(Appendix A) Dissolved manganese concentrations during POLARSTERN Cruise ARK-XXII/2

A total of 773 samples were analysed for dissolved manganese (Mn) in the Arctic Ocean aboard R.V. Polarstern during expedition ARK XXII/2 from 28 July until 07 October 2007 from Tromsø (Norway) to Bremerhaven. Concentrations of Mn were elevated in the surface layer with concentrations of up to 6 nM over the deep Basins and over 20 nM in the Laptev Sea. The general distribution of Mn through the water column is consistent with previous studies, but there are differences in the absolute concentrations that are most likely related to differences in sample area, sampling and filtration. The elevated concentrations of Mn in the surface layer are related to fresh water input. This was visible in the strong negative correlations observed between dissolved Mn and salinity. The correlation between Mn and salinity and the correlation between Mn and the quasi conservative trace water mass tracer PO4*, showed fluvial and melt water input and the Pacific and Atlantic origin of the surface waters. A large portion of the Mn delivered by the Arctic rivers is removed in the shelf seas and does not pass into the central basins. Most likely a benthic flux is at the origin of the elevated concentrations of Mn near the sediments in the Barents and Kara Seas. These elevated concentrations of Mn apparently affected the deep basins as well, as maxima in the concentrations of Mn were observed that corresponded with lowered transmission over the continental slope. A maximum in the concentration of Mn in the deep basin corresponded with anomalies in light transmission, potential temperature and dissolved iron, confirming the hydrothermal origin. The hydrothermal plume was observed throughout the Nansen Basin and over the deep Gakkel Ridge around 2500 m depth and a smaller plume was observed around 3200 m. The concentration of Mn at the Mn maximum around 2500 m depth decreased exponentially, consistent with a first order scavenging model. The concentrations of Mn were extremely low in the deep Makarov Basin (~0.05 nM) and slightly higher in the Eurasian Basin (~0.1 nM) outside the influence of the hydrothermal activity.

Distribution, depositional form and geochemical composition of tephra horizons in ODP Sites 186-1150 and 186-1151

Major element geochemical composition was established for 59 tephra horizons from Ocean Drilling Program Sites 1150 and 1151, located in the Japan forearc. These data, encompassing typically between 15 and 30 individual shard analyses per tephra horizon, were used to investigate the degree to which sediment reworking, postdepositional geochemical alteration, and geochemical uniqueness of individual eruptives facilitate or impede the potential for establishing a tephrostratigraphical framework for the Japan Trench, as well as usage of the tephra record to document arc evolution. Evidence was found that hydration (termed phase 1 alteration) of glass shards increases with age in the Pliocene-Pleistocene, but there is no indication that element leaching (phase 2 alteration) has occurred. Post- or syn-depositional differences in preservational style are shown to have no significant bearing on tephrogeochemical homogeneity and suitability for tephrostratigraphical analysis. Overall, therefore, the volcaniclastic record is suitable for investigating medium- to long-term changes in arc geochemistry and, provided consideration is given to the potential for nonunique geochemical signatures, is suitable for erecting tephrochronological frameworks. A limited number of Pleistocene tephra correlations are suggested in furtherance of this framework goal.