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This work evaluates glacial dust as a source of sediment, and associated iron (Fe), to the Fe‐limited Gulf of Alaska (GoA). A reanalysis of GoA sediment data, using rare earth elements and thorium as provenance tracers, suggests a flux to the ocean surface of Copper River (AK) glacial dust, and associated Fe, that is comparable to the flux of dust from Asia, at least 1,000 km from the narrow mountain valley glacial dust source area. This work suggests dust from Asia may not be the largest source of Fe to the GoA. Dust models fail to accurately simulate this glacial dust transport because their coarse resolution underestimates wind speeds, and the dust flux. This work suggests that glacial dust fluxes may have been important in the geologic past (e.g., the last glacial maximum) from locations where there was more extensive coverage by glaciers than at present. Plain Language Summary: The growth of phytoplankton, the base of the marine food web, is known to be limited by availability of the micronutrient iron in the Gulf of Alaska. We evaluated the importance of glacial dust in this region as a source of iron, and other trace metals, by using concentrations of the rare earth elements and thorium in particles as tracers of their geographic origin. We analyzed for these elements in glacial dust samples from the Copper River valley (Alaska), the largest source of glacier‐derived dust. Together with previously published concentrations for dust from Asia and volcanic material, we estimated the inputs of each source material to the sediments of the Gulf of Alaska. This information, together with published sediment mass accumulation rates, suggests an important contribution of Alaskan glacial dust and associated iron, to surface waters of the Gulf of Alaska, at least 1,000 km from the source. Dust models fail to accurately simulate this dust transport because their coarse spatial resolution substantially underestimates wind speeds. Glacial dust fluxes may have been important sources of iron in the geologic past (e.g., the Last Glacial Maximum) from New Zealand and South America, when there was more extensive glacial coverage. Key Points: Copper River glacial dust contributes substantially to Gulf of Alaska sediments, and associated iron to surface watersDust models lack sufficient spatial resolution to accurately simulate the winds that drive the flux of glacial dust from narrow valleysGlacial dust‐associated iron may have been important in the geologic past in times and locations with more extensive glacial coverage [ABSTRACT FROM AUTHOR]

While modeling efforts have furthered our understanding of marine iron biogeochemistry and its influence on carbon sequestration, observations of dissolved iron (dFe) and its relationship to physical, chemical and biological processes in the ocean are needed to both validate and inform model parameterization. Where iron comes from, how it is transported and recycled, and where iron removal takes place are critical mechanisms that need to be understood to assess the relationship between iron availability and primary production. To this end, hydrographic and trace metal observations across the GO‐SHIP section SR3, south of Tasmania, Australia, have been analyzed in tandem with the novel application of an optimum multiparameter analysis. From the trace‐metal distribution south of Australia, key differences in the drivers of dFe between oceanographic zones of the Southern Ocean were identified. In the subtropical zone, sources of dFe were attributed to waters advected off the continental shelf, and to recirculated modified mode and intermediate water‐masses of the Tasman Outflow. In the subantarctic zone, the seasonal replenishment of dFe in Antarctic surface and mode waters appears to be sustained by iron recycling in the underlying mode and intermediate waters. In the southern zone, the dFe distribution is likely driven by dissolution and scavenging by high concentrations of particles along the Antarctic continental shelf and slope entrained in high salinity shelf water. This approach to trace metal analysis may prove useful in future transects for identifying key mechanisms driving marine dissolved trace metal distributions. Plain Language Summary: Iron is an essential nutrient for the growth of phytoplankton, marine plants that are an integral part of the marine carbon cycle. The Southern Ocean has very low amounts of iron, which largely limits phytoplankton growth. To better understand carbon and iron cycles, investigating the supply and distribution of iron throughout the Southern Ocean is needed to see how phytoplankton responds to current iron sources and into the future as our climate changes. Shipboard observations from a transect south of Tasmania, Australia, to the Antarctic continental margin have been used to assess how iron distributions are influenced by ocean circulation, chemical processes, biological activity, and new sources of iron to the ocean. Different processes were found to influence and control the iron distribution between distinct regions of the Southern Ocean. In the north of the transect, iron was sourced from sediments and the continental shelf around Tasmania, and was also delivered to the study area by local ocean currents around Tasmania. Further south, biological activity within a single water‐mass layer appears to be responsible for maintaining a subsurface iron pool. Closer to Antarctica, ocean currents and biological processes are less important, with high particle concentrations likely driving the iron distribution. Key Points: Application of optimum multiparameter analysis to Southern Ocean dissolved iron as a new approach to trace metal distribution analysisClear differences in the dominant mechanisms that distribute dissolved iron were found between oceanographic zonesObservational evidence for key dissolved iron distribution mechanisms can be used for model validation and optimization at the basin scale [ABSTRACT FROM AUTHOR]

Objective: The purpose of the study was to determine whether dynamic susceptibility contrast perfusion MRI allowed distinction of cerebral abscesses from cystic high-grade brain neoplasms., Conclusion: In this small preliminary study, dynamic susceptibility perfusion MRI allowed distinction of cerebral abscesses from rim-enhancing high-grade gliomas. Validation of these results using a prospective large study is warranted.