Misplaced Pages

#671328

69-596: The Horseshoe Moraine is the name for a series of moraines that cover much of southern Ontario , west of the Niagara Escarpment . A lobe of the horseshoe moraine abuts the well-known Oak Ridges Moraine in the extreme west of the headwaters of the Humber River . The 150 kilometres (93 mi) long Paris-Galt Moraines are considered part of the Horseshoe Moraines. Moraines The word moraine

138-483: A climate change feedback if it is gradually released through meltwater, thus increasing overall carbon dioxide emissions . For comparison, 1400–1650 billion tonnes are contained within the Arctic permafrost . Also for comparison, the annual human caused carbon dioxide emissions amount to around 40 billion tonnes of CO 2 . In Greenland, there is one known area, at Russell Glacier , where meltwater carbon

207-508: A continental glacier , is a mass of glacial ice that covers surrounding terrain and is greater than 50,000 km (19,000 sq mi). The only current ice sheets are the Antarctic ice sheet and the Greenland ice sheet . Ice sheets are bigger than ice shelves or alpine glaciers . Masses of ice covering less than 50,000 km are termed an ice cap . An ice cap will typically feed

276-581: A 1 m tidal oscillation can be felt as much as 100 km from the sea. During larger spring tides , an ice stream will remain almost stationary for hours at a time, before a surge of around a foot in under an hour, just after the peak high tide; a stationary period then takes hold until another surge towards the middle or end of the falling tide. At neap tides, this interaction is less pronounced, and surges instead occur approximately every 12 hours. Increasing global air temperatures due to climate change take around 10,000 years to directly propagate through

345-425: A buttressing effect on the ice sheet, the so-called back stress increases and the grounding line is pushed backwards. The ice sheet is likely to start losing more ice from the new location of the grounding line and so become lighter and less capable of displacing seawater. This eventually pushes the grounding line back even further, creating a self-reinforcing mechanism . Because the entire West Antarctic Ice Sheet

414-426: A higher level of warming. Isostatic rebound of ice-free land may also add around 1 m (3 ft 3 in) to the global sea levels over another 1,000 years. The East Antarctic Ice Sheet (EAIS) lies between 45° west and 168° east longitudinally. It was first formed around 34 million years ago, and it is the largest ice sheet on the entire planet, with far greater volume than the Greenland ice sheet or

483-432: A much greater area than this minimum definition, measuring at 1.7 million km and 14 million km , respectively. Both ice sheets are also very thick, as they consist of a continuous ice layer with an average thickness of 2 km (1 mi). This ice layer forms because most of the snow which falls onto the ice sheet never melts, and is instead compressed by the mass of newer snow layers. This process of ice sheet growth

552-700: A portion of the ice sheet collapses. External factors might also play a role in forcing ice sheets. Dansgaard–Oeschger events are abrupt warmings of the northern hemisphere occurring over the space of perhaps 40 years. While these D–O events occur directly after each Heinrich event, they also occur more frequently – around every 1500 years; from this evidence, paleoclimatologists surmise that the same forcings may drive both Heinrich and D–O events. Hemispheric asynchrony in ice sheet behavior has been observed by linking short-term spikes of methane in Greenland ice cores and Antarctic ice cores. During Dansgaard–Oeschger events ,

621-430: A series of glaciers around its periphery. Although the surface is cold, the base of an ice sheet is generally warmer due to geothermal heat. In places, melting occurs and the melt-water lubricates the ice sheet so that it flows more rapidly. This process produces fast-flowing channels in the ice sheet — these are ice streams . Even stable ice sheets are continually in motion as the ice gradually flows outward from

690-452: A series of transverse ridges running across a valley behind a terminal moraine. They form perpendicular to the lateral moraines that they reside between and are composed of unconsolidated debris deposited by the glacier. They are created during temporary halts in a glacier's retreat. In permafrost areas an advancing glacier may push up thick layers of frozen sediments at its front. An arctic push moraine will then be formed. A medial moraine

759-456: A shallow fjord and stabilized) could have involved MICI, but there weren't enough observations to confirm or refute this theory. The retreat of Greenland ice sheet 's three largest glaciers - Jakobshavn , Helheim , and Kangerdlugssuaq Glacier - did not resemble predictions from ice cliff collapse at least up until the end of 2013, but an event observed at Helheim Glacier in August 2014 may fit

SECTION 10

#1733106098672

828-502: A single moraine, and most moraines record a continuum of processes. Reworking of moraines may lead to the formation of placer deposits of gold as is the case of southernmost Chile . Moraines can be classified either by origin, location with respect to a glacier or former glacier, or by shape. The first approach is suitable for moraines associated with contemporary glaciers—but more difficult to apply to old moraines , which are defined by their particular morphology, since their origin

897-407: A worst-case of about 33 cm (13 in). For comparison, melting has so far contributed 1.4 cm ( 1 ⁄ 2  in) since 1972, while sea level rise from all sources was 15–25 cm (6–10 in) between 1901 and 2018. Historically, ice sheets were viewed as inert components of the carbon cycle and were largely disregarded in global models. In 2010s, research had demonstrated

966-404: Is unstratified and unsorted debris ranging in size from silt -sized glacial flour to large boulders. The individual rock fragments are typically sub-angular to rounded in shape. Moraines may be found on the glacier's surface or deposited as piles or sheets of debris where the glacier has melted. Moraines may form through a number of processes, depending on the characteristics of sediment,

1035-631: Is a ridge of moraine that runs down the center of a valley floor. It forms when two glaciers meet and the debris on the edges of the adjacent valley sides join and are carried on top of the enlarged glacier. As the glacier melts or retreats, the debris is deposited and a ridge down the middle of the valley floor is created. The Kaskawulsh Glacier in the Kluane National Park , Yukon , has a ridge of medial moraine 1 km wide. Supraglacial moraines are created by debris accumulated on top of glacial ice. This debris can accumulate due to ice flow toward

1104-409: Is about 1 million years old. Due to anthropogenic greenhouse gas emissions , the ice sheet is now the warmest it has been in the past 1000 years, and is losing ice at the fastest rate in at least the past 12,000 years. Every summer, parts of the surface melt and ice cliffs calve into the sea. Normally the ice sheet would be replenished by winter snowfall, but due to global warming the ice sheet

1173-426: Is accumulated at the base of the ice as lodgment till with a thin and discontinuous upper layer of supraglacial till deposited as the glacier retreats. It typically is found in the areas between end moraines. Rogen moraines or ribbed moraines are a type of basal moraines that form a series of ribs perpendicular to the ice flow in an ice sheet . The depressions between the ribs are sometimes filled with water, making

1242-456: Is believed that the loss of the ice sheet would take place between 2,000 and 13,000 years in the future, although several centuries of high emissions may shorten this to 500 years. 3.3 m (10 ft 10 in) of sea level rise would occur if the ice sheet collapses but leaves ice caps on the mountains behind. Total sea level rise from West Antarctica increases to 4.3 m (14 ft 1 in) if they melt as well, but this would require

1311-539: Is borrowed from French moraine [mɔ.ʁɛn] , which in turn is derived from the Savoyard Italian morena ('mound of earth'). Morena in this case was derived from Provençal morre ('snout'), itself from Vulgar Latin * murrum ('rounded object'). The term was introduced into geology by Horace Bénédict de Saussure in 1779. Moraines are landforms composed of glacial till deposited primarily by glacial ice. Glacial till, in turn,

1380-441: Is debated. Some moraine types are known only from ancient glaciers, while medial moraines of valley glaciers are poorly preserved and difficult to distinguish after the retreat or melting of the glacier. Lateral moraines are parallel ridges of debris deposited along the sides of a glacier. The unconsolidated debris can be deposited on top of the glacier by frost shattering of the valley walls or from tributary streams flowing into

1449-468: Is evidence of large glaciers in Greenland for most of the past 18 million years, these ice bodies were probably similar to various smaller modern examples, such as Maniitsoq and Flade Isblink , which cover 76,000 and 100,000 square kilometres (29,000 and 39,000 sq mi) around the periphery. Conditions in Greenland were not initially suitable for a single coherent ice sheet to develop, but this began to change around 10 million years ago , during

SECTION 20

#1733106098672

1518-478: Is grounded below the sea level, it would be vulnerable to geologically rapid ice loss in this scenario. In particular, the Thwaites and Pine Island glaciers are most likely to be prone to MISI, and both glaciers have been rapidly thinning and accelerating in recent decades. As the result, sea level rise from the ice sheet could be accelerated by tens of centimeters within the 21st century alone. The majority of

1587-718: Is known to vary on seasonal to interannual timescales. The Wilkes Basin is the only major submarine basin in Antarctica that is not thought to be sensitive to warming. Ultimately, even geologically rapid sea level rise would still most likely require several millennia for the entirety of these ice masses (WAIS and the subglacial basins) to be lost. A related process known as Marine Ice Cliff Instability (MICI) posits that ice cliffs which exceed ~ 90 m ( 295 + 1 ⁄ 2  ft) in above-ground height and are ~ 800 m ( 2,624 + 1 ⁄ 2  ft) in basal (underground) height are likely to collapse under their own weight once

1656-494: Is melting two to five times faster than before 1850, and snowfall has not kept up since 1996. If the Paris Agreement goal of staying below 2 °C (3.6 °F) is achieved, melting of Greenland ice alone would still add around 6 cm ( 2 + 1 ⁄ 2  in) to global sea level rise by the end of the century. If there are no reductions in emissions, melting would add around 13 cm (5 in) by 2100, with

1725-483: Is released into the atmosphere as methane , which has a much larger global warming potential than carbon dioxide. However, it also harbours large numbers of methanotrophic bacteria, which limit those emissions. Normally, the transitions between glacial and interglacial states are governed by Milankovitch cycles , which are patterns in insolation (the amount of sunlight reaching the Earth). These patterns are caused by

1794-478: Is still occurring nowadays, as can be clearly seen in an example that occurred in World War II . A Lockheed P-38 Lightning fighter plane crashed in Greenland in 1942. It was only recovered 50 years later. By then, it had been buried under 81 m (268 feet) of ice which had formed over that time period. Even stable ice sheets are continually in motion as the ice gradually flows outward from the central plateau, which

1863-517: Is still open for debate. The icing of Antarctica began in the Late Palaeocene or middle Eocene between 60 and 45.5 million years ago and escalated during the Eocene–Oligocene extinction event about 34 million years ago. CO 2 levels were then about 760 ppm and had been decreasing from earlier levels in the thousands of ppm. Carbon dioxide decrease, with a tipping point of 600 ppm,

1932-675: Is the segment of the continental ice sheet that covers West Antarctica , the portion of Antarctica on the side of the Transantarctic Mountains that lies in the Western Hemisphere . It is classified as a marine-based ice sheet, meaning that its bed lies well below sea level and its edges flow into floating ice shelves. The WAIS is bounded by the Ross Ice Shelf , the Ronne Ice Shelf , and outlet glaciers that drain into

2001-456: Is the tallest point of the ice sheet, and towards the margins. The ice sheet slope is low around the plateau but increases steeply at the margins. This difference in slope occurs due to an imbalance between high ice accumulation in the central plateau and lower accumulation, as well as higher ablation , at the margins. This imbalance increases the shear stress on a glacier until it begins to flow. The flow velocity and deformation will increase as

2070-506: The Amundsen Sea . As a smaller part of Antarctica, WAIS is also more strongly affected by climate change . There has been warming over the ice sheet since the 1950s, and a substantial retreat of its coastal glaciers since at least the 1990s. Estimates suggest it added around 7.6 ± 3.9 mm ( 19 ⁄ 64  ±  5 ⁄ 32  in) to the global sea level rise between 1992 and 2017, and has been losing ice in

2139-680: The Last Glacial Period at Last Glacial Maximum , the Laurentide Ice Sheet covered much of North America . In the same period, the Weichselian ice sheet covered Northern Europe and the Patagonian Ice Sheet covered southern South America . An ice sheet is a body of ice which covers a land area of continental size - meaning that it exceeds 50,000 km . The currently existing two ice sheets in Greenland and Antarctica have

Horseshoe Moraine - Misplaced Pages Continue

2208-630: The West Antarctic Ice Sheet (WAIS), from which it is separated by the Transantarctic Mountains . The ice sheet is around 2.2 km (1.4 mi) thick on average and is 4,897 m (16,066 ft) at its thickest point. It is also home to the geographic South Pole , South Magnetic Pole and the Amundsen–Scott South Pole Station . The surface of the EAIS is the driest, windiest, and coldest place on Earth. Lack of moisture in

2277-540: The Younger Dryas period which appears consistent with MICI. However, it indicates "relatively rapid" yet still prolonged ice sheet retreat, with a movement of >200 km (120 mi) inland taking place over an estimated 1100 years (from ~12,300 years Before Present to ~11,200 B.P.) In recent years, 2002-2004 fast retreat of Crane Glacier immediately after the collapse of the Larsen B ice shelf (before it reached

2346-548: The 2010s at a rate equivalent to 0.4 millimetres (0.016 inches) of annual sea level rise. While some of its losses are offset by the growth of the East Antarctic ice sheet , Antarctica as a whole will most likely lose enough ice by 2100 to add 11 cm (4.3 in) to sea levels. Further, marine ice sheet instability may increase this amount by tens of centimeters, particularly under high warming. Fresh meltwater from WAIS also contributes to ocean stratification and dilutes

2415-497: The Antarctic winter is cooler at the surface than in its middle layers. Consequently, greenhouse gases actually trap heat in the middle atmosphere and reduce its flow towards the surface while the temperature inversion lasts. Due to these factors, East Antarctica had experienced slight cooling for decades while the rest of the world warmed as the result of climate change . Clear warming over East Antarctica only started to occur since

2484-500: The East Antarctic Ice Sheet would not be affected. Totten Glacier is the largest glacier there which is known to be subject to MISI - yet, its potential contribution to sea level rise is comparable to that of the entire West Antarctic Ice Sheet. Totten Glacier has been losing mass nearly monotonically in recent decades, suggesting rapid retreat is possible in the near future, although the dynamic behavior of Totten Ice Shelf

2553-579: The Rogen moraines look like tigerstripes on aerial photographs . Rogen moraines are named after Lake Rogen in Härjedalen , Sweden , the landform's type locality. Closely related to Rogen moraines, de Geer moraines are till ridges up to 5m high and 10–50m wide running perpendicular to the ice flow. They occur in large groups in low-lying areas. Named for Gerard De Geer , who first described them in 1889, these moraines may have developed from crevasses underneath

2622-635: The SLR was greater than 6 m ( 19 + 1 ⁄ 2  ft). As of 2023, the most recent analysis indicates that the Last Interglacial SLR is unlikely to have been higher than 2.7 m (9 ft), as higher values in other research, such as 5.7 m ( 18 + 1 ⁄ 2  ft), appear inconsistent with the new paleoclimate data from The Bahamas and the known history of the Greenland Ice Sheet. The West Antarctic Ice Sheet (WAIS)

2691-412: The air, high albedo from the snow as well as the surface's consistently high elevation results in the reported cold temperature records of nearly −100 °C (−148 °F). It is the only place on Earth cold enough for atmospheric temperature inversion to occur consistently. That is, while the atmosphere is typically warmest near the surface and becomes cooler at greater elevation, atmosphere during

2760-416: The base of the glacier in as little as 2–18 hours – lubricating the bed and causing the glacier to surge . Water that reaches the bed of a glacier may freeze there, increasing the thickness of the glacier by pushing it up from below. As the margins end at the marine boundary, excess ice is discharged through ice streams or outlet glaciers . Then, it either falls directly into the sea or is accumulated atop

2829-478: The base of the ice as lodgment till . The name "washboard moraine" refers to the fact that, from the air, it resembles a washboard . A Veiki moraine is a kind of hummocky moraine that forms irregular landscapes of ponds and plateaus surrounded by banks. It forms from the irregular melting of ice covered with a thick layer of debris. Veiki moraine is common in northern Sweden and parts of Canada . Ice sheet In glaciology , an ice sheet , also known as

Horseshoe Moraine - Misplaced Pages Continue

2898-427: The boulders and other continental rocks they carried, leaving layers known as ice rafted debris . These so-called Heinrich events , named after their discoverer Hartmut Heinrich , appear to have a 7,000–10,000-year periodicity , and occur during cold periods within the last interglacial. Internal ice sheet "binge-purge" cycles may be responsible for the observed effects, where the ice builds to unstable levels, then

2967-604: The central plateau, which is the tallest point of the ice sheet, and towards the margins. The ice sheet slope is low around the plateau but increases steeply at the margins. Increasing global air temperatures due to climate change take around 10,000 years to directly propagate through the ice before they influence bed temperatures, but may have an effect through increased surface melting, producing more supraglacial lakes . These lakes may feed warm water to glacial bases and facilitate glacial motion. In previous geologic time spans ( glacial periods ) there were other ice sheets. During

3036-402: The collapse of Larsen B, in context. In the 1970s, Johannes Weertman proposed that because seawater is denser than ice, then any ice sheets grounded below sea level inherently become less stable as they melt due to Archimedes' principle . Effectively, these marine ice sheets must have enough mass to exceed the mass of the seawater displaced by the ice, which requires excess thickness. As

3105-515: The continent since the 1957. The Greenland ice sheet is an ice sheet which forms the second largest body of ice in the world. It is an average of 1.67 km (1.0 mi) thick, and over 3 km (1.9 mi) thick at its maximum. It is almost 2,900 kilometres (1,800 mi) long in a north–south direction, with a maximum width of 1,100 kilometres (680 mi) at a latitude of 77°N , near its northern edge. The ice sheet covers 1,710,000 square kilometres (660,000 sq mi), around 80% of

3174-505: The definition. Further, modelling done after the initial hypothesis indicates that ice-cliff instability would require implausibly fast ice shelf collapse (i.e. within an hour for ~ 90 m ( 295 + 1 ⁄ 2  ft)-tall cliffs), unless the ice had already been substantially damaged beforehand. Further, ice cliff breakdown would produce a large number of debris in the coastal waters - known as ice mélange - and multiple studies indicate their build-up would slow or even outright stop

3243-472: The dynamics on the ice, and the location on the glacier in which the moraine is formed. Moraine forming processes may be loosely divided into passive and active . Passive processes involve the placing of chaotic supraglacial sediments onto the landscape with limited reworking, typically forming hummocky moraines. These moraines are composed of supraglacial sediments from the ice surface. Active processes form or rework moraine sediment directly by

3312-522: The equilibrium line between these two processes is approached. This motion is driven by gravity but is controlled by temperature and the strength of individual glacier bases. A number of processes alter these two factors, resulting in cyclic surges of activity interspersed with longer periods of inactivity, on time scales ranging from hourly (i.e. tidal flows) to the centennial (Milankovich cycles). On an unrelated hour-to-hour basis, surges of ice motion can be modulated by tidal activity. The influence of

3381-498: The existence of uniquely adapted microbial communities , high rates of biogeochemical and physical weathering in ice sheets, and storage and cycling of organic carbon in excess of 100 billion tonnes. There is a massive contrast in carbon storage between the two ice sheets. While only about 0.5-27 billion tonnes of pure carbon are present underneath the Greenland ice sheet, 6000-21,000 billion tonnes of pure carbon are thought to be located underneath Antarctica. This carbon can act as

3450-406: The floating ice shelves . Those ice shelves then calve icebergs at their periphery if they experience excess of ice. Ice shelves would also experience accelerated calving due to basal melting. In Antarctica, this is driven by heat fed to the shelf by the circumpolar deep water current, which is 3 °C above the ice's melting point. The presence of ice shelves has a stabilizing influence on

3519-514: The formation of salty Antarctic bottom water , which destabilizes Southern Ocean overturning circulation . In the long term, the West Antarctic Ice Sheet is likely to disappear due to the warming which has already occurred. Paleoclimate evidence suggests that this has already happened during the Eemian period, when the global temperatures were similar to the early 21st century. It

SECTION 50

#1733106098672

3588-515: The glacier behind them, while an absence of an ice shelf becomes destabilizing. For instance, when Larsen B ice shelf in the Antarctic Peninsula had collapsed over three weeks in February 2002, the four glaciers behind it - Crane Glacier , Green Glacier , Hektoria Glacier and Jorum Glacier - all started to flow at a much faster rate, while the two glaciers (Flask and Leppard) stabilized by

3657-493: The glacier is advancing, receding or at equilibrium. The longer the terminus of the glacier stays in one place, the more debris accumulate in the moraine. There are two types of end moraines: terminal and recessional. Terminal moraines mark the maximum advance of the glacier. Recessional moraines are small ridges left as a glacier pauses during its retreat. After a glacier retreats, the end moraine may be destroyed by postglacial erosion. Recessional moraines are often observed as

3726-437: The ice before they influence bed temperatures, but may have an effect through increased surface melting, producing more supraglacial lakes . These lakes may feed warm water to glacial bases and facilitate glacial motion. Lakes of a diameter greater than ~300 m are capable of creating a fluid-filled crevasse to the glacier/bed interface. When these crevasses form, the entirety of the lake's (relatively warm) contents can reach

3795-415: The ice sheet melts and becomes thinner, the weight of the overlying ice decreases. At a certain point, sea water could force itself into the gaps which form at the base of the ice sheet, and marine ice sheet instability (MISI) would occur. Even if the ice sheet is grounded below the sea level, MISI cannot occur as long as there is a stable ice shelf in front of it. The boundary between the ice sheet and

3864-449: The ice sheet. The Kvarken has a very high density of de Geer moraines. End moraines, or terminal moraines , are ridges of unconsolidated debris deposited at the snout or end of the glacier. They usually reflect the shape of the glacier's terminus . Glaciers act much like a conveyor belt, carrying debris from the top of the glacier to the bottom where it deposits it in end moraines. End moraine size and shape are determined by whether

3933-440: The ice shelf, known as the grounding line , is particularly stable if it is constrained in an embayment . In that case, the ice sheet may not be thinning at all, as the amount of ice flowing over the grounding line would be likely to match the annual accumulation of ice from snow upstream. Otherwise, ocean warming at the base of an ice shelf tends to thin it through basal melting. As the ice shelf becomes thinner, it exerts less of

4002-458: The instability soon after it started. Some scientists - including the originators of the hypothesis, Robert DeConto and David Pollard - have suggested that the best way to resolve the question would be to precisely determine sea level rise during the Last Interglacial . MICI can be effectively ruled out if SLR at the time was lower than 4 m (13 ft), while it is very likely if

4071-426: The movement of ice, known as glaciotectonism. These form push moraines and thrust-block moraines, which are often composed of till and reworked proglacial sediment. Moraine may also form by the accumulation of sand and gravel deposits from glacial streams emanating from the ice margin. These fan deposits may coalesce to form a long moraine bank marking the ice margin. Several processes may combine to form and rework

4140-475: The northern hemisphere warmed considerably, dramatically increasing the release of methane from wetlands, that were otherwise tundra during glacial times. This methane quickly distributes evenly across the globe, becoming incorporated in Antarctic and Greenland ice. With this tie, paleoclimatologists have been able to say that the ice sheets on Greenland only began to warm after the Antarctic ice sheet had been warming for several thousand years. Why this pattern occurs

4209-415: The peripheral ice stabilizing them is gone. Their collapse then exposes the ice masses following them to the same instability, potentially resulting in a self-sustaining cycle of cliff collapse and rapid ice sheet retreat - i.e. sea level rise of a meter or more by 2100 from Antarctica alone. This theory had been highly influential - in a 2020 survey of 106 experts, the paper which had advanced this theory

SECTION 60

#1733106098672

4278-565: The remnants of the ice shelf did not accelerate. The collapse of the Larsen B shelf was preceded by thinning of just 1 metre per year, while some other Antarctic ice shelves have displayed thinning of tens of metres per year. Further, increased ocean temperatures of 1 °C may lead to up to 10 metres per year of basal melting. Ice shelves are always stable under mean annual temperatures of −9 °C, but never stable above −5 °C; this places regional warming of 1.5 °C, as preceded

4347-419: The surface in the ablation zone , melting of surface ice or from debris that falls onto the glacier from valley sidewalls. Washboard moraines , also known as minor or corrugated moraines , are low-amplitude geomorphic features caused by glaciers. They consist of low-relief ridges, 1 to 2 meters (3 ft 3 in to 6 ft 7 in) in height and around 100 meters (330 ft) apart, accumulated at

4416-448: The surface of Greenland , or about 12% of the area of the Antarctic ice sheet . The term 'Greenland ice sheet' is often shortened to GIS or GrIS in scientific literature . Greenland has had major glaciers and ice caps for at least 18 million years, but a single ice sheet first covered most of the island some 2.6 million years ago. Since then, it has both grown and contracted significantly. The oldest known ice on Greenland

4485-580: The valley, or may be subglacial debris carried to the surface of the glacier, melted out, and transported to the glacier margin. Lateral moraines can rise up to 140 meters (460 ft) over the valley floor, can be up to 3 kilometers (1.9 mi) long, and are steeper close to the glacier margin (up to 80 degrees) than further away (where slopes are typically 29 to 36 degrees. Ground moraines are till-covered areas with irregular topography and no ridges, often forming gently rolling hills or plains, with relief of less than 10 meters (33 ft). Ground moraine

4554-573: The variations in shape of the Earth's orbit and its angle relative to the Sun, caused by the gravitational pull of other planets as they go through their own orbits. For instance, during at least the last 100,000 years, portions of the ice sheet covering much of North America, the Laurentide Ice Sheet broke apart sending large flotillas of icebergs into the North Atlantic. When these icebergs melted they dropped

4623-460: The year 2000, and was not conclusively detected until the 2020s. In the early 2000s, cooling over East Antarctica seemingly outweighing warming over the rest of the continent was frequently misinterpreted by the media and occasionally used as an argument for climate change denial . After 2009, improvements in Antarctica's instrumental temperature record have proven that the warming over West Antarctica resulted in consistent net warming across

4692-867: Was considered more important than even the year 2014 IPCC Fifth Assessment Report . Sea level rise projections which involve MICI are much larger than the others, particularly under high warming rate. At the same time, this theory has also been highly controversial. It was originally proposed in order to describe how the large sea level rise during the Pliocene and the Last Interglacial could have occurred - yet more recent research found that these sea level rise episodes can be explained without any ice cliff instability taking place. Research in Pine Island Bay in West Antarctica (the location of Thwaites and Pine Island Glacier ) had found seabed gouging by ice from

4761-520: Was the primary agent forcing Antarctic glaciation. The glaciation was favored by an interval when the Earth's orbit favored cool summers but oxygen isotope ratio cycle marker changes were too large to be explained by Antarctic ice-sheet growth alone indicating an ice age of some size. The opening of the Drake Passage may have played a role as well though models of the changes suggest declining CO 2 levels to have been more important. While there

#671328