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Abstract 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.
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This content will become publicly available on April 1, 2026
Mercury Distribution and Speciation Along the U.S. GEOTRACES GP15 Pacific Meridional Transect
Abstract Mercury (Hg) is a bioaccumulative neurotoxin that can concentrate to potentially harmful levels in higher levels of marine food webs following conversion to methylmercury (MeHg). This is of public health concern as seafood is a main protein source for many in the Pacific region. To better understand Hg partitioning and transformations in the Pacific Ocean, Hg species and phases were measured along a meridional section from Alaska to Tahiti in 2018. This allowed the description of Hg concentrations and speciation under a variety of biogeochemical conditions such as the Alaskan shelf, the oligotrophic North Pacific gyre, and near the hydrothermally active Loihi seamount. Filtered HgT concentrations were elevated below 1,000 m near the Loihi Seamount with an average concentration of 1.45 pM, possibly indicating enrichment from hydrothermal venting. Filtered MeHg concentrations were notably higher at depth at the equator and generally lower south of the equator. Total Hg in suspended particles was greatest in the upper 1,000 m near the Alaskan Shelf and decreased in concentration southward. Suspended particle MeHg was greatest in the surface ocean in the upper 300 m near the Intertropical Convergence Zone (ITCZ). For both HgT and MeHg, particle‐associated concentrations appear to be related to organic fraction, and concentrations decreased southward. In general, all measured Hg species had greater concentrations in the northern than southern Pacific Ocean consistent with prior measurements.
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- Award ID(s):
- 2151677
- PAR ID:
- 10585088
- Publisher / Repository:
- American Geophysical Union
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Oceans
- Volume:
- 130
- Issue:
- 4
- ISSN:
- 2169-9275
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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