Seasonal Dynamics of Dissolved Iron on the Antarctic Continental Shelf: Late-Fall Observations From the Terra Nova Bay and Ross Ice Shelf Polynyas.

Autor: Sedwick PN; Department of Ocean and Earth Sciences Old Dominion University Norfolk VA USA., Sohst BM; Department of Ocean and Earth Sciences Old Dominion University Norfolk VA USA., O'Hara C; Department of Ocean and Earth Sciences Old Dominion University Norfolk VA USA., Stammerjohn SE; Institute of Arctic and Alpine Research University of Colorado Boulder CO USA., Loose B; Graduate School of Oceanography University of Rhode Island Narragansett RI USA., Dinniman MS; Center for Coastal Physical Oceanography Old Dominion University Norfolk VA USA., Buck NJ; Cooperative Institute for Climate, Oceans, and Ecosystem Studies University of Washington Seattle WA USA.; NOAA Pacific Marine Environmental Laboratory Seattle WA USA., Resing JA; Cooperative Institute for Climate, Oceans, and Ecosystem Studies University of Washington Seattle WA USA.; NOAA Pacific Marine Environmental Laboratory Seattle WA USA., Ackley SF; Center for Advanced Measurements in Extreme Environments University of Texas at San Antonio San Antonio TX USA.
Jazyk: angličtina
Zdroj: Journal of geophysical research. Oceans [J Geophys Res Oceans] 2022 Oct; Vol. 127 (10), pp. e2022JC018999. Date of Electronic Publication: 2022 Oct 17.
DOI: 10.1029/2022JC018999
Abstrakt: Over the Ross Sea shelf, annual primary production is limited by dissolved iron (DFe) supply. Here, a major source of DFe to surface waters is thought to be vertical resupply from the benthos, which is assumed most prevalent during winter months when katabatic winds drive sea ice formation and convective overturn in coastal polynyas, although the impact of these processes on water-column DFe distributions has not been previously documented. We collected hydrographic data and water-column samples for trace metals analysis in the Terra Nova Bay and Ross Ice Shelf polynyas during April-May 2017 (late austral fall). In the Terra Nova Bay polynya, we observed intense katabatic wind events, and surface mixed layer depths varied from ∼250 to ∼600 m over lateral distances <10 km; there vertical mixing was just starting to excavate the dense, iron-rich Shelf Waters, and there was also evidence of DFe inputs at shallower depths in the water column. In the Ross Ice Shelf polynya, wind speeds were lower, mixed layers were <300 m deep, and DFe distributions were similar to previous, late-summer observations, with concentrations elevated near the seafloor. Corresponding measurements of dissolved manganese and zinc, and particulate iron, manganese, and aluminum, suggest that deep DFe maxima and some mid-depth DFe maxima primarily reflect sedimentary inputs, rather than remineralization. Our data and model simulations imply that vertical resupply of DFe in the Ross Sea occurs mainly during mid-late winter, and may be particularly sensitive to changes in the timing and extent of sea ice production.
(© 2022. The Authors.)
Databáze: MEDLINE
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