Bericht über die "Poseidon"-Reise 111/2 [POS111/2] vom 02.-24.08.1984 in das Gebiet zwischen Azoren und Neufundland

Die Reise diente der Untersuchung des Azorenstromes in Zusammenarbeit mit dem estnischen Forschungsschiff "Arnold Veimer"

A dynamically consistent analysis of circulation and transports in the southwestern Weddell Sea

International audienceAn inverse model is applied for the analysis of hydrographic and current meter data collected on the repeat WOCE section SR4 in the Weddell Sea in 1989?1992. The section crosses the Weddell Sea cyclonic gyre from Kapp Norvegia to the northern end of the Antarctic Peninsula. The concepts of geostrophy, conservation of planetary vorticity and hydrostatics are combined with advective balances of active and passive properties to provide a dynamically consistent circulation pattern. Our variational assimilation scheme allows the calculation of three-dimensional velocities in the section plane. Current speeds are small except along the coasts where they reach up to 12 cm/s. We diagnose a gyre transport of 34 Sverdrup which is associated with a poleward heat transport of 28×1012 W corresponding to an average heat flux of 15 Wm?2 in the Weddell Sea south of the transect. This exceeds the estimated local flux on the transect of 2 Wm?2. As the transect is located mostly in the open ocean, we conclude that the shelf areas contribute significantly to the ocean-atmosphere exchange and are consequently key areas for the contribution of the Weddell Sea to global ocean ventilation. Conversion of water masses occuring south of the section transform 6.6±1.1 Sv of the inflowing warm deep water into approximately equal amounts of Weddell Sea deep water and Weddell Sea bottom water. The volume transport of surface water equals in the in- and outflow. This means that almost all newly formed surface water is involved in the deep and bottom water formation. Comparison with the results obtained by pure velocity interpolation combined with a hydrographic data subset indicates major differences in the derived salt transports and the water mass conversion of the surface water. The differences can be explained by deviations in the structure of the upper ocean currents to which shelf areas contribute significantly. Additionally a rigorous variance analysis is performed. When only hydrographic data are used for the inversion both the gyre transport and the poleward heat transport are substantially lower. They amount to less than 40% of our best estimate while the standard deviations of both quantities are 6.5 Sv and 37×1012 W, respectively. With the help of long-term current meter measurements these errors can be reduced to 2 Sv and 8×1012 W. Our result underlines the importance of velocity data or equivalent information that helps to estimate the absolute velocities

Weddell Sea iceberg drift: Five years of observations

Since 1999, 52 icebergs have been tagged with GPS buoys in the Weddell Seato enable monitoring of their position. The chosen icebergs were of small tomedium size, with a few icebergs larger than 10 km associatedwith the calving of icebergs A38 and A43 from the Ronne Ice Shelf.The majority of icebergs were tagged off Neumayer Station (8E, 70S).It was found that smaller bergs with edges shorter than 200 m had the shortestlife cycle (< 0.5 yr). Iceberg and thus freshwater export out of theWeddell Sea was found to be highly variable. In one year the majority of buoysdeployed remained in the Weddell Sea, constituting about 40 % of the NCEP P-Efreshwater input, whereas in other years all of the tagged icebergs were exported.The observed drifts of icebergs and sea-ice showed a remarkably coherent motion.The analysis of an iceberg - sea-ice buoy array in the western Weddell Seaand an iceberg array in the eastern Weddell Sea showed a coherent sea-iceiceberg drift in sea-ice concentrations above 86 %. Dynamic kinematic parameter(DKP) during the course of coherent movement were low and deviations from the meancourse associated with the passage of low-pressure system. The length scale ofcoherent movement was estimated to be less than 250km; about half the value found forthe Arctic Ocean

Assessment of the structure and variability of Weddell Sea water masses in distinct ocean reanalysis products

We assessed and evaluated the performance of five ocean reanalysis products in reproducing essential hydrographic properties and their associated temporal variability for the Weddell Sea, Antarctica. The products used in this assessment were ECMWF ORAS4 (European Centre for Medium-Range Weather Forecasts Ocean Reanalysis System 4), CFSR (Climate Forecast System Reanalysis), MyOcean UR025.4 (University of Reading), ECCO2 (Estimating the Circulation and Climate of the Ocean, Phase II) and SODA (Simple Ocean Data Assimilation). The present study focuses on the Weddell Sea deep layer, which is composed of the following three main water masses: Warm Deep Water (WDW), Weddell Sea Deep Water (WSDW) and Weddell Sea Bottom Water (WSBW). The MyOcean UR025.4 product provided the most accurate representation of the structure and thermohaline properties of the Weddell Sea water masses when compared with observations. All the ocean reanalysis products analyzed exhibited limited capabilities in representing the surface water masses in the Weddell Sea. The CFSR and ECCO2 products were not able to represent deep water masses with a neutral density ? 28.40 kg m?3, which was considered the WSBW's upper limit throughout the simulation period. The expected WDW warming was only reproduced by the SODA product, whereas the ECCO2 product was able to represent the trends in the WSDW's hydrographic properties. All the assessed ocean reanalyses were able to represent the decrease in the WSBW's density, except the SODA product in the inner Weddell Sea. Improvements in parameterization may have as much impact on the reanalyses assessed as improvements in horizontal resolution primarily because the Southern Ocean lacks in situ data, and the data that are currently available are summer-biased. The choice of the reanalysis product should be made carefully, taking into account the performance, the parameters of interest, and the type of physical processes to be evaluated

Queen Dominance May Reduce Worker Mushroom Body Size in a Social Bee

The mushroom body (MB) is an area of the insect brain involved in learning, memory, and sensory integration. Here, we used the sweat bee Megalopta genalis (Halictidae) to test for differences between queens and workers in the volume of the MB calyces. We used confocal microscopy to measure the volume of the whole brain, MB calyces, optic lobes, and antennal lobes of queens and workers. Queens had larger brains, larger MB calyces, and a larger MB calyces:whole brain ratio than workers, suggesting an effect of social dominance in brain development. This could result from social interactions leading to smaller worker MBs, or larger queen MBs. It could also result from other factors, such as differences in age or sensory experience. To test these explanations, we next compared queens and workers to other groups. We compared newly emerged bees, bees reared in isolation for 10 days, bees initiating new observation nests, and bees initiating new natural nests collected from the field to queens and workers. Queens did not differ from these other groups. We suggest that the effects of queen dominance over workers, rather than differences in age, experience, or reproductive status, are responsible for the queen–worker differences we observed. Worker MB development may be affected by queen aggression directly and/or manipulation of larval nutrition, which is provisioned by the queen. We found no consistent differences in the size of antennal lobes or optic lobes associated with differences in age, experience, reproductive status, or social caste.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150573/1/dneu22705_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150573/2/dneu22705.pd