Impact of updated radiative transfer scheme in RACMO2.3p3 on the surface mass and energy budget of the Greenland ice sheet

Abstract

Abstract. This study evaluates the impact of a new snow and ice albedo and radiative transfer scheme on the surface mass and energy budget for the Greenland ice sheet in the latest version of the regional climate model RACMO2, version 2.3p3. We also evaluate the modeled (sub)surface temperature and snow melt, as subsurface heating by radiation penetration now occurs. The results are compared to the previous model version and are evaluated against stake measurements and automatic weather station data of the K-transect and PROMICE projects. In addition, subsurface snow temperature profiles are compared at the K-transect, Summit and southeast Greenland. The surface mass balance is in good agreement with observations, and only changes considerably with respect to the previous RACMO2 version around the ice margins and in the percolation zone. Snow melt and refreezing, on the other hand, are changed more substantially in various regions due to the changed albedo representation, subsurface energy absorption and melt water percolation. Internal heating leads to considerably higher snow temperatures in summer, in agreement with observations, and introduces a shallow layer of subsurface melt.

Spectral snow albedo in a regional climate model: application to the Greenland and Antarctic ice sheets

“…An important addition in Rp3 is subsurface penetration of shortwave radiation, which allows subsurface absorption and heating of the snowpack. For Greenland, Van Dalum et al (2020b) show that Rp3 as a result predicts higher subsurface snow temperatures that match well with observations at Summit. In the ablation zone, the melting point is reached to a greater depth than in Rp2, enabling subsurface melt.…”

“…In this study, we use the polar (p) version of the Regional Atmospheric Climate Model (RACMO2) to analyse the impact of a spectral snow albedo scheme on the (sub)surface temperature and melt of the AIS. RACMO2 has been especially adapted to model glaciated areas (Noël et al, 2018b;Van Wessem et al, 2018;Van Dalum et al, 2020b;, and has previously been used to investi-gate the snowmelt-albedo feedback (Jakobs et al, 2019). Here, we use the latest version, RACMO2.3p3, henceforth Rp3, which has a spectral snow and ice albedo scheme (Van Dalum et al, 2019, 2020a) that includes radiation penetration, allowing for subsurface heating and subsurface melt.…”

“…The remaining energy contributes to subsurface heating. Beyond the SLED, all absorbed energy leads to subsurface heating (Van Dalum et al, 2020b).…”

“…Rp2 uses the same settings as the Greenland settings in Rp3 (GRL), i.e., a fresh snow SSA of 60 m 2 kg −1 , no snow metamorphism tuning and a refreezing grain size of 1 mm. In GRL, we define a SLED of 5 mm after scale analysis (Van Dalum et al, 2020b). In Rp2, the SLED is not defined, as no radiation penetration occurs and all shortwave radiation contributes to the SEB.…”

How Does the Southern Annular Mode Control Surface Melt in East Antarctica?

“…We examine monthly and daily variables from the polar version of the RACMO2 regional climate model, including surface melt; turbulent, radiative, and conductive heat fluxes; surface (10m) winds; and surface (2m) air temperatures (T 2m ) (van Dalum et al, 2021). RACMO2 has been used extensively in studies of Antarctica's surface climate (e.g., Jakobs et al, 2021;Lenaerts et al, 2012Lenaerts et al, , 2018van Wessem et al, 2014van Wessem et al, , 2018, and the latest version (RACMO2.3p3) contains two key improvements for modeling surface melt: 1) an updated spectral snow and ice albedo scheme, which permits subsurface penetration of shortwave radiation; and 2) an updated multilayer firn module that includes a finer vertical resolution near the surface where melt occurs (van Dalum et al, 2019(van Dalum et al, , 2020(van Dalum et al, , 2022.…”