ARCTIC '98: The Expedition ARK-XIVIl a of RV "Polarsternv in 1998 Edited by Wilfried Jokat with contributions of the participants Ber. Polarforsch. 308 (1999) ISSN 0176 - 5027 Contents ARCTIC '98: ARK XIV/la BREMERHAVEN .TIKSI 27.06.98 .27.07.98 Summary ............................................................................................................................3 Meteorological conditions .................................................................................................. 9 Marine Geophysics .........................................................................................................14 Introduction ..................................................................................................................... 14 GeoscientificKnowledge ................................................................................................. 14 Data Acquisition .setup and problems .......................................................................... 18 Seismic dataprocessing ....................................................................................................18 Preliminary Results .Seismics ....................................................................................... 18 Gravimetry .......................................................................................................................25 Data evaluation .Gravity ............................................................................................... 26 Gravimeter tests ...............................................................................................................26 Recommendations............................................................................................................ 29 Marine Geological Investigations ..................................................................................... 30 High resolution acoustic profiling by the PARASOUND echosounder System ............. 32 Data acquisition System and data description ................................................................. 32 Regional description .........................................................................................................36 Geological sampling, description and methods applied aboard RV POLARSTERN ...... 40 Aerosol sainpling and size-distribution measurements ....................................................40 Sampling of Snow, melt-water ponds and dirty sea ice ................................................... 40 Sampling in the water column using sediment traps ........................................................46 Sea floor sediment sampling and description ................................................................... 47 Physical properties in marine sediments ......................................................................... 49 Continuous whole-core logging of wet bulk density, P-wave velocity and magnetic suceptibility ............................................................................................... 49 Physical properties of discrete samples .......................................................................... 55 Biostratigraphy ................................................................................................................58 Material and methods ...................................................................................................... 58 Results .............................................................................................................................59 Lithostratigraphy .............................................................................................................60 Aerosols ...........................................................................................................................75 Bathymetric measurements .............................................................................................. 76 Introduction .....................................................................................................................76 Survey instrumentation .................................................................................................... 76 System operation .............................................................................................................76 . Navigation ........................................................................................................................76 System software ..............................................................................................................77 Data collection .................................................................................................................77 Data processing ................................................................................................................77 Survey results ..................................................................................................................78 Problems encountered ......................................................................................................78 Summary ..........................................................................................................................81 Biology: Zooplankton and macrozoobenthos.................................................................. 82 Working Plan .................................................................................................................... 82 Methods ...........................................................................................................................83 Preliminary Results .......................................................................................................... 84 Conclusions ...................................................................................................................... 88 Smallest benthic biota of the central Arctic Ocean .......................................................... 90 Sediment sampling and processing ................................................................................... 90 Preliminary results ........................................................................................................... 91 Oceanography .................................................................................................................. 93 Introduction .....................................................................................................................93 Working Programme......................................................................................................... 93 Equipment and methods .................................................................................................. 94 Preliminary results ........................................................................................................... 94 Ice thickness ................................................................................................................... 100 First results .................................................................................................................... 100 References ...................................................................................................................... 105 Station list ......................................................................................................................108 Appendix PARASOUND profiles ................................................................................ 115 Appendix Graphical core description ............................................................................ 134 Appendix Core logging graphs ....................................................................................... 149 Participating Institutions ............................................................................................... 155 Cruise Participants ......................................................................................................... 157 Ship's Crew .................................................................................................................... 159 I ARCTIC '98: ARK XIVIla Bremerhaven - Tiksi (27. Juni - 28. Juli 1998) Summary The expedition ARK XIV/la of RV POLARSTERN and the Russian nuclear ice breaker ARKTIKA was the first attempt to reach the Alpha Ridge in the central Arctic Ocean directly with surface ships in order to sample the area with geoscientific, biological and geophysical methods. The Alpha Ridge is a submarine mountain chain discovered almost 40 years ago by American ice drift station Alpha. While the surrounding deep sea basin shows a water depth of more than 3000 m, the Alpha Ridge has water depths up to 1200 m only. The available scientific information from this region is at least 20 years old. Geophysical measurements and geological sampling were performed from drifting ice station operated by American and Canadian institutions. Four short cores contained material documenting the environment of the Amerasian Basin in its early phase of development. One of the objectives was to try to reach this positions again to retrieve longer cores in the area with the more modern equipment available on POLARSTERN. Although there will be only a maximum of 5 days available for any science on the ridge, all scientific groups were ready to go for retrieving new and exciting material from this area. At the 27th of June 1998 POLARSTERN left Bremerhaven to meet the Russian nuclear ice breaker ARKTIKA at the boundary of the Norwegian-Russian