ESDEarth System DynamicsESDEarth Syst. Dynam.2190-4987Copernicus PublicationsGöttingen, Germany10.5194/esd-7-203-2016Delaying future sea-level rise by storing water in AntarcticaFrielerK.MengelM.https://orcid.org/0000-0001-6724-9685LevermannA.anders.levermann@pik-potsdam.dehttps://orcid.org/0000-0003-4432-4704Potsdam Institute for Climate Impact Research, Potsdam, GermanyInstitute of Physics, Potsdam University, Potsdam,
GermanyLamont-Doherty Earth Observatory, Columbia University, New
York, USAA. Levermann (anders.levermann@pik-potsdam.de)10March20167120321015September201513October201512January201627January2016This work is licensed under a Creative Commons Attribution 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/This article is available from https://esd.copernicus.org/articles/7/203/2016/esd-7-203-2016.htmlThe full text article is available as a PDF file from https://esd.copernicus.org/articles/7/203/2016/esd-7-203-2016.pdf
Even if greenhouse gas emissions were stopped today, sea level would
continue to rise for centuries, with the long-term sea-level commitment of a
2 ∘C warmer world significantly exceeding 2 m. In view of the potential
implications for coastal populations and ecosystems worldwide, we
investigate, from an ice-dynamic perspective, the possibility of delaying
sea-level rise by pumping ocean water onto the surface of the Antarctic ice
sheet. We find that due to wave propagation ice is discharged much faster
back into the ocean than would be expected from a pure advection with
surface velocities. The delay time depends strongly on the distance from the
coastline at which the additional mass is placed and less strongly on the
rate of sea-level rise that is mitigated. A millennium-scale storage of at
least 80 % of the additional ice requires placing it at a distance of at
least 700 km from the coastline. The pumping energy required to elevate the
potential energy of ocean water to mitigate the currently observed
3 mm yr-1 will exceed 7 % of the current global primary energy supply. At
the same time, the approach offers a comprehensive protection for entire
coastlines particularly including regions that cannot be protected by dikes.
Introduction
Anthropogenic emissions of carbon into the atmosphere have increased global
temperatures by almost 1 ∘C during the past two centuries (IPCC,
2013). Even after a complete cessation of carbon emissions, temperatures are
not expected to drop significantly for several centuries. Although the
reduction of short-lived forcing agents has the potential to reduce the
near-term warming by about 0.5∘C, global mean temperatures are not
projected to decline significantly, even under the strongest mitigation
scenario, RCP2.6, which is already accounting for reductions in black
carbon, methane, and other short-lived forcers (van Vuuren et al., 2011). As
a consequence of the climate system's inertia and the ice sheets' response,
mitigating greenhouse-gas emissions in the future can reduce, but will not
stop, sea-level rise for centuries to come (Gillett et al., 2011; IPCC,
2013; Meehl et al., 2005; Solomon et al., 2009; Wigley, 2005). Conservative
estimates for this so-called sea-level commitment are of the order of 2 m per
1 ∘C of global warming above pre-industrial temperatures over a time
period of two millennia (Levermann et al., 2013); estimates of sea-level
sensitivity to warming from paleo-records of earlier warm periods are even
higher (Rohling et al., 2008, 2013). In addition, there is recent evidence
from observations (Rignot et al., 2014) and numerical models
(Favier et al., 2014; Joughin et al., 2014) that the West Antarctic ice
sheet has entered a state of irreversible ice discharge that would cause a
sea-level contribution even without any additional warming. The associated
long-term sea-level rise is estimated to be 1.1 m from the Amundsen Sea
sector, or 3.3 m if the entire marine part of West Antarctica were affected
(Bamber et al., 2009).
Bands of ice mass addition in East Antarctica and ice thickness relaxation
for the 800 km band. Left panel: surface velocities of the ice flow of the
Antarctic ice sheet (blue shading). Grey strips indicate where ice mass was
added to East Antarctica in order to delay future sea-level rise in the
different simulations. The ice was added in strips of 200 km width for 100
years. The right panels show the ice thickness relaxation after the end of the
mass addition to the 800 km band in time steps of 50 years for two
representative sections (left panel, red lines) as an anomaly to the
equilibrium simulation.
As a consequence, global coastal adaptation to ongoing sea-level rise will
be required unless water is taken back out of the ocean. Such local
protection may not be physically possible or economically feasible
everywhere. In southern Florida in the USA, for example, the base rock is
limestone, which makes the construction of levees very difficult (Strauss et
al., 2014). In addition, dams may not be acceptable for some regions that
rely on tourism associated with natural beaches. Local protection will most
likely only be done for areas where valuable assets are at risk and will
not cover entire coastlines, including poor areas and ecosystems.
Here we evaluate the option of delaying global sea-level rise for three
idealized scenarios of linear increases over the 21st century.
Mitigating the currently observed rate (Cazenave and Dieng, 2014) of
∼ 3 mm yr-1 is considered in comparison to the mitigation
of 1 mm yr-1 and a rate of 10 mm yr-1 within the “likely range”
for the end of the century under the high-emission scenario RCP8.5 (IPCC,
2013). Since it might be difficult to store such large water masses in
liquid form on land due to adverse effects on population, regional
ecosystems, and expected changes in the hydrological cycle, we explore
whether it is possible to store it as ice in Antarctica from the perspective
of ice dynamics.
The Antarctic ice sheet is situated on the coldest continent on Earth with
most of its surface temperatures far below the freezing point of ocean water
throughout the year. The water volume equivalent to 1 m of global
sea-level rise would elevate the Antarctic ice sheet by ∼ 25 m
if distributed uniformly. The currently observed ∼ 3 mm yr-1 of
global average sea-level rise due to thermal expansion,
additional water added from glaciers and ice sheets, and changes in land
water storage corresponds to about 1012 m3 yr-1 of
ocean water. Antarctica's currently observed ice loss occurs near the coast
(Shepherd et al., 2012), while the surface in its interior is moving at a
speed of less than 0.1 m yr-1 (Rignot et al., 2011). Because the ice is
continually moving, ocean water put on the ice sheet will only delay
sea-level rise. Here we estimate the associated delay time and its
dependence on the distance from the coast and the application rate.
Ice sheet simulations
Using the Parallel Ice Sheet Model (PISM) (Bueler and Brown, 2009;
Winkelmann et al., 2011) we estimate the ice sheet's response to different
ice addition scenarios. To this end we ran the model to equilibrium in a
100 ka spin-up under constant present-day atmospheric and oceanic boundary
conditions. Surface air temperature (Comiso, 2000) and mass balance (Arthern
et al., 2006) are taken from observations made available in the ALBMAP data
set (Le Brocq et al., 2010). We apply sub-shelf basal melting and refreezing
rates from a 20th century simulation of the Finite Element Southern
Ocean Model (FESOM) (Timmermann et al., 2012). The modeled equilibrium ice
sheet state compares well to the currently observed ice sheet in terms of
surface elevation and grounding line position (supplementary Fig. S2) and
ice velocities (Supplement Figs. S3 and S4). Total modeled ice volume
deviates less than 0.5 % from the observed state (Fretwell et al., 2013).
In our forcing simulations we disturb this equilibrium state with
100-year-long
pulses of increased surface mass balance (SMB) in selected bands
(see Fig. 1). The added surface mass compensates for a 1, 3, and 10 mm yr-1
sea-level rise (ΔSMB = rate of sea-level rise ⋅ global ocean area/area of mass addition). The maximum sea-level drop is therefore 1 m. We construct the bands of surface mass addition
by drawing lines with distances of 200, 300, 400, 500, 600, 700, and 800 km
from the coast, and we use these as the center lines of 200 km wide bands. The
bands are limited to longitudes between 20∘ W and 165∘ E
to only cover the East Antarctic ice sheet because of the currently observed
imbalance in West Antarctica. The rate is applied for 100 years and then set
to zero in order to better estimate the sea-level delay time. Whether the
pumping should be limited needs to be decided by society if such a measure is
ever to be implemented.
By adding the ice to the surface of an equilibrium simulation we do not
account for any drift that might have been caused by previous variations in
the boundary conditions, such as the last deglaciation, the medieval warm
period, or anthropogenic warming. Although a possible drift within the
present-day ice sheet could potentially alter the ice export as reported
here, it can be assumed that the drift is negligible at distances of several
hundred kilometers away from the coast.
To represent the large-scale dynamics reasonably well, we use a 12 km
horizontal resolution for the ice sheet simulations. Our hybrid shallow
approximation ensures stress transmission across the grounding line and a
smooth transition between regimes of fast-flowing, sliding, and slowly
deforming bedrock-frozen ice. The grounding line can freely evolve even at
lower resolution due to a local interpolation of the grounding-line
position, which affects the basal friction and a new driving stress scheme
at the grounding line. The interpolation leads to reversible grounding-line
dynamics consistent with full-Stokes simulations at high resolution
(Feldmann et al., 2014). Although the model is capable of simulating the
coastal dynamics of the ice sheet within limitations, it is important to
note that the results obtained here are predominantly dependent on the ice
flow representation in the interior of the ice sheet, for which large-scale
continental ice-sheet models like PISM and others (Bindschadler et al.,
2013; Calov et al., 2010; Greve et al., 2011; Huybrechts and De Wolde, 1999;
Pollard and Deconto, 2009; Swingedouw et al., 2008) have been designed.
In the standard simulation we do not alter the surface air temperature
during mass addition. To estimate the effect of surface warming due to the
latent heat release of the seawater, we conduct a second set of simulations
that keeps the surface temperature at the freezing point of seawater (-1.9 ∘C) during surface mass addition. This imitates the situation in
which the ice surface remains in a mixed state of ice and water. Since
Antarctica's inland-surface temperatures are far below zero, this
constitutes a strong warming signal that diffuses down into the ice body and
causes ice to soften and flow faster. The maximum injection of latent heat
occurs for the 10 mm yr-1 sea-level-mitigation scenario and the 800 km
band, which has the smallest area. The corresponding addition of 3.2 m yr-1
liquid seawater is equivalent to a latent heat injection of about
35 Wm-2. A warming from -20 to -1.9 ∘C would
increase the long-wave radiative loss to the atmosphere by 70 Wm-2,
according to the Stefan–Boltzmann law, assuming an emissivity of 0.95. If
open-water areas are sustained on the ice sheet, a sensible-heat-dominated
loss can remove heat at a rate of 100 Wm-2 or more as observed in ocean
polynyas (Launiainen and Vihma, 1994). The maximum rate of latent heat
injection of 35 Wm-2 is much smaller than the potential of the
atmosphere to remove the heat. Thus, keeping surface ice temperatures at
freezing point underestimates the atmospheric heat loss so that the
simulations provide an upper bound for the induced warming of ice.
Additional ice discharge compared to mass addition for
different distances from the coast. The fraction of the added ice that is
lost again to the ocean as a function of distance from the coast at which
the additional ice was placed for the simulations without (left panel) and
with (right panel) surface warming. Colors indicate the magnitude of the
mass addition equivalent to 1, 3, and 10 mm yr-1 sea-level rise
mitigation. Markers correspond to the different relaxation times: end of
pulse, 500 years, and 1000 years after the pulse of mass addition ended.
Difference in ice thickness compared to the initial state.
Ice thickness gain at the end of the 100-year-long mass addition (upper
panels) and 1000 years after the forcing ended (lower panels). The
close-to-coast simulation (left panels) has lost most of the added ice to
the ocean after 1000 years while there is a broad ice gain in the 800 km
simulation (right panels). Figures are shown for the strongest scenario of
10 mm yr-1 of sea-level mitigation and without accounting for
latent-heat release.
Results
The ratio of the volume added during the first 100 years and the volume that
is lost again after 1000 years depends strongly on the distance from the
coast (Figs. 2 and 3). Consistent with earlier studies (Huybrechts and
De Wolde, 1999; Winkelmann et al., 2012), an ice volume equivalent to 10–15 %
of the added ice is already lost at the end of the forcing period, when the
ice is added at a distance of 200 km from the coastline, while the sea-level
contribution is strongly delayed at a distance above 500 km from the coast
(Fig. 2). In order to minimize the return flow of the ice into the ocean,
the specific positioning of the ice addition could be varied spatially
making use of slow-moving ice regions. Here we apply a simplified spatial
distribution in order to demonstrate the main process and enable a
conceptual analysis of the simulations.
The time after which the equivalent of a certain equivalent of the added ice
has been discharged into the ocean is much shorter than would be expected
from a mere advection of the added ice mass with the surface velocities of
the ice sheet (Fig. S5 of the Supplement). This is because the ice thickness anomaly
creates an imbalance between the driving stress and the viscous ice flow. As
a consequence, the ice transport occurs in waves from the strip of
perturbation to the coast (Winkelmann et al., 2012) (Fig. 1), where the ice
discharged to the ocean is not the same ice that was added to the ice sheet
earlier. Even though the ice wave also travels partially inland, it is
possible that more ice is transported out of the continent than was
initially added. However, this ice-loss exceedance occurs only several
millennia after the perturbation (Fig. S5 in the Supplement). Whether it is directly
related to the perturbation or a manifestation of a localized multistability
of the ice dynamics is difficult to identify, because the differences
between the initial and final ice topography are within the uncertainty
range of the model performance.
For perturbation areas far from the coast, the discharge rates in the
sensitivity simulation accounting for latent heat release (Fig. 4, thin
lines) are nearly identical to the response without warming (Fig. 4, thick
lines) on the millennial timescale considered. Within the first millennium,
the latent heat release of freezing seawater only alters the discharge when
placed near the coast. After 2000 years, the additional warming can induce a
discharge exceeding 100 % of the added ice in the 200 km simulations
(Fig. S1 in the Supplement).
Discussion
All scenarios considered here assume that the only perturbation of the ice
sheet is the addition of ice mass in bands of the interior of East
Antarctica. At the same time, Antarctica's coastal regions are out of
balance in a number of regions predominantly in West Antarctica but also in East
Antarctica. In this study it is assumed that the addition of ice in the
interior will not interfere with the imbalance at the coast. This might be
an over-simplification, but currently available modeling studies (Favier et
al., 2014; Joughin et al., 2014; Mengel and Levermann, 2014) indicate that
perturbations near the coast will not reach as far inland over time periods
of several centuries. However, a possible interference between the interior
of the ice sheet and its coastal regions needs further investigation,
possibly with higher-resolution regional ice sheet models.
It is possible that ice-dynamic effects, which are not included in these
simulations (such as ice fractures or basal sliding conditions), alter the
results quantitatively. However, the shallow-ice approximation that
dominates the ice dynamics in the model in the interior of Antarctica has
been shown to represent the interior ice sheet flow on multi-centennial and
longer timescales (Greve and Blatter, 2009).
Response of the Antarctic ice sheet to a 100-year surface-mass
addition. Ice volume gain and relaxation (upper panels) and equivalent loss
of the added snow (lower panels) for the close-to-coast (200 km, left
panels) and farthest-inland (800 km, right panels) simulations for the 1, 3,
and 10 mm yr-1 mitigation cases (grey, light blue, and dark blue
colors). Thick lines indicate simulations without surface warming, thin
lines with surface temperature held at seawater freezing point during the
forcing (upper bound). Vertical lines indicate the pulse interval, and
horizontal lines in lower left panel indicate the total ice volume added.
We assume that it would be best to add the additional ice in the form of
snow as opposed to adding it as water which will then freeze. In this
context it has to be noted that the additional ice that is added to the ice
sheet is made of seawater and thereby will have salinity. The rheological
effects of a “salt-ice” layer within an ice sheet are currently unknown
and need further investigation. While initially the “salt ice” will be at
the surface of the ice sheet, the dynamic effect will be dominated by its
gravitational effect, which is covered by the modeled ice dynamics modeled.
However, since snow is falling onto the “salt-ice” layer, this layer's
rheology will become relevant for the ice dynamics. At current and future
snowfall rates (Frieler et al., 2015) this will take several centuries.
The simulations conducted here suggest that pumping ocean water onto the
interior of the Antarctic ice sheet can impose a significant delay of future
sea-level rise. However, as an option to mitigate the sea-level rise to
which we are already committed, a substantial energy problem must be
overcome. Solely in terms of throughput, mitigating sea-level rise of 3 mm yr-1
would require 90 of the largest pump stations currently under
construction in New Orleans, each assumed to pump ∼ 360 m3 s-1,
which corresponds to ∼ 11 × 109 m3 yr-1
(Alyeska Pipeline Service Company, 2013). The
height of the ice sheet of about 4000 m means that it would require a
constant power of 1275 GW to elevate the potential energy of the associated
ocean water. This is equivalent to ∼ 7 % of the global
primary energy supply of the year 2012 (International Energy Agency, 2014).
The power required for the actual pumping may even be higher and reach 2300 GW
under optimistic assumptions (see Sect. S1 in the Supplement). It will
have to be generated by renewable resources to avoid the additional climate
change and sea-level rise associated with fossil fuels. The Antarctic
continent is windy enough to support such pumping using wind energy, with
around 16.7 TW available in a 200 km wide band along the coast of East
Antarctica (Archer and Jacobson, 2005) (see Sect. S2 in the Supplement). Around
8 % of that energy would need to be extracted to compensate for the potential
energy increase of the pumped water alone, which is equivalent to 850 000
wind-energy plants of 1.5 MW, running on full capacity
The scope of such a project is unprecedented and would require major
technical innovations, if possible at all. Therefore, costs cannot be
reliably estimated. Based on simple upscaling of the costs of the Trans-Alaska Pipeline with height, length, and throughput (see Sect. S1
in the Supplement), the costs will be orders of magnitude higher than the costs associated
with local adaptation measures (Hinkel et al., 2014). However, it is
important to note that in this study on sea-level adaptation, protection is
only installed if considered economically favorable. In contrast, storing
water on the Antarctic ice sheet would offer general protection for entire
coastlines and poor regions that would otherwise be left unprotected. The
associated investment could change the mitigation costs by significantly
increasing the demand (thereby technical progress) for renewable energies.
By generating an additional demand for renewable energies of
the order of 10 % of the global energy supply, this approach offers a link
between the mitigation and adaptation problem of climate change.
This study must be complemented by investigations on possible consequences
of the procedure. To name just a few, it is likely that construction of the
pipelines, pump stations, the energy generation, and the water extraction
will induce disturbances in the coastal ecosystems. It should also be
investigated how the water extraction will influence the small- and
large-scale ocean circulation. The ice-rheological changes induced by the
addition of salt water should be investigated together with potential
effects on the basal conditions of the ice.
The heat released from freezing and the pumping process itself is of the
order of 10 TW (latent heat) +1 TW (heat released from pumping). This
corresponds to about 10 % of the maximum increase in latent heat transport
in high northern latitudes under an SRES A1B transient simulation (Held and
Soden, 2006). The latent heat release is considered a major contribution to
the Arctic amplification of global warming. From this perspective, the
pumping-induced energy over Antarctica is not negligible but significantly
smaller than the warming-induced latent heat released in northern high
latitudes. Potential consequences for the atmospheric and oceanic
circulation need to be further explored.
Ethical considerations
The Protocol on Environmental Protection to the Antarctic Treaty
(Secretariat of the Antarctic Treaty, 1991) has declared a clear intention to
minimize human influences on the Antarctic continent. The signing parties
are “Convinced that the development of a comprehensive regime for the
protection of the Antarctic environment and dependent and associated
ecosystems is in the interest of mankind as a whole” and “commit
themselves to the comprehensive protection of the Antarctic environment and
dependent and associated ecosystems and hereby designate Antarctica as a
natural reserve, devoted to peace and science.” The measures proposed here
(if at all feasible) mean a major human intervention, putting the ecosystems
of Antarctica and of the surrounding ocean at a high risk. Thus, the
protection of global coastlines and associated natural and human would not
only have to be weighted against the enormous efforts but also against the
loss of Antarctica as a unique natural reserve.
Storing water on the Antarctic continent also raises questions of
inter-generational justice. When pumping is stopped, the additional
discharge from Antarctica will increase the rate of sea-level rise even
beyond the warming-induced rate. In this way, the approach presented here
means taking out a loan on Antarctica that future generations will have to
pay back. In all simulations considered here, pumping ceases after 100 years: it is investigated as an option to delay part of the sea-level
rise we are already committed to, but not as a permanent measure that may
induce further responses of the ice sheet not captured here.
If at all feasible, the considered scenarios do not at all represent an
alternative to the mitigation of carbon emissions, because the method does
not address any climate-change impact other than sea-level rise.
Furthermore, unmitigated emission might induce a sea-level rise of 10 mm yr-1 and beyond, which increases the impacts on Antarctica and the
burden for future generations when mitigated by pumping of ocean waters.
And, after pumping is stopped, sea level will accelerate quickly towards the
rate that corresponds to the warming level, plus that induced by the
addition of ice to Antarctica.
Although a potential way to delay the committed sea-level rise from an ice-dynamic perspective, whether it is at all possible to locally generate the
required energy poses an open engineering challenge.
The Supplement related to this article is available online at doi:10.5194/esd-7-203-2016-supplement.
Acknowledgements
We thank Hans-Joachim Schellnhuber for very fruitful discussions related to
the development of this article, particularly regarding the
problem of the energy requirements. We thank Hagen Koch from the Potsdam
Institute for Climate Impact Research for the support for the estimation of
the actual pumping energy that may be required in comparison to the pure
consideration of the potential energy.Edited by: I. Didenkulova
ReferencesAlyeska Pipeline Service Company: FACTS, Trans Alaska Pipeline System,
Anchorage, Alaska, available from: www.alyeska-pipe.com (last access: May 2015), 2013.Archer, C. L. and Jacobson, M. Z.: Evaluation of global wind power, J.
Geophys. Res., 110(, 1–20, 10.1029/2004JD005462, 2005.Arthern, R. J., Winebrenner, D. P., and Vaughan, D. G.: Antarctic snow
accumulation mapped using polarization of 4.3-cm wavelength microwave
emission, J. Geophys. Res. Atmos., 111, D06107, 10.1029/2004JD005667, 2006.Bamber, J. L., Riva, R. E. M., Vermeersen, B. L. A., and LeBrocq, A. M.:
Reassessment of the Potential Sea-Level Rise from a Collapse of the West
Antarctic Ice Sheet, Science, 324, 901–903,
10.1126/science.1169335, 2009.Bindschadler, R. a., Nowicki, S., Abe-OUCHI, A., Aschwanden, A., Choi, H.,
Fastook, J., Granzow, G., Greve, R., Gutowski, G., Herzfeld, U., Jackson,
C., Johnson, J., Khroulev, C., Levermann, A., Lipscomb, W. H., Martin, M.
a., Morlighem, M., Parizek, B. R., Pollard, D., Price, S. F., Ren, D.,
Saito, F., Sato, T., Seddik, H., Seroussi, H., Takahashi, K., Walker, R., and
Wang, W. L.: Ice-sheet model sensitivities to environmental forcing and
their use in projecting future sea level (the SeaRISE project), J. Glaciol.,
59, 195–224, 10.3189/2013JoG12J125, 2013.Bueler, E. and Brown, J.: The shallow shelf approximation as a sliding law
in a thermomechanically coupled ice sheet model, J. Geophys. Res., 114,
F03008, 10.1029/2008JF001179, 2009.
Calov, R., Greve, R., Abe-ouchi, A., Bueler, E., Huybrechts, P., Johnson, J.
V, Pattyn, F., Pollard, D., Ritz, C., Saito, F., and Tarasov, L.: Results
from the Ice-Sheet Model Intercomparison Project – Heinrich Event
INtercOmparison ( ISMIP HEINO), 56, 371–383, 2010.Cazenave, A. and Dieng, H.: The rate of sea-level rise, Nat. Clim. Change,
4, 358–361, 10.1038/NCLIMATE2159, 2014.
Comiso, J. C.: Variability and trends in Antarctic surface temperatures from
in situ and satellite infrared measurements, J. Clim., 13, 1674–1696,
2000.Favier, L., Durand, G., Cornford, S. L., Gudmundsson, G. H., Gagliardini,
O., Gillet-Chaulet, F., Zwinger, T., Payne, A. J., and Le Brocq, A. M.:
Retreat of Pine Island Glacier controlled by marine ice-sheet instability,
Nat. Clim. Change, 4, 117–121, 10.1038/nclimate2094, 2014.Feldmann, J., Albrecht, T., Khroulev, C., Pattyn, F., and Levermann, A.:
Resolution-dependent performance of grounding line motion in a shallow model
compared with a full-Stokes model according to the MISMIP3d intercomparison,
J. Glaciol., 60, 353–360, 10.3189/2014JoG13J093, 2014.Fretwell, P., Pritchard, H. D., Vaughan, D. G., Bamber, J. L., Barrand, N.
E., Bell, R., Bianchi, C., Bingham, R. G., Blankenship, D. D., Casassa, G.,
Catania, G., Callens, D., Conway, H., Cook, A. J., Corr, H. F. J., Damaske,
D., Damm, V., Ferraccioli, F., Forsberg, R., Fujita, S., Gim, Y., Gogineni,
P., Griggs, J. A., Hindmarsh, R. C. A., Holmlund, P., Holt, J. W., Jacobel,
R. W., Jenkins, A., Jokat, W., Jordan, T., King, E. C., Kohler, J., Krabill,
W., Riger-Kusk, M., Langley, K. A., Leitchenkov, G., Leuschen, C., Luyendyk,
B. P., Matsuoka, K., Mouginot, J., Nitsche, F. O., Nogi, Y., Nost, O. A.,
Popov, S. V., Rignot, E., Rippin, D. M., Rivera, A., Roberts, J., Ross, N.,
Siegert, M. J., Smith, A. M., Steinhage, D., Studinger, M., Sun, B., Tinto,
B. K., Welch, B. C., Wilson, D., Young, D. A., Xiangbin, C., and Zirizzotti,
A.: Bedmap2: improved ice bed, surface and thickness datasets for
Antarctica, The Cryosphere, 7, 375–393, 10.5194/tc-7-375-2013, 2013.Frieler, K., Clark, P. U., He, F., Buizert, C., Reese, R., Ligtenberg, S. R.
M., van den Broeke, M. R., Winkelmann, R., and Levermann, A.: Consistent
evidence of increasing Antarctic accumulation with warming, Nat. Clim.
Chang., 1–5, 10.1038/nclimate2574, 2015.Gillett, N. P., Arora, V. K., Zickfeld, K.,
Marshall, S. J., and Merryfield, W. J.:
Ongoing climate change following a complete cessation of carbon dioxide
emissions, Nat. Geosci., 4, 83–87, 10.1038/ngeo1047, 2011.
Greve, R. and Blatter, H.: Dynamics of ice sheets and glaciers,
Springer Science & Business Media, 61–109, 2009.Greve, R., Saito, F., and Abe-Ouchi, A.: Initial results of the SeaRISE
numerical experiments with the models SICOPOLIS and IcIES for the Greenland
ice sheet, Ann. Glaciol., 52, 23–30, 10.3189/172756411797252068,
2011.Held, I. M. and Soden, B. J.: Robust responses of the hydrological cycle to
global warming, J. Clim., 19, 5686–5699,
10.1175/2010JCLI4045.1, 2006.
Hinkel, J., Lincke, D., Vafeidis, A. T., Perrette, M., Nicholls, R. J., Tol,
R. S. J., Marzeion, B., Fettweis, X., Ionescu, C., and Levermann, A.: Coastal
flood damages and adaptation costs under 21st century sea-level rise, PNAS,
111, 3292–3297, 2014.
Huybrechts, P. and De Wolde, J.: The dynamic response of the Greenland and
Antarctic ice sheets to multiple-century climatic warming, J. Clim., 12,
2169–2188, 1999.International Energy Agency: Key World Energy Statistics, Paris, France,
available from:
http://www.iea.org/publications/freepublications/publication/KeyWorld2014.pdf,
(last access: May 2015), 2014.
IPCC: Climate Change 2013: The Physical Science Basis. Contribution of
Working Group I to the Fifth Assessment Report of the Intergovernmental
Panel on Climate Change, edited by: Stocker, T. F., Qin, D., Plattner, G.-K.,
Tignor, M., Allen, S. K., Boschung, J., Nauels, A., Xia, Y., Bex, V., and
Midgley, P. M., Cambridge University Press, Cambridge, UK and New York,
NY, USA, 2013.Joughin, I., Smith, B. E., and Medley, B.: Marine ice sheet collapse
potentially under way for the Thwaites Glacier Basin, West Antarctica.,
Science, 344, 735–738, 10.1126/science.1249055, 2014.
Launiainen, J. and Vihma, T.: On the Surface Heat Fluxes in the Weddell Sea,
in The Polar Oceans and Their Role in Shaping the Global Environment, pp.
399–419, American Geophysical Union, Washington, D.C., 1994.Le Brocq, A. M., Payne, A. J., and Vieli, A.: An improved Antarctic dataset
for high resolution numerical ice sheet models (ALBMAP v1), Earth Syst. Sci.
Data, 2, 247–260, 10.5194/essd-2-247-2010, 2010.Levermann, A., Clark, P. U., Marzeion, B., Milne, G. a., Pollard, D., Radic,
V., and Robinson, A.: The multimillennial sea-level commitment of global
warming, P. Natl. Acad. Sci., 110, 13745–13750, 10.1073/pnas.1219414110, 2013.
Meehl, G. A., Washington, W. M., Collins, W. D., Arblaster, J. M., Hu, A.,
Buja, L. E., Strand, W. G., and Teng, H.: How Much More Global Warming and
Sea Level Rise?, Science, 307, 1769–1772, 2005.Mengel, M. and Levermann, A.: Ice plug prevents irreversible discharge from
East Antarctica, Nat. Clim. Chang., 4, 451–455,
10.1038/nclimate2226, 2014.
Pollard, D. and Deconto, R. M.: Modelling West Antarctic ice
sheet growth and collapse through the past five million years, Nature, 458,
329–332, 2009.Rignot, E., Mouginot, J., and Scheuchl, B.: Ice Flow of the Antarctic Ice
Sheet, Science, 333, 1427–1430, 10.1126/science.1208336,
2011.Rignot, E., Mouginot, J., Morlighem, M., Seroussi, H., and Scheuchl, B.:
Widespread, rapid grounding line retreat of Pine Island,
Thwaites, Smith, and Kohler glaciers, West Antarctica, 1–8,
10.1002/2014GL060140.Received, 2014.
Rohling, E. J., Grant, K., Hemleben, C., Siddall, M., Hoogakker, B. A. A.,
Bolshaw, M., and Kucera, M.: High rates of sea-level rise during the last
interglacial period, Nat. Geosci, 1, 38–42, 2008.Rohling, E. J., Haigh, I. D., Foster, G. L., Roberts, A. P., and Grant, K.
M.: A geological perspective on potential future sea-level rise., Sci. Rep.,
3, 3461, 10.1038/srep03461, 2013.Secretariat of the Antarctic Treaty: Protocol on Environmental Protection to
the Antarctic Treaty, available from:
http://www.ats.aq/documents/recatt/Att006_ e.pdf (last access: January 2016), 1991.Shepherd, A., Ivins, E. R., Geruo, A., Barletta, V. R., Bentley, M. J.,
Bettadpur, S., Briggs, K. H., Bromwich, D. H., Forsberg, R., Galin, N.,
Horwath, M., Jacobs, S., Joughin, I., King, M. a., Lenaerts, J. T. M., Li,
J., Ligtenberg, S. R. M., Luckman, A., Luthcke, S. B., McMillan, M.,
Meister, R., Milne, G., Mouginot, J., Muir, A., Nicolas, J. P., Paden, J.,
Payne, a. J., Pritchard, H., Rignot, E., Rott, H., Sorensen, L. S., Scambos,
T. a., Scheuchl, B., Schrama, E. J. O., Smith, B., Sundal, a. V., van
Angelen, J. H., van de Berg, W. J., van den Broeke, M. R., Vaughan, D. G.,
Velicogna, I., Wahr, J., Whitehouse, P. L., Wingham, D. J., Yi, D., Young,
D., and Zwally, H. J.: A Reconciled Estimate of Ice-Sheet Mass Balance,
Science, 338, 1183–1189, 10.1126/science.1228102, 2012.
Solomon, S., Plattner, G.-K., Knutti, R., and Friedlingstein, P.:
Irreversible climate change due to carbon dioxide emissions, P. Natl.
Acad. Sci., 106, 1704–1709, 10.1073/pnas.0812721106, 2009.
Strauss, B., Tebaldi, C., and Kulp, S.: Florida And The Surging Sea – A
Vulnerability Assessment With Projections For Sea Level Rise And Coastal
Flood Risk, Princeton, NJ, USA, 1–59, 2014.Swingedouw, D., Fichefet, T., Hybrechts, P., Goosse, H., Driesschaert, E.,
and Loutre, M. F.: Antarctic ice-sheet melting provides negative feedbacks
on future climate warming, Geophys. Res. Lett., 35, L17705,
10.1029/2008GL034410, 2008.Timmermann, R., Wang, Q., and Hellmer, H. H.: Ice-shelf basal melting in a
global finite-element sea-ice/ice-shelf/ocean model, Ann. Glaciol., 53,
303–314, 10.3189/2012AoG60A156, 2012.Van Vuuren, D. P., Stehfest, E., den Elzen, M. G. J., Kram, T., van Vliet,
J., Deetman, S., Isaac, M., Klein Goldewijk, K., Hof, A., Mendoza Beltran,
A., Oostenrijk, R., and van Ruijven, B.: RCP2.6: exploring the possibility to
keep global mean temperature increase below 2 ∘C, Clim. Change,
109, 95–116, 10.1007/s10584-011-0152-3, 2011.Wigley, T. M. L.: The climate change commitment., Science, 307,
1766–1769, 10.1126/science.1103934, 2005.Winkelmann, R., Martin, M. A., Haseloff, M., Albrecht, T., Bueler, E.,
Khroulev, C., and Levermann, A.: The Potsdam Parallel Ice Sheet Model
(PISM-PIK) Part 1: Model description, Cryosph., 5, 715–726,
10.5194/tc-5-715-2011, 2011.Winkelmann, R., Levermann, A., Martin, M. A., and Frieler, K.: Increased
future ice discharge from Antarctica owing to higher snowfall, Nature,
492, 239–242, 10.1038/nature11616, 2012.