Future surface mass balance of the Antarctic ice sheet and its influence on sea level change, simulated by a regional atmospheric climate model
TL;DR: In this article, a regional atmospheric climate model with multi-layer snow module (RACMO2) is forced at the lateral boundaries by global climate model (GCM) data to assess the future climate and surface mass balance (SMB) of the Antarctic ice sheet (AIS).
Abstract: A regional atmospheric climate model with multi-layer snow module (RACMO2) is forced at the lateral boundaries by global climate model (GCM) data to assess the future climate and surface mass balance (SMB) of the Antarctic ice sheet (AIS). Two different GCMs (ECHAM5 until 2100 and HadCM3 until 2200) and two different emission scenarios (A1B and E1) are used as forcing to capture a realistic range in future climate states. Simulated ice sheet averaged 2 m air temperature (T2m) increases (1.8–3.0 K in 2100 and 2.4–5.3 K in 2200), simultaneously and with the same magnitude as GCM simulated T2m. The SMB and its components increase in magnitude, as they are directly influenced by the temperature increase. Changes in atmospheric circulation around Antarctica play a minor role in future SMB changes. During the next two centuries, the projected increase in liquid water flux from rainfall and snowmelt, together 60–200 Gt year−1, will mostly refreeze in the snow pack, so runoff remains small (10–40 Gt year−1). Sublimation increases by 25–50 %, but remains an order of magnitude smaller than snowfall. The increase in snowfall mainly determines future changes in SMB on the AIS: 6–16 % in 2100 and 8–25 % in 2200. Without any ice dynamical response, this would result in an eustatic sea level drop of 20–43 mm in 2100 and 73–163 mm in 2200, compared to the twentieth century. Averaged over the AIS, a strong relation between \(\Updelta\)SMB and \(\Updelta\hbox{T}_{2{\rm m}}\) of 98 ± 5 Gt w.e. year−1 K−1 is found.
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TL;DR: In this paper, the authors used a continental ice sheet model to show that mechanisms based on recent observations and analysis have the potential to resolve this model-data conflict, and incorporated these mechanisms in their ice-sheet model accelerates the expected collapse of the West Antarctic Ice Sheet to decadal time scales, and also causes retreat into major East Antarctic subglacial basins, producing ∼17 m global sea-level rise within a few thousand years.
412 citations
Cites background or methods from "Future surface mass balance of the ..."
...…of Antarctica today outside the Peninsula, they are substantial enough near sea level around the East Antarctic margin (Tedesco and Monaghan, 2009; Ligtenberg et al., 2013) to produce numerous supraglacial lakes (Vogel et al., 2013), and their rates become much more significant in our…...
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...…with ∼2× PAL CO2 predict very little surface melting of East Antarctica except on narrow strips around the margins, and no overall retreat; in fact, the EAIS volume increases due to greater snowfall in the warmer atmosphere for CO2 up to 2× PAL (Vizcaino et al., 2010; Ligtenberg et al., 2013)....
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...Given proxy records of CO2 of only 1 to 2× PAL since the late Oligocene (Pagani et al., 2005; Beerling and Royer, 2011), these results rule out substantial EAIS retreat due directly to surface mass loss....
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...Although surface melting and rainfall are minor over much of Antarctica today outside the Peninsula, they are substantial enough near sea level around the East Antarctic margin (Tedesco and Monaghan, 2009; Ligtenberg et al., 2013) to produce numerous supraglacial lakes (Vogel et al....
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...Higher-resolution climate model simulations with ∼2× PAL CO2 predict very little surface melting of East Antarctica except on narrow strips around the margins, and no overall retreat; in fact, the EAIS volume increases due to greater snowfall in the warmer atmosphere for CO2 up to 2× PAL (Vizcaino et al., 2010; Ligtenberg et al., 2013)....
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TL;DR: In this article, the authors present regional projections of sea-level change resulting from changing ocean circulation, increased heat uptake and atmospheric pressure in CMIP5 climate models, combined with model and observation-based regional contributions of land ice, groundwater depletion and glacial isostatic adjustment, including gravitational effects due to mass redistribution.
Abstract: We present regional sea-level projections and associated uncertainty estimates for the end of the 21st century. We show regional projections of sea-level change resulting from changing ocean circulation, increased heat uptake and atmospheric pressure in CMIP5 climate models. These are combined with model- and observation-based regional contributions of land ice, groundwater depletion and glacial isostatic adjustment, including gravitational effects due to mass redistribution. A moderate and a warmer climate change scenario are considered, yielding a global mean sea-level rise of 0.54 ±0.19 m and 0.71 ±0.28 m respectively (mean ±1σ). Regionally however, changes reach up to 30 % higher in coastal regions along the North Atlantic Ocean and along the Antarctic Circumpolar Current, and up to 20 % higher in the subtropical and equatorial regions, confirming patterns found in previous studies. Only 50 % of the global mean value is projected for the subpolar North Atlantic Ocean, the Arctic Ocean and off the western Antarctic coast. Uncertainty estimates for each component demonstrate that the land ice contribution dominates the total uncertainty.
324 citations
Cites background from "Future surface mass balance of the ..."
...There are no CMIP5-based results for Antarctica, but CMIP3-based SMB estimates (e.g., Krinner et al. 2007; Ligtenberg et al. 2013) fall within our range, with a tendency for a smaller sea-level fall....
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TL;DR: In this article, the authors evaluate modelled Antarctic ice sheet (AIS) near-surface climate, surfacemass balance (SMB) and surface energy balance (SEB) from the updated polar version of the regional atmospheric climate model, RACMO2 (1979-2016).
Abstract: . We evaluate modelled Antarctic ice sheet (AIS) near-surface climate, surface
mass balance (SMB) and surface energy balance (SEB) from the updated polar
version of the regional atmospheric climate model, RACMO2 (1979–2016). The
updated model, referred to as RACMO2.3p2, incorporates upper-air relaxation,
a revised topography, tuned parameters in the cloud scheme to generate more
precipitation towards the AIS interior and modified snow properties reducing
drifting snow sublimation and increasing surface snowmelt. Comparisons of RACMO2 model output with several independent observational
data show that the existing biases in AIS temperature, radiative fluxes and
SMB components are further reduced with respect to the previous model
version. The model-integrated annual average SMB for the ice sheet including
ice shelves (minus the Antarctic Peninsula, AP) now amounts to
2229 Gt y −1 , with an interannual variability of 109 Gt y −1 . The
largest improvement is found in modelled surface snowmelt, which now compares
well with satellite and weather station observations. For the high-resolution
( ∼ 5.5 km) AP simulation, results remain comparable to earlier
studies. The updated model provides a new, high-resolution data set of the contemporary
near-surface climate and SMB of the AIS; this model version will be used for
future climate scenario projections in a forthcoming study.
293 citations
TL;DR: This work quantifies the impact of twenty-first century climate change on ice-free areas under two Intergovernmental Panel on Climate Change climate forcing scenarios using temperature-index melt modelling and hypothesizes that they could eventually lead to increasing regional-scale biotic homogenization, the extinction of less-competitive species and the spread of invasive species.
Abstract: Antarctic terrestrial biodiversity occurs almost exclusively in ice-free areas that cover less than 1% of the continent. Climate change will alter the extent and configuration of ice-free areas, yet the distribution and severity of these effects remain unclear. Here we quantify the impact of twenty-first century climate change on ice-free areas under two Intergovernmental Panel on Climate Change (IPCC) climate forcing scenarios using temperature-index melt modelling. Under the strongest forcing scenario, ice-free areas could expand by over 17,000 km2 by the end of the century, close to a 25% increase. Most of this expansion will occur in the Antarctic Peninsula, where a threefold increase in ice-free area could drastically change the availability and connectivity of biodiversity habitat. Isolated ice-free areas will coalesce, and while the effects on biodiversity are uncertain, we hypothesize that they could eventually lead to increasing regional-scale biotic homogenization, the extinction of less-competitive species and the spread of invasive species.
245 citations
TL;DR: An approach that combines information about the equilibrium sea level response to global warming and last century's observed contribution from the individual components to constrain projections for this century is presented, which may lead to a better understanding of the gap between process-based and global semiempirical approaches.
Abstract: Sea level has been steadily rising over the past century, predominantly due to anthropogenic climate change. The rate of sea level rise will keep increasing with continued global warming, and, even if temperatures are stabilized through the phasing out of greenhouse gas emissions, sea level is still expected to rise for centuries. This will affect coastal areas worldwide, and robust projections are needed to assess mitigation options and guide adaptation measures. Here we combine the equilibrium response of the main sea level rise contributions with their last century's observed contribution to constrain projections of future sea level rise. Our model is calibrated to a set of observations for each contribution, and the observational and climate uncertainties are combined to produce uncertainty ranges for 21st century sea level rise. We project anthropogenic sea level rise of 28-56 cm, 37-77 cm, and 57-131 cm in 2100 for the greenhouse gas concentration scenarios RCP26, RCP45, and RCP85, respectively. Our uncertainty ranges for total sea level rise overlap with the process-based estimates of the Intergovernmental Panel on Climate Change. The "constrained extrapolation" approach generalizes earlier global semiempirical models and may therefore lead to a better understanding of the discrepancies with process-based projections.
191 citations
Cites background or methods from "Future surface mass balance of the ..."
...Such melting is estimated to be small within this century (37) but may significantly reduce the ice body under strong greenhouse gas forcing in the long term (49)....
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...For the Antarctic SMB, the simple scaling with surface temperature has been shown to be robust in a number of studies (36, 37)....
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References
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01 Jan 2007
TL;DR: The first volume of the IPCC's Fourth Assessment Report as mentioned in this paper was published in 2007 and covers several topics including the extensive range of observations now available for the atmosphere and surface, changes in sea level, assesses the paleoclimatic perspective, climate change causes both natural and anthropogenic, and climate models for projections of global climate.
Abstract: This report is the first volume of the IPCC's Fourth Assessment Report. It covers several topics including the extensive range of observations now available for the atmosphere and surface, changes in sea level, assesses the paleoclimatic perspective, climate change causes both natural and anthropogenic, and climate models for projections of global climate.
32,826 citations
TL;DR: ERA-Interim as discussed by the authors is the latest global atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF), which will extend back to the early part of the twentieth century.
Abstract: ERA-Interim is the latest global atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). The ERA-Interim project was conducted in part to prepare for a new atmospheric reanalysis to replace ERA-40, which will extend back to the early part of the twentieth century. This article describes the forecast model, data assimilation method, and input datasets used to produce ERA-Interim, and discusses the performance of the system. Special emphasis is placed on various difficulties encountered in the production of ERA-40, including the representation of the hydrological cycle, the quality of the stratospheric circulation, and the consistency in time of the reanalysed fields. We provide evidence for substantial improvements in each of these aspects. We also identify areas where further work is needed and describe opportunities and objectives for future reanalysis projects at ECMWF. Copyright © 2011 Royal Meteorological Society
22,055 citations
Book•
01 Jan 2007
TL;DR: In this article, the authors present a historical overview of climate change science, including changes in atmospheric constituents and radiative forcing, as well as changes in snow, ice, and frozen ground.
Abstract: Summary for policymakers -- Technical summary -- Historical overview of climate change science -- Changes in atmospheric constituents and radiative forcing -- Observations: atmospheric surface and climate change -- Observations: changes in snow, ice, and frozen ground -- Observations: ocean climate change and sea level -- Paleoclimate -- Coupling between changes in the climate system and biogeochemistry -- Climate models and their evaluation -- Understanding and attributing climate change -- Global climate projections -- Regional climate projections -- Annex I: Glossary -- Annex II: Contributors to the IPCC WGI Fourth Assessment Report -- Annex III: Reviewers of the IPCC WGI Fourth Assessment Report -- Annex IV: Acronyms.
7,738 citations
European Centre for Medium-Range Weather Forecasts1, Lawrence Livermore National Laboratory2, Chinese Academy of Sciences3, Japan Meteorological Agency4, University of Reading5, Met Office6, Max Planck Society7, Royal Netherlands Meteorological Institute8, National Center for Atmospheric Research9, National Oceanic and Atmospheric Administration10
TL;DR: ERA-40 is a re-analysis of meteorological observations from September 1957 to August 2002 produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) in collaboration with many institutions as mentioned in this paper.
Abstract: ERA-40 is a re-analysis of meteorological observations from September 1957 to August 2002 produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) in collaboration with many institutions. The observing system changed considerably over this re-analysis period, with assimilable data provided by a succession of satellite-borne instruments from the 1970s onwards, supplemented by increasing numbers of observations from aircraft, ocean-buoys and other surface platforms, but with a declining number of radiosonde ascents since the late 1980s. The observations used in ERA-40 were accumulated from many sources. The first part of this paper describes the data acquisition and the principal changes in data type and coverage over the period. It also describes the data assimilation system used for ERA-40. This benefited from many of the changes introduced into operational forecasting since the mid-1990s, when the systems used for the 15-year ECMWF re-analysis (ERA-15) and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) re-analysis were implemented. Several of the improvements are discussed. General aspects of the production of the analyses are also summarized.
A number of results indicative of the overall performance of the data assimilation system, and implicitly of the observing system, are presented and discussed. The comparison of background (short-range) forecasts and analyses with observations, the consistency of the global mass budget, the magnitude of differences between analysis and background fields and the accuracy of medium-range forecasts run from the ERA-40 analyses are illustrated. Several results demonstrate the marked improvement that was made to the observing system for the southern hemisphere in the 1970s, particularly towards the end of the decade. In contrast, the synoptic quality of the analysis for the northern hemisphere is sufficient to provide forecasts that remain skilful well into the medium range for all years. Two particular problems are also examined: excessive precipitation over tropical oceans and a too strong Brewer-Dobson circulation, both of which are pronounced in later years. Several other aspects of the quality of the re-analyses revealed by monitoring and validation studies are summarized. Expectations that the ‘second-generation’ ERA-40 re-analysis would provide products that are better than those from the firstgeneration ERA-15 and NCEP/NCAR re-analyses are found to have been met in most cases. © Royal Meteorological Society, 2005. The contributions of N. A. Rayner and R. W. Saunders are Crown copyright.
7,110 citations
TL;DR: In this paper, the authors examined some aspects of the hydrological cycle that are robust across the models, including the decrease in convective mass fluxes, the increase in horizontal moisture transport, the associated enhancement of the pattern of evaporation minus precipitation and its temporal variance, and decrease in the horizontal sensible heat transport in the extratropics.
Abstract: Using the climate change experiments generated for the Fourth Assessment of the Intergovernmental Panel on Climate Change, this study examines some aspects of the changes in the hydrological cycle that are robust across the models. These responses include the decrease in convective mass fluxes, the increase in horizontal moisture transport, the associated enhancement of the pattern of evaporation minus precipitation and its temporal variance, and the decrease in the horizontal sensible heat transport in the extratropics. A surprising finding is that a robust decrease in extratropical sensible heat transport is found only in the equilibrium climate response, as estimated in slab ocean responses to the doubling of CO2, and not in transient climate change scenarios. All of these robust responses are consequences of the increase in lower-tropospheric water vapor.
3,811 citations
"Future surface mass balance of the ..." refers background in this paper
...On the other hand, changes in ocean circulation may have the potential to enhance melt rates at the bottom of ice shelves by directing warmer water underneath them (Hellmer et al. 2012)....
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