Misplaced Pages

#954045

142-535: The area drained by Pine Island Glacier comprises about 10% of the West Antarctic Ice Sheet . Satellite measurements have shown that the Pine Island Glacier Basin has a greater net contribution of ice to the sea than any other ice drainage basin in the world and this has increased due to recent acceleration of the ice stream. An iceberg about twice the size of Washington, DC broke off from

284-527: A DC-8 research plane, scientists participating in NASA's IceBridge mission discovered a massive crack running about 29 kilometers (18 mi) across the glacier's floating tongue. The rift is 80 metres (260 feet) wide on average and 50 to 60 meters (160 to 200 ft) deep. Another team from the British Antarctic Survey arrived at the ice stream on 8 December 2006 for the first of two field seasons. In

426-520: A 10 km retreat in 2015. In January 2008, British Antarctic Survey (BAS) scientists reported that 2,200 years ago a volcano erupted under the Antarctic ice sheet . This was the biggest Antarctic eruption in the last 10,000 years. The volcano is situated in the Hudson Mountains , close to Pine Island Glacier. The eruption spread a layer of volcanic ash and tephra over the surface of

568-515: A 1968 paper by glaciologist J. H. Mercer. In the 1970s, radar measurements from research flights revealed that glacier beds in Pine Island Bay slope downwards at an angle, well below the sea level . Thus, even a limited warming of ocean currents ice would effectively undermine the ice. In 1981, the Amundsen Sea region had first been described by the researchers as "the weak underbelly" of

710-700: A broad trend of very gradual cooling known as Neoglaciation , which lasted from the end of the HCO to before the Industrial Revolution . From the 10th-14th century, the climate was similar to that of modern times during a period known as the Mediaeval Warm Period (MWP), also known as the Mediaeval Climatic Optimum (MCO). It was found that the warming that is taking place in current years is both more frequent and more spatially homogeneous than what

852-447: A clear effect, The circulation may lose half of its strength by 2050 under the worst climate change scenario , and decline even more afterwards. In the long run, the circulation could collapse entirely: potentially between 1.7 °C (3.1 °F) and 3 °C (5.4 °F), though this is much less certain than with the other tipping points in the climate system . This collapse would likely require multiple centuries to unfold: it

994-484: A doubling time of 10, 20 or 40 years, which would then lead to multi-meter sea level rise in 50, 100 or 200 years. However, it remains a minority view amongst the scientific community. For comparison, a 2020 survey of 106 experts found that their 5%–95% confidence interval of 2100 sea level rise for the high-emission scenario RCP8.5 was 45–165 cm ( 17 + 1 ⁄ 2 –65 in). Their high-level projections also included both ice sheet and ice cliff instability:

1136-407: A flexible material and anchored to the Amundsen Sea floor would be able to interrupt warm water flow. This approach would reduce costs and increase the longevity of the material (conservatively estimated at 25 years for curtain elements and up to 100 years for the foundations) relative to more rigid structures. With them in place, Thwaites Ice Shelf and Pine Island Ice Shelf would presumably regrow to

1278-432: 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 preservation of WAIS may require a persistent reduction of global temperatures to 1 °C (1.8 °F) below the preindustrial level, or to 2 °C (3.6 °F) below the temperature of 2020. Because the collapse of the ice sheet would be preceded by

1420-593: A larger effect on the mid-to-low latitudes and mid-to-high latitudes after ~5600 B.P. Human activity through land use changes already by the Mesolithic had major ecological impacts; it was an important influence on Holocene climatic changes, and is believed to be why the Holocene is an atypical interglacial that has not experienced significant cooling over its course. From the start of the Industrial Revolution onwards, large-scale anthropogenic greenhouse gas emissions caused

1562-552: A marine transgression occurred in southeastern Africa; in the Lake Lungué basin, this sea level highstand occurred from 740 to 910 AD, or from 1,210 to 1,040 BP, as evidenced by the lake's connection to the Indian Ocean at this time. This transgression was followed by a period of transition that lasted until 590 BP, when the region experienced significant aridification and began to be extensively used by humans for livestock herding. In

SECTION 10

#1732851789955

1704-643: A more sustainable sedentary lifestyle . This form of lifestyle change allowed humans to develop towns and villages in centralized locations, which gave rise to the world known today. It is believed that the domestication of plants and animals began in the early part of the Holocene in the tropical areas of the planet. Because these areas had warm, moist temperatures, the climate was perfect for effective farming. Culture development and human population change, specifically in South America, has also been linked to spikes in hydroclimate resulting in climate variability in

1846-567: A much wetter climate from 11,400 to 11,100 BP due to intensification of the ISM. Over the Early Holocene, the region was very wet, but during the Middle Holocene from 6,200 to 3,900 BP, aridification occurred, with the subsequent Late Holocene being relatively arid as a whole. Coastal southwestern India experienced a stronger ISM from 9,690 to 7,560 BP, during the HCO. From 3,510 to 2,550 BP, during

1988-596: A negative excursion in the δ O record lasting 400 years, is the most prominent climatic event occurring in the Holocene Epoch, and may have marked a resurgence of ice cover. It has been suggested that this event was caused by the final drainage of Lake Agassiz , which had been confined by the glaciers, disrupting the thermohaline circulation of the Atlantic . This disruption was the result of an ice dam over Hudson Bay collapsing sending cold lake Agassiz water into

2130-643: A point where only minor and isolated ice caps remained, such as during the Marine isotope stage 31 ~1.07 million years ago, or the Eemian period ~130,000 years ago. West Antarctica has experienced statistically significant warming in recent decades, although there is some uncertainty about its magnitude. In 2015, the warming of the WAIS between 1976 and 2012 was calculated as a range between 0.08 °C (0.14 °F) per decade and 0.96 °C (1.73 °F) per decade. In 2009,

2272-467: A role. Drangajökull, Iceland's northernmost glacier, melted shortly after 9,200 BP. In Northern Germany , the Middle Holocene saw a drastic increase in the amount of raised bogs, most likely related to sea level rise. Although human activity affected geomorphology and landscape evolution in Northern Germany throughout the Holocene, it only became a dominant influence in the last four centuries. In

2414-487: A series of seismic and radar surveys on PIG. They also installed a series of overwintering GPS stations. During the season, a separate BAS team travelled to the field party's location and installed an overwintering autonomous VLF station. This was followed by a radar traverse upstream using snowmobiles . This survey linked previous radar lines. The first ship to reach Pine Island Glacier's ice shelf, in Pine Island Bay,

2556-559: A skiway for the C130s. The remaining members of the team arrived from Rothera Research Station 10 days later in a Twin Otter. Because of unusually good weather in the area that season the survey completed flying their grids by mid-January, and began flying 15 km grids of Thwaites Glacier for a USAP expedition who had been experiencing unusually poor weather in their area that year. Flying over Antarctica's Pine Island Glacier on October 14, 2011, in

2698-483: A state they last had a century ago, thus stabilizing these glaciers. To achieve this, the curtains would have to be placed at a depth of around 600 metres (0.37 miles) (to avoid damage from icebergs which would be regularly drifting above) and be 80 km (50 mi) long. The authors acknowledged that while work on this scale would be unprecedented and face many challenges in the Antarctic (including polar night and

2840-501: A variety of methods, with a view toward further verifying and refining the Blytt–Sernander sequence . This is a classification of climatic periods initially defined by plant remains in peat mosses . Though the method was once thought to be of little interest, based on C dating of peats that was inconsistent with the claimed chronozones, investigators have found a general correspondence across Eurasia and North America . The scheme

2982-512: A very long time from start to end for the ice sheet to disappear, some research indicates that the only way to stop its complete meltdown once triggered, is by lowering the global temperature to 1 °C (1.8 °F) below the preindustrial level; i.e. 2 °C (3.6 °F) below the temperature of 2020. Other researchers have proposed engineering interventions to stabilize Thwaites and Pine Island Glaciers before they are lost. For instance, 2019 research estimated that moving some ocean water from

SECTION 20

#1732851789955

3124-655: Is a substantial volcanic heat source beneath Pine Island Glacier approximately half as large as the active Grimsvötn volcano on Iceland. The same year a study was published concluding that the bedrock below WAIS was uplifted at a higher rate than previously thought, the authors suggested this could eventually help to stabilize the ice sheet. Pine Island Glacier, as well as the better known Thwaites Glacier , can both substantially exacerbate future sea level rise . Consequently, some scientists, most notably Michael J. Wolovick and John C. Moore, have suggested stabilizing them via climate engineering aiming to block warm water flows from

3266-483: Is already experience of laying down pipelines at such depths. Due to the remoteness of Pine Island Glacier, most of the information available on the ice stream comes from airborne or satellite-based measurements. The first expedition to visit the ice stream was a United States over-snow traverse, which spent around a week in the area of PIG during January 1961. They dug snow pits to measure snow accumulation and carried out seismic surveys to measure ice thickness. One of

3408-456: 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

3550-414: Is below it. The weight of the ice has caused the underlying rock to sink by between 0.5 and 1 kilometre (0.31 and 0.62 miles) in a process known as isostatic depression . Under the force of its own weight, the ice sheet deforms and flows slowly over rough bedrock . Ice ridges are the areas where ice sheet movement is slow because it is frozen to the bed, while ice streams flow much faster because there

3692-466: Is liquid water in the sediments beneath them. Those are either the marine sediments which used to cover the ocean floor before the ice sheet froze above them, or they have been created due to erosion from the constant friction of ice against the bedrock. The water in these sediments stays liquid because the Earth's crust below the ice streams is thin and conducts heat from geothermal activity , and because

3834-401: Is most strongly affected by winds and precipitation , and the larger lower cell, which 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 as the result of the natural cycle of Interdecadal Pacific Oscillation , but large flows of meltwater also had

3976-524: Is not expected to diminish Southern Ocean heat and carbon uptake during the 21st century, but is likely to weaken its carbon sink once it is complete, which would be closer to 2300. Other likely impacts include a decline in precipitation in the Southern Hemisphere countries like Australia (with a corresponding increase in the Northern Hemisphere ), and an eventual decline of fisheries in

4118-403: Is one half of the global thermohaline circulation , with the better-known Atlantic meridional overturning circulation being the other. Southern Ocean absorbs by far the most heat and is also the strongest carbon sink of any ocean. Both properties are affected by the strength of the overturning circulation. The overturning circulation consists of two parts – the smaller upper cell, which

4260-563: Is the Greek word for "whole". "Cene" comes from the Greek word kainós ( καινός ), meaning "new". The concept is that this epoch is "entirely new". The suffix '-cene' is used for all the seven epochs of the Cenozoic Era. The International Commission on Stratigraphy has defined the Holocene as starting approximately 11,700 years before 2000 CE (11,650 cal years BP , or 9,700 BCE). The Subcommission on Quaternary Stratigraphy (SQS) regards

4402-677: 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

Pine Island Glacier - Misplaced Pages Continue

4544-458: The Amundsen Sea floor would be able to interrupt warm water flow. This approach would reduce costs and increase the longevity of the material (conservatively estimated at 25 years for curtain elements and up to 100 years for the foundations) relative to more rigid structures. With them in place, Thwaites Ice Shelf and Pine Island Ice Shelf would presumably regrow to a state they last had a century ago, thus stabilizing these glaciers. To achieve this,

4686-597: The Amundsen Sea to the top of the Thwaites and Pine Island Glacier area and freezing it to create at least 7400 billion tonnes of snow would stabilize the ice sheet. This would be enormously expensive, as an equivalent of 12,000 wind turbines would be required to provide power just to move the water to the ice sheet, even before desalinating it (to avoid enhancing surface melt with salt) and turning it to snow. It also assumed local water temperature remaining at early 21st century levels, rather than tripling unavoidably by 2100 as

4828-450: 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

4970-767: The Amundsen Sea Embayment . A total area of 175,000 km (68,000 sq mi), 10 percent of the West Antarctic Ice Sheet, drains out to the sea via Pine Island Glacier, this area is known as the Pine Island Glacier drainage basin. The Pine Island and Thwaites glaciers are two of Antarctica's five largest ice streams . Scientists have found that the flow of these ice streams has accelerated in recent years, and suggested that if they were to melt, global sea levels would rise by 1 to 2 m (3 ft 3 in to 6 ft 7 in), destabilising

5112-533: The East Antarctic Ice Sheet adds meltwater to the Southern Ocean , at a total rate of 1100–1500 billion tons (GT) per year. This meltwater is fresh, and when it mixes with ocean water, the ocean becomes fresher (less salty) as well. This results in the increased stratification and stabilization of the ocean layers, which has a significant impact on Southern Ocean overturning circulation . It

5254-658: The French Alps , geochemistry and lithium isotope signatures in lake sediments have suggested gradual soil formation from the Last Glacial Period to the Holocene climatic optimum , and this soil development was altered by the settlement of human societies. Early anthropogenic activities such as deforestation and agriculture reinforced soil erosion, which peaked in the Middle Ages at an unprecedented level, marking human forcing as

5396-425: The Holocene , and that this process may continue for centuries after it is initiated. As the ice stream accelerates it is also getting steeper. The rate of thinning within the central trunk has quadrupled from 1995 to 2006. If the current rate of acceleration were to continue the main trunk of the glacier could be afloat within 100 years. The ice front stayed in a more or less stable position from 1973 to 2014, with

5538-603: The Intertropical Convergence Zone (ITCZ) produced increased monsoon rainfall over North Africa. The lush vegetation of the Sahara brought an increase in pastoralism . The AHP ended around 5,500 BP, after which the Sahara began to dry and become the desert it is today. A stronger East African Monsoon during the Middle Holocene increased precipitation in East Africa and raised lake levels. Around 800 AD, or 1,150 BP,

5680-717: The Kalahari Desert , Holocene climate was overall very stable and environmental change was of low amplitude. Relatively cool conditions have prevailed since 4,000 BP. In the Middle East, the Holocene brought a warmer and wetter climate, in contrast to the preceding cold, dry Younger Dryas . The Early Holocene saw the advent and spread of agriculture in the Fertile Crescent — sheep , goat , cattle , and later pig were domesticated, as well as cereals, like wheat and barley , and legumes —which would later disperse into much of

5822-617: The Last Glacial Period , which concluded with the Holocene glacial retreat . The Holocene and the preceding Pleistocene together form the Quaternary period. The Holocene is an interglacial period within the ongoing glacial cycles of the Quaternary, and is equivalent to Marine Isotope Stage 1 . The Holocene correlates with the last maximum axial tilt of the Earth towards the Sun, and corresponds with

Pine Island Glacier - Misplaced Pages Continue

5964-664: The Mesolithic , Neolithic , and Bronze Age , are usually used. However, the time periods referenced by these terms vary with the emergence of those technologies in different parts of the world. Some scholars have argued that a third epoch of the Quaternary, the Anthropocene , has now begun. This term has been used to denote the present time-interval in which many geologically significant conditions and processes have been profoundly altered by human activities. The 'Anthropocene' (a term coined by Paul J. Crutzen and Eugene Stoermer in 2000)

6106-628: The North Atlantic ocean . Furthermore, studies show that the melting of Lake Agassiz led to sea-level rise which flooded the North American coastal landscape. The basal peat plant was then used to determine the resulting local sea-level rise of 0.20-0.56m in the Mississippi Delta . Subsequent research, however, suggested that the discharge was probably superimposed upon a longer episode of cooler climate lasting up to 600 years and observed that

6248-565: The Tien Shan , sedimentological evidence from Swan Lake suggests the period between 8,500 and 6,900 BP was relatively warm, with steppe meadow vegetation being predominant. An increase in Cyperaceae from 6,900 to 2,600 BP indicates cooling and humidification of the Tian Shan climate that was interrupted by a warm period between 5,500 and 4,500 BP. After 2,600 BP, an alpine steppe climate prevailed across

6390-965: The last glacial period . Local names for the last glacial period include the Wisconsinan in North America , the Weichselian in Europe, the Devensian in Britain, the Llanquihue in Chile and the Otiran in New Zealand. The Holocene can be subdivided into five time intervals, or chronozones , based on climatic fluctuations: Geologists working in different regions are studying sea levels, peat bogs, and ice-core samples, using

6532-535: The sixth mass extinction or Anthropocene extinction , is an ongoing extinction event of species during the present Holocene epoch (with the more recent time sometimes called Anthropocene) as a result of human activity . The included extinctions span numerous families of fungi , plants , and animals , including mammals , birds , reptiles , amphibians , fish and invertebrates . With widespread degradation of highly biodiverse habitats such as coral reefs and rainforests , as well as other areas,

6674-548: 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

6816-539: The Earth to warm. Likewise, climatic changes have induced substantial changes in human civilisation over the course of the Holocene. During the transition from the last glacial to the Holocene, the Huelmo–Mascardi Cold Reversal in the Southern Hemisphere began before the Younger Dryas, and the maximum warmth flowed south to north from 11,000 to 7,000 years ago. It appears that this was influenced by

6958-576: The Holocene Epoch. A 1,500-year cycle corresponding to the North Atlantic oceanic circulation may have had widespread global distribution in the Late Holocene. From 8,500 BP to 6,700 BP, North Atlantic climate oscillations were highly irregular and erratic because of perturbations from substantial ice discharge into the ocean from the collapsing Laurentide Ice Sheet. The Greenland ice core records indicate that climate changes became more regional and had

7100-474: The Holocene has shown significant variability despite ice core records from Greenland suggesting a more stable climate following the preceding ice age. Marine chemical fluxes during the Holocene were lower than during the Younger Dryas, but were still considerable enough to imply notable changes in the climate. The temporal and spatial extent of climate change during the Holocene is an area of considerable uncertainty, with radiative forcing recently proposed to be

7242-480: The Holocene, however, the domestication of plants and animals allowed humans to develop villages and towns in centralized locations. Archaeological data shows that between 10,000 and 7,000 BP rapid domestication of plants and animals took place in tropical and subtropical parts of Asia , Africa , and Central America . The development of farming allowed humans to transition away from hunter-gatherer nomadic cultures, which did not establish permanent settlements, to

SECTION 50

#1732851789955

7384-658: The International Union of Geological Sciences later formally confirmed, by a near unanimous vote, the rejection of the working group's Anthropocene Epoch proposal for inclusion in the Geologic Time Scale. The Holocene is a geologic epoch that follows directly after the Pleistocene . Continental motions due to plate tectonics are less than a kilometre over a span of only 10,000 years. However, ice melt caused world sea levels to rise about 35 m (115 ft) in

7526-437: The Late Holocene, the ISM became weaker, although this weakening was interrupted by an interval of unusually high ISM strength from 3,400 to 3,200 BP. Southwestern China experienced long-term warming during the Early Holocene up until ~7,000 BP. Northern China experienced an abrupt aridification event approximately 4,000 BP. From around 3,500 to 3,000 BP, northeastern China underwent a prolonged cooling, manifesting itself with

7668-476: The Late Holocene. Animal and plant life have not evolved much during the relatively short Holocene, but there have been major shifts in the richness and abundance of plants and animals. A number of large animals including mammoths and mastodons , saber-toothed cats like Smilodon and Homotherium , and giant sloths went extinct in the late Pleistocene and early Holocene. These extinctions can be mostly attributed to people. In America, it coincided with

7810-454: The Middle Holocene was notable for its warmth, with rhythmic temperature fluctuations every 400-500 and 1,000 years. Before 7,500 BP, the Gulf of Thailand was exposed above sea level and was very arid. A marine transgression occurred from 7,500 to 6,200 BP amidst global warming. During the Middle Holocene, western North America was drier than present, with wetter winters and drier summers. After

7952-625: The Middle to Late Holocene, the coastline of the Levant and Persian Gulf receded, prompting a shift in human settlement patterns following this marine regression. Central Asia experienced glacial-like temperatures until about 8,000 BP, when the Laurentide Ice Sheet collapsed. In Xinjiang , long-term Holocene warming increased meltwater supply during summers, creating large lakes and oases at low altitudes and inducing enhanced moisture recycling. In

8094-608: The PIG until January 5, mapping the sub-glacial terrain of an area roughly the size of Nevada. Due to the remoteness of PIG and the logistical difficulties of caching enough fuel for the 2004–05 expedition and future project(s), BAS used the resources of the United States Antarctic Program (USAP) and their ski-equipped LC130 aircraft. After many weeks of weather delays the first four men arrived from McMurdo Station on 9 November 2004, and began to establish camp and build

8236-471: The Southern Ocean, which could lead to a potential collapse of certain marine ecosystems . Due to limited research to date, few specifics are currently known. The same ice sheet topography which makes marine ice sheet instability possible in the short term, also leaves it vulnerable to disappearing in response to even seemingly limited changes in temperature. This suggestion had first been presented in

8378-530: The Thwaites' grounding line to either physically reinforce it, or to block some fraction of warm water flow. The former would be the simplest intervention, yet equivalent to "the largest civil engineering projects that humanity has ever attempted". It is also only 30% likely to work. Constructions blocking even 50% of the warm water flow are expected to be far more effective, yet far more difficult as well. Some researchers argued that this proposal could be ineffective, or even accelerate sea level rise. The authors of

8520-718: The UK. It completed six successful missions, travelling a total of 500 km (310 mi) under the ice shelf. Autosub is able to map the base of the ice shelf as well as the ocean floor and take various measurements and samples of the water on the way. The success of Autosub 3 was particularly notable because its predecessor Autosub 2 was lost beneath the Fimbul Ice Shelf on only its second such mission. West Antarctic Ice Sheet 78°44′03″S 133°16′41″W  /  78.73417°S 133.27806°W  / -78.73417; -133.27806 The West Antarctic Ice Sheet ( WAIS )

8662-512: The WAIS, with the hypothesis that the collapse of Thwaites Glacier and Pine Island Glacier would trigger the collapse of the entire ice sheet. This had been supported by subsequent research. Now, the potential for the West Antarctic Ice Sheet to disappear after a certain temperature is exceeded is considered one of the tipping points in the climate system . Earlier research suggested it may withstand up to 3 °C (5.4 °F) before it would melt irreversibly, but 1.5 °C (2.7 °F)

SECTION 60

#1732851789955

8804-445: The West Antarctic Ice Sheet loses ice due to the warming ocean water melting its coastal glaciers, it inevitably contributes to sea level rise . However, projections are complicated by additional processes that are difficult to model, such as meltwater from the ice sheet itself changing local circulation due to being warmer and fresher than the ocean water. Another complicated process is hydrofracturing, where meltwater collecting atop

8946-503: The amount of relatively warm circumpolar deep water that can reach the thickest ice. The speed of Pine Island Glacier increased by 77 percent from 1974 to the end of 2013, with half of this increase occurring between 2003 and 2009. This speed up has meant that by the end of 2007 the Pine Island Glacier system had a negative mass balance of 46  gigatonnes per year, which is equivalent to 0.13 mm (0.0051 in) per year global sea level rise . In other words, much more water

9088-520: The arrival of the Clovis people; this culture was known for " Clovis points " which were fashioned on spears for hunting animals. Shrubs, herbs, and mosses had also changed in relative abundance from the Pleistocene to Holocene, identified by permafrost core samples. Throughout the world, ecosystems in cooler climates that were previously regional have been isolated in higher altitude ecological "islands". The 8.2-ka event , an abrupt cold spell recorded as

9230-454: The average annual rate of mass loss since 2002, equivalent to 0.4 millimetres (0.016 inches) of annual sea level rise. Coastal glaciers are typically buttressed by ice shelves , which are massive blocks of floating ice next to a glacier. Yet, the ice shelves melt relatively quickly, as they are constantly in contact with the warming ocean water. Glacier retreat accelerates substantially once they collapse and stop providing structural support to

9372-495: The bed only deepens upstream. This means that as the ice sheet loses mass to melting, an increasing fraction of its height becomes exposed to warm water flows that are no longer displaced by its mass. This hypothesis is known as marine ice sheet instability (MISI) and it has the potential to greatly accelerate ice losses. The lack of knowledge about its specifics introduces substantial uncertainty into projections of 21st century sea level rise. WAIS could be even more vulnerable under

9514-416: The currently insufficient numbers of specialized polar ships and underwater vessels), it would also not require any new technology and there is already experience of laying down pipelines at such depths. Holocene The Holocene ( / ˈ h ɒ l . ə s iː n , - oʊ -, ˈ h oʊ . l ə -, - l oʊ -/ ) is the current geological epoch , beginning approximately 11,700 years ago. It follows

9656-483: The curtains would have to be placed at a depth of around 600 metres (0.37 miles) (to avoid damage from icebergs which would be regularly drifting above) and be 80 km (50 mi) long. The authors acknowledged that while work on this scale would be unprecedented and face many challenges in the Antarctic (including polar night and the currently insufficient numbers of specialized polar ships and underwater vessels), it would also not require any new technology and there

9798-422: The disappearance of the ice sheet by many centuries, but it would still require one of the largest civil engineering interventions in history. The total volume of the entire Antarctic ice sheet is estimated at 26.92 million km (6.46 million cu mi), while the WAIS contains about 2.1 million km (530,000 cu mi) in ice that is above the sea level, and ~1 million km (240,000 cu mi) in ice that

9940-450: The disruption of Bronze Age civilisations in the region. Eastern and southern China, the monsoonal regions of China, were wetter than present in the Early and Middle Holocene. Lake Huguangyan's TOC, δ C wax , δ C org , δ N values suggest the period of peak moisture lasted from 9,200 to 1,800 BP and was attributable to a strong East Asian Summer Monsoon (EASM). Late Holocene cooling events in

10082-473: The early part of the Holocene and another 30 m in the later part of the Holocene. In addition, many areas above about 40 degrees north latitude had been depressed by the weight of the Pleistocene glaciers and rose as much as 180 m (590 ft) due to post-glacial rebound over the late Pleistocene and Holocene, and are still rising today. The sea-level rise and temporary land depression allowed temporary marine incursions into areas that are now far from

10224-427: The end of the last strong phase. Ice core measurements imply that the sea surface temperature (SST) gradient east of New Zealand, across the subtropical front (STF), was around 2 degrees Celsius during the HCO. This temperature gradient is significantly less than modern times, which is around 6 degrees Celsius. A study utilizing five SST proxies from 37°S to 60°S latitude confirmed that the strong temperature gradient

10366-601: The end of the thermal maximum of the HCO around 4,500 BP, the East Greenland Current underwent strengthening. A massive megadrought occurred from 2,800 to 1,850 BP in the Great Basin . Eastern North America underwent abrupt warming and humidification around 10,500 BP and then declined from 9,300 to 9,100 BP. The region has undergone a long term wettening since 5,500 BP occasionally interrupted by intervals of high aridity. A major cool event lasting from 5,500 to 4,700 BP

10508-501: The entire West Antarctic Ice Sheet and perhaps sections of the East Antarctic Ice Sheet. In 1981 Terry Hughes proposed that the region around Pine Island Bay may be a "weak underbelly" of the West Antarctic Ice Sheet. This is based on the fact that, unlike the majority of the large West Antarctic ice streams, those flowing into the Amundsen Sea are not protected from the ocean by large floating ice shelves . Also, although

10650-627: The experts found ice cliff instability research to be just as, or even more influential, as the IPCC Fifth Assessment report. Consequently, when the IPCC Sixth Assessment Report (AR6) was published in 2021–2022, it estimated that while the median increase in sea level rise from the West Antarctic ice sheet melt by 2100 would be ~11 cm (5 in) under all emission scenarios (since the increased warming would intensify

10792-527: The extent of the area affected was unclear. The beginning of the Holocene corresponds with the beginning of the Mesolithic age in most of Europe . In regions such as the Middle East and Anatolia , the term Epipaleolithic is preferred in place of Mesolithic, as they refer to approximately the same time period. Cultures in this period include Hamburgian , Federmesser , and the Natufian culture , during which

10934-399: 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

11076-406: The friction also generates heat, particularly at the margins between ice streams and ice ridges. When ice reaches the coast, it either calves or continues to flow outward onto the water. The result is a large, floating ice shelf affixed to the continent. These ice shelves restrain the flow of ice into the ocean for as long as they are present. The West Antarctic Rift System (WARS) is one of

11218-429: The future. 2023 research had also shown that much of the glacier may survive 500 years into the future. Consequently, the entire WAIS would most likely take around 2,000 years to disintegrate entirely once it crosses its tipping point. Under the highest warming scenario RCP8.5 , this may be shortened to around 500 years, while the longest potential timescale for its disappearance is around 13,000 years. In 1978, it

11360-508: The glacier in February 2020. Pine Island Glacier's ice velocity has accelerated to over 33 feet per day. The ice stream is extremely remote, with the nearest continually occupied research station at Rothera , nearly 1,300 km (810 mi) away. The area is not claimed by any nations and the Antarctic Treaty prohibits any new claims while it is in force. The Antarctic ice sheet is

11502-412: The glacier, and once warm water can flow to the glacier unimpeded. Most ice losses occur at the Amundsen Sea Embayment and its three most vulnerable glaciers – Thwaites Glacier , Pine Island Glacier and Smith Glacier . Around 2005, they were thought to lose 60% more mass than what they have gained, and to contribute about 0.24 millimetres (0.0094 inches) per year to global sea level rise . Of

11644-451: The helicopters were not able to arrive by the NSF 'drop dead' date and the field season was cancelled. Limited science was still accomplished by the team thanks to a series of flights by KBA back onto the glacier; conditions had changed drastically since the last Twin Otter flights. The British Antarctic Survey deployed a small team of four during the 2011–12 summer field season to carry out

11786-522: The human impact. In July 2018, the International Union of Geological Sciences split the Holocene Epoch into three distinct ages based on the climate, Greenlandian (11,700 years ago to 8,200 years ago), Northgrippian (8,200 years ago to 4,200 years ago) and Meghalayan (4,200 years ago to the present), as proposed by International Commission on Stratigraphy . The oldest age, the Greenlandian,

11928-485: The ice sheet is so reflective, its loss would also have some effect on the ice-albedo feedback . A total loss would increase the global temperatures by 0.05 °C (0.090 °F), while the local temperatures would increase by around 1 °C (1.8 °F). Estimates of isostatic rebound after the loss of East Antarctica's subglacial basins suggest sea level rise contributions of between 8 cm (3.1 in) and 57 cm (1 ft 10 in). While it would take

12070-435: The ice sheet may pool into fractures and force them open, further damaging its integrity. Climate change alters winds above Antarctica, which can also affect surface current circulation, but the importance of this process has been disputed. Most importantly, the WAIS has a complex topography which magnifies its vulnerability. The grounding lines of its glaciers are below the sea level by several hundred metres or more, and

12212-612: The ice sheet. Further, oceanographic research explains how this irreversible melting would occur, by indicating that water temperatures in the entire Amundsen Sea are already committed to increase at triple the historical rate throughout the 21st century. However, while the West Antarctic Ice Sheet is likely to be committed to disappearance, it would take a long time. Its most vulnerable parts like Thwaites Glacier, which holds about 65 cm ( 25 + 1 ⁄ 2  in) of sea level rise equivalent, are believed to require "centuries" to collapse entirely. Thwaites' ice loss over

12354-402: The ice sheet. This ash was then buried under the snow and ice. The date of the eruption was estimated from the depth of burial of the ash. This method uses dates calculated from nearby ice cores . The presence of the volcano raises the possibility that volcanic activity could have contributed, or may contribute in the future, to increases in the flow of the glacier. In 2018 it was found that there

12496-579: The icy surface, making it the largest volcanic region on Earth. Fast-moving ice streams in the Siple Coast adjacent to the east edge of the Ross Ice Shelf are influenced by the lubrication provided by water-saturated till within fault-bounded grabens within the rift, which would act to accelerate ice-sheet disintegration at more intense levels of climate change. Like the other ice sheets, West Antarctic Ice Sheet had undergone significant changes in size during its history. Until around 400,000 years ago,

12638-425: The large, relatively stable, East Antarctic Ice Sheet and a smaller, less stable, West Antarctic Ice Sheet. The West Antarctic Ice Sheet is drained into the sea by several large ice streams, most of which flow into either Ross Ice Shelf , or Filchner-Ronne Ice Shelf . Pine Island and Thwaites Glaciers are two major West Antarctic ice streams which do not flow into a large ice shelf. They are part of an area called

12780-475: The largest mass of ice on earth, containing a volume of water equivalent to 57 m (187 ft) of global sea level. The ice sheet forms from snow which falls onto the continent and compacts under its own weight. The ice then moves under its own weight toward the edges of the continent. Most of this transport to the sea is by ice streams (faster moving channels of ice surrounded by slower moving ice walls ) and outlet glaciers . The Antarctic ice sheet consists of

12922-485: The latter genetic connections between currently separate subpopulations; both are impossible unless there was no ice outside of mountain caps in the West Antarctica around 125,000 years ago, during Marine Isotope Stage 5 . Since that period was only 0.5 °C (0.90 °F) to 1.5 °C (2.7 °F) warmer than the preindustrial period, the current levels of warming are also likely to be sufficient to eventually melt

13064-532: The limited information about MISI for a long time. In 2001, IPCC Third Assessment Report mentioned the possibility of such disintegration and provided a vague long-term estimate for what it then described as a hypothetical. In 2007, the IPCC Fourth Assessment Report omitted any mention of it due to increased uncertainty, and a number of scientists criticized that decision as excessively conservative. The 2013/2014 IPCC Fifth Assessment Report (AR5)

13206-435: The loss of Thwaites Glacier and Pine Island Glacier , some have instead proposed interventions to preserve them. In theory, adding thousands of gigatonnes of artificially created snow could stabilize them, but it would be extraordinarily difficult and may not account for the ongoing acceleration of ocean warming in the area. Others suggest that building obstacles to warm water flows beneath glaciers would be able to delay

13348-436: The low-emission RCP2.6 scenario was followed, only contributing a median of 16 cm (5 in). On the other hand, even the minimum estimate of West Antarctica melting under the high-emission scenario would be no less than 60 cm (0 ft), while the median would amount to 1.46 m (5 ft) and the maximum to 2.89 m (10 ft). Ice loss from the West Antarctic Ice Sheet (along with much smaller losses from

13490-451: The major active continental rifts on Earth. It is believed to have a major influence on ice flows in West Antarctica. In western Marie Byrd Land , active glaciers flow through fault-bounded valleys ( grabens ) of the WARS. Sub-ice volcanism has been detected and is known to influence ice flows. In 2017, geologists from Edinburgh University discovered 91 volcanoes located two kilometres below

13632-522: The mid-19th century. The LIA was the coldest interval of time of the past two millennia. Following the Industrial Revolution, warm decadal intervals became more common relative to before as a consequence of anthropogenic greenhouse gases, resulting in progressive global warming. In the late 20th century, anthropogenic forcing superseded variations in solar activity as the dominant driver of climate change, though solar activity has continued to play

13774-698: The mid-Holocene (8.2 - 4.2 k cal BP). Climate change on seasonality and available moisture also allowed for favorable agricultural conditions which promoted human development for Maya and Tiwanaku regions. In the Korean Peninsula , climatic changes fostered a population boom during the Middle Chulmun period from 5,500 to 5,000 BP, but contributed to a subsequent bust during the Late and Final Chulmun periods, from 5,000 to 4,000 BP and from 4,000 to 3,500 BP respectively. The Holocene extinction , otherwise referred to as

13916-570: The most powerful factor affecting surface processes. The sedimentary record from Aitoliko Lagoon indicates that wet winters locally predominated from 210 to 160 BP, followed by dry winter dominance from 160 to 20 BP. North Africa, dominated by the Sahara Desert in the present, was instead a savanna dotted with large lakes during the Early and Middle Holocene, regionally known as the African Humid Period (AHP). The northward migration of

14058-424: The next 30 years would likely be around 5 mm of sea level rise between 2018 and 2050, and between 14 and 42 mm over 100 years. Other research also suggests that Thwaites Glacier would add less than 0.25 mm of global sea level rise per year over the 21st century, although it would increase to over 1 mm per year during its "rapid collapse" phase, which it expected to occur between 200 and 900 years in

14200-576: The ocean cavity below. It was decided that the small crevasse free area was too hard for further landings and so further fieldwork had to be postponed. Therefore, two Global Positioning System (GPS) units and a weather station were positioned as near as possible to PIG. In the 2011–2012 field season, after five weeks of delays, the camp staff was finally able to establish the Main Camp just before New Year. The following week, Bindschadler and his team were able to arrive. Due to additional weather delays,

14342-416: The ocean. Their first proposal focused on Thwaites, and estimated that even reinforcing it physically at weakest points, without building larger structures to block water flows, would be among "the largest civil engineering projects that humanity has ever attempted", yet only 30% likely to work. In 2023, it was proposed that an installation of underwater curtains , made of a flexible material and anchored to

14484-518: The oldest inhabited places still existing on Earth were first settled, such as Tell es-Sultan (Jericho) in the Middle East . There is also evolving archeological evidence of proto-religion at locations such as Göbekli Tepe , as long ago as the 9th millennium BC . The preceding period of the Late Pleistocene had already brought advancements such as the bow and arrow , creating more efficient forms of hunting and replacing spear throwers . In

14626-539: The origin of cycles identified in the North Atlantic region. Climate cyclicity through the Holocene ( Bond events ) has been observed in or near marine settings and is strongly controlled by glacial input to the North Atlantic. Periodicities of ≈2500, ≈1500, and ≈1000 years are generally observed in the North Atlantic. At the same time spectral analyses of the continental record, which is remote from oceanic influence, reveal persistent periodicities of 1,000 and 500 years that may correspond to solar activity variations during

14768-537: The original proposal suggested attempting this intervention on smaller sites, like the Jakobshavn Glacier in Greenland , as a test. They also acknowledged that this intervention cannot prevent sea level rise from the increased ocean heat content , and would be ineffective in the long run without greenhouse gas emission reductions. In 2023, it was proposed that an installation of underwater curtains , made of

14910-544: The past 1.4 million years, and so their melting would require a larger level of warming. 2021 research indicates that isostatic rebound , after the loss of the main portion of the ice sheet, would ultimately add another 1.02 m (3 ft 4 in) to global sea levels. While this effect would start to increase sea levels before 2100, it would take 1000 years for it to cause 83 cm (2 ft 9 in) of sea level rise – at which point, West Antarctica would be 610 m (2,001 ft 4 in) higher than now. Because

15052-553: The period exceeds any likely tectonic uplift of non-glacial origin. Post-glacial rebound in the Scandinavia region resulted in a shrinking Baltic Sea . The region continues to rise, still causing weak earthquakes across Northern Europe. An equivalent event in North America was the rebound of Hudson Bay , as it shrank from its larger, immediate post-glacial Tyrrell Sea phase, to its present boundaries. The climate throughout

15194-527: The rapid proliferation, growth, and impacts of the human species worldwide, including all of its written history , technological revolutions , development of major civilizations , and overall significant transition towards urban living in the present. The human impact on modern-era Earth and its ecosystems may be considered of global significance for the future evolution of living species, including approximately synchronous lithospheric evidence, or more recently hydrospheric and atmospheric evidence of

15336-500: The region were dominantly influenced by solar forcing, with many individual cold snaps linked to solar minima such as the Oort, Wolf , Spörer , and Maunder Minima . A notable cooling event in southeastern China occurred 3,200 BP. Strengthening of the winter monsoon occurred around 5,500, 4,000, and 2,500 BP. Monsoonal regions of China became more arid in the Late Holocene. In the Sea of Japan,

15478-597: The region. Sand dune evolution in the Bayanbulak Basin shows that the region was very dry from the Holocene's beginning until around 6,500 BP, when a wet interval began. In the Tibetan Plateau, the moisture optimum spanned from around 7,500 to 5,500 BP. The Tarim Basin records the onset of significant aridification around 3,000-2,000 BP. After 11,800 BP, and especially between 10,800 and 9,200 BP, Ladakh experienced tremendous moisture increase most likely related to

15620-567: The residual glacial ice remaining in the Northern Hemisphere until the later date. The first major phase of Holocene climate was the Preboreal . At the start of the Preboreal occurred the Preboreal Oscillation (PBO). The Holocene Climatic Optimum (HCO) was a period of warming throughout the globe but was not globally synchronous and uniform. Following the HCO, the global climate entered

15762-621: The scientists on this traverse was Charles R. Bentley , who said "we didn't know we were crossing a glacier at the time." PIG is around 50 km (31 mi) wide at the point visited and at ground level cannot be visually distinguished from the surrounding ice. This expedition was called the "Ellsworth Highland Traverse". In the 2004–2005 field season a team of nine, using a British Antarctic Survey (BAS) Twin Otter aircraft equipped with ice-penetrating radar, completed an aerial survey of PIG and its adjacent ice sheet. The team of seven British and two Americans flew 30 km grid patterns over

15904-555: The sea level. Further, it had been shown in 2021 that the Thwaites Ice Shelf , which restrains the eastern portion of the Thwaites Glacier, could start to collapse within five years. The glacier would start to see major losses "within decades" after the ice shelf's failure, and its annual contribution to sea level rise would increase from the current 4% to 5%, although it would still take centuries to disappear entirely. As

16046-400: The sea. For example, marine fossils from the Holocene epoch have been found in locations such as Vermont and Michigan . Other than higher-latitude temporary marine incursions associated with glacial depression, Holocene fossils are found primarily in lakebed, floodplain , and cave deposits. Holocene marine deposits along low-latitude coastlines are rare because the rise in sea levels during

16188-444: The second field season, they spent three months there from November 2007 to February 2008. Work on the glacier included radar measurements and seismic surveys . In January 2008 Bob Bindschadler of NASA landed on the floating ice shelf of PIG, the first ever landing on this ice shelf, for a reconnaissance mission to investigate the feasibility of drilling through around 500 m (1,600 ft) of ice, to lower instruments into

16330-508: The so-called marine ice cliff instability hypothesis (MICI). It suggests that when a glacier's ice shelf melts, it would not just retreat faster, but rapidly collapse under its own weight if the height of its cliffs was greater than 100 m (330 ft). This particular process has never been observed and was even ruled out by some of the more detailed modelling, but it still adds to the uncertainty in sea level projections. The Intergovernmental Panel on Climate Change has wrestled with

16472-572: The state of WAIS was largely governed by the effects of solar variation on heat content of the Southern Ocean , and it waxed and waned in accordance with a 41,000-year-long cycle. Around 80,000 years ago, its size was comparable to now, but then it grew substantially larger, until its extent reached the margins of Antarctica's continental shelves during the Last Glacial Maximum ~30,000 years ago. It then shrunk to around its preindustrial state some 3,000 years ago. It also at times shrunk to

16614-721: The strengthening of the Indian Summer Monsoon (ISM). From 9,200 to 6,900 BP, relative aridity persisted in Ladakh. A second major humid phase occurred in Ladakh from 6,900 to 4,800 BP, after which the region was again arid. From 900 to 1,200 AD, during the MWP, the ISM was again strong as evidenced by low δ O values from the Ganga Plain. The sediments of Lonar Lake in Maharashtra record dry conditions around 11,400 BP that transitioned into

16756-413: The surface of the glacier is above sea level, the base lies below sea level and slopes downward inland, this suggests that there is no geological barrier to stop a retreat of the ice once it has started. The Pine Island glacier began to retreat in the 1940s. Prior to this retreat, the grounding line of Pine Island Glacier was located on a prominent seabed ridge. This ridge now acts as a barrier, restricting

16898-514: The surface would be gaining mass . This is possible because effects of climate change on the water cycle would add more snow to the surface of the ice sheet, which is soon compressed into more ice, and this could offset some of the losses from the coasts. Afterwards, several major publications in the late 2010s (including the Fourth United States National Climate Assessment in 2017) suggested that if instability

17040-453: The term 'recent' as an incorrect way of referring to the Holocene, preferring the term 'modern' instead to describe current processes. It also observes that the term 'Flandrian' may be used as a synonym for Holocene, although it is becoming outdated. The International Commission on Stratigraphy, however, considers the Holocene to be an epoch following the Pleistocene and specifically following

17182-465: The three, Thwaites Glacier is the best-known, to the point of being nicknamed the "Doomsday Glacier" by some in the press, although many scientists consider it alarmist and inaccurate. The reason for concern about Thwaites is because it had been experiencing substantial mass loss since at least the early 1990s, while its local seabed topography provides no obstacles to rapid retreat, with its most vulnerable parts located 1.5 mi (2.4 km) below

17324-474: The warming of the region since 1957 was estimated as exceeding 0.1 °C (0.18 °F) per decade. This warming is strongest in the Antarctic Peninsula . In 2012, research found that the West Antarctic ice sheet had warmed by 2.4 °C (4.3 °F) since 1958 – around 0.46 °C (0.83 °F) per decade, which was almost double the 2009 estimate. In 2022, Central WAIS warming between 1959 and 2000

17466-462: The water cycle and increase snowfall accumulation over the ice sheet at about the same rate as it would increase ice loss), it can conceivably contribute up to 41 cm (16 in) by 2100 under the low-emission scenario and up to 57 cm (22 in) under the highest-emission one, due to the aforementioned uncertainties. It had also been suggested that by the year 2300, Antarctica's role in sea level rise would only slightly increase from 2100 if

17608-563: The world. This ' Neolithic Revolution ', likely influenced by Holocene climatic changes, included an increase in sedentism and population, eventually resulting in the world's first large-scale state societies in Mesopotamia and Egypt . During the Middle Holocene, the Intertropical Convergence Zone , which governs the incursion of monsoon precipitation through the Arabian Peninsula, shifted southwards, resulting in increased aridity. In

17750-453: Was again unable to describe the risk, but it stated with medium confidence that MISI could add up to several tens of centimeters to 21st century sea level rise. The report projected that in the absence of instability, WAIS would cause around 6 cm (2.4 in) of sea level rise under the low-emission scenario RCP2.6 . High emission scenario RCP8.5 would have slightly lower retreat of WAIS at 4 cm (1.6 in), due to calculations that

17892-417: Was around 2.1 metres above present and occurred about 5,800 to 5,000 BP. Sea levels at Rocas Atoll were likewise higher than present for much of the Late Holocene. The Northwest Australian Summer Monsoon was in a strong phase from 8,500 to 6,400 BP, from 5,000 to 4,000 BP (possibly until 3,000 BP), and from 1,300 to 900 BP, with weak phases in between and the current weak phase beginning around 900 BP after

18034-524: Was being put into the sea by PIG than was being replaced by snowfall. Measurements along the centre of the ice stream by GPS demonstrated that this acceleration is still high nearly 200 km (120 mi) inland, at around 4 percent over 2007. It has been suggested that this recent acceleration could have been triggered by warm ocean waters at the end of PIG, where it has a floating section (ice shelf) approximately 50 km (31 mi) long. It has also been shown that PIG underwent rapid thinning during

18176-506: Was believed that the loss of the ice sheet would cause around 5 m (16 ft 5 in) of sea level rise, Later improvements in modelling had shown that the collapse of the ice grounded below the sea level would cause ~3.3 m (10 ft 10 in) of sea level rise, The additional melting of all the ice caps in West Antarctica that are not in contact with water would increase it to 4.3 m (14 ft 1 in). However, those ice caps have been continuously present for at least

18318-409: Was characterized by a warming following the preceding ice age. The Northgrippian Age is known for vast cooling due to a disruption in ocean circulations that was caused by the melting of glaciers. The most recent age of the Holocene is the present Meghalayan, which began with extreme drought that lasted around 200 years. The word Holocene was formed from two Ancient Greek words. Hólos ( ὅλος )

18460-513: Was coeval with a major humidification before being terminated by a major drought and warming at the end of that interval. During the Early Holocene, relative sea level rose in the Bahia region, causing a landward expansion of mangroves. During the Late Holocene, the mangroves declined as sea level dropped and freshwater supply increased. In the Santa Catarina region, the maximum sea level highstand

18602-592: Was confined to the area immediately south of the STF, and is correlated with reduced westerly winds near New Zealand. Since 7,100 BP, New Zealand experienced 53 cyclones similar in magnitude to Cyclone Bola . Evidence from the Galápagos Islands shows that the El Niño–Southern Oscillation (ENSO) was significantly weaker during the Middle Holocene, but that the strength of ENSO became moderate to high over

18744-414: Was defined for Northern Europe , but the climate changes were claimed to occur more widely. The periods of the scheme include a few of the final pre-Holocene oscillations of the last glacial period and then classify climates of more recent prehistory . Paleontologists have not defined any faunal stages for the Holocene. If subdivision is necessary, periods of human technological development, such as

18886-419: Was discovered by later research. Some engineering interventions have been proposed for Thwaites Glacier and the nearby Pine Island Glacier to physically stabilize its ice or to preserve it. These interventions would block the flow of warm ocean water, which currently renders the collapse of these two glaciers practically inevitable even without further warming. A proposal from 2018 included building sills at

19028-480: Was estimated at 0.31 °C (0.56 °F) per decade, with this change conclusively attributed to increases in greenhouse gas concentrations. The continually increasing ocean heat content forces the melting and retreat of ice sheet's coastal glaciers. Normally, glacier mass balance offsets coastal losses through gains from snowfall at the surface, but between 1996 and 2006, Antarctic ice mass loss had already increased by 75%. Between 2005 and 2010, WAIS melting

19170-531: Was eventually considered a more likely threshold. By 2023, multiple lines of evidence suggested that the real tipping point was around 1 °C (1.8 °F), which has already been reached in the early 21st century. This includes paleoclimate evidence from the Eemian period, such as analysis of silt isotopes in the Bellingshausen Sea , or the genomic history of Antarctica's Turquet's octopus . The former shows specific patterns in silt deposition and

19312-460: Was experienced during the MWP. A warming of +1 degree Celsius occurs 5–40 times more frequently in modern years than during the MWP. The major forcing during the MWP was due to greater solar activity, which led to heterogeneity compared to the greenhouse gas forcing of modern years that leads to more homogeneous warming. This was followed by the Little Ice Age (LIA) from the 13th or 14th century to

19454-550: Was never a formally defined geological unit. The Subcommission on Quaternary Stratigraphy (SQS) of the International Commission on Stratigraphy (ICS) had a working group to determine whether it should be. In May 2019, members of the working group voted in favour of recognizing the Anthropocene as formal chrono-stratigraphic unit, with stratigraphic signals around the mid-twentieth century CE as its base. The exact criteria

19596-538: Was still to be determined, after which the recommendation also had to be approved by the working group's parent bodies (ultimately the International Union of Geological Sciences ). In March 2024, after 15 years of deliberation, the Anthropocene Epoch proposal of the working group was voted down by a wide margin by the SQS, owing largely to its shallow sedimentary record and extremely recent proposed start date. The ICS and

19738-464: Was the USS/USCGC Glacier in 1985. This ship was an icebreaker operated by the U.S. Coast Guard. The mission, known as Deep Freeze , had scientists on board who took sediment samples from the ocean floor. During the summer field season, over two months from January to February 2009, researchers aboard the U.S. Antarctic Program research vessel Nathaniel B. Palmer reached the ice shelf. This

19880-575: Was the second time that the Palmer had successfully made it up to the glacier, the first time being in 1994. In collaboration with the British, the scientists used a robotic submarine to explore the glacier-carved channels on the continental shelf as well as the cavity below the ice shelf and glacier. The submarine, known as Autosub 3 , was developed and built at the National Oceanography Centre in

20022-552: Was thought to have added 0.28 millimetres (0.011 inches) to global sea levels every year. Around 2012, the total mass loss from the West Antarctic Ice Sheet was estimated at 118 ± 9 gigatonnes per year . Subsequent satellite observations revealed that the West Antarctic ice loss increased from 53 ± 29 gigatonnes per year in 1992 to 159 ± 26 gigatonnes per year in 2017, resulting in 7.6 ± 3.9 mm ( 19 ⁄ 64  ±  5 ⁄ 32  in) of Antarctica sea level rise. By 2023, ~150 gigatonnes per year became

20164-491: Was triggered, then the overall sea level rise (combining the melting of West Antarctica with that of the Greenland ice sheet and mountain glaciers , as well as the thermal expansion of seawater) from the high-emission climate change scenario could double, potentially exceeding 2 m (5 ft) by 2100 in the worst case. A 2016 study led by Jim Hansen presented a hypothesis of vulnerable ice sheet collapse leading to near-term exponential sea level rise acceleration, with

#954045