Twenty-first-century warming of a large Antarctic ice-shelf cavity by a redirected coastal current

Hellmer, Hartmut; Kauker, Frank; Timmermann, Ralph; Determann, Jürgen; Rae, Jamie

doi:10.1038/nature11064

Cited by 382 publications

(501 citation statements)

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“…The dynamics of these coupled cryosphere-oceanic systems remain a topic of intense research. Current fine-scale ocean models, suggest increased intrusion of warm deep water on the continental shelf as a result of anthropogenic climate change and thus indicate an increasing risk with increasing warming (Hellmer et al, 2012;Timmermann and Hellmer, 2013). Given the risk of potentially triggering multi-metre SLR on centennial to millennial timescales, this clearly calls for a precautionary approach that is further underscored by evidence from paleo-records, which reveals that past sea-levels might have about 6-9 m above present day for levels for a GMT increase not exceeding 2 • C above pre-industrial levels (Dutton et al, 2015).…”

Section: Resultsmentioning

confidence: 99%

Differential climate impacts for policy-relevant limits to global warming: the case of 1.5 °C and 2 °C

et al. 2016

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Abstract. Robust appraisals of climate impacts at different levels of global-mean temperature increase are vital to guide assessments of dangerous anthropogenic interference with the climate system. The 2015 Paris Agreement includes a two-headed temperature goal: "holding the increase in the global average temperature to well below 2 • C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 • C". Despite the prominence of these two temperature limits, a comprehensive overview of the differences in climate impacts at these levels is still missing. Here we provide an assessment of key impacts of climate change at warming levels of 1.5 • C and 2 • C, including extreme weather events, water availability, agricultural yields, sea-level rise and risk of coral reef loss. Our results reveal substantial differences in impacts between a 1.5 • C and 2 • C warming that are highly relevant for the assessment of dangerous anthropogenic interference with the climate system. For heat-related extremes, the additional 0.5 • C increase in global-mean temperature marks the difference between events at the upper limit of present-day natural variability and a new climate regime, particularly in tropical regions. Similarly, this warming difference is likely to be decisive for the future of tropical coral reefs. In a scenario with an end-of-century warming of 2 • C, virtually all tropical coral reefs are projected to be at risk of severe degradation due to temperature-induced bleaching from 2050 onwards. This fraction is reduced to about 90 % in 2050 and projected to decline to 70 % by 2100 for a 1.5 • C scenario. Analyses of precipitation-related impacts reveal distinct regional differences and hot-spots of change emerge. Regional reduction in median water availability for the Mediterranean is found to nearly double from 9 % to 17 % between 1.5 • C and 2 • C, and the projected lengthening of regional dry spells increases from 7 to 11 %. Projections for agricultural yields differ between crop types as well as world regions. While some (in particular high-latitude) regions may benefit, tropical regions like West Africa, South-East Asia, as well as Central and northern South America are projected to face substantial local yield reductions, particularly for wheat and maize. Best estimate sea-level rise projections based on two illustrative scenarios indicate a 50 cm rise by 2100 relative to year 2000-levels for a 2 • C scenario, and about 10 cm lower levels for a 1.5 • C scenario. In a 1.5 • C scenario, the rate of sea-level rise in 2100 would be reduced by about 30 % compared to a 2 • C scenario. Our findings highlight the importance of regional differentiation to assess both future climate risks and different vulnerabilities to incremental increases in globalmean temperature. The article provides a consistent and comprehensive assessment of existing projections andPublished by Copernicus Publications on behalf of the European Geosciences Union. 328C.-F. Schleussner et al.: Climate impacts at 1.5 • C a...

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Section: Resultsmentioning

confidence: 99%

Differential climate impacts for policy-relevant limits to global warming: the case of 1.5 °C and 2 °C

et al. 2016

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“…2). In particular, the oceanic forcing includes the influx of warm water under the Filchner-Ronne ice shelf reported by Hellmer et al [111], although this only occurs towards the end of the current century. Substantial mass loss is therefore dominated by the ASE and contributes up to 50 mm GMSL by 2100, including a contribution from the retreat of TG.…”

Section: Antarctic Ice Sheetmentioning

confidence: 99%

Recent Progress in Understanding and Projecting Regional and Global Mean Sea Level Change

Clark

Church

Gregory

et al. 2015

Curr Clim Change Rep

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Considerable progress has been made in understanding the present and future regional and global sea level in the 2 years since the publication of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change. Here, we evaluate how the new results affect the AR5's assessment of (i) historical sea level rise, including attribution of that rise and implications for the sea level budget, (ii) projections of the components and of total global mean sea level (GMSL), and (iii) projections of regional variability and emergence of the anthropogenic signal. In each of these cases, new work largely provides additional evidence in support of the AR5 assessment, providing greater confidence in those findings. Recent analyses confirm the twentieth century sea level rise, with some analyses showing a slightly smaller rate before 1990 and some a slightly larger value than reported in the AR5. There is now more evidence of an acceleration in the rate of rise. Ongoing ocean heat uptake and associated thermal expansion have continued since 2000, and are consistent with ocean thermal expansion reported in the AR5. A significant amount of heat is being stored deeper in the water column, with a larger rate of heat uptake since 2000 compared to the previous decades and with the largest storage in the Southern Ocean. The first formal detection studies for ocean thermal expansion and glacier mass loss since the AR5 have confirmed the AR5 finding of a significant anthropogenic contribution to sea level rise over the last 50 years. New projections of glacier loss from two regions suggest smaller contributions to GMSL rise from these regions than in studies assessed by the AR5; additional regional studies are required to further assess whether there are broader implications of these results. Mass loss from the Greenland Ice Sheet, primarily as a result of increased surface melting, and from the Antarctic Ice Sheet, primarily as a result of increased ice discharge, has accelerated. The largest estimates of acceleration in mass loss from the two ice sheets for 2003-2013 equal or exceed the acceleration of GMSL rise calculated from the satellite altimeter sea level record over the longer period of 1993-2014. However, when increased mass gain in land water storage and parts of East Antarctica, and decreased mass loss from glaciers in Alaska and some other regions are taken into account, the net acceleration in the ocean mass gain is consistent with the satellite altimeter record. New studies suggest that a marine ice sheet instability (MISI) may have been initiated in parts of the West Antarctic Ice Sheet (WAIS), but that it will affect only a limited number of ice streams in the twenty-first century. New projections of mass loss from the Greenland and Antarctic Ice Sheets by 2100, including a contribution from parts of WAIS undergoing unstable retreat, suggest a contribution that falls largely within the likely range (i.e., two thirds probability) of the AR5. These new results increase confidence in the AR5 likel...

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“…Coupling with ice sheet models will ultimately require high-resolution 3-D regional ocean modeling (e.g., Dinniman et al, 2011;Hellmer et al, 2012), especially for paleo and future scenarios. For now, we use simple parameterizations that attempt to provide (i) the basic modern spatial distribution, and (ii) paleoclimatic variations that yield results in accord with geologic data.…”

Section: Sub-ice-shelf Oceanic Meltingmentioning

confidence: 99%

Description of a hybrid ice sheet-shelf model, and application to Antarctica

2012

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Abstract. The formulation of a 3-D ice sheet-shelf model is described. The model is designed for long-term continentalscale applications, and has been used mostly in paleoclimatic studies. It uses a hybrid combination of the scaled shallow ice and shallow shelf approximations for ice flow. Floating ice shelves and grounding-line migration are included, with parameterized ice fluxes at grounding lines that allows relatively coarse resolutions to be used. All significant components and parameterizations of the model are described in some detail. Basic results for modern Antarctica are compared with observations, and simulations over the last 5 million years are compared with previously published results. The sensitivity of ice volumes during the last deglaciation to basal sliding coefficients is discussed.

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Twenty-first-century warming of a large Antarctic ice-shelf cavity by a redirected coastal current

Cited by 382 publications

References 30 publications

Differential climate impacts for policy-relevant limits to global warming: the case of 1.5 °C and 2 °C

Differential climate impacts for policy-relevant limits to global warming: the case of 1.5 °C and 2 °C

Recent Progress in Understanding and Projecting Regional and Global Mean Sea Level Change

Description of a hybrid ice sheet-shelf model, and application to Antarctica

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Twenty-first-century warming of a large Antarctic ice-shelf cavity by a redirected coastal current

Cited by 382 publications

References 30 publications

Differential climate impacts for policy-relevant limits to global warming: the case of 1.5 °C and 2 °C

Differential climate impacts for policy-relevant limits to global warming: the case of 1.5 °C and 2 °C

Recent Progress in Understanding and Projecting Regional and Global Mean Sea Level Change

Description of a hybrid ice sheet-shelf model, and application to Antarctica

Contact Info

Product

Resources

About

Differential climate impacts for policy-relevant limits to global warming: the case of 1.5 °C and 2 °C

Differential climate impacts for policy-relevant limits to global warming: the case of 1.5 °C and 2 °C