The 79°N Glacier cavity modulates subglacial iron export to the NE Greenland Shelf

Approximately half of the freshwater discharged from the Greenland and Antarctic Ice Sheets enters the ocean subsurface as a result of basal ice melt, or runoff draining via the grounding line of a deep ice shelf or marine-terminating glacier. Around Antarctica and parts of northern Greenland, this freshwater then experiences prolonged residence times in large cavities beneath floating ice tongues. Due to the inaccessibility of these cavities, it is unclear how they moderate the freshwater associated supply of nutrients such as iron (Fe) to the ocean. Here, we show that subglacial dissolved Fe export from Nioghalvfjerdsbrae (the '79 degrees N Glacier') is decoupled from particulate inputs including freshwater Fe supply, likely due to the prolonged similar to 162-day residence time of Atlantic water beneath Greenland's largest floating ice-tongue. Our findings indicate that the overturning rate and particle-dissolved phase exchanges in ice cavities exert a dominant control on subglacial nutrient supply to shelf regions.

Automated summary

Approximately half of the freshwater discharged from the Greenland and Antarctic Ice Sheets enters the ocean subsurface, where it experiences prolonged residence times in large cavities beneath floating ice tongues. The subglacial dissolved Fe export from Nioghalvfjerdsbrae is decoupled from particulate inputs, likely due to the prolonged residence time of Atlantic water beneath Greenland's largest floating ice-tongue. These findings suggest that the overturning rate and particle-dissolved phase exchanges in ice cavities play a dominant role in controlling subglacial nutrient supply to shelf regions.