Low mercury concentrations in a Greenland glacial fjord attributed to oceanic sources

• Published in: Communications earth & environment Vol. 5; no. 1; pp. 320 - 10
• Main Authors: Lindeman, M. R, Straneo, F, Adams, H. M, Nelson, M. J. S, Schartup, A. T
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 01-12-2024; Nature Portfolio
• Subjects: Coastal waters; Continental shelves; Dimethylmercury; Fjords; Glaciers; Ice sheets; Meltwater; Mercury; Methylmercury; Sediments; Water circulation; Water column; Water masses; Greenland
• ISSN: 2662-4435
• DOI: 10.1038/s43247-024-01474-9

As the role of the Greenland Ice Sheet in the Arctic mercury (Hg) budget draws scrutiny, it is crucial to understand mercury cycling in glacial fjords, which control exchanges with the ocean. We present full water column measurements of total mercury (THg) and methylmercury (MeHg) in Sermilik Fjord, a large fjord in southeast Greenland fed by multiple marine-terminating glaciers, whose circulation and water mass transformations have been extensively studied. We show that THg (0.23-1.1 pM) and MeHg (0.02-0.17 pM) concentrations are similar to those in nearby coastal waters, while the exported glacially-modified waters are relatively depleted in inorganic mercury (Hg(II)), suggesting that inflowing ocean waters from the continental shelf are the dominant source of mercury species to the fjord. We propose that sediments initially suspended in glacier meltwaters scavenge particle-reactive Hg(II) and are subsequently buried, making the fjord a net sink of oceanic mercury.Glacier melt-modified waters in a Greenland fjord contained less mercury than inflowing ocean waters, suggesting meltwaters are low in mercury and glacial sediments may remove oceanic mercury, according to analysis of full water column measurements.