Description: Understanding and responding to the rapidly occurring environmental changes in the Arctic over the past few decades require new approaches in science. This includes improved collaborations within the scientific community but also enhanced dialogue between scientists and societal stakeholders, especially with Arctic communities. As a contribution to the Third International Conference on Arctic Research Planning (ICARPIII), the Arctic in Rapid Transition (ART) network held an international workshop in France, in October 2014, in order to discuss high-priority requirements for future Arctic marine and coastal research from an early-career scientists (ECS) perspective. The discussion encompassed a variety of research fields, including topics of oceanographic conditions, sea-ice monitoring, marine biodiversity, land-ocean interactions, and geological reconstructions, as well as law and governance issues. Participants of the workshop strongly agreed on the need to enhance interdisciplinarity in order to collect comprehensive knowledge about the modern and past Arctic Ocean's geo-ecological dynamics. Such knowledge enables improved predictions of Arctic developments and provides the basis for elaborate decision-making on future actions under plausible environmental and climate scenarios in the high northern latitudes. Priority research sheets resulting from the workshop's discussions were distributed during the ICARPIII meetings in April 2015 in Japan, and are publicly available online.

Description: Recent studies of the vertical flux of organic matter into the deep ocean have prompted the search for key organic compounds (biomarkers) as tracers for its production, flux and burial into the sediment. Particulate matter was collected with sediment traps moored at the Barents Sea continental margin (75°11.78′N/12°29.21′E; water depth 2050 m) at 610, 1840 and 1950 m depth. The compositions of the organic material in the two bottoms near traps differ significantly. This difference cannot be the result of a change of the vertical sedimentation alone. A combination of biomarker analyses, quantitative microscopy and bulk parameter determinations on water and sediment trap samples is used in this study to demonstrate that a turbidity plume event at the shelf edge is a vehicle to transport organic and lithogenic particles at high velocities to the benthos of the lower continental margin. It is suggested that fine particles were advected into the trap at 1850 m, whereas the coarser fraction of higher settling velocities, passing several resuspension loops entered the lower trap.

Description: The development of phytoplankton biomass and composition was investigated on three occasions along a longitudinal transect (6°W) between 60°S and 47°S from October 13 to November 21, 1992 by measurement of photosynthetic pigments with high performance liquid chromatography (HPLC). Measured accessory pigment concentrations were multiplied by conversion factors to derive the proportions of phytoplankton groups contributing to the biomass indicator chlorophyll a. Phytoplankton blooms developed in the Polar Frontal region (PFr) and were dominated (80%) by diatoms. Other groups contributing to the phytoplankton included prymnesiophytes, green algae, autotrophic dinoflagellates, cryptophytes, pelagophytes and micromonadophytes, and their distributions varied with time. In contrast, phytoplankton biomass remained low in the southern Antarctic Circumpolar Current (ACC) and was dominated by flagellates, particularly green algae and prymnesiophytes. Green algae contributed more to total biomass than in previous investigations, partly attributed to “Chlorella-like” type organisms rather than prasinophytes. Cryptophytes decreased during the investigation, possibly due to salp grazing. No bloom was observed at the retreating ice-edge, presumably due to strong wind mixing. Only a slight increase in phytoplankton biomass, composed primarily of diatoms, was found at the ACC-Weddell Gyre front. Cluster analysis revealed that different phytoplankton communities characterised the different water masses of the PFr and southern ACC; the history of different water masses in the PFr could be reconstructed on this basis.

Description: High biogenic silica (BSi) concentrations (maximum: 11.7μmoll−1) were recorded during late November at the southern border of the Polar Frontal region (PFr). Position of the BSi maximum at depth suggested the occurrence of a sinking diatom population. By contrast, siliceous biomass was low (BSi 〈0.6 μmol l−1) in the Marginal Ice Zone (MIZ) despite a sea-ice retreat of 200 km during the study period. Diatoms released from the receding ice were not actively growing. The Permanently Open Ocean Zone also showed very low BSi biomass (〈0.5μmol l−1) and appeared as an area where phytoplankton are not dominated by siliceous organisms, especially in its middle part where BSi/POC (particulate organic carbon) molar ratios ranged between 0.04 and 0.06 at 53°S, from surface to 200 m depth. At the southern border of the PFZ, the bloom coincided with an area of high lithogenic silica concentrations probably of aeolian origin. In addition, BSi/POC molar ratios measured in the PFZ were the highest ever recorded in the surface waters of the Southern Ocean (maximum: 1.75). This could be due to the presence of heavily silicified diatoms such as Fragilariopsis kerguelensis or also could reflect the more rapid recycling of POC as compared to BSi. Within the bloom area BSi concentrations were positively correlated to pyrophaeophytin pigments, possibly indicating the occurrence of a senescent diatom population. High concentrations of BSi (〉 1.5 μmol Si 1−1) extended to 200 m between 49°S and 51°S. Numerous empty frustules also were observed, suggesting significant sedimentation of siliceous particles between 49°S and 51°S. Estimates of the BSi production of the Polar Frontal region are derived from 14C primary production and appropriate BSi/POC ratios, and implications for the total annual production of BSi for the Southern Ocean are discussed.

Description: Small-scale features of the Antarctic Circumpolar Current (ACC) along a meridional section at 6°W between the Polar Front and the ACC-Weddell Gyre Boundary Front are discussed using data collected during the austral spring cruise ANT X/6 of R. V. Polarstern organized within the framework of the European IGBP-JGOFS (Southern Ocean). The section covered three distinct fronts, namely the Polar Front, the Southern Polar Front (also Southern ACC Front), and the ACC-Weddell Gyre Boundary Front. Physical measurements during repeated transects over a period of 6 weeks in October/November revealed a large variability in the Polar Frontal region, indicating meandering and eddy shedding. The positions of the Southern Polar Front and the ACC-Weddell Gyre Boundary Front were observed to be far more stable than that of the Polar Front. A possible reconstruction of the meandering flow field near the Polar Front, based upon the physical observations, is presented. Details in the flow field coincide with the spatial distribution of a number of biological parameters such as phytoplankton biomass and species, and photosynthetic pigments. Although a causal relationship between them is likely, biomass enhancement cannot be understood simply in terms of macronutrients from deeper layers entering the euphotic zone, as substantiated for other oceanic frontal regions, because macronutrients do not limit phytoplankton blooms. This process, however, can be important for the micronutrient iron. Evidence is presented that the Antarctic Zone of the ACC can be subdivided into a number of spheres of influence related to the fronts. Interleaving of water is apparent between positions within such a region, but not between the regions.

Description: Die sechste Ausgabe des „World Ocean Review“ (WOR) widmet sich der Arktis und Antarktis, diesen zwei extremen und ausgesprochen gegensätzlichen Regionen der Erde. Mit profunden Informationen zur Entstehungs- und Entdeckungsgeschichte bietet der WOR 6 ein tiefes Verständnis der Bedeutung der Pole für das Leben auf unserer Erde. Er zeigt zudem die zu beobachtenden Veränderungen in der Tier-und Pflanzenwelt und analysiert die zum Teil schon dramatischen Folgen, die der Klimawandel in diesen äußerst gefährdeten Regionen bewirkt.

Description: This sixth World Ocean Review (WOR) focuses on the Arctic and the Antarctic – two regions which are, in a very real sense, polar opposites, with some of the world’s most extreme conditions. Besides presenting a wealth of facts and figures about the history and exploration of the polar regions, WOR 6 builds a deeper awareness of their key role for life on our planet. It highlights the changes that can be observed in their flora and fauna and analyses the already dramatic impacts of global warming on these extremely fragile regions.

Description: Although the Arctic covers 6% of our planet’s surface and plays a key role in the Earth’s climate it remains one of the least explored ecosystems. The global change induced decline of sea ice has led to increasing anthropogenic presence in the Arctic Ocean. Exploitation of its resources is already underway, and Arctic waters are likely important future shipping lanes as indicated by already increasing numbers of fishing vessels, cruise liners and hydrocarbon prospecting in the area over the past decade. Global estimates of plastic entering the oceans currently exceed results based on empirical evidence by up to three orders of magnitude highlighting that we have not yet identified some of the major sinks of plastic in our oceans. Fragmentation into microplastics could explain part of the discrepancy. Indeed, microplastics were identified from numerous marine ecosystems globally, including the Arctic. Here, we analysed horizons of ice cores from the western and eastern Fram Strait by focal plane array based micro-Fourier transform infrared spectroscopy to assess if sea ice is a sink of microplastic. Ice cores were taken from land-locked and drifting sea ice to distinguish between local entrainment of microplastics vs long-distance transport. Mean concentrations of 2 x 106 particles m-3 in pack ice and 6 x 105 particles m-3 in land-locked ice were detected (numbers of fibers will soon be added). Eleven different polymer types were identified; polyethylene (PE) was the most abundant one. Preliminary results from four further ice cores from the central Arctic range in a similar order but the microplastics composition was very different. Calculation of drift trajectories by back-tracking of the ice floes sampled indicates multiple source areas, which explains the differences in the microplastic composition. Preliminary analysis of snow samples taken from ice floes in the Fram Strait showed numerous fibers of yet unknown but most likely anthropogenic origin indicating atmospheric fallout as a possible pathway. Our results exceed concentrations from the North Pacific by several orders of magnitudes. This can be explained partly by the process of ice formation, during which (organic) particles tend to concentrate by 1-2 orders of magnitude compared with ambient seawater. However, the magnitude of the difference indicates that Arctic sea ice is a temporal sink for microplastics. Increasing quantities of small plastic litter items on the seafloor nearby, which is located in the marginal ice zone corroborate the notion that melting sea ice releases entrained plastic particles and that sea ice acts as a vector of transport both horizontally and vertically to underlying ecosystem compartments.

Description: Between Greenland and Spitsbergen, Fram Strait is a region where cold ice-covered Polar Water exits the Arctic Ocean with the East Greenland Current (EGC) and warm Atlantic Water enters the Arctic Ocean with the West Spitsbergen Current (WSC). In this compilation, we present two different data sets from plankton ecological observations in Fram Strait: (1) long-term measurements of satellite-derived (1998–2012) and in situ chlorophyll a (chl a) measurements (mainly summer cruises, 1991–2012) plus protist compositions (a station in WSC, eight summer cruises, 1998–2011); and (2) short-term measurements of a multidisciplinary approach that includes traditional plankton investigations, remote sensing, zooplankton, microbiological and molecular studies, and biogeochemical analyses carried out during two expeditions in June/July in the years 2010 and 2011. Both summer satellite-derived and in situ chl a concentrations showed slight trends towards higher values in the WSC since 1998 and 1991, respectively. In contrast, no trends were visible in the EGC. The protist composition in the WSC showed differences for the summer months: a dominance of diatoms was replaced by a dominance of Phaeocystis pouchetii and other small pico- and nanoplankton species. The observed differences in eastern Fram Strait were partially due to a warm anomaly in the WSC. Although changes associated with warmer water temperatures were observed, further long-term investigations are needed to distinguish between natural variability and climate change in Fram Strait. Results of two summer studies in 2010 and 2011 revealed the variability in plankton ecology in Fram Strait.