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

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

Observed interannual changes beneath Filchner-Ronne Ice Shelf linked to large-scale atmospheric circulation

Floating ice shelves are the Achilles’ heel of the Antarctic Ice Sheet. They limit Antarctica’s contribution to global sea level rise, yet they can be rapidly melted from beneath by a warming ocean. At Filchner-Ronne Ice Shelf, a decline in sea ice formation may increase basal melt rates and accelerate marine ice sheet mass loss within this century. However, the understanding of this tipping-point behavior largely relies on numerical models. Our new multi-annual observations from five hot-water drilled boreholes through Filchner-Ronne Ice Shelf show that since 2015 there has been an intensification of the density-driven ice shelf cavity-wide circulation in response to reinforced wind-driven sea ice formation in the Ronne polynya. Enhanced southerly winds over Ronne Ice Shelf coincide with westward displacements of the Amundsen Sea Low position, connecting the cavity circulation with changes in large-scale atmospheric circulation patterns as a new aspect of the atmosphere-ocean-ice shelf system

From pole to pole : 33 years of physical oceanography onboard R/V Polarstern

Measuring temperature and salinity profiles in the world's oceans is crucial to understanding ocean dynamics and its influence on the heat budget, the water cycle, the marine environment and on our climate. Since 1983 the German research vessel and icebreaker Polarstern has been the platform of numerous CTD (conductivity, temperature, depth instrument) deployments in the Arctic and the Antarctic. We report on a unique data collection spanning 33 years of polar CTD data. In total 131 data sets (1 data set per cruise leg) containing data from 10 063 CTD casts are now freely available at doi: 10.1594/PANGAEA.860066. During this long period five CTD types with different characteristics and accuracies have been used. Therefore the instruments and processing procedures (sensor calibration, data validation, etc.) are described in detail. This compilation is special not only with regard to the quantity but also the quality of the data -the latter indicated for each data set using defined quality codes. The complete data collection includes a number of repeated sections for which the quality code can be used to investigate and evaluate long-term changes. Beginning with 2010, the salinity measurements presented here are of the highest quality possible in this field owing to the introduction of the OPTIMARE Precision Salinometer.Peer reviewe

Numerical Investigation of the Flow Around a Fuselage/Canard Configuration for a Long Range, Ultra High Capacity Aircraft

Within the scope of the development of a long range, ultra high capacity aircraft (UHCA) at Airbus Industrie also the application of a three surface configuration including a front fuselage canard is discussed. Therefore as a contract work for Airbus Industrie at DLR a numerical study concerning the flow around a fuselage/canard configuration has been performed with the aim to prove the aerodynamic feasibility of such a configuration especially in the high subsonic Mach number range. The fuselage geometry and canard planform has been given by Airbus Industrie as well as the geometrical constraints and the aerodynamic conditions. The investigations have been done using the DLR Euler code CEVCATS developed for the analysis of inviscid compressible flow. In the first part of the study the flow field of the front fuselage has been analyzed in detail

Nachrechnung und Entwurf von transsonischen Tragflügeln für die DO-728/DO-928

In diesem Bericht wurden Ergebnisse präsentiert, in denen verschiedene Flügel- und Flügel-Rumpf-Konfigurationen für das transsonische Verkehrsflugzeug DO-728 (70 Sitzer), bzw. DO-928 (90 Sitzer) der Firma Fairchild-Dornier nachgerechnet und entworfen wurden. Entwurfsziel war, bei vorgegebenen Geometrieanforderungen und bei vorgegebenen Auftriebsbeiwerten geeignete Druckverteilungen im transsonischen Flugbereich zu erlangen. Es wurden sowohl Flügelentwürfe der Firma Fairchild-Dornier nachgerechnet, als auch eigene Entwürfe untersucht. Für die Nachrechnung wurde das FLOWer-Verfahren benutzt um die Navier-Stokes Gleichungen numerisch zu lösen. Die Flügelentwürfe wurden sowohl in den Auslegungspunkten des Reiseflugs sowie im &quot;off-design&quot; untersucht. Es wurden die Widerstandspolare, der machzahlabhängige Widerstandsanstieg und die aerodynamische Gütezahl bestimmt sowie die Entwiklung der Ablösung auf der Flügeloberseite untersucht. Der Rumpfeinfluß wurde durch Analyse der Flügel-Rumpf-Konfiguration bestimmt

Distribution of iodide and iodate in the Atlantic sector of the southern ocean during austral summer

The biogeochemistry of iodine in the waters of the Atlantic sector of the Southern Ocean was investigated during the Polarstern cruise ANTXXIV-3 ZERO&DRAKE. The speciation and distribution of iodine (iodate and iodide) in seawater was examined across gradients of iron concentrations and phytoplankton abundance, ranging from an open ocean region along the Zero Meridian to the Weddell Sea and Drake Passage. Iodine cycling in high latitudes differs from that in low latitudes due to differences in the plankton community composition and the physicochemical characteristics. Iodate concentrations ranged between 400 and 450 nmol L(-1) from the surface to the bottom. Surface concentrations of iodide (17 to over 60 nmol L(-1)) were about an order of magnitude higher than below the pycnocline. The peak values of iodide lay nearly always within the euphotic zone and showed a weak, positive correlation with nitrite concentrations in the upper 200 m. In all vertical profiles a pronounced sub-surface maximum in iodide appears between 50 and 200 m depth indicating an iodide drawdown at the near surface. Iodide distribution in the Weddell Sea showed elevated levels in Weddell Sea Bottom Water (WSBW) indicating slow oxidation kinetics and the potential for iodide as a tracer of WSBW formation. (C) 2011 Elsevier Ltd. All rights reserved

Numerical Investigation on Two Airfoil Design Codes Based on the Euler and Navier-Stokes Equations

Under the framework of the DLR-CAE cooperation topic: 92-16, numerical investigation is carried out on two airfoil analysis/ design codes at the Institute of Design Aerodynamics, DLR, Braunschweig. The first code is the DLR Airfoil Design Method based on the solutions of the Euler/Navier-Stokes eqs., and the other is the ISES Transonic Airfoil Analysis/Design code of MIT, which uses the Euler eqs. with viscous correction. This report summarizes the design part of the investigation where both methods are compared with each other through design studies of transonic airfoils in inviscid and viscous flows. The design examples include the redesign of existing airfoils, design under ill-posed conditions, design with arbitrarily prescribed target C* distributions, modifying NLF airfoilss by changing the slopes of the favourable pressure gradients and the design of new NLF airfoils