Located in northern Greenland, Humboldt glacier (HG) has experienced accelerated retreat since the 1990s. With the potential to contribute 19 cm to global sea-level rise, understanding the systems which drive HG’s retreat is imperative to quantifying how it will change in the next century. Here, we examine the impact of the subglacial hydrologic system, which is comprised of inefficient, distributed drainage that can evolve to efficient subglacial channels when water flux is large. The character of subglacial hydrology impacts subglacial water pressure and thus basal friction, which affects the speed at which the glacier will flow. Currently, many ice sheet models do not take seasonal changes in the subglacial hydrologic system into account when determining basal friction. We use the subglacial hydrology component of the MPAS Albany Land Ice (MALI) ice sheet model to characterize subglacial hydrology at HG during the 21st century, specifically investigating how increases in surface melt transported to the bed change the character of drainage and impact ice effective pressure and associated basal friction. The model exhibits a multi-year persistence, with high melt summers leading to lowered effective pressure which is sustained into the following year, which contrasts with velocity observations from west Greenland. Furthermore, a projected four-fold increase in summer surface melt draining to the glacier bed late in the 21st century causes a substantial change in the character of drainage, with the proportion of total subglacial meltwater conveyed by the channelized system during the late summer nearly doubling. However, this increased channelization has only a slight moderating effect on seasonally-averaged effective pressure as surface melt increases. This suggests that while subglacial channelization can offset some of the impacts of increasing surface melt on ice dynamics, it is insufficient to prevent meltwater-induced speedup of HG in the coming decades.