Forcing and Responses of the Surface Energy Budget at Summit, Greenland Journal Article uri icon



  • Abstract. Greenland ice sheet surface temperatures are controlled by an exchange of energy at the surface, which includes radiative, turbulent and ground heat fluxes. Data collected by multiple projects are leveraged to calculate estimates of all surface energy budget (SEB) terms at Summit, Greenland for the full annual cycle from July 2013–June 2014 and extend to longer periods for the radiative and turbulent SEB terms. Radiative fluxes are measured directly by a suite of broadband radiometers. Turbulent sensible heat flux is primarily estimated via the bulk aerodynamic method, and the turbulent latent heat flux is calculated via a two level approach using measurements at 10 and 2 m. The subsurface heat flux is calculated using a string of thermistors buried in the snow pack. Extensive quality-control data processing produced a data set in which all terms of the SEB are present 75 % of the full annual cycle, despite the harsh conditions. By including a storage term for a near surface layer, the SEB is balanced in this data set to within the aggregated uncertainties for the individual terms. November and August case studies illustrate that surface radiative forcing is driven by synoptically forced cloud characteristics, especially by low-level, liquid-bearing clouds. The annual cycle and seasonal diurnal cycles of all SEB components indicate that the non-radiative terms are anti-correlated to changes in the total radiative flux, and are hence responding to cloud radiative forcing. Generally, the non-radiative SEB terms and the upwelling longwave radiation component compensate for changes in downwelling radiation, although exact partitioning of energy in the response terms varies with season and near-surface characteristics such as stability and moisture availability. Substantial surface warming from low-level clouds typically leads to a change from a very stable to a weakly stable near-surface regime with no solar radiation or from a weakly stable to neutral/unstable regime with solar radiation. Relationships between forcing terms and responding surface fluxes show that the upwelling longwave radiation produces 55–75 % (40–50 %) of the total response in the winter (summer) and the non-radiative terms compensate for the remaining change in the combined downwelling longwave and net shortwave radiation. Because melt conditions are rarely reached at Summit, these relationships are documented for conditions of surface-temperature below 0 °C, with and without solar radiation. This is the first time that forcing and response term relationships have been investigated in detail for the Greenland SEB. These results should both advance understanding of process relationships over the Greenland icecap and be useful for model validation.;

publication date

  • September 23, 2016

has restriction

  • green

Date in CU Experts

  • June 3, 2021 10:01 AM

Full Author List

  • Miller NB; Shupe MD; Cox CJ; Noone D; Persson POG; Steffen K

author count

  • 6

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