NDP - Publications Publications related to data and results obtained in NDP

2016.04.05

TITLE ABSTRACT WHERE PUBLISHED AUTHOR DATE

A high‐resolution hindcast of wind and waves for the North Sea, the Norwegian Sea, and the Barents Sea

A combined high‐resolution atmospheric downscaling and wave hindcast based on the ERA‐40 reanalysis covering the Norwegian Sea, the North Sea, and the Barents Sea is presented. The period covered is from September 1957 to August 2002. The dynamic atmospheric downscaling is performed as a series of short prognostic runs initialized from a blend of ERA‐40 and the previous prognostic run to preserve the fine‐scale surface features from the high‐resolution model while maintaining the large‐scale synoptic field from ERA‐40. The nested WAM wave model hindcast consists of a coarse 50 km model covering the North Atlantic forced with ERA‐40 winds and a nested 10–11 km resolution model forced with downscaled winds.

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 116, C05019, doi:10.1029/2010JC006402, 2011

Reistad, M., Ø. Breivik, H. Haakenstad, O. J. Aarnes, B. R. Furevik & J‐R. Bidlot (Norwegian Meteorological Institute, Oslo, Norway)

2011-05-26

A Probabilistic Design Approach for Riser Collision based on Time- Domain Response Analysis

The present paper is concerned with probabilistic modeling of current magnitude and surface floater motions within the context of riser collision analysis. Furthermore, response statistics obtained as a result of time domain simulation is described. Application in relation to estimation of extreme response and fatigue lifetime is also addressed. A specific Spar

On hold Leira, B. J., T. Holmås & K. Herfjord (NTNU Department of Marine Structures. SINTEF, Marintek. Norsk Hydro, Research Centre)

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Buoy Riser Case study is considered.

Application of DNV-TP-F204 for Determining Riser VIV Safety Factors

Fatigue is often the governing criterion for deepwater riser design. Fatigue assessment methods based on SN curves typically use fatigue safety factors and there is a lack on consensus about the appropriate Design Fatigue Factor (DFF) for VIV that should be applied. A DFF of 20 is commonly used in project specifications to account for a larger uncertainty in prediction of fatigue damage due to VIV, i.e. fatigue life due to VIV should be at least 20 times more than the service life of the riser. Recent case studies and benchmarking assessments, have confirmed that the DFF of 20 for VIV is not always an optimal choice.

OMAE 2005: The 24th International Conference on Offshore Mechanics & Arctic Engineering, 2005 Halkidiki, Greece OMAE2005-67021

Chezhian, M. K. Mørk, M. Rosnæss & T. Meling (Det Norske Veritas, Statoil)

2005-06-12

Acquisition of Critical Metocean Data on the Norwegian Deepwater Frontier

Following the 1996 award of seven deepwater licenses, the offshore industry in Norway has instituted a joint meteorological and oceanographic (metocean) project within the Norwegian Deepwater Programme. An overall and very general data acquisition programme has been established, based on a strategy that has required the full commitment of license management in eight national and international oil companies on investments early in the exploration phase. Because the consequence of excessively conservative criteria and procedures may be quite

Offshore Technology Conference This paper was prepared for presentation at the 1999 OTC held in Houston, Texas. 3-6 May 1999. OTC 10746

Saetre, H. J. (Norske Shell E&P, N-4098 Tananger, Norway)

1999-05-05

different for a deepwater producing system, it is only through a full understanding of the physical environment and accurate engineering procedures that we can hope to carry out deepwater development in a safe and cost effective manner. The data acquisition system has taken advantage of extensive use of moored acoustic Doppler current profilers, 3-dimensional numerical ocean model to simulate currents and current statistics, and remote sensing data from earth orbiting satellites to study velocity anomalies and mesoscale ocean features such as fronts and eddies. Three main issues – the integrated data acquisition system, data correlation analysis and the temporal and spatial variability of the currents – are addressed in the present paper. Although the 4 - 5 year project is not completed yet, it may be concluded that a high proportion of the objectives has been obtained, and that future field developments in the Norwegian deepwater areas can base their design on a sound and viable metocean database

Catastrophic collapse of the volcanic island of Hierro 15 ka ago and the history of landslides in the Canary Islands

Landslides play an important role in the evolution of many volcanic islands, producing huge fields of blocky volcanic debris on their submarine slopes. Sidescan sonar images presented in this paper

Geological Society of America. GEOLOGY, March 1996 Vol. 24, no. 3, p. 231-234

Masson, B. G. (Southampton Oceanography Centre, Southampton SO14

1996-03-01

provide evidence for a large debris avalanche, El Golfo, on the northern flank of Hierm Island in the Canary Islands. Angular blocks, as much as 1.2 km across and 200 m high, cover the debris avalanche surface. El Golfo avalanche is related to both the Canary debris flow and a volcaniclsstic turbidite found in the Madeira ahyssal plain 600 km west of the Canaries. Dating of the turbidite and the failure scarp onshore indicates that the failure pmbably occurred behveen 13 and 17 ka. There appears to be a general correlation between volcsniclastic turbidites in the ahyssal-plain sequence and landslides in the Canaries during the post 750 ka. Tentatively, this correlation suggests that seven major landslides have affected the Canaries in that time.

3ZH. UK)

Contour current driven continental slope-situated sandwaves with effects from secondary current processes on the Barents Sea margin offshore Norway

Seabed data acquired from the southern Barents Sea continental margin offshore Norway reveal detailed morphology of large sandwave fields. Multibeam echosounder bathymetry and backscatter, shallow seismic, sediment samples and seabed video data collected by the MAREANO program have been used to describe and interpret the morphology, distribution and transport of the sandwaves. The bedforms lie on a slope dominated by relict glacial forms and

Marine Geology 353 (2014) 108–127. 0025-3227/Crown Copyright © 2014 Published by Elsevier B.V.

Edward L. King E. L., R. Bøe, V. K. Bellec, L. Rise, J. Skarðhamar, B. Ferré, M. F. J. Dolan (Geological Survey of Canada-Atlantic Dartmouth, Nova Scotia, Canada. Geological Survey of Norway (NGU), Trondheim, Norway.

2014-04-06

muddy/sandy/gravelly sediments. Sandwave migration across small gravity mass failures of the glacial mud constrains the field initiation as early post glacial or later. The contour-parallel nature of the fields and crestlines normal to the bathymetry contours and the geostrophic Norwegian Atlantic Current (NwAC) demonstrate that the NNW-flowing oceanographic circulation is the primary driving current. The fields coincide with the depth range at which a transition between warm, saline and underlying cooler, less saline waters fluctuate across the seabed. Statistically rigorous measurements of height, width and various parameters of slope and symmetry confirm a tendency to downstream (NNW) sandwave migration but with significant exceptions. Anomalous bedform symmetry domains within the fields are tuned to meso-scale topography along (relict) glacial debris flow chutes, indicating current focusing. Upstream and upper slope-derived winnowed sand transport eroded from the glacial sediments is the supposed source.

Institute of Marine Research (IMR), Tromsø, Norway. Department of Geology, University of Tromsø (UiT), Tromsø, Norway)

DeepBlow – A Lagrangian Plume Model for Deep Water Blowouts

Mangler Spill Science & Technology Bulletin, Vol. 6, No. 2, pp. 103-111, 2000. 2000 Elsevier Science Ltd., Great Britain

Johansen, Ø. SINTEF Applied Chemistry, Trondheim, Norway

2000

Deriving Engineering Design Current Profiles from ADCP Measurements on Dynamically Positioned Drilling Rigs

The quality of data recorded using an ADCP on acoustically noisy dynamically positioned drilling rigs is affected by a series of physical constraints on the system, such that the measurement of full depth current profiles is not always easy to achieve. However, full depth current profile time series are required for many engineering applications, so Fugro GEOS have developed data preparation procedures to provide realistic full depth current profile time series in circumstances when these cannot be measured directly.

Oceanology International 2000, Brighton, UK

Jeans, D. R. G. & R. Stephens (Fugro GEOS, Gemini House, Swindon, SN2 5AZ, UK)

2000-03-01

Diurnal tides on the

Barents Sea continental

slope

Observations from March to April 2012 that quantify the diurnal tide at the continental slope connecting the Barents Sea and the Norwegian Sea are presented. The current ellipse for the diurnal tidal harmonic K1 is almost linear, with a cross-slope component of 16cm/s. Extending these results using a high resolution ocean model, the variability is interpreted as continental shelf waves. The results suggest that there is a location along the continental slope where the combined effects of topography, stratification and mean flow lead to conditions favourable to excitation of diurnal continental shelf waves by the large-scale background tide. Also based on the

Deep-Sea Research I 97(2015) 40–51. Published by Elsevier. Journal homepage: www.elsevier.com/locate/dsri

Skarðhamar, J., Ø. Skagseth and J. Albretsen (Institute of Marine Research (IMR), Bergen)

2014-11-25

model marked low-frequency variability is found in the amplitude of the diurnal variability connected to the strength of the background flow, the Norwegian Atlantic Current. Both the measurements and the model results show daily oscillations in temperature, salinity and cross-slope Current velocities, coinciding with modeled diurnal displacements of the pycnocline, between Atlantic Water and Intermediate Water, from approximately 800m on the slope to the shelf break at 400m depth. In general this cross-slope diurnal variability may be of importance for cross-slope fluxes of physical and biological properties, and this exchange could be the strongest during summer.

Dynamics of the Late Weichselian ice sheet on Svalbard inferred from high-resolution sea-floor morphology

In the present study, we use new bathymetric data sets from the fjords and continental shelf areas around Svalbard to reconstruct in detail the flow direction and dynamics of the last Svalbard Ice Sheet. We present examples of the submarine landforms that we use to infer ice-flow directions and dynamics and produce an updated reconstruction of the form and flow of the ice sheet that covered Svalbard and the surrounding shelf seas during the Late Weichselian.

2006: Dynamics of the Late Weichselian ice sheet on Svalbard inferred from high-resolution sea-floor morphology. Boreas, Vol. xx, pp. xx-xx.

Ottesen, D., J. A. Dowdeswell, J. Y. Landvik & J. Mienert (Geological Survey of Norway, N-7491 Trondheim, Norway. Scott Polar Research Institute, University of Cambridge, Cambridge CB2 1ER, U.K. Norwegian University of Life Sciences, IPM, P.O.

2006-12-03

Box 5003, N-1432 Ås, Norway. Department of Geology, University of Tromsø, N-9037 Tromsø, Norway.

Enhanced Risk based Fatigue Criterion

A novel risk based approach for fatigue analyses is proposed. An optimal fatigue safety factor to be used in design is clearly linked to the uncertainty in the fatigue estimate. The design format proposed herein is calibrated to acceptable failure probabilities using structural reliability methods. The design approach, however, does not apply reliability methods. The safety factor as function of the riser location is established from a dedicated set of analyses in short-term sea states in addition to standard industry practice fatigue analyses.

14th International Deep Offshore Technology Conference, New Orleans, Louisiana, USA DOT 2002

Mørk, K., N. Sødahl & M. Chezhian (Det Norske Veritas)

2002-11-13

Estimation of Extreme Response and fatigue Damage for Colliding Risers

For design of deep-water riser arrays, consideration must be made of the possibility for mechanical contact between the different riser pipes. Both the anticipated frequency of collision and the resulting stresses in the pipes need to be estimated. Such an assessment need to cover a certain range of conditions regarding environmental loading and surface floater motions. The present paper outlines a

OMAE'02 21st International Conference on Offshore Mechanics and Arctic Engineering, Oslo, Norway OMAE 2002- 28435

Leira, B. J., T. Holmås & K. Herfjord (NTNU Department of Marine Structures. SINTEF, Marintek. Norsk Hydro, Research Centre)

2002-06-23

procedure which admits the most “critical” conditions to be identified based on an iterative approach.

Experiments on the Relative Mobility of Muddy Subaqueous and Subaerial Debris Flows, and their Capacity to Remobilize Antecedent Deposits

Subaqueous debris flows share many similarities with their subaerial counterparts, but also differ in striking ways. The present treatment is devoted to an experimental comparison of paired subaqueous and subaerial debris flows. The debris slurry consisted of 39% water, 25% kaolin, 24% silt and 12% sand by weight. The debris flows ran down a rectangular channel with a length of 10 m and a width of 0.20 m. (Related to high-latitude deep-sea fans such as the Bear Island Trough Mouth Fan between Norway and Svalbard).

On hold Marine Geology, in press (DRAFT)

Mohrig, D., A. Elverhøi & G. Parker (St. Anthony Falls Laboratory, University of Minnesota, Mississippi, Minneapolis, USA. Department of Geology, University of Oslo, Blindem N-0316, Oslo, Norway

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Flow switching and large-scale deposition by ice streams draining former ice sheets

Fast-flowing ice streams are responsible for the bulk of mass transfer through large ice sheets. We use extensive three-dimensional seismic data from the western Norwegian margin to explain how a several-hundred-kilometer-long ice stream has undergone major switching in flow direction from one glaciation to the next. The direction of ice flow is inferred from the pattern of buildup of thousands of cubic kilometers of glacier-derived debris and observations of large-scale streamlined landforms on former subglacial beds. We demonstrate that ice streams can

Geological Society of America. Geology; April 2006; v. 34; no. 4; p. 313-316

Dowdeswell, J. A., D. Ottesen & L. Rise (Scott Polar Research Institute, University of Cambridge, Cambridge CB2 1ER, UK. Geological Survey of Norway, Trondheim N-7491, Norway)

2006-04-01

undergo major changes in flow direction through modification of their large-scale topographic setting. Whereas ice-stream switching in modern ice sheets has been regarded mainly as a reflection of internal changes in ice-sheet dynamics, switching over successive 100 k.y. glacial cycles may in this case be a response to the effects of continuing sediment deposition and the large-scale development of iceinfluenced continental margins.

Geological and Geotechnical Challenges at Deepwater Sites

As the needs for energy grow, the industry is faced with the exploitation of natural resources in more remote areas and in deeper waters. The paper presents some of the many challenges facing the geologist and the geotechnical engineer with deep water engineering. A good knowledge of the geology is a prerequisite. Geohazards are reviewed and features and characteristics for soils from the Gulf of Mexico and the More and Vøring Basins are described. The geotechnical input required during the exploration and production phases of an offshore structure is discussed. The newly developed suction anchoring system is presented together with aspects of the installation of the anchors.

On hold Lacasse, S. & T. Lunne (Norwegian Geotechnical Institute, Oslo, Norway)

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Impact of gas hydrate formation/dissociation

The impact of formation and dissociation of gas hydrates on water-in-crude oil emulsion

On hold Haukalid, K., K. M. Askvik, K. Folgerø &

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on water-in-crude oil emulsion properties studied by dielectric measurements

properties has been studied using a dielectric probe. The probe was mounted in a high pressure cell that is commonly used to characterize thermodynamic and agglomeration/plugging properties of gas hydrates in crude oil and process water systems. The dielectric measurements proved useful to detect hydrate formation earlier or approximately simultaneously with PVT measurements. The dielectric measurements also provided qualitative information regarding changes in droplet size and emulsion stability. A short wave infrared camera was used to support the dielectric measurements. Live crude oils and associated process waters from North Sea oil fields were used in the measurements.

P. J. Thomas (Department of Physics and Technology, University of Bergen, NO-5007 Bergen, Norway. Statoil ASA, NO-5254 Bergen, Norway. Christian Michelsen Research AS, NO-5892 Bergen, Norway)

Marine Geological Cruises in the Western Barents Sea and Northeastern Norwegian-Greenland Sea.

As part of the European Union (EU) founded project ENAM-II (European North Atlantic Margins: Quantification and modelling of large scale sedimentary processes and fluxes) two marine geological cruises were undertaken by the University of Tromsø, Norway during the summer of 1996. The first cruise, using the University of Tromsø research vessel R/V Jan Mayen, took place during the period from 9 – 22 July. The second cruise, using the research vessel R/V Johan Ruud of the University of Tromsø took place during a 5 day period

European North Atlantic Margins - II: Quantification and Modelling of Large Scale Sedimentary Processes and Fluxes

Vorren, T. O. & S. V. Laberg (Institute of Biology and Geology, University of Tromsø, N-9037 Tromsø, Norway)

1996-07-09

from the 26 – 30 August. The aim of the cruise was to study the Bear Island and Storfjorden TMFs and the two large slides, the Træmadjupet and Andøya slides.

Plio-Pleistocene deposits on the mid-Norwegian margin and their impilcations for late Cenozoic uplift of the Norwegian mainland

A study of seismic data from the mid-Norway margin has identified a wedge of middle Pliocene to recent sediments that has been termed the Naust Formation. Within the area of study north of the Storegga Slide the Naust Formation has a volume of 35 000 km3, and it is estimated that its total volume north of the slide is 80000 km3. The sediments are probably derived from a relatively restricted catchment area; a small area of the shelf and the narrow and relatively low-lying Trøndelag region of Norway. Published studies in adjacent areas suggest that average sedimentation rates during the deposition of this wedge were higher in the late Pliocene to early Pleistocene than during mid- to late Pleistocene times when glaciations were more vigorous and frequent. This apparent paradox is explained by substantial uplift of the Trøndelag area in Pliocene and early Pleistocene times, and erosion of more than 2000 m of rocks, including a Mesozoic cover.

On hold (Neogene Uplift Volume, Global and Planetary Change)

Evans, D., S. McGiveron, A.E. McNeill, Z. H. Harrison, S.R. 0stmo & J.B.L. Wildl (British Geological Survey, Edinburgh, UK. Svitzer Limited, Great Yarmouth NR31 OLT, UK. Norsk Hydro ASA, PO Box 200, N-1321 Stabekk, Norway)

1998-08-04

Practical Considerations for the Use of ADCPs in

Fugro GEOS has over ten years’ experience of deploying RDI Acoustic Doppler Current

Proceedings of the IEEE Sixth Working Conference on Current Measurement,

Jeans, D. R. G. & A. N. Moore

1999-05-04

Offshore Engineering Profilers (ADCPs) from drilling rigs to provide current velocity measurements in support of the offshore industry. In this environment the quality of data recorded using an ADCP is affected by a series of physical constraints on the system. Several of these constraints are considered in this paper, including riser reflection, magnetic influence of the rig structure and acoustic noise due to the rig’s thrusters. A comparison between the performance of Narrowband and Broadband ADCPs is presented. This comparison supports the conclusion that Narrowband ADCPs are generally less susceptible to data loss in acoustically noisy environments than Broadband instruments.

San Diego, California. (Fugro GEOS, Swindon, UK)

Probabilistic Analysis and Design in Relation to Riser-Riser Collision

For design of deep-water riser arrays, consideration must made of the possibility for mechanical contact between the different riser pipes. Both the anticipated frequency of collision and the resulting stresses in the pipes needs to be estimated. Such an assessment need to cover a certain range of conditions regarding environmental loading and surface floater motions. The present paper outlines a procedure which allows the most “critical” conditions to be identified based on an iterative approach. For each “load case”, which corresponds to a certain combination of environmental

On hold Paper No. 2002-JSC-378

Leira, B. J., T. Holmås & K. Herfjord (NTNU Department of Marine Structures. SINTEF, Marintek. Norsk Hydro, Research Centre)

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actions and surface floater motion, the corresponding probability distribution of contact stresses is computed.. Furthermore, the accumulated damage for each load case (referred to a certain duration) is estimated.

Probalistic Modelling and Analysis of Riser Collision

Analysis and design of deep-water riser arrays requires that both collision frequency and resulting stresses in the pipes are addressed. Within a probabilistic context, the joint modelling of the current magnitude and surface floater motions must be taken into account. The present paper gives an outline of the general analysis setup, and response statistics obtained as a result of time domain simulation are described. Utilization of the analysis is also discussed in relation to estimation of extreme response and fatigue lifetime. As an example of application, a specific Spar buoy riser configuration at a water depth of 900m is considered.

OMAE'01 20th International Conference on Offshore Mechanics and Arctic Engineering, Rio de Janeiro, Brazil OMAE2001/SR-2159

Leira, B. J., T. Holmås & K. Herfjord (NTNU Department of Marine Structures. SINTEF, Marintek. Norsk Hydro, Research Centre)

2001-06-03

Risk Based Fatigue Safety Factors for Deepwater Risers

Fatigue is addressed by all recognized standards and codes, which call for adequate safety against fatigue failure. An optimal choice of fatigue safety factor is governed by the uncertainty in the stress response and this is dependent on the structural application, damage contribution type and the prevailing environmental condition among others. Rather than

15th Deep Offshore Technology (International Conference & Exhibition), Marseille, France DOT 2003

Chezhian, M., K. Mørk, N. Sødahl, T. Meling & B. Leira (Det norske Veritas. Statoil. NTNU)

2003-11-19

assuming that the implicit uncertainty in the fatigue estimate can be handled solely from a characteristic SN-curve and a single fatigue factor, the basic principle should be to select a rational safety factor from variability in fatigue estimate from prevailing uncertainty sources and bias related to the applied analyses model. By performing a set of dedicated analyses for the prevailing uncertain input parameters, the resulting uncertainty in the fatigue damage (or equivalent fatigue life) can be estimated. An a-priori reliability based fatigue safety factor calibrated corresponding to recognized safety levels can then be selected. The risk based riser fatigue criterion was proposed by DNV in the DOT 2002 paper, /5/, and now has been further refined, verified and benchmarked. The performance of the proposed fatigue design format has been evaluated by case studies of typical deep-water riser installations, such as Spars, Semi-submersibles, etc and for different riser concepts. Benchmarking has been carried out against the full Level III reliability analysis performed by

Sandwaves and sand transport on the Barents Sea continental slope offshore northern

We integrate morphological, geological and geophysical observations with oceanographic measurements and modelling results to interpret the processes behind the origin and evolution of sandwaves on the upper

Marine and Petroleum Geology 60 (2015) 34-53 © 2014 Elsevier Ltd. All rights reserved

Bøe, R., J. Skarðhamar, L. Rise, M. F. .J. Dolan, V. K. Bellec, M.

2014-10-27

Norway continental slope of the southwestern Barents Sea. Seven sandwave fields covering c. 130 km2 and with a volume of c. 72 _ 106 m3 occur in water depths of c. 475e800 m. Individual sandwaves reach heights up to 6 m. The sandwaves are sinusoidal with asymmetric stosselee side relationships, and time lapse multibeam bathymetry analysis indicates that some sandwaves have migrated up to 10 m towards the NNWover a 4-year time period. This contour current parallel migration is counteracted by currents in several other directions, and the sand unit is thus not a simple contourite. Measurements show prominent diurnal period oscillations and clear spring-neap variations of current direction and speed with along-slope and cross-slope current velocities up to 75 cm s_1 and 65 cm s_1, respectively. Numerical ocean modelling results produce eddies travelling along the slope, positionally stable, daily recurring vortices and bottom current velocity up to 100 cm s_1 in the sandwave fields. Sandwave migration towards the SE is also observed, and the cross-slope currents are capable of transporting sand up and down the slope, as evidenced by ripples migrating normal to the sandwaves. Eroded sand accumulates in the sandwave fields along the boundary between North Atlantic Water and Norwegian Sea Arctic Intermediate Water. This is a consequence of the combined effect of the NNW directed along-slope Norwegian Atlantic Current and tidally induced topographic waves.

www.elsevier.com/locate/marpetgeo Winsborrow, Ø. Skagseth, J. Knies, E. L. King, O. Walderhaug, S. Chand, S. Buenz & J. Mienert (Geological Survey of Norway (NGU), 7491 Trondheim, Norway Institute of Marine Research (IMR), 5817 Bergen, Norway Statoil, Harstad, Norway Geological Survey of Canada-Atlantic (GSC-A), Dartmouth, Nova Scotia, Canada B2Y 4A2 Statoil, Stavanger, Norway University of Tromsø (UiT), Department of Geology, 9037 Tromsø, Norway)

The sandwave fields started to form 11 000e13 000 14C yrs BP or possibly later by current erosion of glacial sediments on the continental shelf and slope.

Satellite studies of ocean

fronts and eddies in for

deepwater development

in the Norwegian

Sea

The background for this study is the requirements from the oil industry to obtain more knowledge about currents and eddies for the deepwater exploration west of Mid-Norway. In this study more than 60 Synthetic Aperture Radar (SAR) scenes from the ERS-2 satellite, each covering 100 by 100 km, were investigated for low wind conditions allowing observation of current patterns and fronts. Location, scale and rotation of eddies was determined from the SAR images. Also altimeter data from ERS and TOPEX POSEIDON satellites were analyzed in order to estimate geostrophic currents in the study area. The results showed that satellite SAR and altimeter data can play an important role to obtain synoptic information about current regimes over larger areas, which is complementary to standard buoy measurements at fixed locations and model simulations.

10th International Offshore and Polar Engineering Conference ISOPE-2000 Seattle

Sandven, S., J. A. Johannessen, K. Kloster, T. Hamre & H. J. Sætre (Nansen Environmental and Remote Sensing Center, N-5059 Bergen, NORWAY. Norske Shell, N-4098 Tananger, NORWAY)

2000-05-10

Slope Stability in the Deep Water Areas off Mid-Norway

Seven deepwater licence areas were awarded in the 15th Norwegian petroleum licensing round on the Mid-Norwegian continental slope in 1996. The knowledge of this area was rather limited, but previous investigations had revealed several slumps

Offshore Technology Conference OTC 8640

Bryn P., S. R. Østmo, R. Lien, K. Berg, & T. I. Tjelta

(Norsk Hydro, Bergen. Statoil, Stavanger)

1998-05-04

and slides including the Storegga Slide, known to be one of the largest in the world. In order to assess the safety and feasibility of exploration activities and field developments in the area, the 7 operators formed a joint project called the "Seabed Project". Under the direction of this project an extensive field programme including massive shallow seismic data acquisition (10.000km) and geotechnical borings with boreholes down to as much as 310m, has been carried out. Furthermore, various laboratory investigations and desk studies on subjects such as the occurrence of gas hydrates, earthquake hazards, submarine slides, slope stability etc., have been performed. The data, including interpretations, geotechnical analyses, gelogical models, etc., have been organised and loaded into a Project Data Base which will be a reference for future studies and investigations in the area. The new data acquired has revealed details on instability features and probable triggering mechanisms of the sediment movements. Several of the slide features, both buried and on the seabed, appear to be associated with sediment weakness planes, earthquake activity, gas hydrates or diapirism.

The Sklinnadjupet slide The Sklinnadjupet Slide Scar is a large buried Elsevier Ltd Rise, L., D. Ottesen, 2006-05-12

and its relation to the Elsterian glaciation on the mid-Norwegian margin

feature on the continental slope southeast of the Vøring Plateau. The mass-flow occurred ca. 250,000 years ago on a slope angle of ca. 0.51, and removed glacial debris from the up to 350-m-thick Naust S sequence on the upper slope. This part of the mid-Norwegian margin appears to have been fairly stable throughout the last 2.8 million years. Naust S represents the third last glacial unit in the Skjoldryggen region, and was deposited during the Elsterian (ca. 400–200 ka BP). During this glaciation, a wide depression was formed on the continental shelf between Haltenbanken and Trænabanken, with the strongest glacial erosion in the west-trending Sklinnadjupet palaeo-trough. This trough leads directly towards the deep, 90-km-wide slide scar, indicating that a local depocentre was formed here before the mass-flow occurred. The shallowest crest of the Helland-Hansen Arch is located below the southern part of the slide scar, and two large craters were formed on the surface of this anticlinal structure. Our model suggests that the deposition of glacial sediments above the Helland-Hansen Arch caused high excess pore pressures along the shallowest crest of this structure and formed a high pore-pressure gradient towards the sea

Marine and Petroleum Geology 23 (2006) 569–583

O. Longva, A. Solheim, E.S. Andersen, & S. Ayers (Geological Survey of Norway, N-7491 Trondheim, Norway. International Center for Geohazards (ICG), Norwegian Geotechnical Institute, N-0806 Oslo, Norway. Hydro ASA, N-0246 Oslo, Norway. Fugro Survey Ltd., Great Yarmouth, Norfolk, NR31 OLT, England)

floor on its western flank. An earthquake possibly triggered the initial slide where the slope was steepest west of the crest. Most of the slide scar was already formed when the slide finally eroded into the anticline.

The Vestfjorden-Trænadjupet palaeo-ice stream drainage system, mid-Norwegian continental shelf

An ice stream in the Vestfjorden-Trænadjupet depressions off northern Norway transported glacial debris to the shelf edge and into the deep sea during the last glaciation. Our interpretation is based mainly on regional and detailed bathymetry, and 2D and 3D seismic data. This palaeo-ice stream was approximately 400 km long and covered an area of ~20,000 km2. Including a complex system of tributary fjords and valleys in Nordland county, the drainage basin had an area of ca. 150,000 km2 within the Fennoscandian Ice Sheet (FIS) during the Last Glacial Maximum (LGM). The location of the palaeo-ice stream prevented large ice masses from reaching the montainous areas of Lofoten and Vesterålen. A local ice dome was established in these areas. The palaeo-ice stream eroded extensively into both Mesozoic and Cenozoic sedimentary rocks, and Quaternary sediments. A pattern of well-developed, subglacial, sedimentary bedforms was produced (e.g., mega-scale lineations, drumlins). Ice-stream shear margin moraines are located on both sides

Elsevier Ltd. Marine Geology 218 (2005) 175– 189

Ottesen, D., L. Rise, J. Knies, L. Olsen & S. Henriksen (Geological Survey of Norway, NO-7491 Trondheim, Norway. Statoil Research Centre, NO-7005 Trondheim, Norway)

2005-03-11

of Trænadjupet, defining the width of the palaeo-ice stream (~90 km at the shelf edge). These moraines are commonly 10–20 m high, a few kilometres wide, and reach several tens of kilometres in length. A large recessional moraine (the Tennholmen Ridge) has been mapped in Vestfjorden. It is 80 m high, 20 km wide and 60 km long. We have interpreted this ridge as a grounding-line moraine, formed during a halt or a readvance of the ice stream during the last deglaciation. The large transport of glacial debris towards the grounding line occurred during this stage. Northeast of the Tennholmen Ridge, several smaller moraine ridges were developed at still-stands during deglaciation.