Natural iron enrichment around the Antarctic Peninsula in the Southern Ocean

[摘要] As part of the US-AMLR program in January-February of 2006, 99 stations inthe South Shetland Islands-Antarctic Peninsula region were sampled tounderstand the variability in hydrographic and biological properties relatedto the abundance and distribution of krill in this area. Concentrations ofdissolved iron (DFe) and total acid-leachable iron (TaLFe) were measured inthe upper 150 m at 16 of these stations (both coastal and pelagic waters) tobetter resolve the factors limiting primary production in this area and indownstream waters of the Scotia Sea. The concentrations of DFe and TaLFe inthe upper mixed layer (UML) were relatively high in Weddell Sea Shelf Waters(~0.6 nM and 15 nM, respectively) and low in Drake Passage waters(~0.2 nM and 0.9 nM, respectively). In the BransfieldStrait, representing a mixture of waters from the Weddell Sea and theAntarctic Circumpolar Current (ACC), concentrations of DFe were ~0.4 nMand of TaLFe ~1.7 nM. The highest concentrations of DFe and TaLFein the UML were found at shallow coastal stations close to Livingston Island(~1.6 nM and 100 nM, respectively). The ratio of TaLFe:DFe variedwith the distance to land: ~45 at the shallow coastal stations, ~15 in the high-salinity waters of Bransfield Strait, and ~4 in ACCwaters. Concentrations of DFe increased slightly with depth in the watercolumn, while that of TaLFe did not show any consistent trend with depth.Our Fe data are discussed in regard to the hydrography and water circulationpatterns in the study area, and with the hypothesis that the relatively highrates of primary production in the central regions of the Scotia Sea arepartially sustained by natural iron enrichment resultingfrom a northeasterly flow of iron-rich coastal waters originating inthe South Shetland Islands-Antarctic Peninsula region.

[学科分类] 地球化学与岩石