Hydraulic suppression of basal glacier melt in sill fjords

Using a conceptual model, we examine how hydraulically controlled exchange flows in silled fjords affect the relationship between the basal glacier melt and the features of warm intermediate Atlantic Water (AW) outside the fjords. We show that an exchange flow can be forced to transit into the hydraulic regime if the AW interface height decreases, the AW temperature increases, or the production of glacially modified water is boosted by subglacial discharge. In the hydraulic regime, the heat transport across the sill becomes a rate-limiting factor for the basal melt, which is suppressed. An interplay between processes near the ice-ocean boundary and the hydraulically controlled exchange flow determines the melt dynamics, and the sensitivity of the basal melt to changes in the AW temperature is reduced. The model results are discussed in relation to observations from the Petermann, Ryder, and 79 & LCIRC; N glaciers in northern Greenland.

Automated summary

Using a conceptual model, this study investigates the impact of hydraulically controlled exchange flows in silled fjords on the relationship between glacier melt and the features of warm intermediate Atlantic Water (AW) outside the fjords. It is found that changes in the AW interface height, temperature, and glacially modified water production can force an exchange flow into the hydraulic regime. In this regime, heat transport across the sill becomes a limiting factor for basal melt and reduces its sensitivity to changes in AW temperature. The model results are compared with observations from glaciers in northern Greenland.