Hopen Island Research Articles

Tidal Wave–Elliptic Island Interaction above the Critical Latitude

Abstract Around Hopen Island, the satellite images and experiments with drifting buoys describe the movement of the drifting ice and depict tidally generated trapped motion. An analytical solution is applied to investigate the trapping phenomenon. A general solution is achieved by the superposition of the incident and reflected (scattered) waves for an elliptically shaped island above the critical latitude. The incident wave simulates the tidal wave propagation toward the island and its prominent feature, an amphidromic point located to the southeast from Hopen Island. The analytical solution for the reflected wave is constructed in elliptic coordinates. Tide amplitudes and cophase lines are analyzed in the island’s vicinity and compared to observations and numerical model results. A simulated drift of Lagrangian water particles constructed with the help of analytical solutions reproduces well the observed clockwise trapped motion of the drifting buoy near Hopen Island. Since the resonance may amplify the semidiurnal incident tide, we have also investigated the natural modes of water oscillations near the island. While this paper focuses on the details of the model used at the specific site of Hopen Island, a similar trapping analysis can be applied to circular or elliptic islands that have a small scale relative to the barotropic Rossby deformation radius. Significance Statement This study aims to understand how the semidiurnal tide propagates and generates strong currents near Hopen Island in the Barents Sea. The trapping of the semidiurnal (M2) tide around Hopen Island leads to an organized dipole structure in sea level, which rotates clockwise. The dipole generates maximum amplitudes of water surface elevation and the strong current near the south and north tips of the island. The abrupt sea level change induced by the dipole sets up often violent currents, which, together with drifting ice, can be dangerous for navigation. The strong tidal currents generate permanent clockwise circulation around the islands, which is essential for biological life and waste disposal as material disposed of near the islands will be trapped for an extended time. Our investigation elucidates the role of dipoles in the local enhancement of tides around the islands.

Tidal Motion Enhancement on Spitsbergen Bank, Barents Sea

AbstractThe higher resolution numerical model investigates the semidiurnal and diurnal tides over the shallow Spitsbergen Bank. The tidal wave is trapped around Bear Island, Hopen Island, and Central Hill at the Bank in the semidiurnal range of oscillations. Semidiurnal waves around Bear and Hopen Islands generate a trapped dipole in the sea level distribution revealed by sea level maximum and minimum traveling on the opposite sides of the island. The dipole induces significant sea‐level differences and amplified velocity around the island perimeter. The role of the tidal currents over the Bank is connected through the mixing and transport to the generation of frontal regions. Tidal mixing directly relates to the local ice formation on Spitsbergen Bank as these areas coincide with the regions of strong tidal currents. The trapping of the semidiurnal tides leads to residual (permanent) circulation of up to 15 cm s−1. As this motion interconnects different bathymetric regions of the Bank, it influences the exchange of properties between these regions. The strength of residual currents shows that the large‐scale slow thermohaline motion cannot be complete without residual tidal motion. The diurnal tides show a different distribution since higher spatial resolution reveals sea‐level variability in many locations. These short‐wavelength shelf waves occur at seamounts, submarine peninsulas, and bays. We investigate in detail the wave dynamics in proximity to Central Hill and Hopen Island. We use observations of the buoys deployed on the ice floes to compare the drift velocity to the computed tidal velocity.

Modeling of Thermodynamic Consolidation of Sea Ice Ridges Drifting in the Water with Changing Temperature

Oceanographic and ice conditions in the region of Spitsbergen Bank in the Barents Sea were investigated in research cruises of the “Polarsyssel” in 2017–2019. Trajectories of ice drift were constructed using GPS data of the buoys deployed on the floes in the research cruises. The duration of the ice season in the region was analyzed using ice charts. The air temperature and wind velocities were analyzed using the data of meteorological stations on Bear Island and Hopen Island. Fieldwork on drifting ice showed the existence of thick consolidated floes with drafts up to 8 m, which were identified as completely consolidated sea ice ridges. The presence of such floes is dangerous for winter navigation along Spitsbergen Bank. A model of thermodynamic consolidation of ice ridges was formulated to investigate the thermodynamic evolution of ice ridges. The observed air and sea water temperatures were used in the boundary conditions on top and bottom surfaces of sea ice rubble. It was shown that the regular interaction of sea ice rubble with Atlantic and Arctic waters in the region of Spitsbergen Bank leads to almost complete consolidation of the ice rubble with an initial macro-porosity 0.2 for 150 days.

Deformation of an ice pack influenced by waves and topographic enhancement of tidal motion near Hopen Island in the Barents Sea

Understanding the physical mechanisms behind the deformation of pack ice floes is important for understanding the dynamics of the local ice regime, and for the calibration and validation of ice dynamics models. In April 2017, six Iridium satellite-tracking beacons were deployed on six pack ice floes in the Barents Sea south of Svalbard in the Norwegian Arctic. The ice tracker deployment was performed as part of an offshore research expedition carried out onboard the Research Vessel (RV) Polarsyssel to characterize the local sea ice environment. In addition to the ice tracker deployments, an anemometer beacon, a wave beacon, and an Acoustic Doppler Current Profiler (ADCP) were deployed on a drifting ice floe to which the vessel was moored for nearly three days, and extensive thickness, salinity, and density measurements were made. The wave beacon recorded the vertical acceleration of the floe so that wave forcing on the floe drift could be estimated. The in-situ wind, ocean current, wave, and ice thickness and density measurements permitted the estimation of met-ocean forcings on the acceleration of the ice floe. On April 28, two days after the last ice tracker was deployed on April 26, the six tracked ice floes rapidly dispersed just to the west-southwest of Hopen Island. The dispersion of the ice floes was dominated by strong shearing within the local ice pack, coinciding with a rapid increase in the speeds of the local tidal currents, which was soon followed by a rapid increase in the wave energy. Each of the six tracked ice floes increased their observed drift speeds in sync with the increase in the local tidal current speeds at different times for each floe, but at approximately the same decrease in water depth as they reached the northern edge of Spitsbergen Bank. The rapid increase in the tidal currents was linked to the topographic enhancement of tidal motion near Hopen Island in the shallower waters of Spitsbergen Bank. The wind and wave measurements made by the anemometer and wave beacons and ice tracker left on the ice floe to which the vessel was moored allowed for an estimate of the relative strength of the wind, tidal, and wave forcings on the local ice field. The results showed that the tidal currents initially dominated the dynamic response of the local ice field compared to the wind, which led to the conclusion that the enhanced tidal current was ultimately the dominant cause of the initial dispersion of the local pack ice field on April 28, and the dispersion was then further enhanced by the increase in wave energy.

High-amplitude internal waves southeast of Spitsbergen

We investigate tidal and higher frequency internal waves southeast of Hopen Island of the Svalbard archipelago using shipborne CTD and ADCP data, model simulations, and satellite observations. The experiment was carried out in the marginal ice zone region. Previous numerical simulations predicted high amplitudes of internal tides here. A series of repeated CTD-casts provide estimates of the vertical displacements of water particles caused by internal waves generated over the continental slope. Peak to peak displacements caused by forced non-propagating internal tides were as high as 50 m. Generation of strong internal tides is also shown based on numerical model revealing high amplitudes (50 m) of vertical displacement over the submarine slope. The development of forced internal tides in the vicinity of the M2 critical latitude is accompanied by generation of short-wave trains of internal solitary waves depicted in satellite observations.

Lichen Diversity on Glacier Moraines in Svalbard

Abstract This paper contributes to studies on the lichen biota of Arctic glacier forelands. The research was carried out in the moraines of three different glaciers in Svalbard: Longyearbreen, Irenebreen and Rieperbreen. In total, 132 lichen taxa and three lichenicolous lichens were recorded. Eight species were recorded for the first time in the Svalbard archipelago: Arthonia gelidae, Buellia elegans, Caloplaca lactea, Cryptodiscus pallidus, Fuscidea kochiana, Merismatium deminutum, Physconia distorta, and Polyblastia schaereriana. One species, Staurothele arctica, was observed for the first time in Spitsbergen (previously recorded only on Hopen island). All the studied glaciers lie in Spitsbergen's warm region. However, Kaffioyra Plain, where Irenebreen is located, is characterized by higher levels of humidity, which may explain its different lichen composition compared to that of the other two moraines. The forelands of Rieperbreen and Longyearbreen are located in the same area of Svalbard, which is als...

Arthropod interactions with bennettitalean roots in a Triassic permineralized peat from Hopen, Svalbard Archipelago (Arctic)

Multiple thin-sections of a Late Triassic (Carnian) siliceous permineralized peat block likely derived from the De Geerdalen Formation on Hopen Island, Svalbard Archipelago, show a dense mass of roots preserving fine anatomical details of various stages of primary and secondary vascular tissue development. The presence of moderately defined rings with few latewood cells in the secondary xylem attests to growth in a seasonal environment. The presence of mucilage bodies and nests of sclerotic cells in the cortical tissues of the roots and pith of subaerial stem fragments, together with scalariform pitting on radial tracheid walls and 2–12 simple pits per cross-field favor bennettitalean affinities for the roots. Evidence of a rich fauna of detritivores inhabiting the peat profile is represented in the form of extensive damage to cortical tissues of dead roots and abundant coprolites preserved both within chambers excavated in the plant tissues and in the peat matrix. Less common gall-like structures within the roots indicate the presence of parasitic organisms in the palaeo-peat ecosystem.

Sea ice and polar bear den ecology at Hopen Island, Svalbard

The maternity denning of polar bears Ursus maritimus was studied at Hopen Island, Svalbard, Norway, using information collected by direct observation and live-capture of females and cubs during den emergence in spring of 1994 to 2008. The number of maternity dens observed annually varied from 0 to 36. The arrival of sea ice at Hopen Island in autumn shifted from late October to mid-December during the period 1979 to 2010. Fewer maternity dens were found on Hopen Island in years when sea ice arrived later in the autumn. There were no significant differ- ences in body mass or litter size between female polar bears denning on Hopen Island and females caught elsewhere in Svalbard; however, females denning on Hopen Island were significantly younger than females denning elsewhere in Svalbard. Later arrival of sea ice in the autumn at Hopen Island was correlated with lower body mass of adult females and their cubs at emergence. The timing of arrival and departure of sea ice is highly variable but a trend of later arrival in autumn may be affecting the denning ecology of polar bears at the southern extent of their range in Svalbard.

Preliminary Analysis of the 21 February 2008 Svalbard (Norway) Seismic Sequence

The Svalbard Archipelago is situated in the northwestern part of the Barents shelf, in close proximity to the passive continental margin. This intraplate region is characterized by some of the highest seismicity in the entire Barents Sea and adjoining continental shelf, surpassed only by the Knipovich ridge ( e.g. , Engen et al. 2003; International Seismological Centre 2001), which, as a spreading plate boundary, is the structure that dominates the regional stress field. Most of the seismic activity (Figure 1) is characterized by smaller events, which often occur in small concentrations sparsely distributed in time. However, earthquakes of moderate to stronger magnitudes do occur in the Svalbard area, such as the 4 July 2003 mb 5.7 event close to Hopen Island ( e.g. , Stange and Schweitzer 2004). A more recent example will be discussed here: the Mw 6.0 earthquake that occurred in Storfjorden, off the coast of the island of Spitsbergen, on 21 February 2008 and initiated an extensive aftershock sequence. The data presented in this contribution cover approximately seven months following the occurrence of the mainshock and involve more than 250 aftershocks included in the NORSAR Regional Reviewed Bulletin (http://www.norsardata.no/NDC/bulletins/regional/), which contains events with an automatic network magnitude ( MGBF ) larger than 2.0. The 2008 seismic activity in Storfjorden coincided temporally with an International Polar Year (IPY) project to study the continental margin in the region between the Mohns and Knipovich ridges and Bear Island, south of Spitsbergen (see http://www.norsar.no/c-24-International-Polar-Year.aspx). This resulted in the mainshock and a significant part of the aftershock sequence being recorded by several temporary seismic stations deployed in the region, in addition to the permanent installations in the European Arctic. Data used in this study were obtained from the NORSAR arrays SPITS and ARCES; the Norwegian National Seismic Network (NNSN) stations KBS, BJO1, and …

Dense overflow from an Arctic fjord: Mean seasonal cycle, variability and wind influence

Storfjorden, an Arctic fjord in the Svalbard archipelago, is separated by a submarine sill from the adjacent shelf areas and produces one of the densest water masses in the Barents Sea. The cold and dense brine-enriched shelf water is produced through ice formation in an annually recurrent polynya in Storfjorden and overflows across the sill. We present current profiles and bottom temperature measurements from the Storfjorden sill from 2003 to 2007, which is the longest time series collected at this site, and study the interannual variability of the overflow and the influence of atmospheric forcing. The mean structure of the overflow averaged over four seasons shows that the overflow is initially strong with high volume transport, about 50 m thick and bottom-enhanced, and then gradually diminishes, becoming increasingly intermittent during the last third of the overflow season. The annual average overflow transport is about 0.03 Sv ( 1 Sv ≡ 10 6 m 3 s - 1 ). Overflow is observed 55% of the total record length of 958 days and cross-sill flow averaged in the bottom 20 m is greater than 10 cm s - 1 for 49% of the overflow duration. The overflow strength increases with decreasing near-bottom temperatures. The annual variability is within 0.01 Sv whereas the seasonal variability can be as large as 0.05 Sv. In spite of the relatively constant annual overflow flux, the onset of the overflow can vary by up to 50 days. Variability on the scale of 1–2 weeks is connected to wind forcing through surface Ekman transport with significant coherence between the current at the Storfjorden sill and wind measured on Hopen Island and Edgeøya. Surface Ekman transport and the ice conditions in the Barents Sea also influence the intra-seasonal development and interannual variability of the overflow.

Cross Correlations of Geomagnetic Field Variations Between Zhongshan and Arctic Stations

AbstractThe occurrence rates of the cross correlations of the inter‐hemispheric geomagnetic field variations are studied statistically with the magnetic data observed at Zhongshan Station, Antarctica and at Ny‐Alesund, Longyearben, Hopen Island, Bear Island and Tromso in the Arctic during Sept. 2000 to Mar. 2003, in which the criterion is that the correlation coefficient within sliding 20 min bin is larger than 0.9. It is shown that the occurrence rates of correlations of geomagnetic field variations between Zhongshan and Arctic stations are related to locations of the Arctic stations, season, local time and geomagnetic active level. Among the 5 stations in the Arctic, Longyearben is correlated most frequently with Zhongshan (17%), Ny‐Alesund or Hopen take the second place. In the equinox, the occurrence rate of correlations is higher than other seasons. In the daily variation of the occurrence rate of correlations, there is a peak in the evening and a valley at noon. The occurrence rate of correlation increases as geomagnetic activities increase.

Conjugate phase studies of ULF waves in the Pc5 band near the cusp

Conjugation of geomagnetic field lines at magnetic high latitude is variable, depending on solar wind and interplanetary magnetic field conditions. In this paper the geomagnetic conjugate point of a location under closed field lines near the cusp has been determined dynamically by examining the conjugate phase relation of ultra low frequency (ULF) waves in the Pc5 band using magnetometer data from high‐latitude ground stations at Longyearben (LYR), Hornsund (HOR), and Hopen Island (HOP) in the Northern Hemisphere and Davis (DAV), Zhongshan (ZHS), and Mawson (MAW) in the Southern Hemisphere. Cross‐spectral and coherency analysis methods are used to select conjugate Pc5 events and derive phase relations. The results show that near the cusp the geomagnetic field lines resonate mainly in the odd mode with the D component out of phase and the H component in phase, when observed at the two ends of the field line. Assuming this phase characteristic, the conjugate of LYR is typically located in the DAV/ZHS‐region and mainly east of Davis by about 10° CGM longitude. In a reverse mapping analysis the conjugates of ZHS and DAV are located in the LYR region, mainly west of LYR by 10°. These results are qualitatively consistent with corresponding locations derived from the Tsyganenko [1996] (T96) model. The relationship of the longitude movement of the conjugate of LYR with respect to the variation of IMF By is quantitatively consistent with the T96 model. However, the expected position of the conjugate site of LYR (DAV/ZHS) derived from Pc5 phase for By = 0 is moved westward (eastward) by about 10° CGM in longitude or ∼300 km from that predicted by the T96 model.

Long-term near-bed observations of velocity and hydrographic properties in the northwest Barents Sea with implications for sediment transport

Combined results from time-series observations of currents and water properties from two moorings and a benthic tripod measuring near-bed velocity profiles are used to evaluate the potential for sediment transport in the Storfjord, east of Hopen Island, and in Olgastretet in the Barents Sea near the southeast Svalbard Archipelago. Current observations include a 15-month time series from each mooring with the lowermost current meter on each mooring positioned at 6 mab and a 5-month time series from the tripod with four current meters located within 1.2 mab. Threshold of grain motion was estimated from seabed sediment characteristics sampled at each site, bed roughness length was calculated from the benthic tripod velocity profiles. Results from the Storfjord and east of Hopen Island suggest that near-bed currents and bottom stresses cannot resuspend sediment in the summer months. Currents exceed the threshold of grain motion during the fall and winter months in response to strong flows forced by surface cooling and winds. Threshold of grain motion occurs for approximately 10 days per year in both the Storfjord and east of Hopen Island. In Olgastretet, measured bottom currents had distinct reversals from north to south over periods of 3–8 days throughout the record. The highest currents (and largest bottom stresses) were directed southward and were high enough to resuspend bottom sediment about 19 days during the deployment period. Near-bottom flows are dominantly southward at all stations during times that sediment threshold velocities are exceeded, thus strong flows exiting the fjords in southern Svalbard during winter may also transport significant quantities of sediment into the deep northern Norwegian Sea.

First contribution to the diatom flora of High Arctic Hopen Island (Svalbard)

First contribution to the diatom flora of High Arctic Hopen Island (Svalbard)

Infanticide and Cannibalism of Juvenile Polar Bears (<i>Ursus maritimus<i/>) in Svalbard

Two instances of infanticide and cannibalism in polar bears (Ursus maritimus) were observed in SE Svalbard, at Hopen Island. In the first, an adult male killed three young cubs at a den site and consumed one of them. In the second, an adult male actively pursued, killed, and consumed a dependent yearling. Infanticide of dependent polar bear offspring by adult males may be more common in Svalbard than in other populations because the population is close to carrying capacity or because geographic features reduce spatial segregation of age and sex classes.

Observation of Adoption in Polar Bears (<i>Ursus maritimus</i>)

We observed a case of adoption of a single four-month-old polar bear cub (Ursus maritimus) into an existing litter of two cubs on Hopen Island, Svalbard. We believe the high density of maternity dens in the study area may increase the likelihood of natural adoption. Speculation about theoretical implications of adoption is of scientific interest. However, we believe that the probability of adoption may increase when family groups are captured, and the scientific interpretation of such events is of questionable value. We urge researchers to exercise caution in handling family groups in high-density den areas.

Water mass distribution and polar front structure in the western Barents Sea

The water mass distribution in the western Barents Sea, the thermohaline structure of the western Barents Sea Polar Front, and the local formation of a dense water mass are described on the basis of an analysis of historical hydrographic data. This study concentrated on the frontal region between Bjørnøya and Hopen Island where Arctic water is found on the Spitsbergen Bank and Atlantic water in the Bear Island Trough and Hopen Trench. The distributions of Atlantic and Arctic waters in relation to topography were consistent with the hypothesis that the location of the polar front is fixed at about the 250 m isobath by the barotropic circulation of Atlantic water within the Bear Island Trough and Hopen Trench. In winter, vertical gradients of temperature and salinity were weak throughout the frontal region, consistent with a barotropic, topographically controlled front. In summer, vertical gradients remained weak below 100 m depth but increased in the upper layer as a result of the presence of fresh, warm surface water produced by melting ice. The topographic control of thermohaline properties at the surface was disrupted by the meltwater pool, and the meltwater contributed to water mass modification in the frontal region. The following seasonal cycle of water mass formation was hypothesized: Summer heating melts the sea ice on the Spitsbergen Bank and produces the surface meltwater pool. This meltwater not only increases vertical thermohaline gradients on the bank but also crosses the front and freshens the surface layer throughout the western Barents Sea. Subsequent winter cooling, which creates ice over the bank, also forms dense water in the Bear Island Trough and Hopen Trench by convective mixing of Atlantic water and the overlying meltwater.

Sea ice fields and atmospheric phenomena in Eurasiatic arctic seas as seen from the NOAA-12 satellite

The image presented in this study is a mosaic showing the Barents and Kara seas area. It was processed from 1.1 km resolution NOAA-12 AVHRR data, acquired in the near-infrared band, on 17 June, 1994, 8h30 GMT and 19 June, 1994, 8h10 GMT. With the exception of the western and southern part of the Barents sea, all the area is cloud-free. Such an event is relatively seldom and enables us to observe diverse surface oceanic features, such as the sea ice distribution, the location of polynyas and the influence of warm waters, remnants of the North Atlantic Drift, on the ice field. The two days lag between the scenes allows us to observe the drifting of ice floes, influenced by winds and currents, especially in the southern part of Franz Josef Land archipelago. Atmospheric lee-waves are observed at Hopen Island and westward of Bear Island.

Changes to the Climate and Flora of Hopen Island during the Last 110 Years

Hopen, a small island in the Barents Sea, is situated within the polar desert region. Altogether 26 vascular plants have been noted in four inventories conducted between 1873 and 1982. The temperature climate following the Little Ice Age has fluctuated considerably but with a clear warming after 1920. New areas have become available to the plants since permanent snowfields have melted. The number of species has increased from 17 in 1873 to 19 in 1982, but the turnover has been relatively large. Hopen does not show island biogeography equilibrium. Instead, the July mean temperature is probably the determining factor for the number of species. Mainly seed-dispersed species have colonized Hopen during this period. The origin of the vascular flora and the migration mechanisms are difficult to interpret if it is considered that the entire Svalbard Archipelago was simultaneously under ice during the Weichsel glaciation.Key words: vascular flora, polar desert region, climatic fluctuations, dispersal, island biogeography

Daily Energy Expenditure and Energy Utilization of Free-Ranging Black-Legged Kittiwakes

Rates of CO2 production by breeding Black-legged Kittiwakes (Rissa tridactyla) (mean mass, 386 g) were measured by using doubly-labeled water. Kittiwakes alternated days on and off the nest, while they brooded their nestlings. Field metabolic rates (FMR) in nonforaging birds averaged 2.43 ml CO2/g hr, or 596 kJ/day. This is 1.9 times the basal metabolic rate (BMR), measured in the laboratory to be 1.31 ml CO2/g-hr, or 314 kJ/day. FMRs in foraging birds averaged 4.04 ml CO2/g hr, or 992 kJ/day which is 3.2 times BMR. The rate of food consumption by an adult kittiwake, calculated on the basis of the chemical composition and digestibility of capelin (Mallotus villosus, the most important dietary item at Hopen Island) was 315 g of fresh matter per bird every other day. A colony of 3,000 breeding pairs of kittiwakes at Hopen Island, using the fishing grounds around the island, would consume about 1,245 kg of fresh fish per day, and add about 76 kg (dry matter) of guano to the marine ecosystem during the chick-rearing period.