Abstract. We introduce the coupled model of the Greenland glacial system IGLOO 1.0,
including the polythermal ice sheet model SICOPOLIS (version 3.3) with hybrid
dynamics, the model of basal hydrology HYDRO and a parameterization of
submarine melt for marine-terminated outlet glaciers. The aim of this glacial
system model is to gain a better understanding of the processes important for
the future contribution of the Greenland ice sheet to sea level rise under
future climate change scenarios. The ice sheet is initialized via a
relaxation towards observed surface elevation, imposing the palaeo-surface
temperature over the last glacial cycle. As a present-day reference, we use
the 1961–1990 standard climatology derived from simulations of the regional
atmosphere model MAR with ERA reanalysis boundary conditions. For the
palaeo-part of the spin-up, we add the temperature anomaly derived from the
GRIP ice core to the years 1961–1990 average surface temperature field. For
our projections, we apply surface temperature and surface mass balance
anomalies derived from RCP 4.5 and RCP 8.5 scenarios created by MAR with
boundary conditions from simulations with three CMIP5 models. The hybrid ice
sheet model is fully coupled with the model of basal hydrology. With this
model and the MAR scenarios, we perform simulations to estimate the
contribution of the Greenland ice sheet to future sea level rise until the
end of the 21st and 23rd centuries. Further on, the impact of
elevation–surface mass balance feedback, introduced via the MAR data, on
future sea level rise is inspected. In our projections, we found the
Greenland ice sheet to contribute between 1.9 and
13.0 cm to global sea level rise until the year 2100 and between 3.5 and 76.4 cm until the year
2300, including our simulated additional sea level rise due to
elevation–surface mass balance feedback. Translated into additional sea
level rise, the strength of this feedback in the year 2100 varies from 0.4 to
1.7 cm, and in the year 2300 it ranges from 1.7 to 21.8 cm. Additionally,
taking the Helheim and Store glaciers as examples, we investigate the role of
ocean warming and surface runoff
change for the melting of outlet glaciers.
It shows that ocean temperature and subglacial discharge are about equally
important for the melting of the examined outlet glaciers.
Mathematical Analysis of a Stefan Problem with Dirichlet–Signorini Boundary Conditions Appearing in Polythermic Ice Sheet Modeling