West Antarctic ice sheet collapse

Main contributors: Johanna Yletyinen

Other contributors: Garry Peterson

Last update: 2013-09-09

Summary

Indication exists for a possible regime shift of collapsed West Antarctic Ice Sheet (WAIS) due to the warming climate. As the atmosphere and ocean warm as an effect of the global warming, ice sheets are predicted to shrink in size, resulting in raised sea level. The WAIS is a marine ice sheet: it is surrounded by floating ice shelves and the main part of the sheet is below sea-level (Oppenheimer 1998). It is considered to be capable of past and future collapses bringing about several meters sea level rise (Mercer 1978; Oppenheimer & Alley 2004). The two WAIS regimes consist of the intact ice sheet and disintegrated WAIS. The global warming-induced future WAIS collapse could cause a sea level rise of approximately 3-5 meters with significant societal and economic impacts. Marine fauna that is adapted to sea ice dynamics would be directly impacted through habitat changes, food web interaction alterations and shifts in marine isotherms (Rogers et al. 2012; Clarke et al. 2007). Many uncertainties remain about the mechanisms of the WAIS system, drivers of the observed change and future scenarios. It is suggested that the warming of the oceanic deep water currently causes significant basal melting and thinning of the ice sheet. A basin-scale ice model study, published in 2014, provides strong evidence that the collapse has already begun (Joughin, Smith & Medley, 2014.)

Categorical attributes

Impacts

Ecosystem type:’

  • Polar

Key ecosystem processes:

  • Water cycling

Biodiversity:

  • Biodiversity

Provisioning services:

  • Fisheries

Regulating services:

  • Climate regulation

Cultural services:

  • Recreation
  • Knowledge and educational values

Human well-being:

  • Livelihoods and economic activity
  • Security of housing & infrastructure
  • Social conflict

Links to other regime shifts:

  • Greenland ice sheet collapse

Drivers

Key drivers:

  • Global climate change

Land use:

  • Conservation
  • Tourism
  • Land use impacts are primarily off-site (e.g. dead zones)

Key attributes

Spatial scale:

  • Sub-continental (e.g. southern Africa
  • Amazon basin)

Time scale:

  • Centuries

Reversibility:

  • Irreversible (on 100 year time scale)

Evidence:

  • Models
  • Paleo-observation
  • Contemporary observations

Confidence: existence of the regime shift

  • Speculative – Regime shift has been proposed, but little evidence as yet

Confidence: mechanisms underlying the regime shift

  • Speculative – Mechanisms have been proposed, but little evidence as yet

Detail information

Alternative regimes

Intact WAIS (full glacial or modern interglacial)

Antarctica is divided into two large ice sheets by the Transantarctic Mountains. A large part of Antarctic ice mass consists of the WAIS, which lies on a marine sediment-draped bed many hundreds of meters below sea level (Joughin & Alley 2011; Bamber et al. 2009). Compared to the East Antarctic ice sheet, the WAIS has rapid ice flow and discharge (Anderson et al. 2002). Ice shelves, which form over the water and float permanently attached to the landmass, serve as buttresses for the inland ice streams of the ice sheets (permanent layer of ice covering land), and are vulnerable to environmental forcing. Ice volume is stable when the water entering and leaving the system are in balance; the net accumulation (mainly snow) balances losses (ice calving, basal melting at the ice sheet margins) (Ivins 2009). The stability of the marine ice sheet is created between local basal restraint of the inland ice and longitudinal stretching of the ice shelves (Joughin & Alley 2011; Ivins 2009), meaning that the marine-based bottom topography, geometry of the interior part and stability of the buttressing ice shelves (Joughin & Alley 2011) contribute to maintaining the regime of the intact WAIS. The Southern Ocean marine environment is in general rich in diversity, whereas the Antarctic terrestrial environment is low in diversity and missing many taxonomic groups (Rogers et al. 2012). In this regime humans have harvested large marine mammals, fish and krill, the latter of which is in direct competition with higher trophic level species (summer breeding colonies) (Rogers et al. 2012). At the present the WAIS appears to be thinning and the extent of sea ice is increasing.

Disintegrated WAIS (extreme interglacial)

Changed internal dynamics, such as complicated ice stream flow changes or natural climatic and oceanic forcing, create instability in the WAIS. Disintegration (collapse) of the WAIS means the nonlinear process, in which the ice sheet would flow at increasing rates into the ocean as its buttressing ice shelves diminish (O’Reilly & ACOS 2013). In the absence of the WAIS, the area would be covered by a broad open sea, punctuated by islands (Scherer 1991). The changes are occurring now and the collapse of the WAIS appears to already be underway, but large uncertainty remains on the timing (Joughin, Smith & Medley 2014, Joughin & Alley 2011). The absence of the WAIS would affect local ecosystems adapted to the presence of ice, and due to the sea level rise, all global coastal ecosystems and coastal human habitats. Marine fauna adapted to the sea ice dynamics would be directly impacted through habitat changes and shifts in marine isotherms, and the changes could cascade to the higher trophic levels, and alter food webs (Rogers et al. 2012; Clarke et al. 2007). The absence of WAIS would leave broad, deep seaways (Joughin & Alley 2011), increasing accessibility for fishing vessels and tourists.

Drivers and causes of the regime shift

Climatic and oceanic forcing appear to cause the WAIS retreats. Geologic evidence shows that the Antarctic ice sheet has shrunk in the past when global temperatures were warmer, for instance during the late Quaternary period (see e.g. Barnes & Hillenbrand 2010). There have been times when parts of the WAIS have been lost to the ocean, causing raised sea levels (Ivins 2009). According to the model by Pollard and DeConto (2009), a collapse from the modern conditions could occur when sub-ice ocean melting increase from 0.1 to 2 m yr-1 under shelf interiors, and from 5 to 10 m yr-1 near exposed shelf edges.

The mechanisms leading to the WAIS collapse are still unclear. It has been suggested that the WAIS collapse could start by the intrusion of ocean water (i.e. sea level rise) between the ice sheet and its ground. As the grounding line retreats, a strong positive feedback would be triggered when ocean water undercuts the ice sheet and causes further separation from the bedrock (Oppenheimer 1998). This feedback with sea level changes driving further retreat is contested by other studies (Alley et al. 2007; Gomez et al. 2010).

At present, main cause for the thinning of the WAIS ice mass is suggested to be the intrusion of relatively warm ocean water beneath the ice. Ice shelves are very sensitive to ocean temperature changes (Turner & Overland 2009) and several studies (see e.g. Price et al. 2008; Thoma et al. 2008, Joughin, Smith & Medley 2014) have shown that increased transport of warm subsurface water significantly contributes to the basal ice-shelf melt. The warm Circumpolar Deep Water (CDW) protrudes into the ice shelves through submarine troughs (Bintanja et al. 2013) and produces large melt rates at the regions where it is able to access the sub-ice-shelf cavities (Jacobs et al. 1992). Although the upper layers of Southern Ocean have cooled, the subsurface sea has in fact warmed (Robertson et al. 2002). The reasons for the warming of the Southern Ocean are not completely know. It is probably caused by multiple processes, such as increased greenhouse gases in the atmosphere, shifts in Southern Annular Mode (SAM, a high-latitude mode, also called Antarctic Oscillation) and changes in sea currents.

Other, less direct contributors to the regime shift found in literature are hydrofracturing of crevasses by surface melting water, changes in landscape (glacier behavior), wind forcing, ocean upwelling, tides and long period waves, changes in stratospheric ozone affecting atmospheric and ocean circulation, and intensification and southward migration of the Southern Ocean Westerlies due to the positive trend in the SAM (e.g. Thompson & Solomon 2002; Goosse et al. 2008; Turner et al. 2009; Joughin, Smith & Medley 2014).

Impacts on ecosystem services and human well-being

Humans mainly use the Antarctica for commercial fishing, conservation, research, and tourism. The Antarctic region also plays a remarkable role in the planetary functions. Shifting the regime to that of the fragmented WAIS would, in short, provide better access for humans to the currently more peripheral areas, and change habitats and food webs of the local marine and terrestrial organisms. The extent of the sea ice affects the regulating ecosystem services of the Antarctica, such as global climate and ocean circulation through ice and snow albedo, CO2 uptake and icescape changes. The Southern Ocean has a rich biodiversity, and fisheries include krill and toothfish. The biogeochemical cycles of the Southern Ocean and the sea ice impact the structure and dynamics of the marine ecosystems (e.g. life cycles of organisms), especially the trophic levels that are adapted to the presence, seasonality and properties of ice (Massom & Stammerjohn 2010; Arrigo 2002; Brierley & Thomas 2002; Thomas et al. 2010; Eicken et al. 1995; Moline et al. 2008; Tynan 2010; Clarke et al. 2007; Rogers et al. 2012). The icescape characteristics, seasonality and dynamics of the sea ice extent affect the magnitude of the changes (Massom & Stammerjohn 2010) but at present the uncertainty of predictions is high.

Cultural ecosystem services in the second regime include possibly increased tourism, increased regional accessibility and societal losses caused by the sea level rise. Sea level rise impacts for coastal areas are submergence or increased flooding, increased erosion, ecosystem changes, increased salinization and forced displacement of coastal population and economy (Nicholls et al. 2011). The economic consequences depend on the time-scale: playing out over a century, the WAIS collapse would damage many coastal communities, whereas occurring over several centruries, the additional time would give possibilities to develop an appropriate risk-mitigation strategy (Dowdeswell et al. 2008; Mercer 1978; Joughin & Alley 2011).

The absence of the WAIS would leave broad, deep seaways (Joughin & Alley 2011). Increased vessel access to more southern locations may have implications on the safety of ocean navigation (Anon 2009). Tourism, the largest commercial activity in the Antarctic, is predicted to increase due to the extended season with reduced sea ice thickness (Anon 2009). The impact of the changes in the sea ice on the biomass and distribution of marine species is a very important issue for the regional management and conservation. Fisheries management and accessibility would change due to the altered sea ice extent (Anon 2009). The increased human presence might be a threat to ecosystems, for instance winter ice has usually provided a relief from the fishing pressure.

Management options

Options for preventing regime shift

Two new studies in 2014 state that since the WAIS has reached the early stage collapse phase, the shift is unstoppable (Joughin, Smith & Medley 2014, NASA in press). Joughin, Smith & Medley argue that it is difficult to foresee stabilization of the system unles CDW recedes sufficienty to reduce present level  of melting.

Regime shift Analysis

Feedback mechanisms

Intact WAIS

Ice albedo feedback (global, well-established). Ice albedo is a strong, positive feedback. The ice cover is more reflective than the ocean or continental surface, resulting in the increase of ice producing further cooling. In contrast, reduced ice coverage, caused by higher surface temperatures, increases insolation.

Ice elevation feedback (local, well-established). The thickness of the ice sheet creates a positive feedback with the altitude-based temperature change. As the ice sheet begins to grow, the accumulation rate can be increased as the elevation of the ice field increases and the atmospheric temperature therefore decreases. This feedback, however, takes place on a long time scale as thousands of years may be required for a kilometer growth in the ice sheet.

Disintegrated WAIS (transition phase)

Sea level rise (regional, contested). A strong positive feedback, which is at present contested, is suggested to form by the higher sea level ocean water, which would further undercut the ice sheet and trigger its separation from the bedrock as the grounding line retreats ( Michael Oppenheimer 1998).

Sea-ice / ocean feedback (regional, speculative). A suggested by Bintanja et al. (2013), negative feedback for increase in the sea ice states that the warm CDW protruding onto continental shelves causes basal melt, in particular in the ice shelves which are very sensitive to ocean temperatures. The melt water has lower density than seawater, and thus accumulates in the top layer of the ocean. Upper layer gets fresher and cold halocline stabilizes the ocean, resulting in less mixing between the cold and warm water. The atmosphere can cool and freeze the fresh and cold water more easily, which results in increased sea ice. The negative feedback is therefore created by the cool and fresh surface water from the ice-shelf melt to shield the surface water from the warmer, deeper waters that cause melting of the ice shelves. In this mechanism the sea-ice induced, upper ocean density changes increase the ocean heat flux available to melt sea ice (Zhang 2007).

Ice albedo feedback (global, well-established). Ice albedo is a strong, positive feedback. The ice cover is more reflective than the ocean or continental surface, resulting in the increase of ice producing further cooling. In contrast, reduced ice coverage, caused by higher surface temperatures, increases insolation. Ice elevation feedback (local, well-established). The thickness of the ice sheet creates a positive feedback with the altitude-based temperature change. As the ice sheet begins to grow, the accumulation rate can be increased as the elevation of the ice field increases and the atmospheric temperature therefore decreases. This feedback, however, takes place on a long time scale as thousands of years may be required for a kilometer growth in the ice sheet.

Drivers

The main external direct drivers that contribute to the shift include:

Oceanic warming: the intrusion of warm ocean water beneath the ice sheet (regional, proposed). The highest melting rates occur where the ice shelves interact with the warmest water (ocean thermal forcing) (Pritchard et al. 2012). Ice shelves are very sensitive to ocean temperature changes (Turner & Overland 2009) and several studies (see e.g. Price et al. 2008; Thoma et al. 2008) have shown that warm subsurface water significantly contributes to the basal ice-shelf melt. Although the upper layers of the Southern Ocean have cooled, the subsurface Southern Ocean has in fact warmed faster than any other part of the world oceans (Robertson et al. 2002). Warming of the CDW causes basal ice-shelf melt, its effectivity depending on how well it can reach the ice shelves (Joughin & Alley 2011). The warm CDW protrudes into the ice shelves through submarine troughs (Bintanja et al. 2013) and produces large melt rates at the regions where it is able to access the sub-ice-shelf cavities (Jacobs et al. 1992). The reasons for the warming of the Southern Ocean are not completely know, but multiple processes, such as increased greenhouse gases in the atmosphere, shift in SAM and changes in currents are suggested.

Sea level rise (global, contested). It has been suggested that the sea level rise would create a positive feedback for increased melting: the ice shelf collapse could start by the intrusion of ocean water between the ice sheet and its ground or by surface melting, and as the grounding line retreats, a strong positive feedback would be triggered when ocean water undercuts the ice sheet and causes further separation from the bedrock (Oppenheimer 1998). The positive feedback with sea level changes driving further retreat is also stated to be unlikely by other studies, doubting that the sea level changes, either from non-WAIS sources or the WAIS, will drive future WAIS loss (Alley et al. 2007; Gomez et al. 2010).

Atmospheric warming (regional, speculative/well-established). The estimated atmospheric temperature increase required for the WAIS to reach the summer time melting point would be ca 5-8°C of local surface atmospheric temperatures and less for ocean warming (Oppenheimer & Alley 2004). In addition, atmospheric warming (well-established) affects oceanic temperatures contributing to the ocean thermal forcing (Pritchard et al. 2012). It has also been suggested that because higher surface temperatures (global warming) might reduce the sea ice formation, it might actually lessen basal melt rates due to reduction in dense high-salinity waters produced by the sea ice formation (Nicholls 1997).

The main external indirect drivers that contribute to the shift include:

Wind forcing (regional, well-established) affects oceanic temperatures contributing to the ocean thermal forcing (Pritchard et al. 2012).

Ocean upwelling (regional, well-established) affects oceanic temperatures contributing to the ocean thermal forcing (Pritchard et al. 2012).

Tides and long period waves (regional, speculative). Tides and long-period waves cause mixing of shallow waters beneath the ice shelf, contributing to the sub-ice shelf melting (Joughin & Alley 2011).

Changes in stratospheric ozone (regional, speculative). The Antarctic ozone hole can affect oceanic and atmospheric circulation. One explanation to the increased sea ice extent is that the change in stratospheric ozone causes altered circulation (Turner et al. 2009).

Natural climatic variability (global/regional, well-established). Natural variation in the SAM (Southern Annular Mode, high-latitude mode, also called the Antarctic Oscillation) affects temperature and winds (Thompson & Solomon 2002). Tropical atmospheric and oceanic conditions, such as El Nino, can also have an impact on high latitudes. The SAM can shift in response to anthropogenic forcing, for instance ozone hole development. It is suggested that the shift to a positive SAM has increased the production of the coastal sea ice.

Slow internal system changes that contribute to the regime shift include:

Ice stream flow changes (regional, speculative). In the past slowdowns and deviations from flow directions have taken place. Switching on and off ice streams may have some effect on grounding line retreat. For instance a small degree of widening of an ice stream may produce large changes in speed. A shear heating could yield a positive feedback (ice stream widens, increase in margin shear heating, further widening and speedup) or a stabilizing feedback in some locations (ice-stream thinning steepens basal temperature, thus conducts more heat away from the bed than is supplied through the geothermal heat flux and friction from sliding, causing basal freezing to exceed the supply of meltwater from other areas). The resulting withdrawal of water from basal till can alter till porosity, and that way change the sensitivity of till to water content. (Joughin & Richard B. Alley 2011 and references therein)

Thermally driven cycling of ice streams (regional, speculative). The sensitivity of till to water content may produce a thermal cycling of ice streams, in which thinning causes basal freezing that stops fast flow. The stagnation results in thickening, which traps geothermal heat, increase melting and reduce till strength to reactive the ice stream and repeat the cycle. (Joughin & Richard B. Alley 2011 and references therein)

Surface melting and ponded water (regional, contested). Surface melting and ponded water may contribute to the ice shelf breakup through hydrofracturing of crevasses (Mercer 1978; Doake et al. 1997; Scambos et al. 2000). Yet it has been stated that the role of surface melt is insignificant at the present, as average summer surface temperatures over most of the WAIS are below freezing (Fyke et al. 2010). The annual mass gain from snowfall is discharged on the ocean (Jacobs et al. 1992).

Glaciers flowing into Amundsen Sea (local, speculative). The impact of the glaciers flowing to the Amundsen Sea on the behavior of ice shelf and glaciers themselves is still uncertain but possible (Thomas et al. 2004). They are suggested to affect the dynamics of the icescape since the glaciers have experienced ground line retreat, thinning and acceleration (Thomas et al. 2004).

Subsurface meltwater (regional, speculative). Subsurface melt of ice shelves may contribute to southern ocean surface cooling and meltwater-induced sea ice expansion (Bintanja et al. 2013). Melt water from the ice shelves has lower density and thus accumulates in the top ocean layer (Price et al. 2008). This upper layer water gets fresher and resulting cold halocline reduces the convective mixing, and the atmosphere cools the upper 100 m more easily. The relatively cold and fresh surface waters can then freeze even more easily. (Southern Ocean exhibits warming of the deeper layers and cooling of the upper layer) (Bintanja et al. 2013).)

Summary of Drivers # Driver (Name) Type (Direct, Indirect, Internal, Shock) Scale (local, regional, global) Uncertainty (speculative, proposed, well-established) 1 Increased ocean temperature (warming of CDW) Direct Regional Proposed 2 Sea level rise Direct Regional/global Proposed 3 Surface melting, ponded water Internal Regional Speculative 4 Subsurface melt water (for sea-ice extent Internal Regional Speculative 5 Glaciers Internal Regional Speculative 6 Wind forcing Indirect Regional Well-established 7 Ocean upwelling Indirect Regional Well-established 8 Atmospheric warming Direct/Indirect Regional/global Well-established/speculative 9 Tides and long-period waves Indirect Regional Speculative 10 Changes in stratospheric ozone Indirect Regional Speculative 11 Natural climatic variability Indirect Regional/global Well-established 12 Ice-stream flow changes Internal Regional Speculative 13 Thermally driven cycling of ice streams Internal Regional Speculative Key thresholds

Threshold of global warming. Stating a tipping point to the ice sheet disintegrations is complex due to temperature changes, oceanic changes and the internal behavior of the ice sheet. A tipping point for the WAIS collapse is likely, but scientific community is still very uncertain about the exact temperature, and it has even been said that for such a complex system, the concept of tipping point may be virtually useless. Suggested threshold has ranged at 1-5°C of global warming (O’Reilly & ACOS 2013; see also M. Oppenheimer & R.B. Alley 2004).

Leverage points

Oceanic warming (regional/global, speculated). Increase in the CDW ocean temperature has been identified as the key mechanism for the melting and thinning of the ice shelves. Counteracting human-induced oceanic warming would require acting against the climate change. However, in two studies published in 2014 (Joughin Smith & Medley; NASA in press) state that the collapse is basically unstoppable and stabilization might be possible only if CDW receded.

Ecosystem service impacts

Humans have mainly used the Antarctica for conservation, research, tourism, and commercial fishing. Cultural ecosystem services include possibly increased tourism, increased accessibility and the societal losses caused by the sea level rise.

Sea level rise impacts for the coastal areas are submergence or increased flooding, increased erosion, ecosystem changes, increased salinization and forced displacement of coastal population and economy (Nicholls et al. 2011). The ice loss from the WAIS is at present equivalent to 0.28 to 0.56 mm yr-1 sea level rise with growing rate for the past two decades (Shepherd & Wingham 2007; Velicogna & Wahr 2006; Rignot et al. 2011). Although the time scale of several meters’ sea level rise from WAIS is highly uncertain, it could happen within a millennium, 300 years being the worst case scenario (R. Thomas et al. 2004). If or when the WAIS deglaciation happens, it will raise the sea level up to ca 3 meters creating huge impact on global infrastructure and society (Bamber et al. 2009). There is no agreement among the experts on the likelihood or rate of the rapid collapse (O’Reilly & ACOS 2013). The economic consequences depend on the time-scale: playing out over a century, the WAIS collapse would damage many coastal communities whereas occurring over a millennium would enable development of an appropriate risk-mitigation strategy (Dowdeswell et al. 2008; Mercer 1978; Joughin & Alley 2011).

The absence of the WAIS would leave broad, deep seaways (Joughin & Alley 2011) which would naturally deepen towards the ice-sheet interior. Increased vessel access to the more southern locations in the conditions where westerly winds would have become stronger (Marshall et al. 2006) may have implications on the safety of ocean navigation (Anon 2009). Tourism, the largest commercial activity in the Antarctic, is predicted to increase and extent in season with reduced sea ice thickness (Anon 2009).

The region of the WAIS turning to open ocean gives rise to changes associated with sea ice presence. Changes in the extent of the sea ice affect the regulating ecosystem services of the Antarctica, but at present the uncertainty of predictions is high. The extent of the ice has a role in the global climate system due to albedo effect and as an important driver of the global ocean circulation. The albedo effect depends on the extent of high albedo snow cover (e.g. Massom & Stammerjohn 2010). Sea ice also has an insulating effect on the ocean: heat that would be given up to the atmosphere remains trapped on the upper layer of the ocean (Anon 2009).

Seasonal brine rejection from sea ice formation and freshwater pulses from ice melt are key determinants for the upper ocean freshwater budgets and formation of cold, dense oxygen-rich Antarctic bottom water (AABW), which is a significant driver of global ocean circulation (Massom & Stammerjohn 2010). Salt added to the ocean in sea ice formation is denser than seawater and sinks toward the bottom, where it may accumulate in depressions and eventually mix. This is important for the formation of Antarctic Bottom Water and global ocean conveyor belt (redistribution of heat and maintenance of climate system) (Bindoff et al. 2000). The characteristics, seasonality and dynamics of sea ice affect the magnitude of these phenomena (Massom & Stammerjohn 2010) and the stability may be disturbed by increasing melting or disintegration of the WAIS.

Changes in the ocean circulation, sea ice coverage, biological activity and temperature will also affect the CO2 uptake of the Southern Ocean, but the mechanisms for future changes are not clear yet, because the data on the carbon uptake in the Southern Ocean is sparse and magnitude of CO2 uptake is still heavily disputed (Caldeira & Duffy 2000; Le Quéré et al. 2007; Sarmiento et al. 1998).

The Southern Ocean has a rich biodiversity and its provisioning ecosystem services are affected by altered habitats. In biogeochemical cycles of the Southern Ocean, the sea ice impacts the structure and dynamics of marine ecosystems (e.g. life cycles of organisms), especially the trophic levels that are adapted to its presence, seasonality and properties (Massom & Stammerjohn 2010; Arrigo 2002; Brierley & Thomas 2002; Thomas et al. 2010; Eicken et al. 1995; Moline et al. 2008; Tynan 2010), e.g. light availability, as substrate for algal biomass, habitat and barrier to air-breathing predators, as well as a barrier separating animals from their food source, for instance Adélie and Emperor penguins (see e.g. Anon 2009). The impact of the changes in sea ice on the biomass and extent of marine species is a very important issue for management and conservation. There already is evidence of species shifts, urging for precautionary approach in conservation while more research is undertaken (Anon 2009). Because of the extreme conditions, fishing in the Southern Ocean is expensive and difficult, and is done is smaller scale than in many other seas. Fisheries management and accessibility changes due to sea ice extent, for instance there might be an increased access for legal and illegal vessels to the more southern locations for longer periods (Anon 2009). This might be a threat to ecosystems since winter ice has usually provided a relief from the fishing pressure.

Summary of Ecosystem Service impacts on different User Groups References (if available) Provisioning Services Freshwater Food Crops Feed, Fuel and Fibre Crops Livestock Fisheries + Wild Food & Products Timber Woodfuel Hydropower Regulating Services Air Quality Regulation Climate Regulation - Water Purification Soil Erosion Regulation Pest & Disease Regulation Pollination Protection against Natural Hazards Cultural Services Recreation + Aesthetic Values - Cognitive & Educational +/- Spiritual & Inspirational Uncertainties and unresolved issues

Several uncertainties remain, largely due to sparse data and the complexity and large size of the system, on the Antarctic dynamics and processes. Large-scale modeling of the WAIS requires a model that is able to combine the flow regimes of grounded and floating ice, and allow simulations to circa 105 years or more (Pollard & DeConto 2009). The lack of quantitative information on the role of ongoing glacial readjustments, the size of WAIS and buttressing ice shelves in previous interglacials as contributing factors, and the role of surrounding ice shelves for the WAIS stability contribute to the uncertaintites as well as interactions between different parts of Antarctica. The mechanisms driving the regime shift, regional warming, response of ice streams and the rate of melting remain uncertain as well as changes in the CDW temperature, location or flow.

Citation

Acknowledge this review as:

Johanna Yletyinen, Garry Peterson. West Antarctic ice sheet collapse. In: Regime Shift Database, www.regimeshifts.org. Last revised: 2013-09-09

References

  • Abram NJ et al. 2013. Acceleration of snow melt in an Antarctic Peninsula ice core during the twentieth century. Nature Geoscience 6, 404u2013411.
  • Abram NJ, et al. 2013. Acceleration of snow melt in an Antarctic Peninsula ice core during the twentieth century. Nature Geoscience 6, 404–411.
  • Alley RB et al. 2007. Effect of sedimentation on ice-sheet grounding-line stability. Science, 315, 1838u201341.
  • Anderson JB et al. 2002. The Antarctic Ice Sheet during the Last Glacial Maximum and its subsequent retreat history: a review. Quaternary Science Reviews, 21, 49u201370
  • Arrigo KR. 2002. Ecological impact of a large Antarctic iceberg. Geophysical Research Letters 29, 8:1-8:4.
  • Bamber JL et al. 2009. Reassessment of the potential sea-level rise from a collapse of the West Antarctic Ice Sheet. Science, 324, 901u20133.
  • Barnes DKA & Hillenbrand CD. 2010. Faunal evidence for a late quaternary trans-Antarctic seaway. Global Change Biology 16, 3297u20133303
  • Bindoff N, Rintoul S & Massom R. 2000. Bottom water formation and polynyas in Adelie Land, Antarctica. Papers and Proceedings of the Royal Society of Tasmania 133, 51u201356.
  • Bintanja R et al. 2013. Important role for ocean warming and increased ice-shelf melt in Antarctic sea-ice expansion. Nature Geoscience 6, 376u2013379.
  • Brierley A & Thomas D. 2002. Ecology of Southern Ocean pack ice. Advances in Marine Biology 43, 171u2013276.
  • Bromwich DH et al. 2012. Central West Antarctica among the most rapidly warming regions on Earth. Nature Geoscience 6, 139u2013145.
  • Caldeira K & Duffy PB. 2000. The Role of the Southern Ocean in Uptake and Storage of Anthropogenic Carbon Dioxide. Science 287, 620u2013622.
  • Clark PU et al. 2002. Sea-Level Fingerprinting as a Direct Test for the Source of Global Meltwater Pulse IA. Science 295, 2438u20132441.
  • Clarke A et al. 2007. Climate change and the marine ecosystem of the western Antarctic Peninsula. Philosophical Transactions of the Royal Society B: Biological Sciences 362, 149u2013166.
  • Doake C et al. 1997. Breakup and conditions for stability of the northern Larsen Ice Shelf, Antarcticae. Nature 391, 778u2013780.
  • Dowdeswell JA et al. 2008. Submarine glacial landforms and rates of ice-stream collapse. Geology 36, 819.
  • Eicken H, Fischer H & Lemke P. 1995. Effects of the snow cover on Antarctic sea ice and potential modulation of its response to climate change. Annals of Glaciology 21, 69u2013376
  • Fairbanks RG, 1989. A 17,000-year glacio-eustatic sea level record: influence of glacial melting rates on the Younger Dryas event and deep-ocean circulation. Nature 342, 637u2013642.
  • Fyke JG et al. 2010. Surface Melting over Ice Shelves and Ice Sheets as Assessed from Modeled Surface Air Temperatures. Journal of Climate 23, 1929u20131936.
  • Gomez N et al. 2010. Sea level as a stabilizing factor for marine-ice-sheet grounding lines. Nature Geoscience 3, 850u2013853.
  • Goosse H et al. 2008. Consistent past half-century trends in the atmosphere, the sea ice and the ocean at high southern latitudes. Climate Dynamics 33, 999u20131016.
  • Hellmer HH et al. 2012. Twenty-first-century warming of a large Antarctic ice-shelf cavity by a redirected coastal current. Nature 485, 225u20138.
  • Ivins ER. 2009. Ice sheet stability and sea level. Science 324, 888u20139.
  • Jacobs S et al. 1992. Melting of ice shelves and the mass balance of Antarctica. Journal of Glaciology 38, 375u2013387.
  • Joughi I, Smith BE, Medley B. 2014. Marine ice sheet collapse underway for the Thwaites Glacier Basin, West Antarctica. Science. Published online 12 May 2014 [DOI:10.1126/science.1249055]
  • Joughin I & Alley RB. 2011. Stability of the West Antarctic ice sheet in a warming world. Nature Geoscience 4, 506u2013513.
  • King M et al. 2012. Lower satellite-gravimetry estimates of Antarctic sea-level contribution. Nature, 491, 586u20139.
  • Kriegler E et al. 2009. Imprecise probability assessment of tipping points in the climate system. Proceedings of the National Academy of Sciences of the United States of America 106, 5041u20135046.
  • Le Quu00e9ru00e9 C et al. 2007. Saturation of the southern ocean CO2 sink due to recent climate change. Science 316, 1735u20138.
  • Lenton TM et al. 2008. Tipping elements in the Earthu2019s climate system. Proceedings of the National Academy of Sciences of the United States of America, 105, 1786u201393.
  • Marshall GJ et al. 2006. The Impact of a Changing Southern Hemisphere Annular Mode on Antarctic Peninsula Summer Temperatures. Journal of Climate, 19, 5388u20135404.
  • Massom RA & Stammerjohn SE. 2010. Antarctic sea ice change and variability u2013 Physical and ecological implications. Polar Science 4, 149u2013186.
  • Mercer JH. 1978. West Antarctic ice sheet and CO2 greenhouse effect: a threat of disaster. Nature 271, 321u2013325.
  • Mercer JH. West Antarctic ice sheet and CO2 greenhouse effect: a threat of disaster. 1978. Nature 271, 321u2013325.
  • Moline MA et al. 2008. High latitude changes in ice dynamics and their impact on polar marine ecosystems. Annals of the New York Academy of Sciences 1134, 267u2013319.
  • NASA 2014.West Antarctic Glacier Loss Appears Unstoppable.(Title for the online news. Geophysical Research Letters article in press). http://www.jpl.nasa.gov/news/news.php?release=2014-148 (accessed 15th May 2014.)
  • Naish T et al. 2009. Obliquity-paced Pliocene West Antarctic ice sheet oscillations. Nature 458, 322u2013328.
  • Nicholls KW. 1997. Predicted reduction in basal melt rates of an Antarctic ice shelf in a warmer climate. Nature 388, 460u2013462.
  • Nicholls RJ et al. 2011. Sea-level rise and its possible impacts given a u201cbeyond 4u00b0C worldu201d in the twenty-first century. Philosophical transactions. Series A, Mathematical, physical, and engineering sciences 369, 161u201381
  • Notz D. 2009. The future of ice sheets and sea ice: between reversible retreat and unstoppable loss. Proceedings of the National Academy of Sciences of the United States of America 106, 20590u20135.
  • Oppenheimer M & Alley RB. The West Antarctic Ice Sheet and Long Term Climate Policy. 2004. Climatic Change 64, 1u201310.
  • Oppenheimer M.1998. Global warming and the stability of the West Antarctic Ice Sheet. Nature 393, 325u2013332.
  • Ou2019Reilly J & ACOS, 2013. Updateu202f: The Future of the West Antarctic Ice Sheet. Information paper submitted by ASOC. XXXVI Antarctic Treaty Consultative Meeting. Brussels.
  • Pollard D & DeConto RM. 2009. Modelling West Antarctic ice sheet growth and collapse through the past five million years. Nature 458, 329u201332.
  • Price MR, Heywood KJ & Nicholls KW. 2008. Ice-shelf u2013 ocean interactions at Fimbul Ice Shelf, Antarctica from oxygen isotope ratio measurements. Ocean Science 4, 89u201398.
  • Pritchard HD et al. 2012. Antarctic ice-sheet loss driven by basal melting of ice shelves. Nature 484, 502u20135.
  • Rignot E et al. 2011. Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise. Geophysical Research Letters 38, 106u2013110.
  • Robertson R. et al. 2002. Long-term temperature trends in the deep waters of the Weddell Sea. Deep-sea Research Part ii-Topical Studies in Oceanography, 49, 4791u20134806.
  • Rogers AD et al. (eds.) 2012. Antarctic Ecosystems: An Extreme Environment in a Changing World., Published Online: 29 FEB 2012. Available at: http://onlinelibrary.wiley.com/book/10.1002/9781444347241.
  • Sarmiento J et al. 1998. Simulated response of the ocean carbon cycle to anthropogenic climate warming. Nature 393, 245u2013249.
  • Scambos TA et al. 2000. The link between climate warming and break-up of ice shelves in the Antarctic Peninsula. Journal of Glaciology, 46, 516u2013530.
  • Scherer RP, 1991. Quaternary and Tertiary microfossils from beneath Ice Stream B: Evidence for a dynamic West Antarctic Ice Sheet history. Palaeogeography, Palaeoclimatology, Palaeoecology, 90, 395u2013412.
  • Schoof C. 2007. Ice sheet grounding line dynamics: Steady states, stability, and hysteresis. Journal of Geophysical Research 112, F03S28.
  • Shepherd A & Wingham D. 2007. Recent sea-level contributions of the Antarctic and Greenland ice sheets. Science 315, 1529u201332.
  • Steig EJ et al. 2013. Recent climate and ice-sheet changes in West Antarctica compared with the past 2,000 years. Nature Geoscience 6, 372u2013375.
  • Thoma M et al. 2008. Modelling Circumpolar Deep Water intrusions on the Amundsen Sea continental shelf, Antarctica. Geophysical Research Letters 35, L18602.
  • Thomas DN & G. S. Dieckmann GS. (eds.) 2010. Sea Ice. Oxford, UK: Wiley-Blackwell. Available at: http://doi.wiley.com/10.1002/9781444317145 [Accessed July 9, 2013].
  • Thomas R et al. 2004. Accelerated sea-level rise from West Antarctica. Science 306, 255u20138.
  • Thompson DWJ & Solomon S. 2002. Interpretation of recent Southern Hemisphere climate change. Science 296, 895u20139.
  • Turner J & Overland J. 2009. Contrasting climate change in the two polar regions. Polar Research 28, 146u2013164.
  • Turner J et al. 2009. Nonu2010annular atmospheric circulation change induced by stratospheric ozone depletion and its role in the recent increase of Antarctic sea ice extent. Geophysical Research Letters 36, L08502.
  • Tynan C. 2010. Sea ice: A critical habitat for polar marine mammals and birds. In Thomas DN & G. S. Dieckmann GS. (eds.) 2010. Sea Ice. Oxford, UK: Wiley-Blackwell. Available at: http://doi.wiley.com/10.1002/9781444317145 [Accessed July 9, 2013].
  • Vaughan DG. 2008. West Antarctic Ice Sheet collapse u2013 the fall and rise of a paradigm. Climatic Change 91, 65u201379.
  • Velicogna I & Wahr J. 2006. Measurements of time-variable gravity show mass loss in Antarctica. Science 311, 1754u20136
  • Worby A et al. 2009 Position Analysis: Changes to Antarctic Sea Ice: Impacts. The Antarctic Climate & Ecosystems Cooperative Research Centre. ISSN 1835-7911.
  • Zhang J. 2007. Increasing Antarctic Sea Ice under Warming Atmospheric and Oceanic Conditions. Journal of Climate 20, 2515u20132529.



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