Multi-year current time series in the eastern North Atlantic Ocean

Time series of currents from an array of 22 subsurface moorings in the Canary and Iberian Basins of the North Atlantic are analyzed with respect to low-frequency variability. The record lengths are usually 1 to 2 years but almost 9 years (site KIEL276, 33N, 22W) in one case. Maximal energies are observed at periods between 50 and 500 days, and high-energy events are found from time to time. The 9-year long series indicates changes in currents with a 3-4 year period, primarily in the zonal component, and anisotropic energy distributions are found for both current components at periods around 200 days. The vertical structure can be well approximated by the barotropic and first-order baroclinic dynamical modes or by one empirical orthogonal function. The regional distribution of spectral properties indicates higher energies in frontal zones and in the neighborhood of the Canary archipelago. In general, the kinetic energy in the month-to-year variability is lower than in the western basins of the North Atlantic

A transatlantic section at 14.5N: Meridional volume and heat fluxes

Two high-resolution hydrographic sections occupied during February, March 1989 in the western and eastern basins of the North Atlantic at 14.5N are combined to study the water mass structure and meridional mass and heat transports. Absolute velocities were determined using these data and an earlier section at 8N in a linear inverse analysis. Mass balance for several layers representing the main water masses in the region and a zero net divergence for the sum of geostrophic and Ekman transport between the two sections are assumed. Using the annual mean of Ekman transports (13.6 Sv, 14.5N), (15.2 Sv, 8N) based on the climatology by Isemer and Hasse (1985) the annual average fluxes for the sections at 8N and 14.5N have been calculated. For the annual mean the strength of the meridional overturning cell at 14.5N amounts to 15.9 Sv with an associated heat transport of 1.22 PW. A similar value can be obtained at 8N where the annual mean heat transport reaches 1.18 PW and the overturning cell measures 15 Sv. The total northward heat transport is strongly dominated by the wind-driven Ekman heat transport. 'In-situ' values of heat transport using the actual wind-driven transports for the respective months yield even higher estimates. Heat transport at 14.5N rises to 1.37 +/- 0.42 PW (February) and the maximum is now at the 8N section, 1.69 +/- 0.52 PW (May). Comparisons of our results with another tropical section at 11N occupied concurrently demonstrate the large variability in heat transport related to changes in the wind field. Due to extremely weak winds in the eastern Atlantic and a resulting low Ekman transport, the 'in-situ' value of heat transport through this section ranged between 0.30 +/- 0.18 PW and 0.59 +/- 0.18 PW depending on the value chosen for the Ekman transport. The lower of the two heat transport estimates results from calculations with the actual observed winds and the other using a monthly climatological mean. That even the computations with the climatological monthly mean give such a low heat transport points to additional changes in the baroclinic structures between 11N and 14.5N

Data Acquisition, Management and Evaluation for Stone Conservation Projects with Digital Mapping

Several years of experience in heritage documentation have given a background to develop methods of digital photogrammetry and mapping. The outcome is the development of a mapping software over a period of 20 years.Main features of the software are image rectification, vector based mapping, quantity survey and data analysis. In Germany, it is mainly used in the field of stone conservation. Small projects can be processed as a single mapping project, whilst complex projects like a cathedral can be organised as a hierarchical project, with several mapping projects for individual object parts. Each mapped element can be connected with additional attributes. This allows visual analysis of mapping activities, quantities and attributes – like in a geographical information system (GIS) for conservators. Tools and procedures for efficient mapping are developed in close cooperation with conservators from different fields. It is shown how large stone objects can be managed efficiently with an example project from the field of natural stone. This applies to the overall data acquisition and data evaluation for condition analysis, conservation planning, accounting documentation and monitoring. Due to the advances in the fields 3D laser scanning and digital photogrammetry within the past 5 years the R&D project „PROQUATO“ (2016 – 2018) was initiated by fokus GmbH Leipzig with the institute for photogrammetry and remote sensing of TU Dresden and Scan 3D GmbH, Berlin. Project results for efficient data processing and functions for 3D mapping will be presented. Current developments deal with the fast processing of point clouds scanned by laser scanner for the use as reference for image rectification, deformation analysis and creation of section lines