The diurnal Energy Balance Model (dEBM): a convenient surface mass balance solution for ice sheets in Earth system modeling

Uta Krebs-Kanzow,Christian B Rodehacke,Paul Gierz,Hu Yang,Shan Xu,Gerrit Lohmann

doi:10.5194/tc-15-2295-2021

Abstract

Abstract. The surface mass balance scheme dEBM (diurnal Energy Balance Model) provides a novel interface between the atmosphere and land ice for Earth system modeling, which is based on the energy balance of glaciated surfaces. In contrast to empirical schemes, dEBM accounts for changes in the Earth’s orbit and atmospheric composition. The scheme only requires monthly atmospheric forcing (precipitation, temperature, shortwave and longwave radiation, and cloud cover). It is also computationally inexpensive, which makes it particularly suitable to investigate the ice sheets' response to long-term climate change. After calibration and validation, we analyze the surface mass balance of the Greenland Ice Sheet (GrIS) based on climate simulations representing two warm climate states: a simulation of the mid-Holocene (approximately 6000 years before present) and a climate projection based on an extreme emission scenario which extends to the year 2100. The former period features an intensified summer insolation while the 21st century is characterized by reduced outgoing longwave radiation. Specifically, we investigate whether the temperature–melt relationship, as used in empirical temperature-index methods, remains stable under changing insolation and atmospheric composition. Our results indicate that the temperature–melt relation is sensitive to changes in insolation on orbital timescales but remains mostly invariant under the projected warming climate of the 21st century.

Highlights

At the surface, land ice gains mass through snow accumulation and loses mass through meltwater runoff and sublimation
Experiments dEBMMAR,ERA and MARERA generally agree with respect to the evolution of integral, annual surface mass balance (SMB) (Fig. 6) with a root-mean-square error of 27 Gt
We evaluate the spatial representation of components of the SMB by comparing experiment dEBMMAR,ERA to the MARERA simulation for the period 1980 to 1999

Summary

Introduction

Land ice gains mass through snow accumulation and loses mass through meltwater runoff and sublimation. The total surface mass balance (SMB) of a healthy ice sheet (i.e., not in the process of disintegration) needs to be positive in the long term, in order to compensate for mass loss at the base, the peripheral surface and the interfaces to oceans or proglacial lakes. Responding directly to climate change, the SMB substantially influences the waxing and waning of large-scale ice sheets in the course of glacial–interglacial cycles on timescales of tens of thousands to 100 000 years (e.g., Hays et al, 1976; Huybers, 2006). The Greenland Ice Sheet is presently shrinking, and surface processes are predicted to amplify Greenland ice loss in the future (Oppenheimer et al, 2021)

Methods

Results

Conclusion