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Abstract Cadmium (Cd) is a trace metal whose distribution in the ocean bears a remarkable resemblance to the nutrient phosphate (PO43−). This resemblance has led to the use of Cd as a proxy for ocean nutrient cycling in paleoceanographic applications, but the processes governing the cycling of Cd in the modern ocean remain unclear. In this study, we use previously published Cd observations and an Artificial Neural Network to produce a dissolved Cd climatology that reproduces the observed subtle deviations between the Cd anddistributions. We use the Cd andclimatologies, along with an ocean circulation inverse model, to diagnose the biogeochemical sources and sinks of dissolved Cd and. Our calculations reveal that dissolved Cd, like, is removed in the surface ocean and has a source in the subsurface, consistent with the simultaneous incorporation of Cd andinto sinking organic particles. However, there are also contrasts between the cycling of dissolved Cd andIn particular, thesurface export ratio varies 8‐fold across latitudes, reaching highest values in the iron‐limited sub‐Antarctic Southern Ocean. This depletes Cd relative toin the low‐latitude thermocline while adding excess Cd to deep waters by the regeneration of Cd‐enriched particles. Also, Cd tends to regenerate slightly deeper thanin the subsurface ocean, and theregeneration ratio reaches a maximum at 700–1,500 m. These contrasts are responsible for a slight concavity in therelationship and should be considered when interpreting paleoceanographic Cd records.
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Aufeis fields as novel groundwater‐dependent ecosystems in the arctic cryosphere
Abstract Riveraufeis(ow′ fīse) are widespread features of the arctic cryosphere. They form when river channels become locally restricted by ice, resulting in cycles of water overflow and freezing and the accumulation of ice, with someaufeisattaining areas of ~ 25 + km2and thicknesses of 6+ m. During winter, unfrozen sediments beneath the insulating ice layer provide perennial groundwater‐habitat that is otherwise restricted in regions of continuous permafrost. Our goal was to assess whetheraufeisfacilitate the occurrence of groundwater invertebrate communities in the Arctic. We focused on a singleaufeisecosystem (~ 5 km2by late winter) along the Kuparuk River in arctic Alaska. Subsurface invertebrates were sampled during June and August 2017 from 50 3.5‐cm diameter PVC wells arranged in a 5 × 10 array covering ~ 40 ha. Surface invertebrates were sampled using a quadrat approach. We documented a rich assemblage of groundwater invertebrates (49 [43–54] taxa,[95% confidence limits]) that was distributed below the sediment surface to a mean depth of ~ 69 ± 2 cm (± 1 SE) throughout the entire well array. Although community structure differed significantly between groundwater and surface habitats, the taxa richness from wells and surface sediments (43 [35–48] taxa) did not differ significantly, which was surprising given lower richness in subsurface habitats of large, riverine gravel‐aquifer systems shown elsewhere. This is the first demonstration of a rich and spatially extensive groundwater fauna in a region of continuous permafrost. Given the geographic extent ofaufeisfields, localized groundwater‐dependent ecosystems may be widespread in the Arctic.
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- Award ID(s):
- 1637459
- PAR ID:
- 10376162
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Limnology and Oceanography
- Volume:
- 66
- Issue:
- 3
- ISSN:
- 0024-3590
- Page Range / eLocation ID:
- p. 607-624
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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