4.2 Greenland Ice Sheet (GrIS)
Figure 2 indicates a near-linear sea level trend for the GrIS versus
average temperature (2051-2100: 0.8±0.2 mm/yr/K), which, as discussed
below, is likely a result of mass loss being dominated by surface mass
balance (SMB) over ice dynamics in the models. In a subset of ISMIP6
model simulations it is possible to separate the role of these two
components of mass loss. We do this using the results presented in
(Payne et al., 2021), and find that the dynamic component of mass loss
is both limited and insensitive to average temperature, whereas the SMB
component has a positive linear relationship with GMST (Fig. 3). As a
result, SMB becomes an increasingly dominant component of mass loss
under SSP5-8.5, from being approximately equal to the dynamic component
in the earlier part of the century, to being a factor of 2-3 greater in
the second half. The ISMIP6 simulations apply a SMB-elevation feedback,
such that melt increases as elevation decreases (Nowicki et al., 2020).
This acts to enhance SMB losses with surface lowering, contributing to
the increasing dominance of this component over the century.