The implication of nonradiative energy fluxes dominating Greenland ice sheet exceptional ablation area surface melt in 2012

Abstract

During two exceptionally large July 2012 multiday Greenland ice sheet melt episodes, nonradiative energy fluxes (sensible, latent, rain, and subsurface collectively) dominated the ablation area surface energy budget of the southern and western ice sheet. On average the nonradiative energy fluxes contributed up to 76% of daily melt energy at nine automatic weather station sites in Greenland. Comprising 6% of the ablation period, these powerful melt episodes resulted in 12–15% of the south and west Greenland automatic weather station annual ablation totals. Analysis of high resolution (~5 km) HIRHAM5 regional climate model output indicates widespread dominance of nonradiative energy fluxes across the western ablation area during these episodes. Yet HIRHAM5 still underestimates melt by up to 56% during these episodes due to a systematic underestimation of turbulent energy fluxes typical of regional climate models. This has implications for underestimating future melt, when exceptional melt episodes are expected to occur more frequently.

Surface Energy Balance Closure and Turbulent Flux Parameterization on a Mid-Latitude Mountain Glacier, Purcell Mountains, Canada

“…Despite extensive cloud cover on DOY 200, daily ablation (0.058 m w.e.) was above the seasonal average (0.049 m w.e./day), with the non-radiative fluxes dominating Q M (57.6%), highlighting the importance of accurate observation or estimation of non-radiative fluxes on glaciers (Fausto et al, 2016).…”

A daily, 1 km resolution data set of downscaled Greenland ice sheet surface mass balance (1958–2015)

“…The fact that f scale > 1 strongly suggests that additional processes might play a role in enhancing surface ablation, e.g. underestimation of modelled sensible heat flux from warm air advection along the GrIS periphery (Noël et al, 2015;Fausto et al, 2016) and uncertainties in cloud representation (Van Tricht et al, 2016). However, as the statistical downscaling approach is not designed to correct for these physical processes, we adopted the empirical approach presented above.…”

Impact of MODIS sensor calibration updates on Greenland Ice Sheet surface reflectance and albedo trends

“…These findings are consistent with the recent study of Polashenski et al (2015), which suggested the dry snow albedo decline in C5 data would disappear in C6 after finding no enhancement in light-absorbing impurity concentrations on the interior Greenland Ice Sheet. The declining trends in wet snow and ice surface reflectance and albedo, independently supported by evidence of increased melt activity (Nghiem et al, 2012;Fausto et al, 2016b), remain statistically significant in C6 data, though at lower magnitude. An examination of spatial, wavelength-specific variability in C6 albedo trends indicates several interesting attributes of GrIS albedo decline that may motivate future work to better understand the mechanisms controlling albedo feedbacks on the ice sheet.…”