The effect of overshooting 1.5 °C global warming on the mass loss of the Greenland ice sheet
<p>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...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-10-01
|
| Series: | Earth System Dynamics |
| Online Access: | https://www.earth-syst-dynam.net/9/1169/2018/esd-9-1169-2018.pdf |
| Summary: | <p>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 (<i>T</i><sub>s</sub>) 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.</p> |
|---|---|
| ISSN: | 2190-4979 2190-4987 |