Effect of near-terminus subglacial hydrology on tidewater glacier submarine melt rates

Submarine melting of Greenlandic tidewater glacier termini is proposed as a possible mechanism driving their recent thinning and retreat. We use a general circulation model, MITgcm, to simulate water circulation driven by subglacial discharge at the terminus of an idealized tidewater glacier. We vary the spatial distribution of subglacial discharge emerging at the grounding line of the glacier and examine the effect on submarine melt volume and distribution. We find that subglacial hydrology exerts an important control on submarine melting; under certain conditions a distributed system can induce a factor 5 more melt than a channelized system, with plumes from a single channel inducing melt over only a localized area. Subglacial hydrology also controls the spatial distribution of melt, which has the potential to control terminus morphology and calving style. Our results highlight the need to constrain near‐terminus subglacial hydrology at tidewater glaciers if we are to represent ocean forcing accurately. Key Points Subglacial hydrology is a strong control on submarine melt rate Melt increase from channelized to distributed can be a factor of 5 Single plumes cannot in isolation drive large submarine melt volumes