Previous studies documented that the low solar activity since the beginning of the 21 st century could directly drive the wintertime climate variability resembling the negative Arctic Oscillation (AO) responses. This study investigates the interdecadal variations of the solar-AO relationship and the related Arctic climate change. Results show that with more solar radiation mild (cold) winters are in the east (west) of Greenland after mid-1980s, in accordance with the positive AO-like pattern, which can be well explained by the coupling between stratosphere and troposphere. By contrast, the solar-related circulation anomalies are totally reversed before mid-1930s, corresponding to the opposite solar-AO connection. INTRODUCTION Arctic Oscillation (AO) is an annular mode, extending from surface to the stratosphere, which represents the dominant interannual variability of the extratropical Northern Hemisphere with a seesaw of sea level pressure (SLP) anomalies between the high and middle latitudes (Thompson and Wallace, 1998). It has been widely documented that the AO has a substantial influence on global weather and climate (e.g. Gong et al., 2001; Park et al., 2011; Chen et al., 2016). For different areas in the entire Arctic region, the impacts of the AO on the surface air temperature/sea ice variations are different (Wang and Ikeda, 2000; Stroeve et al., 2011; Yang et al., 2016). A positive phase of AO favors increased (reduced) sea ice to the west (east) of Greenland through horizontal sea ice and temperature advection (Rigor et al. 2002; Zhang et al. 2003). Previous studies have also demonstrated that the interdecadal variability of the AO and its impacts on the large-scale circulation variations (Li et al., 2014; Chen et al., 2017). For instance, Wei and Su (2014) have reported that the Arctic SLP has experienced a decrease tendency since late-1980s and the rising temperature over Arctic region during the last decades of the 20 th century has close relation with the AO variations (Overland and Wang, 2005a).

The drift of ice floes is what defines the ice loads on hydrotechnical structures, mode of their operation, choice of supply vessels, ice management systems, etc. In comprehensive winter surveys performed on behalf of Rosneft Oil Company over 2013-2017 on the shelf of the Kara, Laptev, and East Siberian Seas, radio buoys allowing for detection of coordinates and signal transmission were used to monitor the drift of ice floes. The paper considers the experimental setup and equipment used, presents the main results of the studies. The obtained data were analyzed to explain the patterns of the drift of large fields of compact ice, the drift velocities of ice formations, their variability (i.e., parameters specified in the documents regulating activities on the Arctic shelf) and dependency on seasonal extrema of the ice thickness. INTRODUCTION The ice cover drift parameters are crucial for designing various types of offshore structures and safe operation of hydrocarbon deposits in the Russian Arctic. The ice cover drift determines the loads on the structure, its operational regimen, the choice of supply vessels, and ice management systems. For many regions of the Russian Arctic, the data on the iceberg drift are unavailable or scarce. Between 2012 and 2017, supported by the Rosneft Oil Company and the Arctic Research Center, AARI completed 12 interdisciplinary expeditions in the Barents, Kara, Laptev, East Siberian, and the Chukchee Seas. Four of them were performed under conditions of maximum ice extent (2013–2015 and 2017) and eight in the open water season (2012–2017) (Fig.1). The winter expedition of 2015 became the largest Arctic expedition in the world over the past 20 years in terms of the scope of work (https://www.rosneft.com/press/news/item/174511/). One of the objectives of these expeditions was to investigate the drift of icebergs and ice floes in the Kara, Laptev, and East Siberian Seas; the task involved using radio buoys allowing for detection of coordinates and signal transmission. In some water areas, it was the first time buoys were used for such purposes. The data sets collected are unique in many respects. The analysis of these data allows one to plot a trajectory of a specific ice formation over the buoy lifetime and calculate its drift parameters. An overview of the winter drift of ice formations surveyed in 2013–2015 is given in (Buzin et al., 2016). In (Buzin et al., 2019) provisional characteristics of iceberg drift in the Russian Arctic Seas were obtained. This paper focuses on ice cover drift patterns.

The problem of assessing ice loads and impacts on facilities of developing offshore oil and gas fields has been one of the most relevant in the world in recent decades. When calculating ice loads, the physical and mechanical properties of ice, corresponding to the natural conditions of the region under consideration, should be taken into account. The lack of reliable initial data holds back the pace of design and construction of facilities, which postpones the development of deposits. Currently, there is no unified approach to the selection of standard values for ice cover parameters. Significant differences in the values of design ice loads determined by regulatory methods are due to the manifestation of high spatiotemporal variability of the parameters of the ice regime and the properties of sea ice when interacting with structures, on the one hand, and the imperfection of calculation methods, on the other. The solution to this problem requires the formulation of a wide range of experimental studies of the ice regime in order to determine the most probable range of variability of the functional parameters that determine the magnitude and nature of the loads throughout the ice period, as well as the features of the state of the ice-structure system in a particular physical and geographical area. INTRODUCTION To date, a large number of studies of sea ice have been carried out. These studies can be divided into laboratory and field tests. The former are necessary for studying the mechanics of ice under controlled test conditions. The second ones make it possible to understand more deeply the properties of the ice cover in natural conditions. In the course of such studies (Borodkin, 2016; Johnston, 2001; Johnston, 2002; Johnston, 2006), the processes of changes in some physicomechanical parameters of ice and the process of its degradation were studied. The main drawback of such studies is that many of them were conducted for a limited time in different periods of the ice season - mainly in the spring-summer period. This information does not always reflect the full picture of changes in the properties of ice and, in particular, its strength. Information on the dynamics of changes in the basic design parameters of ice is very important for assessing loads and impacts on structures and its safe operation. Such information is especially relevant for the following purposes:

Due to an active development of the shelf in the Arctic seas of Russia, it becomes necessary to define the parameters of the ice cover. The measures of the morphometric parameters of hummock masses are necessary to design offshore structures. The Arctic and Antarctic Research Institute, Federal State Budgetary Institution (AARI FSBI), with the support of ROSNEFT OIL COMPANY, Public Joint-Stock Company, conducts research works in the waters of the Arctic seas to collect oceanographic and ice-related data. In the waters of the Kara Sea, Laptev Sea and Chukchi Sea, submerged autonomous buoy stations (SABS) are installed. Such stations contain an upward-looking sonar designed to collect data on the deposition of ice formations drifting over the device. The present thesis is dedicated to the measure of specific morphometric features of the lower ice surface in the waters of the three seas. It contains a brief description of the method for data collection and processing. The thesis gives a comparative analysis of the results obtained with the SABS during several ice seasons in different seas. It envisages intraseasonal (intra-annual), interseasonal (interannual) and spatial variability of the deposition of keel draft of hummocks both within the sea water borders and between the different water areas. INTRODUCTION The offshore territories of the Russian Arctic seas have been actively explored lately. It is impossible to construct and smoothly operate hydraulic structures and communication lines, to plan rationally and implement any transport and cargo operations or to arrange environmental measures on the shelf without taking into account such important element as ice cover. The list of ice cover parameters for different stages of exploration of offshore areas specified by the regulatory documents (ISO, Industry-Specific Construction Standards, Construction Norms and Specifications, etc.) includes the measure of the morphometric parameters of the ice cover, including the assessment of hummock deposition. Since 2012, AARI FSBI, with the support of ROSNEFT OIL COMPANY, PJSC, has been conducting research works in the water areas of the Arctic seas. To collect the oceanographic and ice-related data about the fluctuations of the sea level, current velocities and directions in the water mass, drift speeds and deposition of ice formations, submerged autonomous buoy stations (SABS) are installed annually in particular areas. Each of such stations is equipped with two acoustic devices: an acoustic Doppler current profiler and an upwardlooking sonar for ice profiling.

Ice-free period in the southwestern part of the Kara Sea is limited in average to 2-3 months and has significant interannual variability. A preliminary assessment of the ice-free period duration will allow advanced strategic and tactical planning of platforms operating and drilling activities and, thus, costs optimization of exploration drilling. Duration of ice-free period depends on the date of the sea clearing from the ice and on the date of the stable ice formation. Data analysis was based on historical ice maps and satellite information for a 30-year period from 1989 to 2018. Interannual variability of ice free periods, dates of sea clearing from ice and dates of ice formation are considered in the region of geological structures of the southwestern part of the Kara Sea. It is shown that combination of favorable hydrometeorological conditions that in the last decade increased the ice-free period duration by more than a month. Aanalysis of the main hydrometeorological factors determining ice-free period duration showed possibility to estimate the operational window for exploration drilling in the area of geological structures with a lead time of several months. Introduction East Prinovozemelsky license blocks are located in the southwestern part of the Kara Sea between the Novaya Zemlya archipelago in the west, Yamal peninsula in the south and the Taimyr peninsula in the east. The northeastern border of the sea is an imaginary line between the Cape Zhelaniya and the Dickson Island. Several prospective geological structures have been identified within the boundaries of these license blocks (Fig. 1), and in 2014 the Pobeda field was discovered during exploration drilling at the Universitetskaya structure. Usually exploration drilling in freezing seas is carried out in the ice-free period from floating drilling rigs of various ice classes. In the southwestern part of the Kara Sea the ice-free period is limited in average to 2-3 months (Atlas, 2014; Monograph, 2004) and has significant interannual variability.

ABSTRACT This study investigates the effect of wave obliquity on overtopping for rubble mound breakwaters with a CoreLoc armour layer. In particular, the study is based on experimental investigations on fishing harbours in the Sultanate of Oman, comprising 2D and 3D tests. In both cases, overtopping under perpendicular and oblique cyclonic waves was measured. The physical model tests were carried out in the wave flume and in the wave basin of Padova University. The scales of the experiments have been defined according to the dimension of the available artificial model units (CoreLoc). The overtopping discharge was evaluated in 2D and 3D tests collecting water passing over the structure crest, neglecting the percolation through the upper layer. For the wave basin tests, the overtopping discharge was evaluated in up to 4 different positions. As expected, overtopping discharge is smaller under oblique waves. However, the measurements are very dis-homogenous along the crest. Visually, it looks like the incident oblique wave is scattered by the initial portion of the breakwater and propagates along the structure, merging with the same wave. Crests and troughs are combined in specific points, determined by wave obliquity and wavelength. Possible scattering points are the roundhead, breakwater bents and other discontinuities. The aim of this paper is to verify if the experimental reduction of overtopping due to wave obliquity can be interpreted by a diffraction pattern. INTRODUCTION Overtopping can cause severe damage to people and structures, therefore it is an essential factor in the design of a harbour. The prediction of the average overtopping rate for a particular structure geometry, water level, and wave conditions is usually based on empirical formulae (EuroTop, 2018; Formentin et al., 2018), fitted to full-scale measurements or model test results. Prototype scale measurements are provided e.g. by Troch et al. (2004), who described the wave overtopping at the Zeebrugge (BE) rubble mound breakwater during the period 1999–2003. Similarly, Briganti et al. (2005) presented field measurements at the Rome yacht harbour rubble mound breakwater in Ostia (Italy), carried out during the winter season 2003–2004. Among the several experimental investigations carried out at small scale, there are several noteworthy extensive studies, such as Bruce et al. (2009), that focused on the influence of various types of armour units, and Franco et al (2009), that focused on scale effects.

ABSTRACT In this work an intercomparison of two wave reanalysis products, namely ERA5 and CFSR-W (WW3 hereafter), is presented. The datasets are assessed by means of several statistical features, such as seasonal variability, quantiles of the probability distribution, annual and inter-annual variability, and several error metrics. Both datasets cover a period of 31 years (1979–2009), a fact that assures that most of the long-scale features are equally present in both datasets. The analysis performed is depicted both on a global and regional basis. The results are also assessed on the basis of a global satellite altimeter dataset. INTRODUCTION The study of ocean wave climate is of great importance for a large number of applications, including among others: ocean climate change studies, design of ships and offshore/coastal structures, planning of sea operations, wind and wave energy conversion. There various sources of wave data, namely (i) visual observations (Gulev and Grigorieva, 2006), (ii) satellite altimeters (Lefévre and Cotton, 2001; Young et al., 2011), (iii) in situ buoy measurements, and (iv) numerical wave models (The WAMDI Group, 1988; Tolman et al., 2002). Each one of them have its own advantages and disadvantages. The great advantage of numerical models is their wide coverage on a high time and space resolution in a global scale, making it possible to produce long-term wind and wave climatologies. The quality of wave data is heavily dependent on the quality of the wind forcing, improvements on the physical modelling and assimilation techniques among others. At least two meteorological centers (NCEP and ECMWF) work constantly the last decades towards the improvement of their forecast models. For this, apart from the results of their operational versions, they perform from time to time reanalysis studies to offer homogenized wave products. Stopa (2018, Table 1) summarizes most of the well known wind datasets used throughout the years to generate global wave hindcasts. These wind products led to several global reanalyses of wave datasets the last decades. Among them, it is worth noted ERA-15, ERA-40, ERA-Interim from ECMWF (Sterl and Caires, 2005; Rascle and Ardhuin, 2013), NCEP/NCAR, CSFR-W from NCEP (Cox and Swail, 2001; Chawla et al., 2013; Rascle and Ardhuin, 2013). Other climatologies include HIPOCAS (Guedes Soares et al., 2002), GOW1 and 2 (Reguero et al., 2012; Perez et al., 2017).

ABSTRACT The characteristics of a headland bay coast are quite distinguished from that of a straight-line coast in terms of landform-dynamics. The main differences are the alongshore variations in the erosion and accretion processes. This paper analyzed measurements of cross-shore profiles of the Narrabeen beach with a typical storm-wave event that happened in June 2012. By integrating NearCom and CSHORE models, this study enables a highly computationally-efficient simulation system which joins subaerial and subtidal morphodynamic simulations. This research shows that the morphologic responses of a Narrabeen beach are rapid in the alongshore direction. The simulated results not only make up for the gaps in the discontinuous measurements in space but also reveal the temporal variations of beach erosion and accretion during storm-wave events. INTRODUCTION Headland sandy bay is a mountainous type of coastal landforms. In this type of coastal landform, bays and headlands are closely related. Due to the cape-shaped topography, the headland beach is often suffering from the cape-wave induced strong erosion. The characteristics of headland bay coast are different from that of a straight-line coast in terms of dynamic landforms. One of the distinct characteristics of the headland embayment is the alongshore variation in sediment process. Li (2006) points out that the wave energy alongshore change are far more complex than that of a straight-line coast. Feng et al. (2016) based on the South Atlantic Bay further shows the morphology-induced strong tidal-surge interactions. Lots of effort have been given to revealing the erosion and restoration process of a beach profile before and after the storm (Lee et al. 1998, Fritz et al. 2007, Fiore et al. 2009). However, due to the limited measurements, few studies fully unfolded the varied distributions in coastal responses to storm-waves in headland sandy bays, either in space or in time. Splinter et al. (2018) through the measurements on a headland bay shows that initial beach profile plays a vital role in beach rosion. However, how does initial profile affects the alongshore beach variation? What are the dominant mechanisms that correspond to the rosion and accretion process of a headland sandy bay? These questions remained unknown and was beyond the scope of an observational study. Therefore, it is essential to revisit the impact of storm-waves on the headland bay and to uncover alongshore variations in each responses by integrated technical means. The Narrabeen embayment is located on the southeastern coastline of Australia and is a typical headland sandy bay. By choosing Narrabeen beach as the study site, the following words will first give an introduction of a typical torm-wave event happened on the Narrabeen beach, based on wave-data and measured beach profiles. The following sections will describe he integrated numerical methods and the results from the model data. Analysis will be focus on the alongshore variation in beach rosion and the corresponding factors, such as wave parameter, dune toe elevation, subaerial and subtidal beach profile. This paper nded with key findings and major conclusions.

ABSTRACT Icebergs are ice formations that confer high risks for marine activities. Drifting and entering the Arctic offshore waters, icebergs greatly influence the operational regime of hydrotechnical structures, choice of supply vessels and ice management system, etc. To track ice formations in the Arctic shelf, radio buoys allowing for detection of coordinates and signal transmission were extensively used in the scope of field surveys for Rosneft Oil Company throughout 2012–2017. In the present paper, we focus on the main results obtained for the iceberg drift. The aspects of experimental design and key drift parameters, such as velocity and its variability in summer and winter, are discussed. The revealed difference between the iceberg drift patterns in the southwestern Kara Sea and the Laptev Sea can be explained in the first place by the fact that the masses and sizes of icebergs originating from two archipelagos, Novaya Zemlya and Severnaya Zemlya, are different. INTRODUCTION Icebergs are ice formations that confer high risks for navigation; their drift is among factors influencing the safety of hydrotechnical objects in the Arctic Offshore (Mironov, Frolov, 2010; DRAFT ISO/DIS 35104). Even though technical means have progressed significantly after the infamous iceberg-caused tragedies of XX century that led to enormous human and ship losses (Titanic, 1912, Hans Hedtoft, 1959), there are still minor ones (Overseas Ohio, 1994) and near-emergency events (Sea Rose FPSO, 2017) (Tangborn et al., 1998; Hill, 2000; Enquiry report, 2018). Understanding patterns of the iceberg drift and the respective morphometric parameters is essential for designing hydrotechnical structures and safe exploration of hydrocarbon deposits in the seas of the Russian Arctic. Drifting and entering the waters near the prospective deposit icebergs significantly influence the operational regime of hydrotechnical structures, choice of supply vessels and ice management system, etc. For many regions of the Russian Arctic, the data on the iceberg drift are not available or scarce.

ABSTRACT The application of CFD is expanding in the analysis of hydrodynamic loads in ships and offshore structures. However, CFD results in wave impact problems are still difficult to be sure that it has high accuracy. This is because researchers apply CFD analysis according to different levels of techniques and procedures. In order to have reliable CFD results on wave impact problems, a proper standard of CFD analysis needs to be prepared. For this purpose, it is important to verify the CFD results with reliable experimental results. It is motivated to carry out the model test of slamming and green water load on FPSO for the validation of CFD results. The present study considers slamming and green water loads acting FPSO based on the model test. A 1/50-scale model test was performed on the ocean basin of KRISO. The slamming load acting on the bow of FPSO was measured under breaking waves and the slamming impact was recorded using a high-speed camera. In order to see the variability of the slamming load, it was repeated 20 times for each condition. The green water load on the side wall of FPSO was measured in regular and irregular waves. The measured slamming and green water loads are presented and those characteristics are discussed. INTRODUCTION The slamming and green water loads are important factors that should be considered in the design of ships and offshore structures. The slamming and green water loads have been studied for a long time using analytical, numerical and experimental methods. Von Karman (1929) and Wagner (1932) estimated the slamming impact load on a simple structure based on the analytical method, and many types of research have been carried out based on their pioneering research works. However, it still needs more researches to evaluate the slamming load acting on the ship and offshore structures(Kapsenberg, 2011). Nowadays, many researchers performed model tests on the wave impact problems. In the previous studies, many researchers used pressure sensors to measure the slamming load(Kapsenberg et al., 2002; Hermundstad and Moan, 2005; Kapsenberg and Thornhull, 2010; Voogt and Buchner, 2004). Recently, the use of force sensors is expanding in model tests(Kim et al., 2014; Huang et al., 2015, 2017; Ha et al., 2018; Kim et al., 2019). The influence of the thermal shock on the pressure sensor is gradually being clarified, and a force sensor is applied to overcome the sensitivity of the pressure sensor. Nevertheless, there are not many reliable experimental results on slamming load due to the large uncertainty of the model test. Therefore, it is necessary to evaluate a lot of accurate results based on model tests for the validation of CFD results and to continuously study uncertainties related to the experiment on the slamming problem. The green water is also a field in which a lot of research is carried out as well as the slamming problem. Recently, experimental researches on the green water has been actively carried out(Buchner, 2002; Lee et al., 2012; Xiao et al., 2014; Silva et al., 2016a, 2016b). In the previous studies, the deck impact mainly caused by the green water on the bow has been studied. Recently, the influence of green water generated on the side wall of a ship has become an issue. There are still many uncertainties on the experimental results of the green water, and it is necessary to evaluate reliable experimental results for the validation of CFD analysis.

ABSTRACT The results of the studies of physical-mechanical properties of bottom formations obtained by engineering-geological investigations of hydrothermal ore targets of the Russian Exploration Area (REA) in the axial zone of the Mid-Atlantic ridge (MAR) are presented. The hydrothermal ore targets studied are the Ashadze, Semenov, Pobeda ore clusters, the Yubileinoye and Kholmistoye ore fields and several exploration blocks in the REA outside the targets. Determinations of physical-mechanical properties of polymetallic sulphides (PMS), host rocks and bottom sediments were carried out both at onboard and stationary laboratories. The main regularities of variability of physical- mechanical properties of bottom formations and the factors determining them were presented. Also reported is the influence of hydrothermal processes on the formation of physical-mechanical properties of igneous rocks and bottom sediments. INTRODUCTION At present, Russian geological and engineering-geological studies of hydrothermal ore fields are performed in the northern near-equatorial part of the MAR (Fig. 1), within the REA of 10,000 km 2 (100 exploration blocks 10×10 km each, grouped in 7 clusters from A to G) [Kondratenko et al., 2017]. The targets of the study are ore objects of different scale. These are ore bodies (natural accumulations of PMS), ore fields (structurally unified local areas of seabed, featuring the groups PMS of spatially close ore bodies within one hydrothermal system) and ore clusters (ore-bearing seabed areas, containing groups PMS of ore fields and individual ore bodies). As of 2017, as a result of many years of expeditionary exploration, 18 ore fields had been identified in the REA, 11 of them were combined into 4 ore clusters [Beltenev et al., 2013, 2015, Cherkashev et al., 2013]. Since 2012, only in the northern and central parts of the REA the Pobeda ore cluster and the ore fields Yubileinoye, Kholmistoye and the Surprise ore occurrence have been discovered. Engineering-geological investigations are an integral part of the contractual works of the Russian Federation on the MAR. This work is concentrated mainly in the identified ore fields. It aims at a comprehensive assessment of the engineering-geological conditions of exploration and exploitation of potential PMS deposits. Considerable attention is paid to the study of physical-mechanical properties of bottom formations, which are part of the most important components of engineering-geological conditions of mining, as it determines the choice of methods for the future mining of sulfide ore deposits, technology of mining operations and the design features of mining equipment.

ABSTRACT In this paper, 3-dimensional contours are developed and applied to the joint distribution of sea states and individual wave heights to obtain a combined long-term and short-term description of extreme ocean waves associated with a certain return period. The 3-dimensional environmental contours utilizes the direct sampling approach that has recently been proposed as an alternative to the traditional IFORM-approach for estimating environmental contours. The paper outlines the extension of the direct sampling approach to environmental contours to 3-dimensional problems and presents an algorithm for constructing such contours in a 3-dimensional space. Moreover, the contours will be applied to the trivariate problem of jointly extreme significant wave height, wave period and individual wave height. Contours corresponding to different quantiles of the individual wave height in a sea state will be established, i.e. the median individual wave height, the upper quartile individual wave height, the upper decile individual wave height and the maximum individual wave height in a sea state. This will illustrate the usefulness of 3-dimensional environmental contours and demonstrate that the direct sampling approach to environmental contours can be extended to higher dimensions. INTRODUCTION Environmental contours are often used in marine design and ocean engineering applications for identification of extreme environmental conditions that may result in extreme loads and responses. Most often, environmental contours are applied to two-dimensional problems and a typical application is to establish contours for wave parameters such as significant wave height and wave period. These are sea state parameters and such contours describe the long-term variability of sea states. The short-term variability of individual wave heights can then be described conditioned on a particular sea state, and it may be of interest to provide a joint description of extreme ocean waves taking both the long-term variability of sea states and the short-term variability of individual wave heights into account. Other examples of trivariate problems that may benefit from 3-dimensional environmental contours are the joint description of significant wave height, wave period and wind speed, and the joint distribution of wave heights, currents and sea water level.

ABSTRACT Variability of winter sea ice in the Barents Sea and its correlations with external atmospheric forcing have been investigated in a statistical approach based on NSIDC sea ice concentration (SIC) and ECWWF surface air temperature (SAT), wind velocity datasets for the period 1979–2016. The relative SIC, defined as the ratio between sea ice area and extent, indicates that the ice regime is towards lower-concentration conditions. The SIC regression results reveal that the most remarkable ice loss occurs in the northeastern Barents Sea, particularly between 74°-78°N and 42°-67°E. The empirical orthogonal decomposition of SIC has distinguished two principal modes of SIC anomaly. The first principal mode describes 57.7% of the total variance and represents SIC multi-year decreasing trends. The SAT and wind field play a fundamental role in sea ice loss. Additionally, the second principal mode (11.3%) behaves as southeast/central anomaly seesaw, revealing sea ice anomalies are in anti-phase in both corresponding zones. Besides, the wavelet variances of the time coefficient of the two principal components for SIC, SAT and wind velocity anomaly have been analyzed. The most significant peaks for three parameters are with similar variation periods. Accurately, the sea ice is experiencing a decreasing process with uncertain oscillations in some periods due to unsteady synoptic process. INTRODUCTION For the past few decades, the Arctic sea ice cover has been decreasing at a sharp pace than before and has become a focus on climate change research. A series of investigations reveal that the most remarkable sea ice loss in summer has occurred in the Pacific sector while in winter the most pronouncing ice plummet is in the Barents Sea and Kara Sea (Johannessen et al., 2004; Su et al., 2011; Yang et al., 2016). Hence, a large number of scholars have concentrated on the dynamical and thermodynamic mechanism of atmosphere-ice-ocean in the Barents Sea.

ABSTRACT Wind speed variability in the Northern North Atlantic has been successfully modelled by a spatio-temporal transformed Gaussian field in our previous study. It was shown that this type of model does not describe correctly the extreme wind speeds attributed to tropical storms and hurricanes. This spatio-temporal model was generalized to include the possibility of the occurrence of rare severe storms. In that work, the daily wind speed variability was modelled by the transformed Gaussian field, and then random components were added to model rare events with extreme wind speeds. The model was termed the hybrid model. The transformed Gaussian and the hybrid models are locally stationary and homogeneous random fields with localized dependence structure, which is described by time and space dependent parameters with a natural physical interpretation. In the present study, these models are used to describe the variability of wind speed in other areas, i.e., the Caribbean sea, the South China Sea and the Arctic area. In most locations, the transformed Gaussian field is a sufficiently accurate model. However, in some regions, e.g. Laptev and the Beaufort Sea at the Arctic, this model severely underestimates the frequencies of extreme winds. In this study, the hybrid model is used to describe the wind variation in these regions. There are also locations, e.g. along the east coast of Greenland, most of the coast areas of the South China Sea, where frequencies of high wind speeds are severely overestimated by the transformed Gaussian model. In this paper, the models are fitted to ERA-Interim reanalysis wind data and used to find long-term distributions of wind speed, to estimate wind speed return values, e.g. 100-year extreme wind speed, and to compute the expected yearly frequency of events that wind speed exceeds a fixed threshold value. INTRODUCTION Strong winds over oceans can create dangerous MetOcean conditions to challenge the safety of ships and offshore engineering related activities, such as oil and gas drilling rigs or renewable wind/wave energy installations. Waves and the related storm surge from high wind events have also great impact to coastal communities. A correct prediction of frequencies of high speeds is important in estimation various risks of potentially harmful responses.

ABSTRACT Sea-ice research has made great progress over the past thirty to forty years due in large part to improved measurements arising from earth observing satellites and year-long continuous measurements of the underside of sea ice from below using subsurface instrumented moorings. The geometry of sea-ice is highly variable and complex with horizontal scale sizes of discrete sea-ice floes ranging from one meter or less to 50 km or more. The vertical scale size, or ice thickness, which is much harder to measure, ranges from 5 cm or less to over 50 m. Sea-ice motion is highly dynamic within the Arctic as indicated by large spatial variations over distance scales ranging from tens of meters to several thousand kilometers (basin scale) as well as on seasonal and interannual time scales. Large internal ice stress conditions can develop which result in the cessation of sea-ice motion which can also impede ship movements through the sea-ice. Given the highly deformed and fractured nature of the floating sea-ice cover, very different responses to nearly identical wind forcing of sea-ice floes can occur over distances as small as a few kilometers. The improved understandings of the sea-ice regime as realized from past, present, and future Arctic research, is essential to realizing the goal of safe and sustainable Arctic activities. INTRODUCTION The purpose of this paper is to provide a review and update of sea-ice research including recent findings. The paper also summarizes the outstanding sea-ice research issues which are important to Arctic development activities. The motivation for sea-ice research has always involved geographic and scientific exploration of the vast and largely unknown Arctic, combined with national security and sovereignty dating back to the middle of the last century. In the latter part of the 20 th century, sea-ice research broadened to address the needs of offshore oil and gas exploration and production (Hamilton, 2011). As the sea-ice extent in the Arctic has been reduced over the past two decades, the shipping season for passages through the Arctic has been expanded along its continental margins through the Northern Sea Route off Russia and the Northwest Passage off Canada and the United States. Commercial shipping by ice-class vessels is already becoming more common, especially via the Northern Sea Route off Russia, and the prospect of shipping directly across the central Arctic Ocean is also being contemplated within the next few decades (Smith and Stephenson, 2013). To support Arctic shipping, sea-ice research is required for the development of safe and efficient shipping using these sea routes. In addition, sea-ice research is being conducted to study and better support the use of the Arctic by indigenous peoples who have traditionally used sea-ice as a means of transportation for subsistence hunting and travel based on the extensive traditional knowledge of sea-ice.

ABSTRACT Data for maximum pit depths obtained from intelligent pigging runs for several older operational water injection pipelines (WIPs) has been used extensively for prediction of likely future pipe wall penetration. Often such data do not fit extreme value distributions very well. Also, they provide no insight about the pitting corrosion mechanisms involved. A more satisfactory approach is outlined in which the development of extreme values of pit depth with increased exposure time is related to the trends in pit depth data as shown on standard Gumbel EV plots. It is shown that the uncertainty in the value of the deepest pit depths at any point in time is related to the corrosion phase at that time, and thus the underlying physical-chemical processes at that time. This presents a more rational approach to extrapolation of Gumbel EV data, such as for water injection pipelines. INTRODUCTION Perforation by pitting of pipelines such as water injection pipelines used in the oil and gas industries is a potentially critical issue for operations. Water injection pipelines often are used to convey waters such as ‘produced’ water (i.e., water extracted from crude oil) or seawater, or aquifer waters into oil reservoirs to drive out as much as possible any remaining oil or gas reserves (Bai & Bai 2012). This is done under high pressure (typically around 200 bar). The main concern for corrosion is internal corrosion. To try to reduce this, typically the water used for injection is filtered and also has its oxygen content reduced (nominally to around 20 ppb oxygen but often to only a higher level) in an attempt to create oxygen starvation, on the basis that this will reduce the severity of corrosion. Mostly the pipelines are carbon steels, and not cathodically protected, largely for economic reasons, although the effectiveness of cathodic protection, particularly for offshore locations, has not been established.

ABSTRACT Sloshing model tests or wave impact tests in flumes show large variability of local impact pressure measurements. One of the reasons of such variability is the generation of free surface instabilities by the shearing gas flow at the free surface just before the impacts (Kelvin-Helmholtz and possibly Rayleigh-Plateau when fragmentation occurs). Our long-term objective is to study the influence of surface tension (or Weber number) and viscosity (or Reynolds number) on the development of gas-liquid interface instabilities until fragmentation for breaking wave impacts and to relate the statistical distributions describing these instabilities to those of the pressure measurements. To better understand the first steps of development of free surface instabilities around the crest of breaking waves, a bi-fluid high-fidelity front-tracking software based on the Navier-Stokes equations has been developed. Named CADYF, this software simulates separated two-phase incompressible viscous flows with surface tension. The numerical method uses adaptivity in space (adaptive remeshing) and time (hp-adaptivity) to yield accurate predictions while keeping computational cost low. As first application, the simple experiment carried out by Thorpe (1969), enabling the generation of Kelvin-Helmholtz instability in a rectangular tube completely filled with two liquids of different densities, is simulated. Numerical results are compared to experimental results and to simulations from Strubelj and Tiselj (2011). A parametric study is performed varying the surface tension and the viscosities of the fluids at constant ratio of viscosity. The evolutions of the main parameters describing the Kelvin-Helmholtz instability are provided in dimensionless form giving some clues about the scaling process. INTRODUCTION The context of the present study is the sloshing assessment of Liquefied Natural Gas (LNG) tanks on floating structures based on sloshing model tests. The model tank, most of the time at scale 1:40, is put on the platform of a six-degree-of-freedom motion generator. The liquid inside the model tank is water, the ullage gas is a mixture of Sulfur Hexafluoride (SF 6 ) and Nitrogen tuned in order to keep the gas-to-liquid density ratio the same as in the reality with LNG and Natural Gas (NG). The excitations are down-scaled from ship motions calculated at scale 1 with a boundary element method (BEM) according to Froude-scaling. Numerous pressure sensors, arranged in rectangular arrays, are placed in the locations submitted to liquid impacts. All conditions (sea-states, loading cases and speeds of the floater, incidences of the wave with regard to the floater, filling levels) that the floating structure is expected to encounter during its life are studied. Long-term distributions of pressure peaks are built for different sizes of the loaded area, mixing all conditions with an estimated probability of occurrence. Because of the high variability of the local pressure measurements, the conditions, especially those which are contributing the most, are needed to be tested many times in order to build a converged long-term pressure peak distribution. This leads to sloshing model tests running night and days during many weeks (at least seven in GTT) to perform a reliable sloshing assessment.

ABSTRACT Seismic damage assessment plays an important role in performance-based design engineering and seismic risk analysis. This assessment is dealt with in terms of fragility curves. An approach to estimate seismic fragility of a pier-supported wharf is developed in this paper. The damage or performance state of the specific wharf structure is determined by the capacity spectrum method proposed by ATC-40. The probability distribution for a so-called fragility curve is expressed in a lognormal cumulative probability density function and the two parameters associated with the distribution are estimated by the maximum likelihood method, treating each event of damage as a realization from a Bernoulli experiment. In this paper, we consider the uncertainty associated with the ground motion by collecting the records of ground motion near the site and analyzing the probabilistic characteristics of the records. We also analyze the uncertainties associated with the capacity spectrum and the thresholds of different damage states by considering the factors of material and soil properties that affect the overall capacity of the structure. Finally, fragility curves considering the above three type of uncertainties are constructed and compared for the target pier-supported wharf. INTRODUCTION Seismic fragility curves is a statistical tool representing the probability of reaching a given performance or damage states as a function of an engineering demand parameters, e.g. earthquake ground motion intensity. They can be obtained either by statistical analysis of the observed failure during past earthquake (the empirical approach) or by structural modeling of the seismic performance of the structural systems (the analytical approach). The empirical fragility curves were attained by utilizing the damage data associated with a past earthquake. A set of empirical fragility curves for highway bridges was developed based on actual damage data from the 1995 Kobe earthquake (Yamazaki et al., 2000). The fragility curves were assumed to follow cumulative lognormal distribution functions. On the other hand, the analytical fragility curves were represented by two-parameter lognormal distribution functions and estimated by the maximum likelihood method and traditional optimization scheme. (Shinozuka et al., 2000).

ABSTRACT Four offshore steels consisting of two forgings and two plates have been tested for both Charpy transition behavior and for CTOD transition behavior. Charpy transition results for the F22 provided a smooth transition curve with the most variability in energy near the middle of the transition. The other three steels showed a different behavior, where the highly ductile behavior and the much more brittle behavior could be found at the same temperature on repeat specimens over a limited temperature range. The range of CTOD behavior for API 2Y Grade 60 plate is large enough that the Master Curve distribution does a poor job of covering the entire range of behavior and one of the inhomogeneous Master Curve methods would better describe the results. The CTOD results from the other three steels have less variability, but each has a different temperature shift compared to the Charpy transition, so these results do not appear to allow any tightening of that relationship compared to existing Master Curve models. INTRODUCTION The Master Curve approach, developed by Wallin (1989) and included in BS 7910 Annex J (2015), provides a lower bound estimate of fracture toughness ( K mat ) from Charpy V-notch (CVN) test data for steels. This approach, being developed over 25 years ago, could possibly be providing over-conservative K mat values when used on modern steel forgings and structural steel. The basis for the Master Curve correlation with CVN data has been well established for nuclear steels and thin, higher strength steels, but not for thicker modern steels commonly used in the offshore industry today. This program has been designed to collect data on which new K mat - CVN correlations can be checked, using data from current steels used in the oil & gas industry, with particular attention to structural and forging steels. Primary steels of interest were forging materials such as F22, 4130, A707, and 8630 and offshore structural steels such as 2W and 2Y in both grades 50 and 60. EWI was able to source material for some of these grades, including materials already at EWI.

ABSTRACT The article briefly presents a novel methodology of weather window estimation for offshore operations and mainly focuses on effects of met-ocean condition forecasting uncertainties on weather window predictions when using the proposed methodology. It is demonstrated that the proposed methodology has the capacity to retain the uncertainties of met-ocean condition forecasting and transfer them into uncertainties of probability of operation failure. In addition to that, improvements to the failure function, used to define operation failure are presented. The failure function is modified to include stochastic variables, representing met-ocean forecasting uncertainties and the results of such modification are given in terms of predicted weather windows for a selected test case. INTRODUCTION Typically, costs of installation of offshore wind turbines contribute significantly to initial capital expenditures (CAPEX) of an offshore wind farm. These costs can amount to 10–20% of CAPEX, according to (Brown, et al., 2015), (Esteva Fàbrega & Gomis Bellmunt, 2014) and (Moné, et al., 2015) and up to half of that can be attributed purely to costs of transportation equipment, (Fingersh, et al., 2006). Furthermore, as indicated in (Nielsen & Sørensen, 2011) and (Santos, et al., 2015), operation and maintenance costs contribute 25–30% to the total Levelized Cost of Energy (LCOE), where up to 73% of this contribution is again related entirely to costs of transportation systems. Since the European Commision set the 20–20–20 goals in 2008, among whitch the contribution of renewable energy in the total energy pool is expected to reach 20%, the total installed capacity of offshore wind turbines increased more than 7 times (from 1.5GW in 2008 to 11GW in 2015, according to (European Wind Energy Associacion, 2016)) and is expected to increase in the future. This implies that new offshore wind farms will have to move even further offshore, and the costs associated to installation and maintenance of such farms will increase accordingly.