Abstract
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.
Highlights
Since the last decade of the 20th century, the Greenland ice sheet (GrIS) has lost mass with accelerating speed (e. g. Helm et al, 2014; Talpe et al, 2017), shaping one of the most important contributors to sea level rise (Shepherd et al, 2012; Rietbroek et al, 2016; Forsberg et al, 2017)
We introduce the coupled model of the Greenland glacial system IGLOO 1.0, including the polythermal ice sheet model SICOPOLIS with hybrid dynamics, the model of basal hydrology HYDRO and a parameterization of submarine melt for marine-terminated outlet glaciers
We investigate the response of GrIS outlet glaciers to global warming with IGLOO in a separate paper (Beckmann et al, 2018a)
Summary
Since the last decade of the 20th century, the Greenland ice sheet (GrIS) has lost mass with accelerating speed (e. g. Helm et al, 2014; Talpe et al, 2017), shaping one of the most important contributors to sea level rise (Shepherd et al, 2012; Rietbroek et al, 2016; Forsberg et al, 2017). G. Helm et al, 2014; Talpe et al, 2017), shaping one of the most important contributors to sea level rise (Shepherd et al, 2012; Rietbroek et al, 2016; Forsberg et al, 2017). This mass loss is driven by decreasing surface mass balance (SMB), and by increasing ice discharge via outlet glaciers. Understanding the processes determining the GrIS ice loss is vital for estimates of its contribution to future sea level rise.
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