(Table 1) Summary of sampling points described and main petrographic, morphological and geochemical characteristics

Targeted sampling on the Dolgovskoy Mound (northern Shatsky Ridge) revealed the presence of spectacular laterally extensive and differently shaped authigenic carbonates. The sampling stations were selected based on sidescan sonar and profiler images that show patchy backscatter and irregular and discontinuous reflections in the near subsurface. The interpretation of acoustic data from the top part of the mound supports the seafloor observations and the sampling that revealed the presence of a complex subsurface plumbing system characterized by carbonates and gas. The crusts sampled consist of carbonate cemented layered hemipelagic sedimentary Unit 1 associated with several centimetres thick microbial mats. Three different carbonate morphologies were observed: (a) tabular slabs, (b) subsurface cavernous carbonates consisting of void chambers up to 20 cm**3 in size and (c) chimney and tubular conduits vertically oriented or forming a subhorizontal network in the subsurface. The methanogenic origin of the carbonates is established based on visual observations of fluids seepage structures, 13C depletion of the carbonates (d13C varying between -36.7 per mil and -27.4 per mil), and by thin carbonate layers present within the thick microbial mats. Laboratory experiments with a Hele-Shaw cell were conducted in order to simulate the gas seepage through contrasting grain size media present on the seafloor. Combined petrography, visual observations and sandbox simulations allowed a characterization of the dynamics and the structures of the plumbing system in the near subsurface. Based on sample observations and the experiments, three observed morphologies of authigenic carbonates are interpreted, respectively, as (a) Darcian porous flow through the finely laminated clayey/coccolith-rich layers, (b) gas accumulation chambers at sites where significant fluid escape was impeded by thicker clayey layers forming the laminated Unit1 and (c) focussed vertical fluid venting and subhorizontal migration of overpressured fluids released from (b). The Hele-Shaw cell experiments represent a promising tool for investigating shallow fluid flow pathways in marine systems.

Maps of coastal and marine geomorphology between Albenga and Savona (NW Mediterranean Sea, Italy)

In this paper, we present a map describing the main geomorphological features of the coastal and marine area between the towns of Albenga and Savona (Ligurian Sea, NW Mediterranean) corresponding to a coastal stretch of ~40 km. To produce this map, we collated data from the literature, orthophotos, perspective photos, multibeam and side scan sonar data, and undertook direct surveys to ground truth data obtained using indirect techniques. We divided the information into nine thematic layers, including bathymetry, natural coastal types, geomorphological elements, seafloor coverage (both geological and biological), coastal and nearshore dynamics, human influence on coastal and marine environments, coastal occupation and protected areas.

(Table 1) Sea level during storm surges at various sites along the german Baltic Sea coast

A seawall was constructed in 1897 along the steep coast of Streckelsberg, Usedom Island to stop the cliff retreat. It was destroyed several times by storm induced sea floods, reconstructed and gradually extended to a length of 450 m. After the severe storm event of 1/2.3.1949, no more repair work was implemented. The ruins were no longer capable of preventing further erosion of the Streckelsberg cliff. A new protective structure became a necessity against ongoing erosion, and to check the lowering of the abrasion platform. The construction of three breakwaters began in 1995. A severe storm occurred on 3/4.11.1995 before their completion. Coastal bottom sediment mapping using a sidescan-sonar carried out two days later showed that a channel system down to a depth of 1.5 m was cut into the sand layer covering the sea floor on both sides of the Koserow Bank. The bottom of these channels was paved with gravel and boulders. This layer was encountered in the whole surveyed area below a mobile sand layer. Discharged bodies of fine sand half a meter high and erosional cavities several m2 in diameter around boulders led to the conclusion that an intensive sediment movement down to a depth of 11 m had taken place during the storm. A storm related direction of sediment discharge could not be identified. The existing section of the breakwaters withstood the severe storm.

Digital terrain model (DTM) of the central Fram Strait

Based on data from R/V Polarstern multibeam sonar surveys between 1984 and 1997 a high resolution bathymetry has been generated for the central Fram Strait. The area ensonified covers approx. 36,500 sqkm between 78°N-80°N and 0°E-7.5°E. Basic outcome of the investigation is a Digital Terrain Model (DTM) with 100 m grid spacing which was utilized for contouring and generation of a new series of bathymetric charts (AWI BCFS).

Bathymetry grids and maps of Mozambique Ridge compiled from cruises 64PE305, 64PE306, SO-87, SO-182, SO-183, ME-33/2, ME-63/1 bathymetry

Based on data from R.V. Pelagia, R.V. Sonne and R.V. Meteor multibeam sonar surveys, a high resolution bathymetry was generated for the Mozambique Ridge. The mapping area is divided into five sheets, one overview and four sub-sheets. The boundaries are (west/east/south/north): Sheet 1: 28°30' E/37°00' E/36°20' S/24°50' S; Sheet 2: 32°45' E/36°45' E/28°20' S/25°20' S; Sheet 3: 31°30' E/36°45' E/30°20' S/28°10' S; Sheet 4: 30°30' E/36°30' E/33°15' S/30°15' S; Sheet 5: 28°30' E/36°10' E/36°20' S/33°10' S. Each sheet was generated twice: one from swath sonar bathymetry only, the other one is completed with depths from ETOPO2 predicted bathymetry. Basic outcome of the investigation are Digital Terrain Models (DTM), one for each sheet with 0.05 arcmin (~91 meter) grid spacing and one for the entire area (sheet 1) with 0.1 arcmin grid spacing. The DTM's were utilized for contouring and generating maps. The grid formats are NetCDF (Network Common Data Form) and ASCII (ESRI ArcGIS exchange format). The Maps are formatted as jpg-images and as small sized PNG (Portable Network Graphics) preview images. The provided maps have a paper size of DIN A0 (1189 x 841 mm).

Bathymetry grids and maps of Mozambique Basin compiled from cruise SO183 bathymetry

Based on data from R/V Sonne multibeam sonar surveys in 2005 a high resolution bathymetry was generated for the Mozambique Basin. The area covers approx. 466,475 sqkm. The mapping area is divided into four sheets with boundaries (west/east/south/north): Sheet I (north-west), 37:00/39:45/-24:00/-20:20; Sheet II (north-east), 39:45/42:30/-24:00/-20:20; Sheet III (south-west), 37:00/39:45/-27:40/-24:00; Sheet IV (south-east), 39:45/42:30/-27:40/-24:00. Basic outcome of the investigation are Digital Terrain Models (DTM), one for each sheet with 0.05 arcmin (~91 meter) grid spacing and one for the entire area with 0.1 arcmin grid spacing. The DTM's were utilized for contouring and generating maps. Moreover the measured bathymetry was combined and compared with GEBCO bathymetry and predicted bathymetry, derived from altimeter satellites. The provided maps have a paper size of DIN A0 (1188.9 x 841 mm).

Sea ice draft measured by upward looking sonars in the Weddell Sea (Antarctica)

The presented database contains time-referenced sea ice draft values from upward looking sonar (ULS) measurements in the Weddell Sea, Antarctica. The sea ice draft data can be used to infer the thickness of the ice. They were collected during the period 1990-2008. In total, the database includes measurements from 13 locations in the Weddell Sea and was generated from more than 3.7 million measurements of sea ice draft. The files contain uncorrected raw drafts, corrected drafts and the basic parameters measured by the ULS. The measurement principle, the data processing procedure and the quality control are described in detail. To account for the unknown speed of sound in the water column above the ULS, two correction methods were applied to the draft data. The first method is based on defining a reference level from the identification of open water leads. The second method uses a model of sound speed in the oceanic mixed layer and is applied to ice draft in austral winter. Both methods are discussed and their accuracy is estimated. Finally, selected results of the processing are presented.