The impact of climate oscillations on the surface energy budget over the Greenland Ice Sheet in a changing climate

Abstract

Abstract. Climate change is particularly strong in Greenland primarily as a result of changes in advection of heat and moisture fluxes from lower latitudes. The atmospheric structures involved influence the surface mass balance and their pattern are largely explained by climate oscillations which describe the internal climate variability. Based on a clustering method, we combine the Greenland Blocking Index and the North Atlantic Oscillation index with the vertically integrated water vapor to analyze inter-seasonal and regional impacts of the North Atlantic influence on the surface energy components over the Greenland Ice Sheet. In comparison to the reference period (1959–1990), the atmosphere has become warmer and moister during recent decades (1991–2020) for contrasting atmospheric circulation patterns. Particularly in the northern regions, increases in tropospheric water vapor enhance incoming longwave radiation and thus contribute to surface warming. Surface warming is most evident in winter, although its magnitude and spatial extent depend on the prevailing atmospheric configuration. Relative to the reference period, increases in sensible heat flux in the summer ablation zone are found irrespective of the atmospheric circulation pattern. Especially in the northern ablation zone, these are explained by the stronger katabatic winds which are partly driven by the larger surface pressure gradients between the ice/snow-covered surface and adjacent seas, and by the larger temperature gradient between near-surface air and the air above. Increases in net shortwave radiation are mainly connected to high-pressure systems. Whereas in the southern part of Greenland the atmosphere has gotten optical thinner, thus allowing more incoming shortwave radiation to reach the surface, in the northern part the incoming shortwave radiation flux has changed little with respect to the reference period, but the surface albedo decreased due to the expansion of the bare ice area.

Precipitation trends (1958–2021) on Ammassalik island, south-east Greenland

“…The temperature trend in Tasiilaq from 1990 to 2019 (+0.8 °C/ decade, p=0.02) is similar in magnitude to reported trends for the GrIS over the same period (Hanna et al, 2021), while the temperature increase over MIT during this period is significantly weaker (non-significant, +0.2 °C/decade, p=0.25). Several studies have previously highlighted the beginning of the 1990s as a period with accelerated mass loss for the GrIS (Mouginot et al, 2019;Hanna et al, 2021) which has also been objectively determined by a break-point analysis (Silva et al, 2022). While we did not perform any break point analysis here, we see a strong difference between the subperiod 1960-1989 and 1990-2019 (particularly for T 2m ).…”