Description: Pteropods are important organisms in highlatitude ecosystems, and they are expected to severely suffer from climate change in the near future. In this study, sedimentation patterns of two pteropod species, the polar Limacina helicina and the subarctic boreal L. retroversa, are presented. Time series data received by moored sediment traps at the Long-Term Ecological Research (LTER) Observatory HAUSGARTEN in eastern Fram Strait were analyzed during the years 2008 to 2012. Results were derived from four different deployment depths (200, 1,250, 2,400, and 2,550 m) at two different sites (79°N 04'200E; 79°430N 04'300E). A species-specific sedimentation pattern was present at all depths and at both sites showing maximal flux rates during September/October for L. helicina and in November/December for L. retroversa. The polar L. helicina was outnumbered by L. retroversa (55–99 %) at both positions and at all depths supporting the recently observed trend toward the dominance of the subarctic boreal species. The largest decrease in pteropod abundance occurred within the mesopelagic zone (*200–1,250 m), indicating loss via microbial degradation and grazing. Pteropod carbonate (aragonite) amounted up to *75 % of the total carbonate flux at 200 m and 2–13 % of the aragonite found in the shallow traps arrived at the deep sediment traps (*160 m above the seafloor), revealing the significance of pteropods in carbonate export at Fram Strait. Our results emphasize the relevance and the need for continuation of long-term studies to detect and trace changes in pteropod abundances and community composition and thus in the vertical transport of aragonite.

Description: Current meters measured temperature and velocity on 12 moorings from 1997 to 2014 in the deep Fram Strait between Svalbard and Greenland at the only deep passage from the Nordic Seas to the Arctic Ocean. The sill depth in Fram Strait is 2545 m. The observed temperatures vary between the colder Greenland Sea Deep Water and the warmer Eurasian Basin Deep Water. Both end members show a linear warming trend of 0.11±0.02°C/decade (GSDW) and 0.05±0.01°C/decade (EBDW) in agreement with the deep water warming observed in the basins to the north and south. At the current warming rates, GSDW and EBDW will reach the same temperature of -0.71°C in 2020. The deep water on the approximately 40 km wide plateau near the sill in Fram Strait is a mixture of the two end members with both contributing similar amounts. This water mass is continuously formed by mixing in Fram Strait and subsequently exported out of Fram Strait. Individual measurements are approximately normally distributed around the average of the two end members. Meridionally, the mixing is confined to the plateau region. Measurements less than 20 km to the north and south have properties much closer to the properties in the respective basins (Eurasian Basin and Greenland Sea) than to the mixed water on the plateau. The temperature distribution around Fram Strait indicates that the mean flow cannot be responsible for the deep water exchange across the sill. Rather, a coherence analysis shows that energetic mesoscale flows with periods of approximately 1-2 weeks advect the deep water masses across Fram Strait. These flows appear to be barotropically forced by upper ocean mesoscale variability. We conclude that these mesoscale flows make Fram Strait a hot spot of deep water mixing in the Arctic Mediterranean. The fate of the mixed water is not clear, but after the 1990s, it does not reflect the properties of Norwegian Sea Deep Water. We propose that it currently mostly fills the deep Greenland Sea.

Description: As part of the HAUSGARTEN long-term observatory, sediment trap deployments were carried out before, during, and after the anomalously warm Atlantic Water inflow observed from 2005 to 2007 in the eastern Fram Strait. Downward export of particulate organic carbon (POC), zooplankton fecal pellet carbon (FPC), and biogenic particulate silica (bPSi) were measured from August 2002 to June 2003 and from July 2004 to July 2008 to indirectly assess the impact of the warm anomaly on phytoplankton and zooplankton communities in the region. Lower and less frequent bPSi fluxes were observed during most of the warm anomaly period, reflecting a shift in phytoplankton community composition towards dominance of small-sized phytoplankton under warmer conditions. Lower FPC fluxes observed concurrently with the lower bPSi fluxes may indicate a decrease in fecal pellet production due to changing feeding conditions. In addition, the export of smaller fecal pellets in fall 2005 and spring 2006 suggests a dominance of smaller zooplankton during the warm anomaly. Nonetheless, bPSi and FPC export always increased in the presence of ice cover in the area above the sediment trap, even during the warm anomaly period, suggesting that sea ice is a key factor influencing the frequency of export events in the eastern Fram Strait. The scarcity of ice over the sampling area in 2005 and 2006 may partly be due to the warm anomaly, although solar radiation and ice drift due to wind stress also govern ice cover extent in the region. Overall, the warm anomaly resulted in a shift in the composition of the export fluxes when associated with an absence of ice cover in the eastern Fram Strait.

Description: Sea ice volume and extent currently experience massive reduction in the Arctic Ocean due to climate change. Our long-term study aims at tracing effects of environmental changes in pelagic and benthic systems and investigate accompanying impacts on the fate of organic matter produced in the upper water column on its way down to the seafloor. Since the start of our observations in 1999, we have already seen some effects and will present selected data sets from the upper water column and benthic data during summer expeditions as well as results from vertical particle flux measurements that were obtained from annually deployed sediment traps at the LTER (Long-Term Ecological Research) observatory HAUSGARTEN in the eastern Fram Strait (79°/4°E) and on fewer occasions in the central Arctic Ocean (CAO). Highest biomass was found in the eastern Fram Strait and lowest in the heavily ice-covered regions in the CAO. Flux rates of POC where at least one order of magnitude lower in the CAO than in the eastern Fram Strait. While in the CAO ice algae dominate the recognizable flux fraction, faecal material prevailed in eastern Fram Strait traps. This points towards different systems of organic matter production and modification and, thus, different mechanisms determine the efficiency of the biological carbon pump. These differences are also reflected in the benthic communities in the CAO and in the eastern Fram Strait. These first results have shown the importance of long-term observations and encouraged the continuation of the Arctic Ocean Observing System FRAM (FRontiers in Arctic marine Monitoring) to record environmental and biological data at high temporal and spatial resolution.