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Friday, December 13, 2024

Climate change in Antarctica

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Climate_change_in_Antarctica

Climate change caused by greenhouse gas emissions from human activities occurs everywhere on Earth, and while Antarctica is less vulnerable to it than any other continent, climate change in Antarctica has been observed. Since 1959, there has been an average temperature increase of >0.05 °C/decade since 1957 across the continent, although it had been uneven. West Antarctica warmed by over 0.1 °C/decade from the 1950s to the 2000s, and the exposed Antarctic Peninsula has warmed by 3 °C (5.4 °F) since the mid-20th century. The colder, stabler East Antarctica had been experiencing cooling until the 2000s. Around Antarctica, the Southern Ocean has absorbed more oceanic heat than any other ocean, and has seen strong warming at depths below 2,000 m (6,600 ft). Around the West Antarctic, the ocean has warmed by 1 °C (1.8 °F) since 1955.

The warming of the Southern Ocean around Antarctica has caused the weakening or collapse of ice shelves, which float just offshore of glaciers and stabilize them. Many coastal glaciers have been losing mass and retreating, causing net-annual ice loss across Antarctica, although the East Antarctic ice sheet continues to gain ice inland. By 2100, net ice loss from Antarctica is expected to add about 11 cm (5 in) to global sea level rise. Marine ice sheet instability may cause West Antarctica to contribute tens of centimeters more if it is triggered before 2100. With higher warming, instability would be much more likely, and could double global, 21st-century sea-level rise.

The fresh, 1100-1500 billion tons (GT) per year of meltwater from the ice dilutes the saline Antarctic bottom water, weakening the lower cell of the Southern Ocean overturning circulation (SOOC). According to some research, a full collapse of the SOOC may occur a between 1.7 °C (3.1 °F) and 3 °C (5.4 °F) of global warming, although the full effects are expected to occur over multiple centuries; these include less precipitation in the Southern Hemisphere but more in the Northern Hemisphere, an eventual decline of fisheries in the Southern Ocean and a potential collapse of certain marine ecosystems. While many Antarctic species remain undiscovered, there are documented increases in Antarctic flora, and large fauna such as penguins are already having difficulty retaining suitable habitat. On ice-free land, permafrost thaws release greenhouse gases and formerly frozen pollution.

The West Antarctic ice sheet is likely to completely melt unless temperatures are reduced by 2 °C (3.6 °F) below 2020 levels. The loss of this ice sheet would take between 2,000 and 13,000 years, although several centuries of high greenhouse emissions could shorten this time to 500 years. A sea-level rise of 3.3 m (10 ft 10 in) would occur if the ice sheet collapses, leaving ice caps on the mountains, and 4.3 m (14 ft 1 in) if those ice caps also melt. Isostatic rebound may contribute an additional 1 m (3 ft 3 in) to global sea levels over another 1,000 years. The far-stabler East Antarctic ice sheet may only cause a sea-level rise of 0.5 m (1 ft 8 in) – 0.9 m (2 ft 11 in) from the current level of warming, a small fraction of the 53.3 m (175 ft) contained in the full ice sheet. With global warming of around 3 °C (5.4 °F), vulnerable areas like Wilkes Basin and Aurora Basin may collapse over around 2,000 years, potentially adding up to 6.4 m (21 ft 0 in) to sea levels. The complete melting and disappearance of the East Antarctic ice sheet would require at least 10,000 years and would only occur if global warming reaches 5 °C (9.0 °F) to 10 °C (18 °F).

Temperature and weather changes

Antarctica is the coldest, driest continent on Earth, and has the highest average elevation. Antarctica's dryness means the air contains little water vapor and conducts heat poorly. The Southern Ocean surrounding the continent is far more effective at absorbing heat than any other ocean. The presence of extensive, year-around sea ice, which has a high albedo (reflectivity), adds to the albedo of the ice sheets' own bright, white surface. Antarctica's coldness means it is the only place on Earth where an atmospheric temperature inversion occurs every winter; elsewhere on Earth, the atmosphere is at its warmest near the surface and becomes cooler as elevation increases. During the Antarctic winter, the surface of central Antarctica becomes cooler than middle layers of the atmosphere; this means greenhouse gases trap heat in the middle atmosphere, and reduce its flow toward the surface and toward space, rather than preventing the flow of heat from the lower atmosphere to the upper layers. This effect lasts until the end of the Antarctic winter. Early climate models predicted temperature trends over Antarctica would emerge more slowly and be more subtle than those elsewhere.

There were fewer than twenty permanent weather stations across the continent and only two in the continent's interior. Automatic weather stations were deployed relatively late, and their observational record was brief for much of the 20th century satellite temperature measurements began in 1981 and are typically limited to cloud-free conditions. Thus, datasets representing the entire continent only began to appear by the very end of the 20th century. The exception was the Antarctic Peninsula, where warming was pronounced and well-documented; it was eventually found to have warmed by 3 °C (5.4 °F) since the mid 20th century. Based on this limited data, several papers published in the early 2000s said there had been an overall cooling over continental Antarctica outside the Peninsula.

A 2002 analysis led by Peter Doran received widespread media coverage after it also indicated stronger cooling than warming between 1966 and 2000, and found the McMurdo Dry Valleys in East Antarctica had experienced cooling of 0.7 °C per decade, a local trend that was confirmed by subsequent research at McMurdo. Multiple journalists said these findings were "contradictory" to global warming, even though the paper noted the limited data and found warming over 42% of the continent.What became known as the Antarctic Cooling Controversy received further attention in 2004, when Michael Crichton wrote that novel State of Fear, which said a conspiracy among climate scientists to make up global warming, and said Doran's study definitively proved there was no warming in Antarctica outside of the Peninsula. Relatively few scientists responded to the book at the time, but it was mentioned in a 2006 US Senate hearing in support of climate change denial. Peter Doran published a statement in The New York Times decrying the misinterpretation of his work. The British Antarctic Survey and NASA also issued statements affirming the strength of climate science after the hearing.

By 2009, researchers were able to combine historical weather-station data with satellite measurements to create consistent temperature records going back to 1957 that demonstrated warming of >0.05 °C/decade since 1957 across the continent, with cooling in East Antarctica offset by the average temperature increase of at least 0.176 ± 0.06 °C per decade in West Antarctica. Subsequent research confirmed clear warming over West Antarctica in the 20th century, with the only uncertainty being the magnitude. During 2012-2013, estimates based on WAIS Divide ice cores and revised temperature records from Byrd Station suggested a much-larger West-Antarctica warming of 2.4 °C (4.3 °F) since 1958, or around 0.46 °C (0.83 °F) per decade, although there has been uncertainty about it. In 2022, a study narrowed the warming of the Central area of the West Antarctic Ice Sheet between 1959 and 2000 to 0.31 °C (0.56 °F) per decade, and conclusively attributed it to increases in greenhouse gas concentrations caused by human activity.

Between 2000 and 2020, local changes in atmospheric circulation patterns like the Interdecadal Pacific Oscillation (IPO) and the Southern Annular Mode (SAM) slowed or partially reversed the warming of West Antarctica , with the Antarctic Peninsula experiencing cooling from 2002.

While a variability in those patterns is natural, ozone depletion had also led the SAM to be stronger than it had been in the past 600 years of observations. Studies predicted a reversal in the SAM once the ozone layer began to recover following the Montreal Protocol, starting from 2002, and these changes are consistent with their predictions. As these patterns reversed, the East Antarctica interior demonstrated clear warming over those two decades. In particular, the South Pole warmed by 0.61 ± 0.34 °C per decade between 1990 and 2020, which is three times the global average. The Antarctica-wide warming trend continued after 2000, and in February 2020, the continent recorded its highest temperature of 18.3 °C, which is one degree higher than the previous record of 17.5 °C in March 2015.

Models predict under the most intense climate change scenario, known as RCP8.5, Antarctic temperatures will rise by 4 °C (7.2 °F) on average by 2100; this rise will be accompanied by a 30% increase in precipitation and a 30% decrease in sea ice. RCPs were developed in the late 2000s, and early 2020s research considers RCP8.5 much less likely than the more-moderate scenarios like RCP 4.5, which lie in between the worst-case scenario and the Paris Agreement goals.

Effects on ocean currents

Between 1971 and 2018, over 90% of thermal energy from global heating entered the oceans. The Southern Ocean absorbs the most heat; after 2005, it accounted for between 67% and 98% of all heat entering the oceans. The temperature in the ocean's upper layer in West Antarctica has warmed by 1 °C (1.8 °F) since 1955, and the Antarctic Circumpolar Current (ACC) is also warming faster than the average. It is also a highly important carbon sink. These properties are connected to the Southern Ocean overturning circulation (SOOC), one half of the global thermohaline circulation. It is important estimates on when global warming will reach 2 °C (3.6 °F) – inevitable in all scenarios where greenhouse gas emissions have not been significantly lowered – depend on the strength of the circulation more than any factor other than the overall emissions.

The overturning circulation has two parts; the smaller upper cell, which is most-strongly affected by winds and precipitation, and the larger lower cell that is defined by the temperature and salinity of Antarctic bottom water. Since the 1970s, the upper cell has strengthened by 50-60% while the lower cell has weakened by 10-20%. Some of this was due to the natural cycle of Interdecadal Pacific Oscillation (IPO) but there is a clear effect of climate change, because it alters winds and precipitation through shifts in the Southern Annular Mode (SAM) pattern. Fresh meltwater from the erosion of the West Antarctic ice sheet dilutes the more-saline Antarctic bottom water,which flows at a rate of 1100-1500 billion tons (GT) per year. During the 2010s, a temporary reduction in ice-shelf melting in West Antarctica allowed for the partial recovery of Antarctic bottom water and the lower cell of the circulation. Greater melting and further decline of the circulation is expected in the future.

As bottom water weakens while the flow of warmer, fresher waters strengthens near the surface, the surface waters become more buoyant, and less likely to sink and mix with the lower layers, increasing ocean stratification. One study says the strength of the circulation would halve by 2050 under the worst climate-change scenario, with greater losses occurring afterwards. Paleoclimate evidence shows the entire circulation has significantly weakened or completely collapsed in the past; preliminary research says such a collapse may become likely once global warming reaches between 1.7 °C (3.1 °F) and 3 °C (5.4 °F), but this estimate is much-less certain than for the majority of tipping points in the climate system. Such a collapse would be prolonged; one estimate says it would occur before 2300. As with the better-studied Atlantic meridional overturning circulation (AMOC), a major slowing or collapse of the SOOC would have substantial regional and global effects. Some likely effects include a decline in precipitation in Southern Hemisphere countries like Australia, a corresponding increase in precipitation in the Northern Hemisphere, and an eventual decline of fisheries in the Southern Ocean, which could lead to a potential collapse of some marine ecosystems. These effects are expected to occur over centuries, but there has been limited research to date and few specifics are currently known.

Effects on the cryosphere

Observed changes in ice mass

Contrasting temperature trends across parts of Antarctica mean some locations, particularly at the coasts, lose mass while locations further inland continue to gain mass. These contrasting trends and the remoteness of the region make estimating an average trend difficult. In 2018, a systematic review of all previous studies and data by the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) estimated an increase in the West Antarctic ice sheet from 53 ± 29 Gt (gigatonnes) in 1992 to 159 ± 26 Gt in the final five years of the study. On the Antarctic Peninsula, the study estimated a loss of 20 ± 15 Gt per year with an increase in loss of roughly 15 Gt per year after 2000, a significant quantity of which was the loss of ice shelves. The review's overall estimate was that Antarctica lost 2,720 ± 1,390 gigatons of ice from 1992 to 2017, averaging 109 ± 56 Gt per year. This would amount to 7.6 mm (0.30 in) of sea-level rise. A 2021 analysis of data from four research satellite systems – Envisat, European Remote-Sensing Satellite, GRACE and GRACE-FO, and ICESat – indicated an annual mass loss of about 12 Gt from 2012 to 2016 due to much-greater ice gain in East Antarctica than earlier estimated, which offset most of the losses from West Antarctica. The East Antarctic ice sheet can still gain mass despite warming because effects of climate change on the water cycle increase precipitation over its surface, which then freezes and helps to accrete more ice.

Black carbon pollution

Black carbon from incomplete fuel combustion is carried long distances by wind. If it reaches Antarctica, black carbon accumulates on snow and ice, reducing the reflectivity and causing it to absorb more energy. This accelerates melting and can create an ice-albedo feedback loop in which meltwater itself absorbs more heat from sunlight. Due to its remoteness, Antarctica has the cleanest snow in the world, and some research says the effects of black carbon across West and East Antarctica is minimal with an albedo reduction of about 0.5% in one 47-year ice core.

The highest concentrations of black carbon are found on the Antarctic Peninsula, where human activity is higher than elsewhere. Black carbon deposits near common tourist sites and research stations increase summer seasonal melting by between about 5 to 23 kg (11 to 51 lb) of snow per m².

21st-century ice loss and sea-level rise

By 2100, net ice loss from Antarctica is expected to add about 11 cm (4.3 in) to global sea-level rise. Other processes may cause West Antarctica to contribute more to sea-level rise. Marine ice-sheet instability is the potential for warm water currents to enter between the seafloor and the base of the ice sheet once the sheet is no longer heavy enough to displace such flows. Marine ice-cliff instability may cause ice cliffs taller than 100 m (330 ft) to collapse under their own weight once they are no longer buttressed by ice shelves. This process has never been observed and it only occurs in some models. By 2100, these processes may increase sea-level rise caused by Antarctica to 41 cm (16 in) under the low-emission scenario and by 57 cm (22 in) under the high-emission scenario.

Some scientists have given greater estimates but all agree melting in Antarctica would have a greater impact and would be much more likely to occur under higher warming scenarios, where it may double the overall 21st-century sea-level rise to 2 m (7 ft) or more. According to one study, if the Paris Agreement is followed and global warming is limited to 2 °C (3.6 °F), the loss of ice in Antarctica will continue at the 2020 rate for the rest of the 21st century, but if a trajectory leading to 3 °C (5.4 °F) is followed, Antarctica ice loss will accelerate after 2060 and start adding 0.5 cm (0.20 in) per year to global sea levels by 2100.

Long-term sea level rise

Sea levels will continue to rise long after 2100 but potentially at very different rates. According to the most-recent reports of the Intergovernmental Panel on Climate Change (SROCC and the IPCC Sixth Assessment Report), there will be a median rise of 16 cm (6.3 in) and maximum rise of 37 cm (15 in) under the low-emission scenario. The highest-emission scenario results in a median rise of 1.46 m (5 ft) with a minimum of 60 cm (2 ft) and a maximum of 2.89 m (9+1⁄2 ft).

Over longer timescales, the West Antarctic ice sheet, which is much smaller than the East Antarctic ice sheet and is grounded deep below sea level, is considered highly vulnerable. The melting of all of the ice in West Antarctica would increase global sea-level rise to 4.3 m (14 ft 1 in). Mountain ice caps that are not in contact with water are less vulnerable than the majority of the ice sheet, which is located below sea level. The collapse of the West Antarctic ice sheet would cause around 3.3 m (10 ft 10 in) of sea-level rise. This kind of collapse is now considered almost inevitable because it appears to have occurred during the Eemian period 125,000 years ago, when temperatures were similar to those in the early 21st century.The Amundsen Sea also appears to be warming at rates that, if continued, make the ice sheet's collapse inevitable.

The only way to reverse ice loss from West Antarctica once triggered is to lower the global temperature to 1 °C (1.8 °F) below the pre-industrial level, to 2 °C (3.6 °F) below the temperature of 2020. Other researchers said a climate engineering intervention to stabilize the ice sheet's glaciers may delay its loss by centuries and give the environment more time to adapt. This is an uncertain proposal and would be one of the most-expensive projects ever attempted. Otherwise, the disappearance of the West Antarctic ice sheet would take an estimated 2,000 years. The loss of West Antarctica ice would take at least 500 years and possibly as long as 13,000 years. Once the ice sheet is lost, the isostatic rebound of the land previously covered by the ice sheet would result in an additional 1 m (3 ft 3 in) of sea-level rise over the following 1,000 years.

The East Antarctic ice sheet is far more stable than the West Antarctic ice sheet. The loss of the entire East Antarctic ice sheet would require global warming of between 5 °C (9.0 °F) and 10 °C (18 °F), and a minimum of 10,000 years. Some of its parts, such as Totten Glacier and Wilkes Basin, are in vulnerable subglacial basins that lie below sea level. Estimates suggest the irreversible loss of those basins would begin once global warming reaches 3 °C (5.4 °F), although this loss may become irreversible at warming of between 2 °C (3.6 °F) and 6 °C (11 °F). After global warming reaches the critical threshold for the collapse of these subglacial basins, their loss will likely occur over around 2,000 years, although the loss may be as fast as 500 years or as slow as 10,000 years.

The loss of all of this ice would add between 1.4 m (4 ft 7 in) and 6.4 m (21 ft 0 in) to sea levels, depending on the ice sheet model used. Isostatic rebound of the newly ice-free land would add between 8 cm (3.1 in) and 57 cm (1 ft 10 in). Evidence from the Pleistocene shows partial loss can occur at lower warming levels; Wilkes Basin is estimated to have lost enough ice to add 0.5 m (1 ft 8 in) to sea levels between 115,000 and 129,000 years ago during the Eemian, and about 0.9 m (2 ft 11 in) between 318,000 and 339,000 years ago during Marine Isotope Stage 9.

Permafrost thaw

Antarctica has much less permafrost than the Arctic. Antarctic permafrost is subject to thaw. The permafrost in Antarctica traps various compounds, including persistent organic pollutants (POPs) like polycyclic aromatic hydrocarbons, many of which are known carcinogens or can cause liver damage; and polychlorinated biphenyls such as hexachlorobenzene (HCB) and DDT, which are associated with decreased reproductive success and immunohematological disorders. Antarctic soils also contain heavy metals, including mercury, lead and cadmium, all of which can cause endocrine disruption, DNA damage, immunotoxicity and reproductive toxicity. These compounds are released when contaminated permafrost thaws; this can change the chemistry of surface water. Bioaccumulation and biomagnification spread these compounds throughout the food web. Permafrost thaw also results in greenhouse gas emissions, though the limited volume of Antarctic permafrost relative to Arctic permafrost means Antarctic permafrost is not considered a significant cause of climate change.

Ecological effects

Marine ecosystems

Nearly all of the species in Antarctic are marine; by 2015, 8,354 species had been discovered in Antarctica and taxonomically accepted; of these species, only 57 were not marine. Antarctica may have up to 17,000 species; while 90% of the ocean around Antarctica is deeper than 1,000 m (3,281 ft), only 30% of the benthic-sample locations were taken at that depth. On the Antarctic continental shelves, bethnic-zone biomass may increase due to oceanic warming, which is likely to be of most benefit to seaweed. Around 12% of the native benthic species may be outcompeted and go extinct. These estimates are preliminary; the vulnerabilities of most Antarctic species have yet to be assessed.

Unlike the Arctic, there has been little change in marine primary production across the Southern Ocean in the available observations. Estimates say an increase in Southern Ocean primary production could occur after 2100; this increase would block many nutrients from travelling to other oceans, leading to decreased production elsewhere. Some microbial communities appear to have been negatively affected by ocean acidification and there is a risk future acidification would threaten the eggs of pteropods, a type of zooplankton.

Antarctic krill are a key species in the Antarctic food web; they feed on phytoplankton, and are the main food for fish and penguins. Krill are likely to abandon the fastest-warming areas, such as the Weddell Sea, while icefish may find shelf waters around Antarctic islands unsuitable. The shifts or declines in krill and copepod numbers are known to prevent the recovery in numbers of baleen whale following the declines caused by historical whaling. Without a reversal in temperature increases, baleen whales are likely to be forced to adapt their migratory patterns or face local extinction. Many other marine species are expected to move into Antarctic waters as the oceans continue to warm, forcing native species to compete with them. Some research says at 3 °C (5.4 °F) of warming, the diversity of Antarctic species would decline by nearly 17% and the suitable climate area would shrink by 50%.

Penguins

Penguins are the highest species in the Antarctic food web and are already being substantially affected by climate change. Numbers of Adélie penguins, chinstrap penguins, emperor penguin and king penguins have already been declining, while the number of gentoo penguins has increased. Gentoo penguins, which are ice intolerant and use mosses as nesting material, have been able to spread into previously inaccessible territories and substantially increase in number. The vulnerable penguin species can respond through acclimatization, adaptation, or range shift. Range shift through dispersal leads to colonization elsewhere but results in local extinction.

Climate change is particularly threatening to penguins. As early as 2008, it was estimated every Southern Ocean temperature increase of 0.26 °C (0.47 °F) reduces king penguin populations by nine percent. Under the worst-case warming scenario, king penguins will permanently lose at least two of their current eight breeding sites, and 70% of the species (1.1 million pairs) will have to relocate to avoid extinction. Emperor penguin populations may be at a similar risk; with no climate mitigation, 80% of populations are at risk of extinction by 2100. With Paris-Agreement temperature goals in place, that number may fall to 31% under the 2 °C (3.6 °F) goal, and to 19% under the 1.5 °C (2.7 °F) goal.

A 27-year study of the largest colony of Magellanic penguins that was published in 2014 found extreme weather caused by climate change kills seven percent of penguin chicks in an average year, accounting for up to 50% of all chick deaths in some years. Since 1987, the number of breeding pairs in the colony has fallen by 24%. Chinstrap penguins are also in decline, mainly due to a corresponding decline of Antarctic krill. It is estimated while Adélie penguins will retain some habitat past 2099, one-third of colonies along the West Antarctic Peninsula – around 20% of the species – will be in decline by 2060.

Terrestrial ecosystems

On the Antarctic continent, plants are mainly found in coastal areas; the commonest plants are lichens, followed by mosses and ice algae. In the Antarctic Peninsula, green snow algae have a combined biomass of around 1,300 t (2,900,000 lb). As glaciers retreat, they expose areas that often become colonized by pioneer lichen species. The reduction in precipitation in East Antarctica had turned many green mosses from green to red or brown as they respond to this drought. Schistidium antarctici had declined, while the desiccation-tolerant species Bryum pseudotriquetrum and Ceratodon purpureus have increased. The Antarctic ozone hole has led to an increase in UV-B radiation, which also causes observed damage to plant cells and photosynthesis.

The only vascular plants on continental Antarctica are Deschampsia antarctica and Colobanthus quitensis, which are found on the Antarctic Peninsula. Increased temperatures have boosted photosynthesis and allowed these species to increase their population and range. Other plant species are increasingly likely to spread to Antarctica as the climate continues to warm and as human activity on the continent increases.

Effects of human development

Tourism in Antarctica has significantly increased since 2020; 74,400 tourists arrived there in late 2019 and early 2020. The development of Antarctica for the purposes of industry, tourism, and an increase in research facilities may put pressure on the continent and threaten its status as largely untouched land. Regulated tourism in Antarctica brings about awareness, and encourages the investment and public support needed to preserve Antarctica's distinctive environment. An unmitigated loss of ice on land and sea could greatly reduce its attractiveness.

Policy can be used to increase climate-change resilience through the protection of ecosystems. Ships that operate in Antarctic waters adhere to the international Polar Code, which includes regulations and safety measures such as operational training and assessments, the control of oil discharge, appropriate sewage disposal, and the prevention of pollution by toxic liquids. Antarctic Specially Protected Areas (ASPA) and Antarctic Specially Managed Areas (ASMA) are designated by the Antarctic Treaty to protect flora and fauna. Both ASPAs and ASMAs restrict entry but to different extents, with ASPAs being the highest level of protection. Designation of ASPAs has decreased 84% since the 1980s despite a rapid increase in tourism, which may bring additional stressors to the natural environment and ecosystems. To alleviate stress on Antarctic ecosystems posed by climate change and the rapid increase in tourism, much of the scientific community advocates for an increase in protected areas like ASPAs to improve Antarctica's resilience to rising temperatures.

Climate of Antarctica

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Climate_of_Antarctica

The climate of Antarctica is the coldest on Earth. The continent is also extremely dry (it is a desert), averaging 166 mm (6.5 in) of precipitation per year. Snow rarely melts on most parts of the continent, and, after being compressed, becomes the glacier ice that makes up the ice sheet. Weather fronts rarely penetrate far into the continent, because of the katabatic winds. Most of Antarctica has an ice-cap climate (Köppen classification EF) with extremely cold and dry weather.

Temperature

The highest temperature ever recorded on Antarctica was 19.8 °C (67.6 °F) recorded at Signy Research Station, Signy Island on 30 January 1982.

The highest temperature on the Antarctic mainland was 18.3 °C (64.9 °F) at the Esperanza Base (Argentina) on 6 February 2020.

The lowest air temperature record, the lowest reliably measured temperature on Antarctica was set on 21 July 1983, when a temperature of −89.2 °C (−128.6 °F) was observed at Vostok Station. For comparison, this is 10.7 °C (19.3 °F) colder than subliming dry ice (at sea level pressure). The elevation of the location is 3,488 meters (11,444 feet).

Satellite measurements have identified even lower ground temperatures, with −93.2 °C (−135.8 °F) having been observed at the cloud-free East Antarctic Plateau on 10 August 2010.

The lowest recorded temperature of any location on Earth's surface at 81.8°S 63.5°E was revised with new data in 2018 in nearly 100 locations, ranging from −93.2 °C (−135.8 °F)^[7] to −98 °C (−144.4 °F). This unnamed part of the Antarctic plateau, between Dome A and Dome F, was measured on 10 August 2010, and the temperature was deduced from radiance measured by the Landsat 8 and other satellites. It was discovered during a National Snow and Ice Data Center review of stored data in December 2013 but revised by researchers on 25 June 2018. This temperature is not directly comparable to the –89.2 °C reading quoted above, since it is a skin temperature deduced from satellite-measured upwelling radiance, rather than a thermometer-measured temperature of the air 1.5 m (5 ft) above the ground surface.

The mean annual temperature of the interior is −43.5 °C (−46.3 °F). The coast is warmer; on the coast Antarctic average temperatures are around −10 °C (14.0 °F) (in the warmest parts of Antarctica) and in the elevated inland they average about −55 °C (−67.0 °F) in Vostok. Monthly means at McMurdo Station range from −26 °C (−14.8 °F) in August to −3 °C (26.6 °F) in January. At the South Pole, the highest temperature ever recorded was −12.3 °C (9.9 °F) on 25 December 2011. Along the Antarctic Peninsula, temperatures as high as 18.3 °C (64.9 °F) have been recorded, though the summer temperature is below 0 °C (32 °F) most of the time. Severe low temperatures vary with latitude, elevation, and distance from the ocean. East Antarctica is colder than West Antarctica because of its higher elevation. The Antarctic Peninsula has the most moderate climate. Higher temperatures occur in January along the coast and average slightly below freezing.

Precipitation

The total precipitation on Antarctica, averaged over the entire continent, is about 166 millimetres (6.5 inches) per year (Vaughan et al., J. Clim., 1999). The actual rates vary widely, from high values over the Peninsula (380 to 640 millimetres (15 to 25 inches) a year) to very low values (as little as 50 millimetres (2.0 inches) in the high interior (Bromwich, Reviews of Geophysics, 1988). Areas that receive less than 250 millimetres (9.8 inches) of precipitation per year are classified as deserts. Almost all Antarctic precipitation falls as snow. Rainfall is rare and mainly occurs during the summer in coastal areas and surrounding islands. Note that the quoted precipitation is a measure of its equivalence to water, rather than being the actual depth of snow. The air in Antarctica is also very dry. The low temperatures result in a very low absolute humidity, which means that dry skin and cracked lips are a continual problem for scientists and expeditioners working on the continent.

Weather condition classification

The weather in Antarctica can be highly variable, and the weather conditions can often change dramatically in short periods of time. There are various classifications for describing weather conditions in Antarctica; restrictions given to workers during the different conditions vary by station and nation.

Ice cover

Nearly all of Antarctica is covered by a sheet of ice that is, on average, at least 1,500 m (5,000 ft) thick. Antarctica contains 90% of the world's ice and more than 70% of its fresh water. If all the land-ice covering Antarctica were to melt — around 30×10⁶ km³ (7.2×10⁶ cu mi) of ice — the seas would rise by over 60 m (200 ft). The Antarctic is so cold that even with increases of a few degrees, temperatures would generally remain below the melting point of ice. Higher temperatures are expected to lead to more precipitation, which takes the form of snow. This would increase the amount of ice in Antarctica, offsetting approximately one third of the expected sea level rise from thermal expansion of the oceans. During a recent decade, East Antarctica thickened at an average rate of about 1.8 cm (11⁄16 in) per year while West Antarctica showed an overall thinning of 0.9 cm (3⁄8 in) per year. For the contribution of Antarctica to present and future sea level change, see sea level rise. Because ice flows, albeit slowly, the ice within the ice sheet is younger than the age of the sheet itself.

Morphometric data for Antarctica (from Drewry, 1983)
Surface	Area		Mean ice thickness (m)	Volume
Surface	(km²)	Percent	Mean ice thickness (m)	(km³)	Percent
Inland ice sheet	11,965,700	85.97	2,450	29,324,700	97.00
Ice shelves	1,541,710	11.08	475	731,900	2.43
Ice rises	78,970	0.57	670	53,100	0.18
Glacier ice (total)	13,586,380		2,160	30,109,800
Rock outcrop	331,690	2.38
Antarctica (total)	13,918,070	100.00	2,160	30,109,800	100.00

Regional ice data (from Drewry and others, 1982; Drewry, 1983)
Region	Area (km²)	Mean ice thickness (m)	Volume (km³)
East Antarctica
Inland ice	9,855,570	2,630	25,920,100
Ice shelves	293,510	400	117,400
Ice rises	4,090	400	1,600
West Antarctica (excluding Antarctic Peninsula)
Inland ice sheet	1,809,760	1,780	3,221,400
Ice shelves	104,860	375	39,300
Ice rises	3,550	375	1,300
Antarctic Peninsula
Inland ice sheet	300,380	610	183,200
Ice shelves	144,750	300	43,400
Ice rises	1,570	300	500
Ross Ice Shelf
Ice shelf	525,840	427	224,500
Ice rises	10,320	500	5,100
Filchner-Ronne Ice Shelf
Ice shelf	472,760	650	307,300
Ice rises	59,440	750	44,600

Ice shelves

About 75% of the coastline of Antarctica is ice shelf. The majority of ice shelf consists of floating ice, and a lesser amount consists of glaciers that move slowly from the land mass into the sea. Ice shelves lose mass through breakup of glacial ice (calving), or basal melting due to warm ocean water under the ice.

Melting or breakup of floating shelf ice does not directly affect global sea levels; however, ice shelves have a buttressing effect on the ice flow behind them. If ice shelves break up, the ice flow behind them may accelerate, resulting in increasing melt of the Antarctic ice sheet and an increasing contribution to sea level rise.

Known changes in coastline ice around the Antarctic Peninsula:

1936–1989: Wordie Ice Shelf significantly reduced in size.
1995: Ice in the Prince Gustav Channel disintegrated.
Parts of the Larsen Ice Shelf broke up in recent decades.
- 1995: The Larsen A ice shelf disintegrated in January 1995.
- 2001: 3,250 km² (1,250 sq mi) of the Larsen B ice shelf disintegrated in February 2001. It had been gradually retreating before the breakup event.
- 2015: A study concluded that the remaining Larsen B ice-shelf will disintegrate by the end of the decade, based on observations of faster flow and rapid thinning of glaciers in the area.

The George VI Ice Shelf, which may be on the brink of instability, has probably existed for approximately 8,000 years, after melting 1,500 years earlier. Warm ocean currents may have been the cause of the melting. Not only are the ice sheets losing mass, they are losing mass at an accelerating rate.

Climate change

Climate change caused by greenhouse gas emissions from human activities occurs everywhere on Earth, and while Antarctica is less vulnerable to it than any other continent, climate change in Antarctica has been observed. Since 1959, there has been an average temperature increase of >0.05 °C/decade since 1957 across the continent, although it had been uneven. West Antarctica warmed by over 0.1 °C/decade from the 1950s to the 2000s, and the exposed Antarctic Peninsula has warmed by 3 °C (5.4 °F) since the mid-20th century. The colder, stabler East Antarctica had been experiencing cooling until the 2000s. Around Antarctica, the Southern Ocean has absorbed more oceanic heat than any other ocean, and has seen strong warming at depths below 2,000 m (6,600 ft). Around the West Antarctic, the ocean has warmed by 1 °C (1.8 °F) since 1955.

The warming of the Southern Ocean around Antarctica has caused the weakening or collapse of ice shelves, which float just offshore of glaciers and stabilize them. Many coastal glaciers have been losing mass and retreating, causing net-annual ice loss across Antarctica, although the East Antarctic ice sheet continues to gain ice inland. By 2100, net ice loss from Antarctica is expected to add about 11 cm (5 in) to global sea level rise. Marine ice sheet instability may cause West Antarctica to contribute tens of centimeters more if it is triggered before 2100.With higher warming, instability would be much more likely, and could double global, 21st-century sea-level rise.

Thursday, December 12, 2024

Ecomusicology

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Ecomusicology

Ecomusicology is an area of study that explores the relationships between music or sound, and the natural environment. It is a study which encompasses a variety of academic disciplines including musicology, biology, ecology and anthropology. Ecomusicology combines these disciplines to explore how sound is produced by natural environments and, more broadly how cultural values and concerns about nature are expressed through sonic mediums. Ecomusicology explores the ways that music is composed to replicate natural imagery, as well as how sounds produced within the natural environment are used within musical composition. Ecological studies of sounds produced by animals within their habitat are also considered to be part of the field of ecomusicology. In the 21st century, studies within the field the ecomusicology have also become increasingly interested in the sustainability of music production and performance.

Ecomusicology is concerned with the study of music, culture, and nature, and considers musical and sonic issues, both textual and performative, related to ecology and the natural environment. It is in essence a mixture of ecocriticism and musicology (rather than "ecology" and "musicology"), in Charles Seeger's holistic definition. Ecomusicology is regarded as a field of research rather than a specific academic discipline. Because ecomusicology focuses on a vast variety of disciplines as well as areas of research, it can be imagined as a space in which studies of sound in relation with the environment are conducted.

Ecomusicology's relevance to such a wide range of other research areas is exactly what makes it somewhat ambiguous to define. On one hand, ecomusicology is a unique field of research which helps to make connections between a variety of music-related and environmental studies. Yet, by functioning as a collective term, it is often difficult to frame ecomusicology within a static set of descriptive definitions. Musicologist Aaron S. Allen, the author of multiple published works on ecomusicology, defines ecomusicology as "the study of music, culture, and nature in all the complexities of those terms. Ecomusicology considers musical and sonic issues, both textual and performative, related to ecology and the natural environment."

Background

Ecomusicology as a field of study is often traced back to musical composer and environmentalist R. Murray Schafer who used the term to explain the sonic nature of particular physical environments or soundscapes. The idea of sound or music as something which creates or captures a particular atmosphere, was initially professed by Murray R. Schafer through his development of the concept of soundscape ecology in the late 1970s. Schafer used this term to encompass the vast acoustic environment which constitutes all the varied sounds, audible to the human ear. A soundscape might entail for example, the all audible sounds heard within a specific area of land, such as a mountain range, a forest or field.

From the 1970s, there has been an increase in interest in the term ecomusicology, which was established as a term in the early 21st century in North American and Scandinavian circles. As a field, ecomusicology was created out of a common area of interest between the fields of ecocriticism and musicology, expressed by a range of scholars and artists such as composers, acoustic ecologists, ethnomusicologists, biomusicologists, and others.

Ecomusicology embraces what is today considered the field of historical musicology, ethnomusicology, and related interdisciplinary fields, which while at the same time may enable specialists within each of these fields to interact with academics in the other fields in their approach, it also provides individuals with flexibility to approach an ecocritical study of music through a variety of disciplines and fields.

In 2011, the Society for Ethnomusicology established an Ecomusicology Special Interest Group (ESIG).

In October 2012, the first international ecomusicology-conference took place in New Orleans, U.S.

Sustainability and environmental ethics

Ecomusicology considers aspects of environmental sustainability within music production and performance. For example, the relationship between a demand for a certain musical instrument as well as the costs and impacts of its production, has been an area of interest for Ecomusicologists investigating the sustainability of the consumption and production of music or musical instruments. This includes the impact which the demand for musical instruments, merchandise or live experiences such as concerts has on the natural environment. Music-Journalist and Anthropologist Mark Pedelty, has written on the Ecomusicological relationship between human musical activities and the health of the environment. Having written about the pollutive impacts that international music touring often has on the environment, Pedelty explores Ecomusicological concerns of ethicality regarding the production of carbon emissions created by vehicles used to a move band members, instruments and/or any extensive staging or crew.

Live Earth Concert at Wembley Stadium, 2007

Part of ecomusicology's investigation of environmental ethics, are the ways in which discussions around projects of sustainability are positioned within popular music and media. In 2010, music magazine Rolling Stone compiled a list of "The 15 Most Eco-Friendly Rockers", selecting artists based on various criteria regarding their support or consideration for the environment within their musical practice. This included assessments of the amount of money donated to environmentally sustainable causes, or an artist's effort to perform and act in carbon-neutral ways. Some of the artists included Green Day for their work with the Natural Resources Defence Council, as well as hip-hop group The Roots for hosting multiple music events aimed at promoting social and environmental awareness.

Environmental activism and ecocriticism

A key area of focus for studies within ecomusicology are the ways in which sound and music is used to create or express concerns about the environment. Jeff Todd Titon has described ecomusicology which focuses more on conceptual aspects of ecocriticism as "the study of music, culture, sound and nature in a period of environmental crisis." The occurrence of live music events aimed at promoting awareness about environmental destruction and climate change is one area in which ecomusicology continues to be engaged.

Numerous music events including Live Earth in 2007 and, more recently, Make It Rain (Australia, 2020) among others, have either been involved in promoting climate-change awareness, or to raising funds for the alleviation of the effects of climate change on humans and animals. The investigation of eco-friendly organisations such as Reverb is also relevant to Ecomusicological inquiry. These organisations are often aimed at working with artists to reduce or offset the carbon footprint of their performance and touring emissions, as well as engaging audiences in environmental activism by reducing waste production at music events.

Ecomusicology also considers the relationships between music or sound, and the promotion of ideas surrounding environmental activism. Ecomusicologists may for example examine the conceptual basis of songs written specifically about environmental degradation or, consider how and to what effect the use of simple short, repetitive vocal chants may assist in voicing the environmental concerns central to projects of climate activism. The ways in which music has been used to prompt social and political action to protect the environment is of notable relevance to the focuses of ecomusicology at large.

Representations of the natural world

Ecomusicology investigates the creation of music which attempts to reflect or capture feelings or experiences provoked by the natural environment. Experiences of nature which are often expressed through poetry or art, are frequently analysed within ecomusicology to identify the cognitive and emotional impacts which specific sounds might have on humans.

Ecology

Ecomusicology is often closely paired with the study of ecology, assisting in the analysis of the behavioural patterns of animals and ecosystems through the investigation of sound data. Ecological studies of bird and the characteristics of their song, have revealed ways in which sounds and spaces in their natural environment have shaped certain behaviours. Here, ecomusicology applies concepts related to sound and music theory with research regarding animal behaviours to reveal information about how sound is manipulated by animals in relation to their environment.

By measuring musicological qualities such as volume, pitch and frequency within a particular bird's song, Ecologists have discovered that certain birds will sing louder in noisier, built-environments compared to birds of the same species found in rural environments. Similarly, some birds may pitch their song differently in order to be heard across greater distances or more densely vegetative, and therefore more sound-absorbent environments. Other ecological studies on non-human animals include research on whale vocalization as well as the acoustics of bat and insect communication otherwise known as biophonics.

Research methods

Ecomusicology utilises both qualitative and quantitative methods of data collection, however, the type of data as well as methods of data collection vary depending on what the subject of study may be. Ecomusicological research aimed at understanding aspects of social engagement with ecocritism might for example primarily involve the use of qualitative data collected through interviews and field research of particular social events. Conversely, research regarding the communicative behaviours of certain animal species would likely be pursued through a comparison of quantitative data collected through audio recordings of a specific environment.

Environment-focused

Ecomusicological field research of animal behaviours within a particular environment often includes methods of passive recording/listening. This is usually undertaken with the use of multi-directional Microphone which are often hidden and left within a species' habitat to record the array of sounds created in its environment. Hydrophones (microphones that can be submerged beneath water) may also be used to collect sound data from marine environments. By replaying passive (data collected without being present at the source) recordings, Ecologists are able to study the amount, frequency and variation of a particular sound within that environment to reveal insights about the population or behaviours of a particular animal species.

Human-focused

Human-focused studies in ecomusicology are often conducted using similar field research methods to that of anthropology or sociology. This includes conducting interviews, collecting various numerical data, surveys as well as on-site observation. There are three main ways in which the study of non-humans enhances the study of human music: the context of the non-human's sound, the agency or behavior of the non-human, and the interaction between the human and non-human. As an example of contextualizing a non-human's sound, study of the peacock's call altered the interpretation of northeastern Brazilian folklore; works about the peacock were interpreted as love songs until better understanding of this particular call elucidated that it was resistance to the military dictatorship in Brazil. Studying agency includes the relationship that humans have with animal behavior; migratory patterns of the Picazuro pigeon predicted major droughts, demonstrating the interconnectedness of rural and urban communities through nature. Finally, the study of human and non-human interaction focuses on the manner in which humans interpret the sounds of nonhumans. Luis Gonzaga, a popular Brazilian singer, popularized a folk song about the laughing falcon, which many used to understand the birds' call as an indicator of major drought. These varied methods of data collection are used to make a qualitative analysis of the ways in which sound and music may influence behaviours as well as systems of value and meaning within a particular social context.

The idea of "place" has also served as a common theme of human-focused ecomusicological research. Having worked with the Kaluli people in Papua New Guinea, ethnomusicologist Steven Feld studied the confluence of myth and ecology in Kaluli aesthetics reflected in weeping, poetics, and sound. According to Feld, for the Kaluli, sound, as a system of symbols, functions as a way of communicating deeply felt sentiments and reconfiguring mythic principles. The form and performance of Kaluli weeping, poetics, and song, tied to Kaluli origin myths and the natural environment, embody and express cultural meanings. Using sound as an expressive, performative modality, the Kaluli signify the symbolic circle of their myth, "the boy who became a muni bird." Feld's analysis suggests that this theme of "becoming a bird" serves as a core metaphor of Kaluli aesthetics that "mediat[es] social sentiments in sound forms." Culturally constituted performance codes confer performers with the ability to symbolize bird communication. Kaluli aesthetics elicit comparisons between performers and certain birds of the natural environment in the Southern Highlands Province of Papua New Guinea. Through his research, Feld theorized the concept of acoustemology (sound as a way of knowing) by analyzing how acoustics and epistemology conjoin.

Musical theory and instrumentation

Ecomusicology considers the ways in which musical instruments and other forms of sound manipulation are used to recreate or represent features of specific environments or soundscapes. Music produced within the conceptual spectrum of ecomusicology often tries to replicate sounds found in the natural environment. This can include the use of orchestral instruments or vocal sounds to mimic sounds produced within the natural environment, such as the melodic chirp of a bird's song, or the rhythmic gushing of stream. Sound effects are also used in a variety of ways to recreate sound textures produced within particular environments. An example might be the application of echo or reverb effects to an instrument to reproduce the distant echoing of sound as it rebounds off hard surfaces across a canyon or valley.

The work of composer and sound-artist Maggi Payne often features the creation and combination of different sounds to convey natural processes or reflect elements of the natural environment. In her sound work Distant Thunder, Payne uses a combination of different sound sources including "boiling water, a resonant floor furnace, and unrolling adhesive tape" to recreate the distinctive soundscape of desert storm.

A common feature of musical compositions related to ecomusicology, is the use of field recordings that capture the ambient sound produced within a specific environment. Field recordings can originate from urban settings to rural or natural environments, or anywhere else where an audio recording device may be used to record the sounds produced within a particular location. The creation and use of field recordings form part of ecomusicology's analysis of soundscapes and the ways in which different environments may be experienced through their distinctive aural features.

Also of interest to studies within ecomusicology, are the ways in which sound is processed and manipulated through technological software to compose new soundscapes or sound environments. Musical composition methods which involve music production software has allowed for music's relationship with nature to be imagined in new ways, many of which are useful and relevant to ecomusicological analysis.

Education

Since its increased presence within academic discourse in the 21st century, a number of teaching methods have been devised to integrate the study of ecomusicology into school learning environments. Daniel J. Shevock, an academic of musicology who has written extensively on Ecomusicological theory, has designed and taught a variety of lessons concerning ideas and practices of ecomusicology which can be applied to primary/highschool learning environments.

Shevock has outlined a series of possible practice-based learning activities focused on informing students about environmental concerns central to the study of ecomusicology. This includes tasks which involve the creation of songs or poems inspired by the natural environment or other social concerns about sustainability and the health of ecologies. Shevock has also devised a range of theoretical tasks which include listening to and discussing the conceptual and structural elements of nature-focused music.

As a field of study which encompasses more than one area of interest, both Allen and Shevock have discussed the potential advantages that studies of ecomusicology might have in extending an understanding of other subject areas taught within schools. For example, the teaching of some of ecomusicology's research methods and findings within the study of ecologies, may be useful in expanding students' comprehension of some ideas taught within the subject of biology. The "wild pedagogies" approach has also been proposed as an innovative way of integrating music studies into environmental concerns within both schools and university education.