Kara Gates Research Articles

The influence of heavy shipping traffic on the structure and dynamics of sea ice in the southwestern Kara Sea

The development of the Northern Sea Route and the beginning of year-round transit shipping require not only the production of new icebreakers and ice-class vessels, but also the development of a specialized hydrometeorological support system for ice shipping. For the analysis of satellite data and the development and validation of ice forecasts, actual field data on the ice cover is required. This data can only be obtained from shipboard observations; however, scientific expeditions are rarely organized during the winter. In order to obtain new data over the area of intensive shipping, two expeditions were organized on board of nuclear icebreakers in the southwestern Kara Sea (“LED-SMP” expeditions) in 2023 and 2024. Specialized hydrometeorological maintenance of ice shipping in the southwestern Kara Sea together with the research expeditions “LED-SMP” carried out in the same place and time on board the nuclear icebreakers revealed the influence of the technogenic factor on the sea ice structure and dynamics was revealed. In winter and spring, two main routes are used for navigation in the southwestern Kara Sea: through the Kara Gate Strait and north of Cape Zhelaniya. In April 2024, a unique situation occurred when, due to the difficult ice conditions east of the Kara Gate Strait, the entire ship traffic was directed north of Cape Zhelaniya. In preparing a long-term ice forecast, it was noted that after the redirection the natural development of ice processes changed. At the beginning of the winter period 2024,

Multi-Sensor Observations Reveal Large-Amplitude Nonlinear Internal Waves in the Kara Gates, Arctic Ocean

We present multi-sensor measurements from satellites, unmanned aerial vehicle, marine radar, thermal profilers, and repeated conductivity–temperature–depth casts made in the Kara Gates strait connecting the Barents and the Kara Seas during spring tide in August 2021. Analysis of the field data during an 18-h period from four stations provides evidence that a complex sill in the Kara Gates is the site of regular production of intense large-amplitude nonlinear internal waves. Satellite data show a presence of a relatively warm northeastward surface current from the Barents Sea toward the Kara Sea attaining 0.8–0.9 m/s. Triangle-shaped measurements using three thermal profilers revealed pronounced vertical thermocline oscillations up to 40 m associated with propagation of short-period nonlinear internal waves of depression generated by stratified flow passing a system of shallow sills in the strait. The most intense waves were recorded during the ebb tide slackening and reversal when the background flow was predominantly supercritical. Observed internal waves had wavelengths of ~100 m and traveled northeastward with phase speeds of 0.8–0.9 m/s. The total internal wave energy per unit crest length for the largest waves was estimated to be equal to 1.0–1.8 MJ/m.

Properties of Short-Period Internal Waves in the Kara Gates Strait Revealed from Spaceborne SAR Data

This paper presents the results of identification of surface manifestations (SM) of short-period internal waves (SIW) in Sentinel-1 A/B synthetic aperture radar (SAR) images of the Kara Gates Strait in August–September 2021. 44 SM of SIW trains were detected in 47 SAR images. Statistics of occurrence, propagation direction and spatial characteristics of SIWs in the study area are given. During two months, satellite observations cover almost all phases of spring-neap tidal cycle. The use of a detailed topography of the study area made it possible to identify certain regions with a more frequent presence of the SIW leading crests with a particular focus made on the shallow (< 100 m) part of the strait. Each identified region is then described in terms of water depth, dimensionless slope, amplitudes of tidal current velocity and properties of SIWs. The obtained results were then compared with the results of previous studies.

Water, heat and salt balance of the south-eastern part of the Barents Sea

The south-eastern part of the Barents Sea is located away from the main currents, with a combination of climatic, hydrological and oceanological processes creating conditions that make the region different from the rest of the Barents Sea such that it is seen as a separate region and called sometimes the Pechora Sea. Despite the intensive economic activity in the south-eastern part of the Barents Sea, it is not yet clear to what extent the general Atlantic water transport in the Barents Sea and, consequently, the transport of heat and salt, affects this region. Therefore, the aim of this study was to assess advective flows at open boundaries, as well as other components of the water, heat and salt balances of the south-eastern part of the Barents Sea. Based on monthly average data from the MERCATOR GLORYS12V1 reanalysis for the period 1993–2018, we calculated water transport, heat and salt flows at the boundaries of the south-eastern part of the Barents Sea (at 50° E in the west, at 71° N in the north and in the Kara Gate Strait); to close the balances, an assessment was made of sea-atmosphere interaction characteristics on the sea surface based on ECMWF ERA5 reanalysis data. Water, heat and salt balances were combined with a residual not exceeding 1.6 %. Linear trends for the characteristics obtained were calculated. It is revealed that the average long-term resulting water transport in the south-eastern part of the Barents Sea is directed from the north-west of the region to the Kara Gate Strait (0.40 Sv). This current is associated with the Atlantic waters and also carries heat and salt. The resulting heat input (5.92 TW) creates a heat excess in the water area, which is compensated for by interaction with the atmosphere (1.86 TW). The salt flow through the region is estimated at 13.98 t/s. During the study period, all the main flows have a statistically significant positive trend in the incoming and outgoing parts of the balances: water transport — 0.005 Sv per year; salt flow — 0.18 t/s per year. This indicates an increase in the transit of Atlantic waters through the south-eastern part of the Barents Sea. An increase in the advective heat flux (0.15 TW per year) across the western border is accompanied by an increase in its release into the atmosphere (0.07 TW per year) and an increase in evaporation of 6.9 mm per year. Sea levels are also rising at a rate of 0.27 cm per year. Thus, the increasing dynamics of the processes in the region is a factor to take into account in conducting economic activities.

Surface microplastics in the Kara Sea: from the Kara Gate to the 83°N

Despite ongoing research into microplastics pollution in the Arctic Ocean, the region remains underexplored. In the Eurasian Arctic studies mainly focus on the Barents Sea, while there are only limited and variable data from few stations in the Kara Sea. The study aims to perform an extensive survey of microplastics floating on the sea surface in the Kara Sea. The sampling throughout the Kara Sea was carried out using a neuston net in the August 2021 starting from the Kara Gate strait, reaching 83N latitude and ending in the north-eastern part of the Barents Sea along the border with the Kara Sea. Average abundance of microplastics was 0.124 ± 0.383 items/m3 in the Kara Sea. The Kara Gate exhibited the highest abundance of microplastics (0.93 ± 0.73 items/m3), suggesting that it is an important source of the microplastics pollution of the Kara Sea. The results suggest that the Ob and Yenisey rivers do not substantially contribute to the microplastic pollution of the Kara Sea due to significantly lower concentrations in the river plume water (0.008 ± 0.009 items/m3) compared to the other regions of the Kara Sea. Further, the river plume differs in chemical composition of microplastics dominated by expanded polystyrene (EPS) particles (52%) in contrast to other regions where the predominant polymer is polyethylene (PE) (64-77%). The study highlights the potential of the Kara Sea to accumulate the microplastics due to its semi-enclosed nature and complex interaction between inflow of waters originating from the North Atlantic and Ob-Yenisey river plume.

Strait of Kara Gates: A Region of Strong Internal Tides in the Arctic Seas

This is a review paper about measurements of internal tides in the Kara Gates Strait. Kara Gates is one of the straits where intense internal tides are generated by tidal currents overflowing the transversal sill of the strait. Tidal currents are superimposed on a constant current from the Barents to the Kara Sea. Field studies of internal waves in the strait were carried out in 1997, 2007, 2015, and 2016. Analysis of measurements on moorings and towed CTD in scanning mode is presented. Field studies are supported by model simulations of generation and propagation of internal tides.

High-Resolution Radar Sensing Sea Surface States During AMK-82 Cruise

Every year situation when theArctic seas are free of ice is becoming more frequent. It allows scientists to study hard-to-reach areas using well-equipped research vessels instead of icebreakers. During the COVID-19 pandemic, the successful expedition of the research vessel “Academician Mstislav Keldysh” with more than 60 scientists from 15 countries across the four Arctic seas (Barents, Kara, Laptev, and East Siberian) on September–November 2020 seems like a real wonder. One of the expedition tasks was remote sensing of different hydrophysical processes by their manifestation on the sea surface using marine radar. This article proposes the method of generating high spatial resolution radar maps of the sea surface and algorithms of hydrophysical processes identification. This article also presents examples of registered processes, such as wind waves, ice fields with different types of ice (grease ice, pancake ice, nilas, and young ice), manifestations of internal waves observed in the Kara Gate and Vilkitsky Strait, as well as manifestations of intense methane seeps on the sea surface. This article contains quantitative estimations of the physical parameters of the observed processes underlying the effectiveness of Doppler marine radars in harsh conditions of the Arctic seas.

Analysis of ice conditions of year-round navigation of Arc7 vessels in the southwestern part of the Kara Sea

Since 2006, a new generation of reinforced ice class Arc7 vessels has been operating on the Northern Sea Route. Safe and efficient sailing of this type of vessels in sea ice demands a detailed study of ice conditions. Accumulation and analysis of data on ice and hydrometeorological conditions for the entire Arctic in comparison with ice conditions along the route of vessels is an essential part of the development of optimal variants and optimal routes for ice navigation.The main aim of the study was to generalize the conditions of ice navigation of Norilskiy Nickel vessels along the optimal navigational routes in the south-western part of the Kara Sea. Based on the reports on sailing obtained from vessels of the “Norilskiy Nickel” type for the 2006–2014 period, we calculated the probability of choosing the optimal route along the Murmansk – Dudinka passage: through the Kara Gate Strait (seaward, central or coastal route) or the north of Cape Zhelaniya. During the year, vessels move predominantly through the Kara Gate. However, for three month per year, from April to June, the most appropriate route lies to the north of the Zhelaniya Cape. In April – May it is, on average, every second navigation, and in June – more than 80 % of all navigation. The features of the ice regime determining the choice of the specific navigation route, are described. The speeds of vessels of the “Norilskiy Nickel” type along various navigation routes in drifting sea ice of the Kara Sea are calculated. The fastest speed in drifting ice was recorded in the winter navigations of 2007–2008 and 2011–2012, in the January-May of these years the average speed was 10.2 and 11.2, correspondingly. The minimum speed in these years, even during the months of maximum ice cover growth, was not less than 4.8 knots. In other years, the average speeds were in the range of 9.2–9.8 knots. During the whole period of study, ice conditions that were extremely difficult for navigation formed three times: at the end of May 2009, at the end of March 2010 and in the middle of March 2011, these are considered in more detail in the present article.

Vessel movement velocity as the integral parameter of ice navigation conditions

The publication is considered methodology and preliminary results of computer processing of vector ice charts and simulation of ice navigation by empirical statistical model, which was designed in the AARI. The model is result of generalization of multi-year special ship ice observations, produced by the AARI scientists. The Institute has unique archive of ice charts, which were made by recognition of satellite images, their composition and vectorization. The archive covers the period since 1997. Average navigation velocity and total time expenditure for sailing along a route can be used as the objective indexes of the ice navigation conditions. In the article is presented detailed description of the technique for preparing data for numerical experiments with the empirical statistical model by applying the ice charts from the archive. The data preparing is processed in ArcGIS by means of specially designed computer programs. The numerical experiments simulate ice navigation of “Arctica” nuclear icebreaker. The comparison between the average navigation velocity and time expenditure for sailing along the route “Sabetta Port – Kara Gate Strait” at simulation of ice conditions in the first ten-day interval of May 1998 and the same temporal interval of 2019 indicates significant improve of the ice navigation conditions.

Habitat Use by the Polar Bear (Ursus maritimus) along the Coastline throughout the Year According to Satellite Monitoring Data

A female polar bear (Ursus maritimus) has been captured and tagged with a satellite collar of the Argos system on Vaigach Island. The data of the location relative to the coastline in the Kara Gate from April 2016 to September 2017 have been analyzed. An analysis of the polar bear movement pattern has revealed periods of its greater (on the ice) and less (on the land) mobility and a movement direction. The largest area of the polar bear habitat on an average monthly scale was in May 2016, when moving on the finely crushed ice; the smallest area was in January 2017 on the land without ice. We have estimated the distance to the coast to analyze the use of environmental resources (27% of the time on the coast, 33% on the inland, and 40% in the offshore). As follows from the comparison with our previous studies, the bears adhere to the land even during the sea-ice season.

Combining data from different sampling methods to study the development of an alien crabChionoecetes opilioinvasion in the remote and pristine Arctic Kara Sea

Data obtained using three different types of sampling gear is compared and combined to assess the size composition and density of a non-indigenous snow crab population Chionoecetes opilio in the previously free of alien species Kara Sea benthos. The Sigsbee trawl has small mesh and catches even recently settled crabs. The large bottom trawl is able to catch large crabs, but does not retain younger crabs, due to its large mesh. Video sampling allows the observation of larger crabs, although some smaller crabs can also be spotted. The combined use of such gear could provide full scope data of the existing size groups in a population. The density of the crabs was calculated from the video footage. The highest figures were in Blagopoluchiya Bay at 0.87 crabs/m2, where the settlement seems to be reaching its first peak of population growth after the introduction. High density in the Kara Gates Strait at 0.55 crabs/m2, could be due to the close proximity of the Barents Sea from where the crabs can enter by both larval dispersal and active adult migration. All size groups have been present in most sampled areas, which suggest successful settlement and growth of crabs over a number of years. Again, this was not the case in Blagopoluchiya Bay with high density of small crabs (<30 mm CW), which confirms its recent population growth. Male to female ratio was strikingly different between the bays of the Novaya Zemlya Archipelago and west of the Yamal Peninsula (0.8 and 3.8 respectively). Seventy five ovigerous females were caught in 2016, which confirms the presence of a reproducing population in the Kara Sea. The spatial structure of the snow crab population in the Kara Sea is still in the process of formation. The presented data indicates that this process may lead to a complex system, which is based on local recruitment and transport of larvae from the Barents Sea and across the western Kara shelf; formation of nursery grounds; active migration of adults and their concentration in the areas of the shelf with appropriate feeding conditions.

The variability of ice conditions along the Northern sea route for the period 1997–2018

The paper discusses the methodology and results of electronic ice charts processing. The charts taken from AARI archive. The Barents, Kara, Laptev, East Siberian and Chukchi seas Ice maps reflect ice conditions for the period from 1997 to 2018 for the April-May inter-annual interval. The total stage lengths of «Sabetta – the Kara Gate –Murmansk» and «Sabetta – the Vilkitski Strait – the Bering Strait» standard routes were calculated at certain conditions of ice navigation. The route “Sabetta – the Bering Strait” was divided into sections within the Kara sea, Laptev Sea, East Siberian and Chukchi Seas for analysis. The purpose of the study is to obtain the values of the length of the routes in different categories of ice and to analyze changes trend of navigation in ice conditions for the period 1997-2018. The series were checked for the presence of trends using the integral curves method. The homogeneity of the series was checked using Wilcoxon - Mann-Whitney and Siegel - Tukey rank non-parametric criteria. Most of the series proved to be non-homogeneous. The following conclusions were made: there was some improvement of ice navigation conditions along the route Sabetta ‒ the Kara Gate – Murmansk due to the decrease of the route length in hard ice conditions. The ice navigation conditions along the Sabetta ‒ the Bering Strait route changed little, if at all, the navigation conditions along the route within the Kara Sea and the Laptev Sea have changed for the worse, and within the East Siberian Sea ice conditions scarcely changed. Some slight improvement of the navigation conditions was noted within the Chukchi Sea. In general, the decrease of the route Sabetta – the Bering Strait length in compact drift ice with total concentration equal to 9 tenths or more and in the presence of old ice is partially compensated by increase of the route length in compact ice in the presence of thick first-year ice. The decrease and the increase are relatively equal.

Use by polar bear (ursus maritimus) of the habitat along coastline throughout the year according to satellite monitoring data

A polar bear female (Ursus maritimus) was captured and marked by satellite collar of the Argos system on Vaygach Island. Data of location relative to the coastline in the Kara Gate from April 2016 to September 2017 was analyzed. An analysis of the polar bear trajectory revealed periods of its greater (when on ice) and less (on land) mobility and directed of movement. The largest area of the polar bear habitat on an average monthly scale was in May 2016, when moving on small-hit ice, the smallest – in January 2017, when on land with no ice. We estimated the distance to the coast to analysis for resource use (27% of the time on the coast, 33% on land, 40% in the water area). Comparison with our previous studies has shown, there is a commitment to land, even during the season of sea ice presence.

Analysis of the interannual variability of ice conditions along the route "Sabetta – Murmansk» for the period 1997-2018

«Вестник Санкт-Петербургского университета. Науки о Земле» — научно-теоретический рецензируемый журнал, обобщающий результаты исследований в области геологии, гидрогеологии и геохимии, петрологии и экологии, ландшафтного планирования и геоморфологии, экономической и социальной географии.

Development of snow crab Chionoecetes opilio (Crustacea: Decapoda: Oregonidae) invasion in the Kara Sea

With current climate trends, longer ice-free periods and increased human activity are observed in the previously hard to access Arctic Siberian seas. This provides for a rare opportunity to observe the progress of species invasion in pristine areas. The snow crab, Chionoecetes opilio, is a unique example of an alien Brachyura crab in the Arctic. Its distribution, population size structure, as well as biotic and abiotic conditions affecting its survival in the Kara Sea are discussed. Crabs were collected using trawl sampling in 2014. It has been estimated that the invasion took place in the late 2000s through the northern and eastern borders with the Barents Sea. Presently, snow crabs are found throughout the western part of the sea, from Kara Gates to St. Anna Trough; the entire area between Yamal Peninsula and Novaya Zemlya; and the northeastern shelf of the sea. Benthic abiotic conditions of the Kara Sea are unlikely to limit survival and further progress of snow crab population. However, the length of the ice-free period could limit its reproduction potential. The collected data do not allow us to presume the existence of a reproducing population, yet the presence of a settler-size group in the central part of the western Kara shelf could indicate local recruitment. Food availability in the Kara Sea is unlikely to limit growth of early benthic stages of snow crabs such as those collected in 2014. However, the question remains open whether benthic productivity is sufficient to allow these crabs to reach commercial sizes.

Internal tide in the Kara Gates Strait

We observed strong internal tidal waves in the Kara Gates Strait. Internal tides are superimposed over a system of mean currents from the Barents to the Kara Sea. Field studies of internal tides in the Kara Gates were performed in 1997, 2007, and 2015. In 2015, we analyzed data from towed CTD measurements, numerical model calculations, and satellite images in the region. An internal tidal wave with a period of 12.4 h is generated due to the interaction between the currents of the barotropic tide and the bottom relief on the slopes of a ridge that crosses the strait from Novaya Zemlya to the continent. The depths of the ridge crest are 30–40 m. A constant current of relatively warm water flows from the Barents to the Kara Sea. An internal wave propagates in both directions from the ridge. In the Barents Sea, internal waves are intensified by the current from the Barents to the Kara Sea. Internal bores followed by a packet of short-period internal waves are found in both directions from the strait. Satellite images show that short-period internal waves are generated after the internal bore. A hydraulic jump was found on the eastern side of the strait. Numerical modeling agrees with the experimental results.

Ice retreat in the Russian Arctic seas and assessment of the availability of the Northern Sea Route from satellite passive microwave observations

This paper presents data on the sea ice area decline in the Northern Hemisphere and in the Russian Arctic seas, on the Northern Sea Route in particular, calculated from passive microwave satellite data. Observations show that the Arctic sea ice has reduced by an average of 5% per decade from November 1978 to the present day. It is noted that, since 2007, the highest sea ice area variability has been observed, which increases the uncertainty of the forecast of the ice coverage in the Arctic seas and thus increases risk for ships in ice-covered waters of northern seas. It is demonstrated that the decrease in summer sea ice area, observed at the end of the melt season, is much more intense than the total decrease in the Arctic sea ice area. On average it is 13% for September for the Arctic as a whole and from 24 to 40% per decade for the seas of the Russian Arctic. The study of changes in the ice conditions in the Northern Sea Route has been carried out for one of the optimal sailing routes. The results indicate a decrease in the ice concentration on the route in the summer months and almost complete route opening in September for the period from 2008 and 2012. It is shown that data from microwave radiometers can be used in the study of ice conditions in the Kara Gates and Vilkitsky Strait. The ice concentration reduction in both water channels is indicated. In the Kara Gates it is 15% and in the Vilkitsky Strait it is 9.5% per decade.

Characteristics of short-period internal waves in the Kara Sea inferred from satellite SAR data

In this paper we present the results of short-period internal wave (SIW) observations in the Kara Sea on the basis of satellite ENVISAT ASAR data between July and October 2007. Altogether, 248 internal wave (IW) packets and solitons are identified in 89 SAR images. Detailed spatial statistics of IW signatures and their properties in the Kara Sea is presented. The primary regions of IW activity are the areas near the Kara Gates Strait, the southeastern part of the Novaya Zemlya Trough, and in the vicinity of Cape Zhelaniya. We identify the regions where large IW packets are observed with wavelengths up to 2–3 km and the front length exceeding 200 km. The mean interpacket distance for observed IWs is about 20 km, but it may reach 50–60 km. Consequent IW packets are observed to travel up to 500 km from the presumed generation points. The results of satellite observations are compared with results of previous studies.

Circulation in the southwestern part of the Kara Sea in September 2007

During cruise 54 of the R/V Akademik Mstislav Keldysh to the southwestern Kara Sea (September 6 to October 7, 2007), a large amount of hydrophysical data with unique spatial resolution was obtained on the basis of measurements using different instruments. The analysis of the data gave us the possibility to study the dynamics and hydrological structure of the southwestern Kara Sea basin. The main elements of the general circulation are the following: the Yamal Current, the Eastern Novaya Zemlya Current, and the St. Anna Trough Current. All these currents are topographically controlled; they flow over the bottom slopes along the isobaths. The Yamal Current begins at the Kara Gates Strait and turns to the east as part of the cyclonic circulation. Then, it turns to the north and propagates along the Yamal coast over the 100-m isobath. The Eastern Novaya Zemlya Current (its core is located over the eastern slope of the Novaya Zemlya Trough) flows to the northeast. Near the northern edge of Novaya Zemlya, it encounters the St. Anna Trough Current, separates from the coast, and flows practically to the east merging with the continuation of the Yamal Current. A strong frontal zone is formed in the region where the two currents merge above the threshold that separates the St. Anna Trough from the Novaya Zemlya Trough and divides the warm and saline Arctic waters from the cooler and fresher waters of the southwestern part of the Kara Sea. This threshold, whose depth does not exceed 100–150 m, is a barrier that prevents the spreading of the Barents Sea and Arctic waters to the southwestern part of the Kara Sea basin through the St. Anna Trough.

Strong internal tides in the Kara Gates Strait

We analyze towed CTD measurements, numerical model calculations, and radar images in the Strait of Kara Gates. The measurements were made during an expedition in September 2007. Strong internal tides propagating from the Kara Strait to the Barents Sea were recorded. The internal waves are intensified by the opposite current from the Barents Sea. An internal bore followed by a packet of short‐period internal waves is found southwest of the strait. Radar images show that short‐period internal waves are generated after the internal bore. A hydraulic jump is found on the eastern side of the strait. Numerical modeling agrees with the experimental results.