Spatial Variability of the Snowmelt‐Albedo Feedback in Antarctica

Abstract

Surface melt is an important process for the stability of ice shelves, and therewith the Antarctic ice sheet. In Antarctica, absorption of solar radiation is mostly the largest energy source for surface melt, which is further enhanced by the snowmelt‐albedo feedback (SMAF): Refrozen snow has a lower albedo than new snow, which causes it to absorb more solar radiation, further increasing the energy available for surface melt. This feedback has previously been shown to increase surface melt by approximately a factor of 2.5 at Neumayer Station in East Antarctica. In this study, we use a regional climate model to quantify SMAF for the entire Antarctic ice sheet. We find that it is most effective on ice shelves in East Antarctica, and is less important in the Antarctic Peninsula and on the Ross and Filchner‐Ronne ice shelves. We identify a relationship between SMAF and average summer 2 m air temperatures, and find that SMAF is most important around 265 ± 2 K. On a subseasonal scale, we identify several parameters that contribute to SMAF: the length of dry periods, the time between significant snowfall events and snowmelt events, and prevailing temperatures. We then apply the same temperature dependency of SMAF to the Greenland ice sheet and find that it is potentially active in a narrow band around the ice sheet, and finally discuss how the importance of SMAF could change in a warming climate.

Short-Term Meteorological and Environmental Signals Recorded in a Firn Core from a High-Accumulation Site on Plateau Laclavere, Antarctic Peninsula

“…This is supported by the statistically significant positive correlation of MLT of OH-12 with ERA5 near-surface air temperatures at the site (r = 0.5, p < 0.0001; Table 5). In addition, increased insolation on cloud-free days and hence the absorption of solar radiation by the snowpack can further trigger surface melt [100]. However, due to the exposed position of the study site, high wind speeds may occur year-round (Supplementary Figure S4).…”

The evolution of future Antarctic surface melt using PISM-dEBM-simple

“…This overestimation is mainly caused by the high temperature sensitivity of the PDD model and is amplified by our treatment of the monthly mean temperature inputs at the iceatmosphere interface. Because the PDD model is tuned in a way that all surface melt is caused by temperatures only -which is in contrast to in situ observations showing that in the cold Antarctic climate, insolation is usually the predominant energy source for melt at the surface (Jonsell et al, 2012;King et al, 2015;Broeke et al, 2005b;Jakobs et al, 2020Jakobs et al, , 2021 cf. also Fig.…”

“…Especially the changes in snow grain sizes, e.g., due to snow aging, are an important factor that is neglected in the model but plays a major role for the albedo. While snow aging generally leads to a reduction in albedo, and its neglect should therefore in principle lead to an underestimation of melt rates at the end of the melt season, there are important processes that act in the opposite direction: a major caveat of the scheme is that it neglects the influence of changes in snow cover thickness that could mitigate the melt-induced reduction in albedo after heavy snowfall events or inhibit the melt-albedo feedback (Picard et al, 2012;Jakobs et al, 2021). However, on the long timescales considered here individual snowfall events are likely to only play a minor role as compared to the mean surface conditions.…”

“…Surface melt can also be enhanced by the positive melt-albedo feedback: when snow or ice melt, meltwater at the surface or refreezing meltwater in the snow and firn layers decrease the albedo (i.e., the reflectivity) of the surface, leading to a higher absorption of incoming solar radiation and in return more intense melt (Jakobs et al, 2019). This feedback has been shown to play a crucial role over large parts of the Antarctic Ice Sheet to accelerate surface melt (Jakobs et al, 2021). Particularly in long-term ice-sheet model simulations and sea-level rise projections it is therefore decisive to include this melt-albedo feedback in addition to mechanisms like the surface-elevation-melt feedback (Fyke et al, 2018).…”

Opposite Effects of Mineral Dust Nonsphericity and Size on Dust‐Induced Snow Albedo Reduction

“…Snowpack is a crucial component of the cryosphere, serving as a huge water reservoir for river catchments, and it is especially important for the regional sustainability of ecosystems and communities (Barnett et al., 2005; Hugonnet et al., 2021; Sturm et al., 2017). The surface energy budget of snow‐covered regions, and the ablation rate of the snowpack in particular, are significantly affected by snow albedo (Flanner et al., 2011; Jakobs et al., 2021; Riihelä et al., 2021; Zhang et al., 2021). Numerous observations and model simulations have shown that light‐absorbing particles (LAPs; e.g., black carbon (BC) and mineral dust (hereafter referred to as dust)) within the snowpack can reduce snow albedo and accelerate snow melting by enhancing the absorption of solar radiation (Chylek et al., 1983; Dumont et al., 2020; Hadley & Kirchstetter, 2012; Liou et al., 2014; Shi et al., 2020; Skiles & Painter, 2019), which has important implications for regional climate, hydrology, and ecological systems (Hansen & Nazarenko, 2004; Matt et al., 2018; Oaida et al., 2015; Qian et al., 2011; Yasunari et al., 2012).…”