(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.

Dissolved aluminium measured on water bottle samples during POLARSTERN cruise ARK-XXII/2 (SPACE)

Concentrations of dissolved (0.2 µm filtered) aluminium (Al) have been determined for the first time in the Eurasian part of the Arctic Ocean over the entire water column during expedition ARK XXII/2 aboard R.V. Polarstern (2007). An unprecedented number of 666 samples was analysed for 44 stations along 5 ocean transects. Dissolved Al in surface layer water (SLW) was very low, close to 1 nM, with lowest SLW concentrations towards the Canadian part of the Arctic Ocean and higher values adjacent to and in the shelf seas. The low SLW concentrations indicate no or little influence from aeolian dust input. Dissolved Al showed a nutrient-type increase with depth up to 28 nM, but large differences existed between the different deep Arctic basins. The differences in concentrations of Al between water masses and basins could largely be related to the different origins of the water masses. In the SLW and intermediate water layers, Atlantic and Pacific inflows were of importance. Deep shelf convection appeared to influence the Al distribution in the deep Eurasian Basin. The Al distribution of the deep Makarov Basin provides evidence for Eurasian Basin water inflow into the deep Makarov Basin. A strong correlation between Al and Silicon (Si) was observed in all basins. This correlation and the nutrient-like profile indicate a strong biological influence on the cycling and distribution of Al. The biological influence can be direct by the incorporation of Al in biogenic silica, indirect by preferential scavenging of Al onto biogenic siliceous particles, or by a combination of both processes. From the slope of the overall Al-Si relationship in the intermediate water layer (AIDW; ~ 200-2000 m depth), an Al/Si ratio of 2.2 atoms Al per 1000 atoms Si was derived. This ratio is consistent with the range of previously reported Al/Si uptake ratio in biogenic opal frustules of diatoms. In the deepest waters (>2000 m depth) a steeper slope of the Al-Si relationship of 7.4 to 13 atoms Al per 1000 atoms Si likely results from entrainment of cold shelf water into the deep basins, carrying the signal of dissolution of terrigenous particles with a much higher Al:Si ratio of crustal abundance. Only a small enrichment with such crustal Al and Si component may readily account for the higher Al:Si slope in the deepest waters.

Dissolved iron measurements from 32 stations in the Central Arctic Ocean and Arctic Shelf Sea during POLARSTERN expedition ARK-XXII/2

Concentrations of dissolved (<0.2 µm) Fe (DFe) in the Arctic shelf seas and in the surface waters of the central Arctic Ocean are presented. In the Barents and Kara seas, near-surface DFe minima indicate depletion of DFe by phytoplankton growth. Below the surface, lower DFe concentrations in the Kara Sea (~0.4-0.6 nM) than in the Barents Sea (~0.6-0.8 nM) likely reflect scavenging removal or biological depletion of DFe. Very high DFe concentrations (>10 nM) in the bottom waters of the Laptev Sea shelf may be attributed to either sediment resuspension, sinking of brine or regeneration of DFe in the lower layers. A significant correlation (R2 = 0.60) between salinity and DFe is observed. Using d18O, salinity, nutrients and total alkalinity data, the main source for the high (>2 nM) DFe concentrations in the Amundsen and Makarov Basins is identified as (Eurasian) river water, transported with the Transpolar Drift (TPD). On the North American side of the TPD, the DFe concentrations are low (<0.8 nM) and variations are determined by the effects of sea-ice meltwater, biological depletion and remineralization and scavenging in halocline waters from the shelf. This distribution pattern of DFe is also supported by the ratio between unfiltered and dissolved Fe (high (>4) above the shelf and low (<4) off the shelf).

Fluorescence of dissolved organic matter un marine sediments

The fluorescence of porewaters from marine sediment cores from six different areas was measured. In most cases, fluorescence was affected primarily by the diagenesis of organic carbon first through sulfate reduction and subsequently by methane generation. Typically, fluorescence, dissolved organic carbon (DOC), absorbance, alkalinity, and ammonium ion concentrations correlate quite well, increasing in the upper sections of anoxic sediments and co-varying in deeper sections of these cores. The good correlation of DOC with fluorescence in the three cores in which DOC was measured indicates that fluorescence can be used to make a first order estimate of DOC concentration in anoxic porewaters. Data are consistent with a model in which labile organic matter in the sediments is broken down by sulfur reducing bacteria to low molecular weight monomers. These monomers are either remineralized to CO2 or polymerize to form dissolved, fluorescent, high molecular weight molecules. The few exceptions to this model involve hydrothermally generated hydrocarbons that are formed in situ in the Guaymas Basin or are horizontally advected along the decollement in the Nankai Trench.

Concentrations of carbon of dissolved and particulate total and colored organic matter in the Gulf of Riga in 1980 and 1981

Concentration, distribution, and dynamics of yellow substance were studied during 1980-1982. Colored material accounted for 17-41% of dissolved organic matter and 2-14% of suspended organic matter. A relationship of yellow substance levels with salinity is analyzed. Absorption spectra of suspended particles are studied, occurrence of yellow-colored particles in suspended phase and their distribution in the Gulf of Riga are described. Concentration of suspended yellow organic matter in the upper layer of the gulf was inversely correlated with salinity. Calculations show that 10% of terrigenous humus is flocculated in the gulf during spring.

(Table 2) 230Th, 230Th xs and 232Th concentrations in dissolved, particulate and total (dissolved+small particles) for all KEOPS stations, Marion Dufresne cruise MD145

In the context of the KErguelen Ocean and Plateau compared Study (KEOPS, 19 January-13 February 2005), particle dynamics were investigated using thorium isotope measurements over and off the Kerguelen plateau. Dissolved and particulate 230Th and 232Th samples were collected at nine stations. Dissolved excess 230Th concentrations (230Thxs) vary from 0.5 to 20.8 fg/kg and particulate 230Thxs concentrations from 0.1 to 10.0 fg/kg. Dissolved and particulate 232Th concentration ranges are 16.8-450.2 pg/kg and 3.8-502.8 pg/kg, respectively. The 230Thxs concentrations increase linearly with depth down to the bottom at most of the plateau stations and down to 1000 m at the off-plateau stations. This linear trend is observed down to the bottom (1550 m) at Kerfix, the open-ocean "upstream" station located west of the Kerguelen plateau. A simple reversible scavenging model applied to these data allowed the estimation of adsorption rate constant (k1~=0.2-0.8 per year), desorption rate constant (k-1~=1-8 per year) and partition coefficients (average K=0.16±0.07). Calculated particle settling velocities S deduced from this simple model are ca. 500 m/year at most of the plateau stations and 800 m/year at all the off-plateau stations. The plateau settling velocities are relatively low for such a productive site, compared to the surrounding HNLC areas. The difference might reflect the fact that lateral advection is neglected in this model. Taking this advection into account allows the reconstruction of the observed 230Thxs linear distributions, but only if faster settling velocities are considered. This implies that the 1D model strongly underestimates the settling velocity of the particles. In the deep layers, the occurrence of intense boundary scavenging along the escarpment due to bottom sediment re-suspension and interaction with a nepheloid layer, yielding a removal of ?50% of the Th stock along the northwestward transect, is suggested.