Greenland Surface Melt Dominated by Solar and Sensible Heating

Abstract

The Greenland Ice Sheet is the primary source of global Barystatic sea‐level rise, and at least half of its recent mass‐loss acceleration is caused by surface meltwater runoff. Previous studies on surface melt have examined various thermodynamic and dynamic drivers, yet their contributions are not compared using unified observations. We use decade‐long in‐situ measurements from automatic weather stations throughout the ablation zone to assess energy components and identify the leading physical processes in this area. Large melt events exceeding 3σ contribute only ∼2% to total surface melt since 2007. The day‐to‐day variability of all melt is dominated by sensible heat exchange (31 ± 7%) and shortwave radiation (28 ± 5%). Sensible and solar heating correlate with the occurrence of dry and fast gravity‐driven winds. These katabatic winds increase sensible heating of the surface mainly by enhancing vertical mixing that reduces the temperature inversion. The concomitant low humidity and clear skies yield increased solar heating.

Wind‐Associated Melt Trends and Contrasts Between the Greenland and Antarctic Ice Sheets

“…On the northern portion of the GIS, downslope wind-associated surface melt is primarily driven by the SHF over 70% of the melt area. These results are consistent with Wang et al (2021) who focused on sub-monthly melt timescales to show that sensible heat drives the melt variability, while we show that shortwave absorption supplies most of the absolute power for total melt.…”

“…Directionally consistent katabatic winds on the margins of the GIS and AIS, and föhn winds in the Antarctic Peninsula (AP) and northwestern Greenland, enhance surface melt rates (Datta et al., 2019; Laffin et al., 2021, 2022; Lenaerts et al., 2017; Mattingly et al., 2023; Wang et al., 2021). Katabatic winds originate in the cold, high, and dry ice sheet interior where relatively dense surface air drains downslope toward warmer regions.…”

The Determination of the Snow Optical Grain Diameter and Snowmelt Area on the Greenland Ice Sheet Using Spaceborne Optical Observations

“…for weakly absorbing media in the visible and near infrared regions of the electromagnetic spectrum such as snow. In Equation (7), k abs and k ext are the coefficients of absorption and extinction of the snow and g is the asymmetry parameter defined as the average cosine of the scattering angle inside the snowpack. k abs and k ext can be expressed, using the geometrical optics approximation for weakly absorbing grains [69], as:…”

“…Surface snow then undergoes melt in the spring and summer, until it either melts away and exposes a dark underlying glacial ice [5,6], or until the melt stops. The surface melt intensity is governed by sensible heat flux and absorption of solar radiation at the surface [7] and the latter is largely controlled by the snow optical properties: the shape and size of its grains, the presence of water and the concentration of light-absorbing impurities [8][9][10][11].…”

Observed and Parameterized Roughness Lengths for Momentum and Heat Over Rough Ice Surfaces

“…Yet, state‐of‐the‐art regional climate models (RCMs) still show considerable differences in modeled melt in the ablation area (Fettweis et al., 2020), the area where the surface mass balance is negative and bare ice is at the surface during the melting season. In the ablation area, both the interdiurnal and interannual variability in surface melt are strongly influenced by the turbulent exchange of sensible and latent heat at the surface, that is, the sensible heat flux (SHF) and latent heat flux (LHF) (Van den Broeke et al., 2011; Wang et al., 2021).…”