Abstract
Abstract. We propose a surface melt scheme for glaciated land surfaces, which only requires monthly mean short-wave radiation and temperature as inputs, yet implicitly accounts for the diurnal cycle of short-wave radiation. The scheme is deduced from the energy balance of a daily melt period, which is defined by a minimum solar elevation angle. The scheme yields a better spatial representation of melting than common empirical schemes when applied to the Greenland Ice Sheet, using a 1948–2016 regional climate and snowpack simulation as a reference. The scheme is physically constrained and can be adapted to other regions or time periods.
Highlights
The surface melt of ice sheets, ice caps and glaciers results in freshwater run-off, which represents an important freshwater source and directly influences the sea level on centennial to glacial–interglacial timescales
Melt rates can be separated from integral observations such as the World Glacier Monitoring Service (WGMS) (Zemp et al, 2015, and references therein) or the changes in ice mass detected by the Gravity Recovery and Climate Experiment (GRACE) (Tapley et al, 2004; Wouters et al, 2014), which requires additional information about other components of the mass balance, such as basal melting, accumulation, sublimation and refreezing (Sasgen et al, 2012; Tedesco and Fettweis, 2012)
Together with suitable schemes for albedo and refreezing, it may replace empirical surface melt schemes which are commonly used in ice sheet modelling on long timescales
Summary
The surface melt of ice sheets, ice caps and glaciers results in freshwater run-off, which represents an important freshwater source and directly influences the sea level on centennial to glacial–interglacial timescales. The PDD scheme is computationally inexpensive and requires only seasonal or monthly near-surface air temperatures as input It has been applied in the context of long climate simulations Another empirical approach uses a linear function of solar radiation and temperature to predict surface melt This approach was originally used to estimate ablation rates of glacial ice sheets (Pollard, 1980; Pollard et al, 1980). We deduce a more simplified scheme from the energy balance, which is formally similar to the ETIM and ITM schemes but incorporates physically constrained parameters This new scheme only requires monthly means of temperature and solar radiation as input but implicitly resolves the diurnal cycle of radiation. In a first application on the Greenland Ice Sheet (GrIS) we use a simulation of Greenland’s climate of the years 1948 to 2016 with the stateof-the-art regional climate and snowpack model MAR (version 3.5.2 forced with reanalysis data from the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP) for the years 1948–2016, Kalnay et al, 1996; Fettweis et al, 2017) as a reference
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