oversees more than 247.3 million acres (1,001,000 km ) of land, or one-eighth of the United States's total landmass. The Bureau was created by Congress during the presidency of Harry S. Truman in 1946 by combining two existing agencies: the United States General Land Office and the Grazing Service . The agency manages the federal government's nearly 700 million acres (2,800,000 km ) of subsurface mineral estate located beneath federal, state and private lands severed from their surface rights by

3696-633: The Biden administration, the BLM is working on a pilot project called "outcomes-based grazing", to see if cattle grazing can help achieve conservation, agency director Tracy Stone-Manning said in an interview published in April 2022. In June 2022, the BLM finalized two acquisitions in Colorado and Wyoming, acquiring over 40,000 acres of previously inaccessible land. The acquisition in Wyoming for 35,670 acres

3780-566: The DOI decision to allow drilling. The decision stipulated that no surface drilling would be allowed on land considered crucial for molting geese or caribou, and a maximum of 2,100 acres (8.5 km) in seven different zones could be permanently disturbed on the surface. On September 25, 2006, the U.S. District Court for the District of Alaska issued a decision that removed the wildlife habitat around Teshekpuk Lake from an oil and gas lease sale that

3864-448: The Earth's temperature gets warmer. Furthermore, the sea ice itself functions to help keep polar climates cool, since the ice exists in expansive enough amounts to maintain a cold environment. At this, sea ice's relationship with global warming is cyclical; the ice helps to maintain cool climates, but as the global temperature increases, the ice melts and is less effective in keeping those climates cold. The bright, shiny surface ( albedo ) of

3948-536: The National Conservation Lands include nearly 2,400 miles of Wild and Scenic Rivers , and nearly 6,000 miles of National Scenic and Historic Trails . There are more than 63,000 oil and gas wells on BLM public lands. Total energy leases generated approximately $ 5.4 billion in 2013, an amount divided among the Treasury , the states, and Native American groups. The BLM's roots go back to

4032-568: The National Parks and Public Land Legacy Restoration Fund each year for five years for needed maintenance for critical facilities and infrastructure in national parks, forests, wildlife refuges, recreation areas and American Indian schools. The Act also committed $ 900 million a year in royalties from offshore oil and natural gas to permanently fund the Land and Water Conservation Fund investments in conservation and recreation opportunities across

4116-570: The Revolutionary War, military bounty land was promised to soldiers who fought for the colonies. After the war, the Treaty of Paris of 1783 , signed by the United States, the UK , France , and Spain , ceded territory to the United States. In the 1780s, other states relinquished their own claims to land in modern-day Ohio . By this time, the United States needed revenue to function and land

4200-764: The Secretary of Interior and the CEO of ConocoPhillips. Environmentalists and the region's Iñupiat have also cited the impacts of global climate change as a reason to oppose drilling in land near Teshekpuk Lake. As Teshekpuk Lake will be affected by the ConocoPhilips Willow project , the Alaska Native corporation of the village of Nuiqsut suggested its protection in August 2022. Sea ice Sea ice arises as seawater freezes. Because ice

4284-609: The Trump administration, the BLM offered millions of acres of available Federal lands for 10-year leases for commercial development, potentially in oil and gas and mining, with the stated goal of "promoting American energy security". The BLM holds quarterly oil and gas lease sales. According to a June 18, 2018 article in The Atlantic , under the tenure of then- United States Secretary of the Interior , Ryan Zinke "practically gave away hundreds of thousands of acres of open land across

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4368-561: The United States another "700 million acres of sub-surface mineral estate" is under their management. The statement also said that these "diverse activities authorized on these lands generated $ 96 billion in sales of goods and services throughout the American economy in fiscal year 2017" while supporting over 468,000 jobs". On August 4, 2020, President Trump signed the Great American Outdoors Act into law, committing up to $ 1.9 billion from energy development revenues to

4452-803: The United States. There are several herds of horses and burros roaming free on 26.9 million acres of range spread out in ten western states. It is essential to maintain a balance that keeps herd management land and animal population healthy. Some programs and partnerships include the Mustang Heritage Foundation, U.S. Border Patrol, Idaho 4H, Napa Mustang Days and Little Book Cliffs Darting Team. These partnerships help with adoption and animal population as well as education and raising awareness about wild horses and burros. In 2009, BLM opened Renewable Energy Coordination Offices in order to approve and oversee wind, solar, biomass, and geothermal projects on BLM-managed lands. The offices were located in

4536-799: The West, leasing it to energy companies for pennies on the dollar." The Salt Lake Tribune reported that in March 2019, the price per acre for leases near the Golden Spike National Historical Park , in Utah were "$ 1.50 an acre for the next two years". By September 11, 2018, the Department of Interior was offering 2.9 million acres to be leased to commercial operations including drilling for oil and gas and mining in New Mexico, Colorado, Arizona, and other states where public land

4620-435: The amount of melting ice. Though the size of the ice floes is affected by the seasons, even a small change in global temperature can greatly affect the amount of sea ice and due to the shrinking reflective surface that keeps the ocean cool, this sparks a cycle of ice shrinking and temperatures warming. As a result, the polar regions are the most susceptible places to climate change on the planet. Furthermore, sea ice affects

4704-557: The annual cycle of solar insolation and of ocean and atmospheric temperature and of variability in this annual cycle. In the Arctic, the area of ocean covered by sea ice increases over winter from a minimum in September to a maximum in March or sometimes February, before melting over the summer. In the Antarctic, where the seasons are reversed, the annual minimum is typically in February and the annual maximum in September or October and

4788-399: The arctic environment, permafrost dynamics and thermokarst, lake ice systems, coastal and lake shoreline erosion, aquatic and terrestrial ecology, near-surface geophysics, and paleoecological studies. In July 2007, a study reported that the disappearance of sea ice near Teshekpuk Lake has been causing rapid erosion in the marshy, wildlife-rich area. In some places, the sea has pushed in half

4872-415: The bottom of the ocean. This cold water moves along the ocean floor towards the equator, while warmer water on the ocean surface moves in the direction of the poles. This is referred to as " conveyor belt motion" and is a regularly occurring process. In order to gain a better understanding about the variability, numerical sea ice models are used to perform sensitivity studies . The two main ingredients are

4956-499: The coastline. Only the top layer of water needs to cool to the freezing point. Convection of the surface layer involves the top 100–150 m (330–490 ft), down to the pycnocline of increased density. In calm water, the first sea ice to form on the surface is a skim of separate crystals which initially are in the form of tiny discs, floating flat on the surface and of diameter less than 0.3 cm (0.12 in). Each disc has its c-axis vertical and grows outwards laterally. At

5040-401: The country. Also in August 2020, the BLM headquarters was relocated to Grand Junction, Colorado , by an order signed by Interior Secretary David Bernhardt . The relocation was praised by Republican Western politicians but criticized by Democrats as a move to weaken the agency through the loss of experienced staffers, who opted to stay in Washington, D.C. Some ranchers were concerned about

5124-508: The early successes of the adoption program, the BLM has struggled to maintain acceptable herd levels, as without natural predators, herd sizes can double every four years. As of 2014, there were more than 49,000 horses and burros on BLM-managed land, exceeding the BLM's estimated "appropriate management level" (AML) by almost 22,500. The Bureau of Land Management has implemented several programs and has developed partnerships as part of their management plan for preserving wild burros and horses in

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5208-582: The entire Arctic, habitat to a variety of arctic wildlife , including the resident Teshekpuk Lake caribou herd (64,000 animals), large numbers of shorebirds and migratory waterfowl and several freshwater and anadromous fish species. Fish species include broad whitefish ( Coregonus nasus ), Arctic grayling ( Thymallus arcticus ), Burbot ( Lota lota ), Arctic cisco ( Coregonus autumnalis ), lake trout ( Salvelinus namaycush ), Dolly Varden ( Salvelinus malma ), Chinook salmon ( Oncorhynchus tshawytscha ) and chum salmon ( Oncorhynchus keta ). The lake

5292-613: The existence of "icebergs" of solid diamond and corresponding seas of liquid carbon on the ice giants , Neptune and Uranus . This is due to extreme pressure and heat at the core, that would turn carbon into a supercritical fluid . Bureau of Land Management The Bureau of Land Management ( BLM ) is an agency within the United States Department of the Interior responsible for administering U.S. federal lands . Headquartered in Washington, D.C. ,

5376-403: The first "ice free" Arctic summer might occur vary. Antarctic sea ice extent gradually increased in the period of satellite observations, which began in 1979, until a rapid decline in southern hemisphere spring of 2016. Sea ice provides an ecosystem for various polar species, particularly the polar bear , whose environment is being threatened as global warming causes the ice to melt more as

5460-712: The grey ice stage) or ridge (at the grey-white ice stage). First-year sea ice is ice that is thicker than young ice but has no more than one year growth. In other words, it is ice that grows in the fall and winter (after it has gone through the new ice – nilas – young ice stages and grows further) but does not survive the spring and summer months (it melts away). The thickness of this ice typically ranges from 0.3 m (0.98 ft) to 2 m (6.6 ft). First-year ice may be further divided into thin (30 cm (0.98 ft) to 70 cm (2.3 ft)), medium (70 cm (2.3 ft) to 120 cm (3.9 ft)) and thick (>120 cm (3.9 ft)). Old sea ice

5544-403: The ice also serves a role in maintaining cooler polar temperatures by reflecting much of the sunlight that hits it back into space. As the sea ice melts, its surface area shrinks, diminishing the size of the reflective surface and therefore causing the earth to absorb more of the sun's heat. As the ice melts it lowers the albedo thus causing more heat to be absorbed by the Earth and further increase

5628-422: The ice growth period, its bulk brine volume is typically below 5%. Air volume fraction during ice growth period is typically around 1–2 %, but may substantially increase upon ice warming. Air volume of sea ice in can be as high as 15 % in summer and 4 % in autumn. Both brine and air volumes influence sea-ice density values, which are typically around 840–910 kg/m for first-year ice. Sea-ice density

5712-571: The ice is riddled with brine-filled channels which sustain sympagic organisms such as bacteria, algae, copepods and annelids, which in turn provide food for animals such as krill and specialised fish like the bald notothen , fed upon in turn by larger animals such as emperor penguins and minke whales . A decline of seasonal sea ice puts the survival of Arctic species such as ringed seals and polar bears at risk. Other element and compounds have been speculated to exist as oceans and seas on extraterrestrial planets. Scientists notably suspect

5796-426: The ice surface during the melt season lower the albedo such that more solar radiation is absorbed, leading to a feedback where melt is accelerated. The presence of melt ponds is affected by the permeability of the sea ice (i.e. whether meltwater can drain) and the topography of the sea ice surface (i.e. the presence of natural basins for the melt ponds to form in). First year ice is flatter than multiyear ice due to

5880-484: The interaction between fast ice and the drifting pack ice. Level ice is sea ice that has not been affected by deformation and is therefore relatively flat. Leads and polynyas are areas of open water that occur within sea ice expanses even though air temperatures are below freezing and provide a direct interaction between the ocean and the atmosphere, which is important for the wildlife. Leads are narrow and linear – they vary in width from meter to km scale. During

5964-440: The isolation of Grand Junction compared to other Western cities, having limited flights and road access. After the announcement, 87% of D.C.-based employees left, prompting former lead career BLM official Steve Ellis to state "the bureau lost a tremendous amount of expertise...[of] very seasoned people." On September 17, 2021, Secretary Deb Haaland announced that the headquarters would be moved back to Washington, D.C. Under

6048-650: The lack of dynamic ridging, so ponds tend to have greater area. They also have lower albedo since they are on thinner ice, which blocks less of the solar radiation from reaching the dark ocean below. Sea ice is a composite material made up of pure ice, liquid brine, air, and salt. The volumetric fractions of these components—ice, brine, and air—determine the key physical properties of sea ice, including thermal conductivity, heat capacity, latent heat, density, elastic modulus, and mechanical strength. Brine volume fraction depends on sea-ice salinity and temperature, while sea-ice salinity mainly depends on ice age and thickness. During

6132-869: The law directed the BLM to ensure these places are protected for future generations, similar to national parks and wildlife refuges . Source: BLM Resources and Statistics The BLM, through its Office of Law Enforcement & Security, functions as a federal law enforcement agency of the United States Government. BLM law enforcement rangers and special agents receive their training through Federal Law Enforcement Training Centers (FLETC). Full-time staffing for these positions approaches 300. Uniformed rangers enforce laws and regulations governing BLM lands and resources. As part of that mission, these BLM rangers carry firearms and defensive equipment, make arrests, execute search warrants, complete reports and testify in court. They seek to establish

6216-407: The movement of ocean waters. In the freezing process, much of the salt in ocean water is squeezed out of the frozen crystal formations, though some remains frozen in the ice. This salt becomes trapped beneath the sea ice, creating a higher concentration of salt in the water beneath ice floes. This concentration of salt contributes to the salinated water's density and this cold, denser water sinks to

6300-566: The presence of sea ice abutting the calving fronts of ice shelves has been shown to influence glacier flow and potentially the stability of the Antarctic ice sheet . The growth and melt rate are also affected by the state of the ice itself. During growth, the ice thickening due to freezing (as opposed to dynamics) is itself dependent on the thickness, so that the ice growth slows as the ice thickens. Likewise, during melt, thinner sea ice melts faster. This leads to different behaviour between multiyear and first year ice. In addition, melt ponds on

6384-467: The public rangelands by establishment of advisory boards that set grazing fees. The Oregon and California Revested Lands Sustained Yield Management Act of 1937, commonly referred as the O&;C Act, required sustained yield management of the timberlands in western Oregon. In 1946, the Grazing Service was merged with the United States General Land Office to form the Bureau of Land Management within

6468-610: The removal of excess animals; the killing of lame, old, or sick animals; the private placement or adoption of excess animals; and even the killing of healthy animals if range management required it. The killing of healthy or unhealthy horses has almost never occurred. Pursuant to the Public Rangelands Improvement Act of 1978 , the BLM has established 179 "herd management areas" (HMAs) covering 31.6 million acres (128,000 km ) acres where feral horses can be found on federal lands. In 1973, BLM began

6552-602: The same, ranchers hold nearly 18,000 permits and leases for livestock grazing on 155 million acres (630,000 km ) of BLM public lands. The agency manages 221 wilderness areas , 29 national monuments and some 636 other protected areas as part of the National Conservation Lands (formerly known as the National Landscape Conservation System), totaling about 36 million acres (150,000 km ). In addition

6636-638: The territories, patenting land that was surveyed via the corresponding Office of the Surveyor General of a particular territory. This pattern gradually spread across the entire United States. The laws that spurred this system with the exception of the General Mining Law of 1872 and the Desert Land Act of 1877 have since been repealed or superseded. In the early 20th century, Congress took additional steps toward recognizing

6720-548: The value of the assets on public lands and directed the Executive Branch to manage activities on the remaining public lands. The Mineral Leasing Act of 1920 allowed leasing, exploration, and production of selected commodities, such as coal , oil , gas , and sodium to take place on public lands. The Taylor Grazing Act of 1934 established the United States Grazing Service to manage

6804-464: The winter, the water in leads quickly freezes up. They are also used for navigation purposes – even when refrozen, the ice in leads is thinner, allowing icebreakers access to an easier sail path and submarines to surface more easily. Polynyas are more uniform in size than leads and are also larger – two types are recognized: 1) Sensible-heat polynyas , caused by the upwelling of warmer water and 2) Latent-heat polynyas , resulting from persistent winds from

6888-589: Was held on September 27. The court found that the U.S. government's environmental analysis had violated federal environmental laws. The ruling struck down the Interior Department's leasing plan for the area, prohibiting the Bureau of Land Management (BLM) from leasing more than 400,000 acres (1,600 km) around the lake. Prior to the decision, led by a coalition of environmental organizations and Alaskan Natives, U.S. citizens sent over 300,000 comments to

6972-457: Was so successful that BLM allowed it to go nationwide in 1976. The Adopt-a-Horse program quickly became the primary method of removing excess feral horses from BLM land given the lack of other viable methods. The BLM also uses limited amounts of contraceptives in the herd, in the form of PZP vaccinations; advocates say that additional use of these vaccines would help to diminish the excess number of horses currently under BLM management. Despite

7056-420: Was sold as a source of income for the government. In order to sell the land, surveys needed to be conducted. The Land Ordinance of 1785 instructed a geographer to oversee this work as undertaken by a group of surveyors. The first years of surveying were completed by trial and error; once the territory of Ohio had been surveyed, a modern public land survey system had been developed. In 1812, Congress established

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