Abstract. Understanding the behavior of the Greenland ice sheet in a warmer climate,
and particularly its surface mass balance (SMB), is important for assessing
Greenland's potential contribution to future sea level rise. The Eemian
interglacial period, the most recent warmer-than-present period in Earth's
history approximately 125 000 years ago, provides an analogue for a warm
summer climate over Greenland. The Eemian is characterized by a positive
Northern Hemisphere summer insolation anomaly, which complicates Eemian SMB
calculations based on positive degree day estimates. In this study, we use
Eemian global and regional climate simulations in combination with three
types of SMB models – a simple positive degree day, an intermediate
complexity, and a full surface energy balance model – to evaluate the
importance of regional climate and model complexity for estimates of
Greenland's SMB. We find that all SMB
models perform well under the relatively cool pre-industrial and late Eemian.
For the relatively warm early Eemian, the differences between SMB models are
large, which is associated with whether insolation is included in the
respective models. For all simulated time slices, there is a systematic
difference between globally and regionally forced SMB models, due to the
different representation of the regional climate over Greenland. We conclude
that both the resolution of the simulated climate as well as the method used
to estimate the SMB are important for an accurate simulation of Greenland's
SMB. Whether model resolution or the SMB method is most important depends on
the climate state and in particular the prevailing insolation pattern. We
suggest that future Eemian climate model intercomparison studies should
include SMB estimates and a scheme to capture SMB uncertainties.