Abstract
Abstract. This study presents simulations of Greenland surface melt for the Eemian interglacial period (∼130 000 to 115 000 years ago) derived from regional climate simulations with a coupled surface energy balance model. Surface melt is of high relevance due to its potential effect on ice core observations, e.g., lowering the preserved total air content (TAC) used to infer past surface elevation. An investigation of surface melt is particularly interesting for warm periods with high surface melt, such as the Eemian interglacial period. Furthermore, Eemian ice is the deepest and most compressed ice preserved on Greenland, resulting in our inability to identify melt layers visually. Therefore, simulating Eemian melt rates and associated melt layers is beneficial to improve the reconstruction of past surface elevation. Estimated TAC, based on simulated melt during the Eemian, could explain the lower TAC observations. The simulations show Eemian surface melt at all deep Greenland ice core locations and an average of up to ∼30 melt days per year at Dye-3, corresponding to more than 600 mm water equivalent (w.e.) of annual melt. For higher ice sheet locations, between 60 and 150 mmw.e.yr-1 on average are simulated. At the summit of Greenland, this yields a refreezing ratio of more than 25 % of the annual accumulation. As a consequence, high melt rates during warm periods should be considered when interpreting Greenland TAC fluctuations as surface elevation changes. In addition to estimating the influence of melt on past TAC in ice cores, the simulated surface melt could potentially be used to identify coring locations where Greenland ice is best preserved.
Highlights
The Eemian interglacial period (∼ 130 000 to 115 000 years ago; hereafter ∼ 130 to 115 ka) was the last period with a warmer-than-present summer climate on Greenland (CAPE Last Interglacial Project Members, 2006; Otto-Bliesner et al, 2013; Capron et al, 2014)
The results indicate that Greenland ice core records from warm periods, such as the Eemian interglacial period, might be more affected by surface melt than previously considered (Sect. 5)
Using regional climate simulations, this study shows surface melt at all Greenland ice core locations during the Eemian interglacial period (e.g., GRIP, GISP2: ∼ 60 mm w.e. yr−1; NGRIP: ∼ 150 mm w.e. yr−1)
Summary
The Eemian interglacial period (∼ 130 000 to 115 000 years ago; hereafter ∼ 130 to 115 ka) was the last period with a warmer-than-present summer climate on Greenland (CAPE Last Interglacial Project Members, 2006; Otto-Bliesner et al, 2013; Capron et al, 2014). Favorable orbital parameters (higher obliquity and eccentricity compared to today) during the early Eemian period caused a positive northern summer insolation anomaly (and negative winter anomaly) at high latitudes, which led to a stronger seasonality (Yin and Berger, 2010). This stronger seasonality with relatively warm summer seasons is favorable for high melt rates across the Greenland ice sheet. Other ice core measurements such as δ18O, δD, and deuterium excess appear to be only marginally affected (NEEM community members, 2013). Refrozen melt has the potential to form impermeable ice layers (melt layers ) that alter the diffusion of ice core signals
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