A reliable estimate of surface mass balance (SMB), including its components, change, and drivers, is pivotal for understanding past, present, and future ice sheet mass balance and sea level change. Large temporal SMB variability, predominantly driven by snowfall anomalies, challenges the detection of longer-term trends in Antarctic mass balance. As the atmosphere warms, episodes of pervasive melt are becoming frequent over Greenland Ice Sheet and Antarctic ice shelves. Melt water can be partly stored in firn, crevasses, surface or buried ponds and rivers, impacting hydrofracture, cryohydrologic warming, firn pore-space depletion, and snow/ice darkening. Our assessment of ice sheet mass balance depends on the accurate representation of these processes in ice sheet and climate models and evaluation using observations. We invite papers that study processes such as snowfall, snow redistribution, firn densification, meltwater retention, surface water storage and drainage, and albedo, using remote sensing, ground-based measurements, and modeling approaches.