I’m no fan of geoengineering (see this paper from 1996 ) but these specific proposals seem local, potentially reversible interventions to slow down melting, so could be worth investigating. Even if we get to net zero and stabilise the global surface temperature, it would take much longer (decades-centuries) to stabilise ice- melt, deep-ocean warming and consequent sea-level rise, there is a lot of inertia.
Their second approach focuses on meltwater, but thatt has to flow somewhere, maybe better focus to keep ice solid - e.g. I’m surprised no mention is made of the ice-surface albedo - e.g. minimising soot, algae. Minimising aviation-cirrus from planes passing over greenland might also help.