Climate change under a scenario near 1.5 °C of global warming: monsoon intensification, ocean warming and steric sea level rise

Abstract. We present climatic consequences of the Representative Concentration Pathways (RCPs) using the coupled climate model CLIMBER-3α, which contains a statistical-dynamical atmosphere and a three-dimensional ocean model. We compare those with emulations of 19 state-of-the-art atmosphere-ocean general circulation models (AOGCM) using MAGICC6. The RCPs are designed as standard scenarios for the forthcoming IPCC Fifth Assessment Report to span the full range of future greenhouse gas (GHG) concentrations pathways currently discussed. The lowest of the RCP scenarios, RCP3-PD, is projected in CLIMBER-3α to imply a maximal warming by the middle of the 21st century slightly above 1.5 °C and a slow decline of temperatures thereafter, approaching today's level by 2500. We identify two mechanisms that slow down global cooling after GHG concentrations peak: The known inertia induced by mixing-related oceanic heat uptake; and a change in oceanic convection that enhances ocean heat loss in high latitudes, reducing the surface cooling rate by almost 50%. Steric sea level rise under the RCP3-PD scenario continues for 200 years after the peak in surface air temperatures, stabilizing around 2250 at 30 cm. This contrasts with around 1.3 m of steric sea level rise by 2250, and 2 m by 2500, under the highest scenario, RCP8.5. Maximum oceanic warming at intermediate depth (300–800 m) is found to exceed that of the sea surface by the second half of the 21st century under RCP3-PD. This intermediate-depth warming persists for centuries even after surface temperatures have returned to present-day values, with potential consequences for marine ecosystems, oceanic methane hydrates, and ice-shelf stability. Due to an enhanced land-ocean temperature contrast, all scenarios yield an intensification of monsoon rainfall under global warming.

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Climate change under a scenario near 1.5 °C of global warming: monsoon intensification, ocean warming and steric sea level rise

Earth System Dynamics Discussions ◽

10.5194/esdd-1-297-2010 ◽

2010 ◽

Vol 1 (1) ◽

pp. 297-324 ◽

Cited By ~ 10

Author(s):

J. Schewe ◽

A. Levermann ◽

M. Meinshausen

Keyword(s):

Global Warming ◽

Sea Level Rise ◽

Sea Level ◽

21St Century ◽

General Circulation ◽

Full Range ◽

General Circulation Models ◽

Surface Cooling ◽

Steric Sea Level ◽

Intermediate Depth

Abstract. We present climatic consequences of the Representative Concentration Pathways (RCPs) using the coupled climate model CLIMBER-3α, which contains a statistical-dynamical atmosphere and a three-dimensional ocean model. We compare those with emulations of 19 state-of-the-art atmosphere-ocean general circulation models (AOGCM) using MAGICC6. The RCPs are designed as standard scenarios for the forthcoming IPCC Fifth Assessment Report to span the full range of possible future greenhouse gas (GHG) concentrations pathways. The lowest of the RCP scenarios, RCP3-PD, is projected in CLIMBER-3α to imply a maximal warming by the middle of the 21st century slightly above 1.5 °C and a slow decline of temperatures thereafter, approaching today's level by 2500. We identify two mechanisms that slow down global cooling after GHG concentrations peak: The known inertia induced by mixing-related oceanic heat uptake; and a change in oceanic convection that enhances ocean heat loss in high latitudes, reducing the surface cooling rate by almost 50%. Steric sea level rise under the RCP3-PD scenario continues for 200 years after the peak in surface air temperatures, stabilizing around 2250 at 30 cm. This contrasts with around 2 m of steric sea level rise by 2500 under the highest scenario, RCP8.5. Maximum oceanic warming at intermediate depth (300–800 m) is found to exceed that of the sea surface by the second half of the 21st century under RCP3-PD. This intermediate-depth warming persists for centuries even after surface temperatures have returned to present-day values, with potential consequences for marine ecosystems, oceanic methane hydrates, and ice-shelf stability. Due to an enhanced land-ocean temperature contrast, all scenarios yield an intensification of monsoon rainfall under global warming.

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21st century ocean forcing of the Greenland Ice Sheet for modeling of sea level contribution

10.5194/tc-2019-222 ◽

2019 ◽

Cited By ~ 1

Author(s):

Donald A. Slater ◽

Denis Felikson ◽

Fiamma Straneo ◽

Heiko Goelzer ◽

Christopher M. Little ◽

...

Keyword(s):

Sea Level ◽

21St Century ◽

General Circulation ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

General Circulation Models ◽

Glacier Retreat ◽

Small Scale ◽

Intergovernmental Panel ◽

Continental Scale

Abstract. Changes in the ocean are expected to be an important determinant of the Greenland Ice Sheet's future sea level contribution. Yet representing these changes in continental-scale ice sheet models remains challenging due to the small scale of the key physics, and limitations in processing understanding. Here we present the ocean forcing strategy for Greenland Ice Sheet models taking part in the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6), the primary community effort to provide 21st century sea level projections for the Intergovernmental Panel on Climate Change 6th Assessment Report. Beginning from global atmosphere-ocean general circulation models, we describe two complementary approaches to provide ocean boundary conditions for Greenland Ice Sheet models, termed the retreat and submarine melt implementations. The retreat implementation parameterizes glacier retreat as a function of projected submarine melting, is designed to be implementable by all ice sheet models, and results in retreat of around 1 and 15 km by 2100 in RCP2.6 and 8.5 scenarios respectively. The submarine melt implementation provides estimated submarine melting only, leaving the ice sheet model to solve for the resulting calving and glacier retreat, and suggests submarine melt rates will change little under RCP2.6 but will approximately triple by 2100 under RCP8.5. Both implementations have necessarily made use of simplifying assumptions and poorly-constrained parameterisations and as such, further research on submarine melting, calving and fjord-shelf exchange should remain a priority. Nevertheless, the presented framework will allow an ensemble of Greenland Ice Sheet models to be systematically and consistently forced by the ocean for the first time, and should therefore result in a significant improvement in projections of the Greenland ice sheet's contribution to future sea level change.

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A scaling approach to project regional sea level rise and its uncertainties

Earth System Dynamics ◽

10.5194/esd-4-11-2013 ◽

2013 ◽

Vol 4 (1) ◽

pp. 11-29 ◽

Cited By ~ 77

Author(s):

M. Perrette ◽

F. Landerer ◽

R. Riva ◽

K. Frieler ◽

M. Meinshausen

Keyword(s):

Climate Change ◽

Sea Level Rise ◽

Sea Level ◽

General Circulation ◽

Ice Sheets ◽

General Circulation Models ◽

Ice Melt ◽

Probabilistic Forecasts ◽

Regional Sea Level ◽

Global Mean

Abstract. Climate change causes global mean sea level to rise due to thermal expansion of seawater and loss of land ice from mountain glaciers, ice caps and ice sheets. Locally, sea level can strongly deviate from the global mean rise due to changes in wind and ocean currents. In addition, gravitational adjustments redistribute seawater away from shrinking ice masses. However, the land ice contribution to sea level rise (SLR) remains very challenging to model, and comprehensive regional sea level projections, which include appropriate gravitational adjustments, are still a nascent field (Katsman et al., 2011; Slangen et al., 2011). Here, we present an alternative approach to derive regional sea level changes for a range of emission and land ice melt scenarios, combining probabilistic forecasts of a simple climate model (MAGICC6) with the new CMIP5 general circulation models. The contribution from ice sheets varies considerably depending on the assumptions for the ice sheet projections, and thus represents sizeable uncertainties for future sea level rise. However, several consistent and robust patterns emerge from our analysis: at low latitudes, especially in the Indian Ocean and Western Pacific, sea level will likely rise more than the global mean (mostly by 10–20%). Around the northeastern Atlantic and the northeastern Pacific coasts, sea level will rise less than the global average or, in some rare cases, even fall. In the northwestern Atlantic, along the American coast, a strong dynamic sea level rise is counteracted by gravitational depression due to Greenland ice melt; whether sea level will be above- or below-average will depend on the relative contribution of these two factors. Our regional sea level projections and the diagnosed uncertainties provide an improved basis for coastal impact analysis and infrastructure planning for adaptation to climate change.

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The effect of overshooting 1.5 °C global warming on the mass loss of the Greenland ice sheet

Earth System Dynamics ◽

10.5194/esd-9-1169-2018 ◽

2018 ◽

Vol 9 (4) ◽

pp. 1169-1189 ◽

Cited By ~ 6

Author(s):

Martin Rückamp ◽

Ulrike Falk ◽

Katja Frieler ◽

Stefan Lange ◽

Angelika Humbert

Keyword(s):

Global Warming ◽

Mass Loss ◽

Mass Balance ◽

Sea Level Rise ◽

Sea Level ◽

21St Century ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Surface Mass Balance ◽

Surface Mass

Abstract. Sea-level rise associated with changing climate is expected to pose a major challenge for societies. Based on the efforts of COP21 to limit global warming to 2.0 ∘C or even 1.5 ∘C by the end of the 21st century (Paris Agreement), we simulate the future contribution of the Greenland ice sheet (GrIS) to sea-level change under the low emission Representative Concentration Pathway (RCP) 2.6 scenario. The Ice Sheet System Model (ISSM) with higher-order approximation is used and initialized with a hybrid approach of spin-up and data assimilation. For three general circulation models (GCMs: HadGEM2-ES, IPSL-CM5A-LR, MIROC5) the projections are conducted up to 2300 with forcing fields for surface mass balance (SMB) and ice surface temperature (Ts) computed by the surface energy balance model of intermediate complexity (SEMIC). The projected sea-level rise ranges between 21–38 mm by 2100 and 36–85 mm by 2300. According to the three GCMs used, global warming will exceed 1.5 ∘C early in the 21st century. The RCP2.6 peak and decline scenario is therefore manually adjusted in another set of experiments to suppress the 1.5 ∘C overshooting effect. These scenarios show a sea-level contribution that is on average about 38 % and 31 % less by 2100 and 2300, respectively. For some experiments, the rate of mass loss in the 23rd century does not exclude a stable ice sheet in the future. This is due to a spatially integrated SMB that remains positive and reaches values similar to the present day in the latter half of the simulation period. Although the mean SMB is reduced in the warmer climate, a future steady-state ice sheet with lower surface elevation and hence volume might be possible. Our results indicate that uncertainties in the projections stem from the underlying GCM climate data used to calculate the surface mass balance. However, the RCP2.6 scenario will lead to significant changes in the GrIS, including elevation changes of up to 100 m. The sea-level contribution estimated in this study may serve as a lower bound for the RCP2.6 scenario, as the currently observed sea-level rise is not reached in any of the experiments; this is attributed to processes (e.g. ocean forcing) not yet represented by the model, but proven to play a major role in GrIS mass loss.

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Change in mass balance of polar ice sheets and sea level from high-resolution GCM simulations of greenhouse warming

Annals of Glaciology ◽

10.3189/172756400781820741 ◽

2000 ◽

Vol 30 ◽

pp. 197-203 ◽

Cited By ~ 26

Author(s):

Martin Wild ◽

Atsumu Ohmura

Keyword(s):

Mass Balance ◽

Sea Level Rise ◽

Sea Level ◽

General Circulation ◽

Ice Sheets ◽

General Circulation Models ◽

Dominant Factor ◽

Greenhouse Warming ◽

Sea Level Changes ◽

And Sea Level

AbstractFor projecting future sea level, the mass-balance changes on Greenland and Antarctica are considered to be crucial. Promising tools for such estimates are general circulation models (GCM). Until recently, a major impediment was their coarse grid resolution (3°-6°) causing substantial uncertainties in the mass-balance calculations of the poorly resolved ice sheets. The present study is based on a new climate-change experiment of the highest resolution currently feasible (1.1 °) performed with the ECHAM4 T106 GCM, thereby increasing confidence in the projected mass-balance and sea-level changes. This new experiment, with doubled CO2 concentration, suggests that the mass gain in Antarctica due to increased accumulation exceeds the melt-induced mass loss in Greenland by a factor of three. The resulting mass-balance change on both ice sheets is equivalent to a net sea-level decrease of 0.6 mm a"1 under doubled CO2 conditions. This may compensate for a significant portion of the melt-induced sea-level rise from the smaller glaciers and ice caps, thus leaving thermal expansion as the dominant factor for sea-level rise over the next decades. This compensating effect, however, no longer applies should atmospheric CO2 concentration reach levels well above "doubled the present value". On the contrary, under these conditions, the greenhouse warming would become large enough to induce substantial melting also on the Antarctic ice sheet, thereby significantly accelerating global sea-level rise.

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Steric Sea Level Changes from Ocean Reanalyses at Global and Regional Scales

Water ◽

10.3390/w11101987 ◽

2019 ◽

Vol 11 (10) ◽

pp. 1987

Author(s):

Andrea Storto ◽

Antonio Bonaduce ◽

Xiangbo Feng ◽

Chunxue Yang

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

General Circulation ◽

Climate Projections ◽

Sea Level Changes ◽

Steric Sea Level ◽

Skill Scores ◽

Ocean Reanalyses ◽

Recent Climate ◽

Sea Level Trend

Sea level has risen significantly in the recent decades and is expected to rise further based on recent climate projections. Ocean reanalyses that synthetize information from observing networks, dynamical ocean general circulation models, and atmospheric forcing data offer an attractive way to evaluate sea level trend and variability and partition the causes of such sea level changes at both global and regional scales. Here, we review recent utilization of reanalyses for steric sea level trend investigations. State-of-the-science ocean reanalysis products are then used to further infer steric sea level changes. In particular, we used an ensemble of centennial reanalyses at moderate spatial resolution (between 0.5 × 0.5 and 1 × 1 degree) and an ensemble of eddy-permitting reanalyses to quantify the trends and their uncertainty over the last century and the last two decades, respectively. All the datasets showed good performance in reproducing sea level changes. Centennial reanalyses reveal a 1900–2010 trend of steric sea level equal to 0.47 ± 0.04 mm year−1, in agreement with previous studies, with unprecedented rise since the mid-1990s. During the altimetry era, the latest vintage of reanalyses is shown to outperform the previous ones in terms of skill scores against the independent satellite data. They consistently reproduce global and regional upper ocean steric expansion and the association with climate variability, such as ENSO. However, the mass contribution to the global mean sea level rise is varying with products and its representability needs to be improved, as well as the contribution of deep and abyssal waters to the steric sea level rise. Similarly, high-resolution regional reanalyses for the European seas provide valuable information on sea level trends, their patterns, and their causes.

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Simple models for the simulation of submarine melt for a Greenland glacial system model

The Cryosphere ◽

10.5194/tc-12-301-2018 ◽

2018 ◽

Vol 12 (1) ◽

pp. 301-323 ◽

Cited By ~ 5

Author(s):

Johanna Beckmann ◽

Mahé Perrette ◽

Andrey Ganopolski

Keyword(s):

High Resolution ◽

Simple Model ◽

Sea Level Rise ◽

Sea Level ◽

General Circulation ◽

Greenland Ice Sheet ◽

General Circulation Models ◽

Model Parameters ◽

Plume Model ◽

Simple Models

Abstract. Two hundred marine-terminating Greenland outlet glaciers deliver more than half of the annually accumulated ice into the ocean and have played an important role in the Greenland ice sheet mass loss observed since the mid-1990s. Submarine melt may play a crucial role in the mass balance and position of the grounding line of these outlet glaciers. As the ocean warms, it is expected that submarine melt will increase, potentially driving outlet glaciers retreat and contributing to sea level rise. Projections of the future contribution of outlet glaciers to sea level rise are hampered by the necessity to use models with extremely high resolution of the order of a few hundred meters. That requirement in not only demanded when modeling outlet glaciers as a stand alone model but also when coupling them with high-resolution 3-D ocean models. In addition, fjord bathymetry data are mostly missing or inaccurate (errors of several hundreds of meters), which questions the benefit of using computationally expensive 3-D models for future predictions. Here we propose an alternative approach built on the use of a computationally efficient simple model of submarine melt based on turbulent plume theory. We show that such a simple model is in reasonable agreement with several available modeling studies. We performed a suite of experiments to analyze sensitivity of these simple models to model parameters and climate characteristics. We found that the computationally cheap plume model demonstrates qualitatively similar behavior as 3-D general circulation models. To match results of the 3-D models in a quantitative manner, a scaling factor of the order of 1 is needed for the plume models. We applied this approach to model submarine melt for six representative Greenland glaciers and found that the application of a line plume can produce submarine melt compatible with observational data. Our results show that the line plume model is more appropriate than the cone plume model for simulating the average submarine melting of real glaciers in Greenland.

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Elimination of the Greenland Ice Sheet in a High CO2 Climate

Journal of Climate ◽

10.1175/jcli3482.1 ◽

2005 ◽

Vol 18 (17) ◽

pp. 3409-3427 ◽

Cited By ~ 173

Author(s):

J. K. Ridley ◽

P. Huybrechts ◽

J. M. Gregory ◽

J. A. Lowe

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

General Circulation ◽

Climate Changes ◽

Regional Climate ◽

Ice Sheet ◽

Carbon Dioxide Concentration ◽

Greenland Ice Sheet ◽

General Circulation Models ◽

Ice Dynamics

Abstract Projections of future global sea level depend on reliable estimates of changes in the size of polar ice sheets. Calculating this directly from global general circulation models (GCMs) is unreliable because the coarse resolution of 100 km or more is unable to capture narrow ablation zones, and ice dynamics is not usually taken into account in GCMs. To overcome these problems a high-resolution (20 km) dynamic ice sheet model has been coupled to the third Hadley Centre Coupled Ocean–Atmosphere GCM (HadCM3). A novel feature is the use of two-way coupling, so that climate changes in the GCM drive ice mass changes in the ice sheet model that, in turn, can alter the future climate through changes in orography, surface albedo, and freshwater input to the model ocean. At the start of the main experiment the atmospheric carbon dioxide concentration was increased to 4 times the preindustrial level and held constant for 3000 yr. By the end of this period the Greenland ice sheet is almost completely ablated and has made a direct contribution of approximately 7 m to global average sea level, causing a peak rate of sea level rise of 5 mm yr−1 early in the simulation. The effect of ice sheet depletion on global and regional climate has been examined and it was found that apart from the sea level rise, the long-term effect on global climate is small. However, there are some significant regional climate changes that appear to have reduced the rate at which the ice sheet ablates.

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The effect of overshooting 1.5 °C global warming on the mass loss of the Greenland Ice Sheet

10.5194/esd-2017-103 ◽

2017 ◽

Author(s):

Martin Rückamp ◽

Ulrike Falk ◽

Katja Frieler ◽

Stefan Lange ◽

Angelika Humbert

Keyword(s):

Mass Loss ◽

Sea Level Rise ◽

Sea Level ◽

General Circulation ◽

Order Approximation ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

General Circulation Models ◽

Surface Mass ◽

Atmospheric Forcings

Abstract. Sea level rise associated with changing climate is expected to pose a major challenge for societies. Here, we estimate the future contribution of the Greenland ice sheet (GrIS) to sea level change in terms of different ice sheet atmospheric forcings arising from three general circulation models (GCMs), HadGEM2-ES, IPSL-CM5A-LR and MIROC5, for RCP2.6. We run the ice sheet model ISSM with higher order approximation and use a spin-up/inversion scheme to estimate the present day state. The forcing fields for surface mass balance (SMB) and ice surface temperature Ts are computed by the SEMIC model (Krapp et al., 2017) and applied as anomalies to RACMO2.3 fields. According to the three GCMs, warming of 1.5 °C has been reached at GrIS by 2005 (HadGEM2-ES, MIROC5) or as early as 1995 (IPSL-CM5A-LR). Forcing fields suffer from underestimation of polar amplification (MIROC5) and implausible distribution of changes in Ts (IPSL-CM5A-LR). HadGEM2-ES is the most plausible forcing, with globally a peak and decline behaviour leading to overshooting of 1.5 °C and over GrIS a slight recovery of SMB towards values of about half the present day SMB. We find sea level to rise for HadGEM2-ES by 71 mm by 2100 and 189 mm by 2300. Simulated an observed sea level rise 2002–2014 is of the same magnitude, but with a temporal lag to be at least five years (HadGEM2-ES). By end of 22nd century sea level contribution is still 0.46 mm/a for HadGEM2-ES. Hence, even a RCP2.6 peak and decline scenario will lead to significant changes of GrIS including elevation changes up to 100 m and loss of floating tongues. The values of this study may serve as a lower bound, as processes proven to play a major role in GrIS mass loss are not yet represented by the model, but are considerably larger than other studies.

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Using global sea-level rise targets to find optimal temperature overshoot profile

10.5194/egusphere-egu2020-13753 ◽

2020 ◽

Author(s):

Chao Li ◽

Hermann Held ◽

Sascha Hokamp ◽

Jochem Marotzke

Keyword(s):

Global Warming ◽

Sea Level Rise ◽

Climate Policy ◽

Sea Level ◽

21St Century ◽

Carbon Emissions ◽

Ice Sheet ◽

Climate Target ◽

Surface Warming ◽

Global Sea Level

Even if surface warming could be kept below 2.0&#176;C or 1.5&#176;C by 2100, global sea-level rise will occur&#160;for several centuries or even millennia. One possible interpretation of a successful climate policy for the next few decades could be that it should avoid global-warming induced impacts on climate, ecosystems and human societies not only within this century, but also for the next centuries and beyond. Here, we perform a proof-of-concept study to introduce a constraint on SLR as a new climate target and compare the economic impact to that of a corresponding temperature target.In the 21st yearly session of the Conference of the Parties in Paris in 2015, SLR threats to the Small Island Developing States (SIDS) prompted a commitment to strive for a lower global temperature target goal of limiting surface warming below 1.5&#176;C. However, an SLR target more directly relates to their existential threats. We here substantially augmented the climate model of&#160;the optimizing climate-energy-economy model MIND (Model of Investment and Technological Development) from an impulse-response model to a three-layer ocean model with much-improved representation of ocean heat uptake. We introduce a global total SLR model with four components, one due to ocean thermal expansion, one due to Greenland ice-sheet melting, one due to Antarctic ice-sheet melting, and one due to mountain glaciers and ice cap melting. The newly developed integrated-assessment framework has enabled us to investigate, for the first time, a sea-level rise climate target.Our results emphasize a key effect of carbon emissions pathways on the future SLR after the 21st century. The shape of carbon emissions pathways will strongly influence future SLR after the 21st century and generally affect SIDS over centuries. To reduce SLR-induced impacts on SIDS, a target is required that not only keeps surface warming below a certain level but also reduces surface warming substantially thereafter. We find that a global SLR target will provide a more sustainable and a lower-cost solution to limit both short-term and long-term climate changes for stakeholders who primarily care about SLR among all global warming impact categories compared to a temperature target with the same SLR by 2200.We find that the SLR target can provide a temperature overshoot profile through a physical constraint rather than arbitrarily defining an overshoot range of temperature as acceptable. Temperature targets with a limited overshoot have been invoked to make the 2.0&#176; and 1.5&#176;C targets feasible in the context of real-world United Nations climate policy; however, rational constraints on the temperature overshoot have been unclear. SLR targets can be viewed as a reinterpretation of the 2.0&#176; and 1.5&#176;C targets and can provide a rational justification of a certain temperature overshoot for stakeholders who primarily care about SLR. Our present framework with reinterpretation of the widely agreed temperature targets can, in principle, be transferred from SLR targets to impact-related climate targets and can be used to identify a more sustainable path toward meeting the Paris Agreement.

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