Six logistically and scientifically interlinked research projects were coordinated under the framework of the Biogeochemistry Programme. The Biogeochemistry Programme partners represented many international research institutions and were funded by external grants totalling over 10 Million SEK. While unified symbiotically by common sampling techniques and underlying biogeochemical processes, the research projects may be divided into Element Biogeochemistry (projects 1–3, below) and Environmental Biogeochemistry (projects 4–6):

• Dynamics of surface-water export fluxes of carbon and other biogeochemically-important elements
• The speciation and fluxes of iron and rare earth elements in Arctic surface waters
• The distribution of long-lived radioisotopes as tracers of particle provenance and water mass transport in the Arctic Ocean
• Long-range transport and fate processes of persistent organic pollutants (POPs) in the Arctic
• Uptake and food-web transfer of POPs in the plankton community in the productive marginal ice zone
• Occurrence and effects of currently used pesticides in the Arctic Environment

The ”carbon” and ”iron” projects seek to contribute knowledge on both the controlling aggregation/settling mechanisms and fluxes of these key elements in surface waters of the marginal ice zone as well as in the high Arctic basins. These objectives contribute to the goals of the international Joint Global Ocean Flux Study (JGOFS; a core programme within the International Geosphere-Biosphere Programme, IGBP). This is particularly timely as JGOFS was neither able to cover the Arctic Ocean in its twelve years of field activities nor to afford detailed mechanistic studies of what governs the subsurface export rates of carbon. Such information is necessary for predicting the effects of changing external conditions. The limited data on carbon export flux in the Arctic suggests that the Arctic ice-edge seasonally exhibits the highest biogenic organic carbon export-to-production ratio of anywhere in the world’s oceans (Buesseler, 1998), while lower, measurable carbon export fluxes were also revealed in the perennially ice-covered Canadian Basin during the 1994 U.S.–Canadian Arctic Ocean Section to the North Pole (Moran et al., 1997). Hence a key objective of Arctic Ocean 2001 was to provide the first transect of carbon export through the Eurasian basins to the North Pole. In order to get a view of the export intensity integrated over a monthly time-scale, we developed procedures for coupling the surface ocean carbon and iron stocks to onboard measurements of the natural ²³⁴Th ”settling clock”.

Long-lived radioisotope systems have the potential to apportion the sources of particles and water masses by fingerprinting the lithology and geological age of the weathered material from different source regions. Because these long-lived isotopes may also be preserved in the underlying sediments, isotopes of Nd, Sr, Hf, Th, and Be may be interpretable to shed light on variations in the properties of the overlying waters. An objective during Arctic Ocean 2001 was thus to establish a modern-day calibration of these putative paleotracers of historical circulation and sediment transport in the Arctic Ocean by a close coupling with the core hydrographic activities performed during Arctic Ocean 2001. For instance, the ratio of the ¹⁴³Nd and ¹⁴⁴Nd isotopes (expressed as ε_Nd) holds the potential to add information on the Arctic freshwater balance. Limited data on e_Nd (and ε_Sr) show that the isotopic composition varies between different Eurasian river basins emptying into the Arctic Ocean (e.g., Huh et al., 1998). Our activities during Arctic Ocean 2001 will provide the first ε_Nd data for the different water masses in the Arctic Ocean, enabling application of these novel and potentially powerful tools.

The levels of persistent organic pollutants (POPs) found in animals and the native human population in the Arctic are remarkably high and have been extensively monitored (AMAP, 1998). The objectives of the POP research projects of Arctic Ocean 2001 were to study quantitatively the (a) large-scale dispersal processes of POPs into the Eurasian Arctic basins, and (b) mechanisms of uptake into the base of the Arctic food web. Because many POPs are semivolatile, it has been suggested that they evaporate from temperate latitudes and condense in the Polar Regions (Wania and Mackay, 1995). This ”global pollutant distillation” scenario may be interpreted such that POPs would be concentrated in the Arctic. However, this notion has not been proven for ecotoxicologically important pollutants such as polychlorinated biphenyls (PCBs). Since the PCBs are composed of 209 different compounds/congeners, spanning a range in e.g., volatility, the relative congener distribution (a fingerprint) holds diagnostic information about the processes affecting their fate and transport in the environment. In fact, a recent Arctic sediment study showed that the more volatile PCB congeners indeed are enriched relative to heavier congeners in Baffin Bay sediments, while, importantly, all PCBs were present at lower concentrations than in Baltic or Mediterranean sediments (”global fractionation”; Gustafsson et al., 2001). To improve our knowledge on the ”global distillation/fractionation” process, a transect for individual PCBs was retrieved from the new seawater intake system inside the ultraclean laboratory from surface waters along 55–90°N. Further, the importance of the Arctic as a global repository of POPs will be assessed by tallying the total POP inventory in the major Eurasian Arctic water masses by combining in situ deep-water POP filtrations-extractions, as part of Arctic Ocean 2001, with previous samplings in the Greenland Sea and other Arctic areas by German colleagues.

The mechanisms behind the high concentrations of POPs in Arctic fish, sea birds, and marine mammals were the urgent objective of an EU project (FAMIZ) during Arctic Ocean 2001. Based on limited available data, the ratio of the concentrations of e.g., PCBs in fish and marine mammals to the concentrations in the surrounding seawater appears to be much higher in the Arctic than in other areas. During the expedition samples were collected to test two hypothetical explanations. The first possibility centers around formation of microenvironments where physical processes coinciding with the bloom and subsequent carbon transfer to the food web in both time and space will cause locally elevated concentrations of POPs in the bioavailable (dissolved) phase. Of particular importance is whether POPs transported by ice-rafted sediments and snow (both suspected of containing high POP levels) could eventually contribute to locally elevated exposures, e.g. to ice algae dwelling in brine pockets. The other hypothesis that is under evaluation focuses on specific properties of the Arctic micro-food web. The number of trophic transfers and the effective growth rate of animals in the food web will affect the total effect of biomagnification from the primary producers up to the top consumers. It is possible that the biomagnification potential of the Arctic planktonic food web differs substantially from that of the Baltic or the North Atlantic.

The sixth Biogeochemistry Programme project focused on the occurrence and effects of currently used pesticides in the Arctic environment. Modern pesticides and plant protection products are considered to be so water soluble (thus less likely to evaporate) and so rapidly degradable that long-range transport is unlikely. However, during the Arctic Ocean 1996 expedition Kylin and colleagues made preliminary observations of triazine herbicides and organophosporous insecticides in the Arctic. A key objective of the Arctic Ocean 2001project was thus to follow-up and systematically investigate the presence and distribution of such compounds in the various Arctic regimes visited during this summer´s expedition.

The biogeochemistry field activities

To test the hypotheses of the Biogeochemistry Programme projects, many technically advanced sampling systems were applied to Arctic matrices such as the atmosphere, surface water, deep water, ice, snow, brine, ice-rafted sediments, and diver-assisted extractions. Gratefully, all of our field-equipment and approaches performed very well under these high-Arctic conditions. Several Biogeochemistry Programme scientists played instrumental roles throughout the design, construction, and testing of both the new permanent ship-based laboratory and, in particular, the new twin-line seawater intake system. This modern ship-laboratory, with its ultraclean-room facility, was efficiently used and provided many possibilities for coordination and execution of sampling activities that otherwise would not have been possible. Its role in lifting Oden to the status of a modern research platform for marine chemical/biogeochemical research can hardly be overestimated.

Surface seawater was probed on-line with a Hydrolab Surveyor Sonde hooked up to the seaweater intake line in the laboratory that provided a continuous record of temperature, salinity, pH, and dissolved oxygen. Trace metals such as iron and many trace organic pollutants were continuously sampled on-line from the seawater intake inside the ultraclean room facility. Such projects would not have been possible without this new facility. The Biogeochemistry Programme laboratory activities also involved many different forms of filtration, ranging from small cross-flow ultrafiltration systems to sample submicron colloidal particles for the Element Biogeochemistry Programme projects to the 300 kg Ceraflo tangential-flow filtration system, in stainless steel and ceramics, designed to harvest the microbial community from many cubic meters of seawater. Specially-designed adsorbers for truly dissolved components of inorganic elements (DGT) and hydrophobic organic pollutants (PUFs) were also employed. The clean room was frequently visited by scientists from nearly all Biogeochemistry Programme projects for non-contaminating handling of filters and adsorbers from various sampling equipment.

The Niskin and the cleaner 20-60 L Go-Flo bottles attached to the CTD rig were important core sampling devices for many Biogeochemistry Programme parameters. We also deployed programmable and microprocessor-controlled in situ sampling systems (Kiel in situ pumps; KISPs) on the hydrowire to sample large volumes of seawater for PCBs and Nd isotopes from the deeper water masses in the Nansen, Amundsen, and Makarov Basins. Snow, ice, brine, and ice-rafted debris were sampled with specially crafted methodology. Two large and specially designed stainless steel systems afforded both the building of stamina for the ice team and efficient and non-contaminating melting of the pristine ice cores. Further, two specially-trained research ice divers immersed at least twice a day during leg 1 for diving-based sampling of ice algae. During the long drift station in the high Arctic, an ice camp was established for clean sampling of iron and other trace metals well away from the ship. A small mobile sampling house was used as the base and detailed profiles of the upper 200 m were obtained with several active and passive sampling techniques through carefully and cleanly drilled ice holes.

Some simpler analyses using spectrophotometers were performed directly onboard for transparent exopolymer particles (TEP) and optical properties of the suspended organic matter. An onboard method for precipitation, preparation of sample targets, and quantification of ²³⁴Th with low-level beta counter techniques was established because the 24 d half-life of this natural radioisotope would not have allowed waiting for shore based facilities during this long expedition. The preliminary ²³⁴Th data suggest a significant carbon export in the Barents Sea Marginal Ice Zone. Measurable export fluxes were also detected underneath the ice in the high Arctic basins, extending the 1994 Canadian Basin transect to the full passage of the high Arctic Ocean.

The multitude of Biogeochemistry Programme samples will now be exposed to advanced shore-based analytical facilities and we anticipate exciting new knowledge about the Arctic system to be contributed in the coming years.