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We investigate the underwater acoustic scattering from various distributed "ice balls" floating on the water, aiming to understand acoustic scattering in the marginal ice zone (MIZ). The MIZ, including a wide range of heterogeneous ice cover, significantly impacts acoustic propagation. We use acoustic modelling, simulation, and laboratory experiments to understand the acoustic scattering from various distributed ice balls. The acoustic scattering fields from a single sound source (90 kHz) in water are analyzed based on selected principal scattering waves between the surfaces of ice and water. The target strengths are calculated using the plate element method and physical acoustic methods, which are validated with water tank experimental data. The methodology is then extended to multiple ice ball cases, specifically considering a single ice ball, equally spaced ice balls of the same size, and randomly distributed ice balls of various sizes. Additionally, experimental measurements under similar conditions are conducted in a laboratory water tank. The scattering intensities at different receiving positions are simulated and compared with lab experiments. The results show good agreement between experimental and numerical results, with an absolute error of less than 3 dB. Scattering intensity is positively correlated with water surface reflection when the receiving angle is close to the mirror reflection angle of the incident wave. Our approach sets the groundwork for further research to address more complex ice–water interfaces with various ice covers in the MIZ. [ABSTRACT FROM AUTHOR]

The modern Arctic is characterized by a decreased ice cover and significant interannual variability. However, the reaction of the High Arctic ecosystem to such changes is still being determined. This study tested the hypothesis that the key drivers of changes in phytoplankton are the position and intensity of Atlantic water (AW) flow. The research was conducted in August 2017 in the northern part of the Barents Sea and in August 2020 in the Nansen Basin. In 2017, the Nansen Basin was ice covered; in 2020, the Nansen Basin had open water up to 83° N. A comparative analysis of phytoplankton composition, dominant species, abundance, and biomass at the boundary of the ice and open water in the marginal ice zone (MIZ) as well as in the open water was carried out. The total biomass of the phytoplankton in the photic layer of MIZ is one and a half orders of magnitude greater than in open water. In 2017, the maximum abundance and biomass of phytoplankton in the MIZ were formed by cold-water diatoms Thalassiosira spp. (T. gravida, T. rotula, T. hyalina, T. nordenskioeldii), associated with first-year ice. They were confined to the northern shelf of the Barents Sea. The large diatom Porosira glacialis grew intensively in the MIZ of the Nansen Basin under the influence of Atlantic waters. A seasonal thermocline, above which the concentrations of silicon and nitrogen were close to zero, and deep maxima of phytoplankton abundance and biomass were recorded in the open water. Atlantic species—haptophyte Phaeocystis pouchettii and large diatom Eucampia groenlandica—formed these maxima. P. pouchettii were observed in the Nansen Basin in the Atlantic water (AW) flow (2020); E. groenlandica demonstrated a high biomass (4848 mg m−3, 179.5 mg C m−3) in the Franz Victoria trench (2017). Such high biomass of this species in the northern Barents Sea shelf has not been observed before. The variability of the phytoplankton composition and biomass in the Franz Victoria trench and in the Nansen Basin is related to the intensity of the AW, which comes from the Frame Strait as the Atlantic Water Boundary Current. [ABSTRACT FROM AUTHOR]

The Antarctic marginal ice zone, the regularly wave‐affected outer band of the sea ice covered Southern Ocean, typically contains an unconsolidated ice cover comprised of smaller, thinner floes than the inner ice pack. Thus, it is a highly dynamic region and susceptible to rapid expansion and contraction, making it a focal area for understanding and predicting the response of Antarctic sea ice to a changing climate. This novel study uses unsupervised statistical clustering of sea ice data simulated by a global sea ice model (standalone CICE6 combined with a wave propagation module and prescribed ocean) to address the outstanding challenge of separating the marginal ice zone from the inner ice pack in sea ice data sets. The method identifies a marginal ice zone with the desired characteristics and floe size is shown to be the key variable in the classification. Simulated marginal ice zone widths are similar to those derived from satellite observations of wave penetration distances, but contrast with those using the standard 15%–80% areal sea ice concentration proxy, particularly during austral winter. The simulated marginal ice zone is found to undergo a seasonal transition due to new ice formation in winter, increased drift in spring, and increased rates of wave‐induced breakup and melting in summer. The understanding gained from the study motivates incorporation of wave and floe‐scale processes in sea ice models, and the methods are available for application to outputs from high‐resolution and coupled sea ice–ocean–wave models for more detailed studies of the marginal ice zone (in both hemispheres). Plain Language Summary: The record‐setting responses of Antarctic sea ice extent to climate change over recent decades have generated intense research interest in the marginal ice zone at the outskirts of the ice cover. The presence of ocean waves in this region creates a granular ice cover composed of small floes, affecting heat fluxes between the atmosphere and ocean, whilst shielding inner‐pack ice, fast ice, and ice shelves from waves. Studies of the marginal ice zone are hindered by the lack of a pragmatic approach to extract the marginal ice zone from sea ice data, which aligns with its characterization as the regularly wave‐affected sea ice region. Most studies use a concentration‐based proxy, although it overlooks large wave‐affected areas. We develop new insights into the evolution of the marginal ice zone by applying a modern machine‐learning approach to model outputs, leveraging recent modeling advances. Our findings reveal a marginal ice zone composed of young, small floes during winter and older, fractured floes during summer. Simulated widths are consistent with wave‐penetration distance observations and provide evidence of the marginal ice zone's unique properties, including high melt rates. The proposed approach may provide the basis for future studies on its contribution to Antarctic sea ice variability. Key Points: A new method to identify the Antarctic marginal ice zone is proposed based on statistical clustering of sea ice propertiesSimulated marginal ice zone widths are similar to satellite observations of wave penetration distancesNew understanding gained of differences in ice melt rates and drift speeds between the marginal ice zone and the interior ice pack [ABSTRACT FROM AUTHOR]

Numerical modeling of waves in sea ice covered regions of the oceans is important for many applications, from short-term forecasting and ship route planning up to climate modeling. In spite of a substantial progress in wave-in-ice research that took place in recent years, spectral wave models - the main tool for wave modeling at regional and larger scales - still don't capture the underlying physics and have rather poor predictive skills. This article discusses recent developments in wave observations and spectral wave modeling in sea ice, identifies problems and shortcomings of the approaches used so far, and sketches future directions that, in the opinion of the author, have the potential to improve the performance of wave-in-ice models. [ABSTRACT FROM AUTHOR]

High-resolution observations of short-term changes in sea ice are critical to understanding ice dynamics and also provide important information used in advice to shipping, especially in the Arctic. Although individual satellite sensors provide periodic sea ice observations with spatial resolutions of tens of meters, information regarding changes that occur over short time intervals of minutes or hours is limited. In this study, a gridded ice–water classification dataset with a high temporal resolution was developed based on observations acquired by multiple satellite sensors in the Marginal Ice Zone (MIZ). This dataset – DynIceData – which combines Sentinel-1 Synthetic Aperture Radar (SAR) data with Gaofen-3 (GF-3) SAR and SDGSAT-1 thermal infrared imagery was used to obtain observations of the MIZ with a range of temporal resolutions ranging from minutes to tens of hours. The areas of the Arctic covered include the Kara Sea, Beaufort Sea, and Greenland Sea during the period from August 2021 to August 2022. Object-oriented segmentation and thresholding were used to obtain the ice–water classification map from Sentinel-1 and GF-3 SAR image pairs and Sentinel-1 SAR and SDGSAT-1 thermal image pairs. The time interval between the images in each pair ranged from 1 minute to 68 hours. Ten-kilometer grid sample granules with a spatial resolution of 25 m for the GF-3 SAR data and 30 m for the SDGSAT-1 thermal data were used. The classification was verified as having an overall accuracy of at least 95.58%. The DynIceData dataset consists of 7338 samples, which could be used as reference data for further research on rapid changes in sea ice patterns at different short time scales and provide support for research on thermodynamic and dynamic models of sea ice in combination with other environmental data, thus potentially improving the accuracy of sea ice forecasting using Artificial Intelligence. The dataset can be accessed at https://doi.org/10.57760/sciencedb.j00001.00784.

The interaction between waves and ice has a crucial impact on the seasonal change in the sea ice extent. However, our comprehension of this phenomenon is restricted by a lack of observations. In recent years, availability of the low-cost and accurate Inertial Motion Units has enabled the development of affordable wave research devices. Despite advancements in designing innovative open-source instruments optimized for deployment on ice floes, their customizability and survivability remain limited, especially in open waters. This study presents a novel design concept for an affordable and customizable wave buoy, aimed for wave measurements in marginal ice zones. The central focus of this wave buoy design is the application of 3D printing as rapid prototyping technology. By utilizing the high customizability offered by 3D printing, the previously developed solar-powered wave buoy was customized to install a battery pack. Preliminary results from field deployments in the Pacific and Arctic Oceans demonstrate that the performance of the instruments is promising. The accuracy of frequency wave spectra measurements is found to be comparable to that of considerably more expensive instruments. Finally, the study concludes with a general evaluation of using rapid prototyping technologies for buoy designs and proposes recommendations for future designs. [ABSTRACT FROM AUTHOR]

Arctic cyclone activity is an important component of the local climate, and the frequent occurrence of extreme summer storms has raised widespread scientific interest. In this paper, we investigated the distinctive structural characteristics of intense summer Arctic cyclones by utilizing ERA‐Interim reanalysis data and employing a deep learning algorithm for cyclone detection. We found that the northern edge of Eurasia (i.e., the marginal ice zone (MIZ)) and the Alpha Ridge of Arctic Ocean (AR, i.e. central Arctic) are the two most active regions for intense Arctic cyclone activities in summer (from June to September). However, the surface conditions and coupling frequency between surface cyclone and tropopause polar vortices (TPVs) are distinct over these two regions. By further analysis of 100 intense cyclone activities in these two areas, respectively, we found that cyclones in MIZ are often smaller in size but higher in intensity at their maximum intensity, and their life cycles are generally shorter. MIZ cyclones are typically accompanied by a large Eady growth rate and frontal structure in the lower troposphere and their intensification primarily attributed to the thermal‐baroclinic process. In contrast, cyclones in AR are more frequently associated with higher potential vorticity (PV) values and pronounced PV downward intrusion from the stratosphere, as well as notable "upper warm‐lower cold" structures. The downward intrusion of TPVs and stratosphere vortices contribute to a decrease in the upper and column air mass deficit, leading to the intensification of surface Arctic cyclones in these regions. Plain Language Summary: In this study, we researched intense summer storms in the Arctic. We found that there are two main areas where these storms occur: the marginal ice zone (MIZ) near Eurasia and the Alpha Ridge (AR) in the central Arctic. However, storms in these two areas have different characteristics. In the MIZ, the storms are smaller but stronger, and they do not last as long. They are mainly driven by instability in the lower troposphere. On the other hand, the storms in AR respond more to the downward intrusion of potential vorticity from the stratosphere. These storms have a unique structure where the upper air is warmer than their surroundings, and the lower air is colder than their surroundings, especially in AR. This structure makes them more intense and longer‐lasting. Exploring these differences helps us understand how Arctic storms work, and how they might be affected by climate change. Key Points: Both the marginal ice zone (MIZ) and Alpha Ridge exhibit active summer Arctic cyclone activities, especially for intense stormsIn the MIZ, baroclinic instability plays a more prominent role in the intensification and maintenance of cyclonesCyclones in Alpha Ridge are more commonly accompanied by potential vorticity downward intrusion, and "upper warm‐lower cold" structures [ABSTRACT FROM AUTHOR]

The interaction problem of waves with a body floating near the marginal ice zone is studied, where the marginal ice zone is modeled as an array of multiple uniformly sized floating ice sheets. The linear velocity potential theory is applied for fluid flow, and the thin elastic plate mode is utilized to describe the ice sheet deflection. A hybrid method is used to solve the disturbed velocity potential; i.e., around the floating body, a boundary integral equation is established, while in the domain covered by ice sheets, the velocity potential is expanded into an eigenfunction series, and in the far-field with a free surface, a similar eigenfunction expansion is used to satisfy the radiation condition. The boundary integral equation and the coefficients of the eigenfunction expansions are solved together based on the continuous conditions of pressure and velocity on the interface between the sub-domains. Extensive results for the equivalent Young's modulus of the ice sheet array and hydrodynamic force on the body are provided, and the effect of individual ice sheet length as well as wave parameters are investigated in detail. [ABSTRACT FROM AUTHOR]

Numerical modeling of waves in sea ice covered regions of the oceans is important for many applications, from short-term forecasting and ship route planning up to climate modeling. In spite of a substantial progress in wave-in-ice research that took place in recent years, spectral wave models – the main tool for wave modeling at regional and larger scales – still don’t capture the underlying physics and have rather poor predictive skills. This article discusses recent developments in wave observations and spectral wave modeling in sea ice, identifies problems and shortcomings of the approaches used so far, and sketches future directions that, in the opinion of the author, have the potential to improve the performance of wave-in-ice models.

The modern Arctic is characterized by a decreased ice cover and significant interannual variability. However, the reaction of the High Arctic ecosystem to such changes is still being determined. This study tested the hypothesis that the key drivers of changes in phytoplankton are the position and intensity of Atlantic water (AW) flow. The research was conducted in August 2017 in the northern part of the Barents Sea and in August 2020 in the Nansen Basin. In 2017, the Nansen Basin was ice covered; in 2020, the Nansen Basin had open water up to 83° N. A comparative analysis of phytoplankton composition, dominant species, abundance, and biomass at the boundary of the ice and open water in the marginal ice zone (MIZ) as well as in the open water was carried out. The total biomass of the phytoplankton in the photic layer of MIZ is one and a half orders of magnitude greater than in open water. In 2017, the maximum abundance and biomass of phytoplankton in the MIZ were formed by cold-water diatoms Thalassiosira spp. (T. gravida, T. rotula, T. hyalina, T. nordenskioeldii), associated with first-year ice. They were confined to the northern shelf of the Barents Sea. The large diatom Porosira glacialis grew intensively in the MIZ of the Nansen Basin under the influence of Atlantic waters. A seasonal thermocline, above which the concentrations of silicon and nitrogen were close to zero, and deep maxima of phytoplankton abundance and biomass were recorded in the open water. Atlantic species—haptophyte Phaeocystis pouchettii and large diatom Eucampia groenlandica—formed these maxima. P. pouchettii were observed in the Nansen Basin in the Atlantic water (AW) flow (2020); E. groenlandica demonstrated a high biomass (4848 mg m−3, 179.5 mg C m−3) in the Franz Victoria trench (2017). Such high biomass of this species in the northern Barents Sea shelf has not been observed before. The variability of the phytoplankton composition and biomass in the Franz Victoria trench and in the Nansen Basin is related to the intensity of the AW, which comes from the Frame Strait as the Atlantic Water Boundary Current.

We investigate the underwater acoustic scattering from various distributed “ice balls” floating on the water, aiming to understand acoustic scattering in the marginal ice zone (MIZ). The MIZ, including a wide range of heterogeneous ice cover, significantly impacts acoustic propagation. We use acoustic modelling, simulation, and laboratory experiments to understand the acoustic scattering from various distributed ice balls. The acoustic scattering fields from a single sound source (90 kHz) in water are analyzed based on selected principal scattering waves between the surfaces of ice and water. The target strengths are calculated using the plate element method and physical acoustic methods, which are validated with water tank experimental data. The methodology is then extended to multiple ice ball cases, specifically considering a single ice ball, equally spaced ice balls of the same size, and randomly distributed ice balls of various sizes. Additionally, experimental measurements under similar conditions are conducted in a laboratory water tank. The scattering intensities at different receiving positions are simulated and compared with lab experiments. The results show good agreement between experimental and numerical results, with an absolute error of less than 3 dB. Scattering intensity is positively correlated with water surface reflection when the receiving angle is close to the mirror reflection angle of the incident wave. Our approach sets the groundwork for further research to address more complex ice–water interfaces with various ice covers in the MIZ.

The marginal ice zone (MIZ) is located at the junction of ice-covered areas and open water, where waves cause ice floes to break up and change their state of motion, thus threatening the safety of ships navigating the ice. This study employs the Structured Arbitrary Lagrangian–Eulerian (S-ALE) method and the numerical wave-making method based on dynamic boundary conditions to numerically examine the motion response of ice floes in waves. The longitudinal motion of ice floes in waves can be classified into two distinct states, namely irregular and regular, depending on the wavelength. In the short-wave range, the ice floes exhibit primarily irregular motion, whereas in the long-wave range, their motion becomes regular, resembling that of isolated ice floes. The longitudinal motion response of the ice floes remains unaffected by their size. However, the longitudinal velocity, surge velocity, and displacement of the ice floes are influenced by the wavelength. Furthermore, the numerical calculations are compared to the model test conducted in a towing tank using paraffin artificial ices, revealing a qualitative agreement between the experimental and numerical results. [ABSTRACT FROM AUTHOR]

The study of Antarctic first‐year sea‐ice biogeochemistry has been limited by samples mostly being collected in pack ice during summer, with few winter data available. Measurements from the Antarctic marginal ice zone (AMIZ) have proven even more difficult to obtain. The AMIZ is a broad, circumpolar feature of the Southern Ocean found at different latitudes during the year where light and nutrients are high enough to sustain primary production and influence ecosystem functioning. We present the first biogeochemical data set from growing ice collected in the Atlantic AMIZ during winter 2019, including measurements from young pancake ice (YI) and consolidated first‐year ice (FYI). Measurements of sea‐ice temperature, salinity, crystal structure, δ18O, chlorophyll, and nutrient concentrations were used to investigate the winter sea‐ice habitat and decipher the conditions under which the ice formed and grew. Model simulations support the hypothesis that nutrient accumulation in advancing sea ice cannot be explained by passive seawater entrainment and thermodynamics alone. Our data confirm that winter sea ice is biogeochemically active and accumulates remineralized nutrients. We further propose that mechanical thickening enhances the reservoir of nutrients during the ice growth season. The biogeochemical transition from YI to FYI does not appear to be a linear progression of thickness with habitat space reduction as sea ice consolidates. Instead, FYI bulk biogeochemistry results from multiple cycles of rafting of YI, which conserves the biogeochemical properties of YI in the FYI, ultimately increasing the overall nutrient and chlorophyll content. Plain Language Summary: The Antarctic marginal ice zone (AMIZ) is a region of intense air‐sea interactions where sea ice begins to form during winter. It is generally assumed that little to no biological activity occurs in winter sea ice, with the chemical and biological composition of the ice instead set by seawater that is incorporated during ice formation. We sampled young ice (YI) and first‐year ice (FYI; collectively, growing sea ice) in the Atlantic AMIZ in winter 2019, the first such collection from this region. Our measurements of sea‐ice crystal structure and oxygen isotopes suggest that the FYI formed from repeated breaking and piling up of younger ice. This idea is supported by model experiments showing that the FYI was the result of more than just temperature‐driven thickening of YI. Additionally, our measurements and modeling of nutrients and chlorophyll in the ice strongly suggest that the biological community was active during winter. Our findings challenge the assumption that winter sea ice is biologically inactive and suggest that the biological and chemical signatures of YI are conserved as growing ice is broken up and reformed. The results of our study will help to improve and validate future modeling efforts. Key Points: We present the first biogeochemical data for young and growing sea ice in the Atlantic Antarctic marginal ice zoneWinter sea ice is biogeochemically active and acts as a reservoir of concentrated nutrients during the ice growth seasonThe biogeochemical signature of individual floes is conserved during rafting, leading to enhanced nutrients and chlorophyll‐a in first‐year sea ice [ABSTRACT FROM AUTHOR]

The seasonally ice-covered marine region of the European Arctic has experienced warming and sea ice loss in the last two decades. During expeditions in August 2020 and 2021, new data on size-fractioned primary production (PP), chlorophyll a concentration, phytoplankton biomass and composition and carbon fixation rates in the dark were obtained in the marginal ice zone (MIZ) of the Barents Sea, Nansen Basin and Greenland Sea to better understand the response of Arctic ecosystems to ongoing climate changes. Four different situations were observed in the study region: (i) a bloom of the large-cell diatom Podosira glacialis, whose biomass was trapped in a strong halocline at the edge of a dense ice cover; (ii) a bloom of the chain-like colonies of Thalassiosira diatoms on the shelf in mixed waters in fields of shallow ice that could be supported by "fresh" elements in the polynya condition, as well as by terrestrial run-off and drifting ices; at the late stage, this bloom was accompanied by intensive growth of Phaeocystis pouchetti; (iii) dominance of small-cell phytoplankton under weakened stratification and the significant influence of the Atlantic water, depleted of microelements and silicates; (iv) dominance of dinoflagellates of eutrophic water in the contact zone between the water masses of Arctic origin and Atlantic origin in clear water under conditions of increased light intensity. The >10 µm phytoplankton cell size group increased its relative contribution to PP as a response to stratification, light and nutrient load associated with sea ice conditions. Small phytoplankton with sizes < 2 µm formed the basis of total PP in the MIZ regardless of the state of the sea ice. [ABSTRACT FROM AUTHOR]

Accurate prediction of ocean surface wave attenuation in polar marginal ice zones remains a challenge. In this article, an alternative approach to the problem is introduced, in which the ice layer is represented with a modified version of the vegetation damping parameterization in a phase-resolved wave model. The new representation is evaluated by comparison to theory and measured data under varied wave and ice conditions. Model-estimated profiles of RMS water velocity and Reynolds stress under ice layers with different drag coefficients are found to be qualitatively comparable to a range of nondimensional profiles computed using viscous layer theory. Modeled profiles appear somewhat vertically "stretched" relative to theoretical results, and in this respect, they more closely resemble measurements obtained during a recent wave–ice laboratory experiment. Estimated values of the wave attenuation coefficient and wavenumber in ice from the adapted model align well with theory and with a range of lab and field datasets. Several additional model ice parameters are available to facilitate a more nuanced representation of surface ice effects and will be investigated further in an upcoming companion study. [ABSTRACT FROM AUTHOR]

Wave energy propagating into the Antarctic marginal ice zone effects the quality and extent of the sea ice, and wave propagation is therefore an important factor for understanding and predicting changes in sea ice cover. Wave‐sea ice interactions are notoriously hard to model and in situ observations of wave activity in the Antarctic marginal ice zone are scarce, due to the extreme conditions of the region. Here, we provide new in situ data from two drifting Surface Wave Instrument Float with Tracking (SWIFT) buoys deployed in the Weddell Sea in the austral winter and spring of 2019. The buoy location ranges from open water to more than 200 km into the sea ice. We estimate the attenuation of swell with wave periods 8–18 s, and find an attenuation coefficient α = 4 · 10−6 to 7 · 10−5 m−1 in spring, and approximately five‐fold larger in winter. The attenuation coefficients show a power law frequency dependence, with power coefficient close to literature. The in situ data also shows a change in wave direction, where wave direction tends to be more perpendicular to the ice edge in sea ice compared to open water. A possible explanation for this might be a change in the dispersion relation caused by sea ice. These observations can help shed further light on the influence of sea ice on waves propagating into marginal ice zones, aiding development of coupled wave‐sea ice models. Plain Language Summary: Changes in the sea ice extent around Antarctica affects the global climate, and it is therefore important to accurately represent sea ice in climate models. One feature that is generally missing in climate models is the interaction between ocean waves and sea ice. Ocean waves change the sea ice, for example, by breaking up ice floes into smaller ones. At the same time, the sea ice reduces the strength of the waves so that the wave height decreases and eventually disappears far into the sea ice. How far into the sea ice waves reach depends both on the size of the waves and on the sea ice, and can be very different depending on for example, ice thickness, size of floes and age. In order to better represent the wave‐sea ice interactions in climate models, simple but accurate models of how fast sea ice reduces the strength of waves is needed. Using wave buoys, we measured the wave activity in the Antarctic sea ice during two expeditions in 2019. We found a notable difference between spring and winter, where the waves were reduced much faster in winter than in spring. This can help to improve predictions of sea ice cover. Key Points: SWIFT buoy data show that frequency dependence of wave attenuation in Antarctic sea ice follows a power lawBoth wave attenuation and the frequency dependence of attenuation were stronger in austral winter than in springObservations suggest a change in wave direction in sea ice compared to open water [ABSTRACT FROM AUTHOR]

The interaction problem of waves with a body floating near the marginal ice zone is studied, where the marginal ice zone is modeled as an array of multiple uniformly sized floating ice sheets. The linear velocity potential theory is applied for fluid flow, and the thin elastic plate mode is utilized to describe the ice sheet deflection. A hybrid method is used to solve the disturbed velocity potential; i.e., around the floating body, a boundary integral equation is established, while in the domain covered by ice sheets, the velocity potential is expanded into an eigenfunction series, and in the far-field with a free surface, a similar eigenfunction expansion is used to satisfy the radiation condition. The boundary integral equation and the coefficients of the eigenfunction expansions are solved together based on the continuous conditions of pressure and velocity on the interface between the sub-domains. Extensive results for the equivalent Young’s modulus of the ice sheet array and hydrodynamic force on the body are provided, and the effect of individual ice sheet length as well as wave parameters are investigated in detail.

The environmental variations and their interactions with the biosphere are vital in the Arctic Ocean during the summer sea-ice melting period in the current scenario of climate change. Hence, we analysed the vertical distribution of bacterial and archaeal communities in the western Arctic Ocean from sea surface melt-ponds to deep water up to a 3040 m depth. The distribution of microbial communities showed a clear stratification with significant differences among different water depths, and the water masses in the Arctic Ocean – surface mixed layer, Atlantic water mass and deep Arctic water – appeared as a major factor explaining their distribution in the water column. A total of 34 bacterial phyla were detected in the seawater and 10 bacterial phyla in melt-ponds. Proteobacteria was the dominant phyla in the seawater irrespective of depth, whereas Bacteroidota was the dominant phyla in the melt-ponds. A fast expectation-maximization microbial source tracking analysis revealed that only limited dispersion of the bacterial community was possible across the stratified water column. The surface water mass contributed 21% of the microbial community to the deep chlorophyll maximum (DCM), while the DCM waters contributed only 3% of the microbial communities to the deeper water masses. Atlantic water mass contributed 37% to the microbial community of the deep Arctic water. Oligotrophic heterotrophic bacteria were dominant in the melt-ponds and surface waters, whereas chemoautotrophic and mixotrophic bacterial and archaeal communities were abundant in deeper waters. Chlorophyll and ammonium were the major environmental factors that determined the surface microbial communities, whereas inorganic nutrient concentrations controlled the deep-water communities. [ABSTRACT FROM AUTHOR]

The automatic detection and analysis of ocean eddies in the marginal ice zone via remote sensing is a very challenging task but of critical importance for scientific applications and anthropogenic activities. Therefore, as one of the first steps toward the automation of the eddy detection process, we investigated the potential of applying YOLOv5, a deep convolutional neural network architecture, to specifically collected and labeled high-resolution synthetic aperture radar data for a very dynamic area over the Fram Strait. Our approach involved fine-tuning pre-trained YOLOv5 models on a sparse dataset and achieved accurate results with minimal training data. The performances of the models were evaluated using several metrics, and the best model was selected by visual examination. The experimental results obtained from the validation and test datasets consistently demonstrated the robustness and effectiveness of the chosen model to identify submesoscale and mesoscale eddies with different structures. Moreover, our work provides a foundation for automated eddy detection in the marginal ice zone using synthetic aperture radar imagery and contributes to advancing oceanography research. [ABSTRACT FROM AUTHOR]

In August 2020, during a dramatical summer retreat of sea ice in the Nansen Basin, a study of phytoplankton was conducted on the transect from two northern stations in the marginal ice zone (MIZ) (north of 83° N m and east of 38° E) through the open water to the southern station located in the Franz Victoria Trench. The presence of melted polar surface waters (mPSW), polar surface waters (PSW), and Atlantic waters (AW) were characteristic of the MIZ. There are only two water masses in open water, namely PSW and AW, at the southernmost station; the contribution of AW was minimal. In the MIZ, first-year and multiyear ice species and Atlantic species were noted; Atlantic species and first-year ice species were in open water, and only ice flora was at the southernmost station. The maximum phytoplankton biomass (30 g · m−3) was recorded at the northernmost station of the MIZ, and 99% of the phytoplankton consisted of a large diatom Porosira glacialis. Intensive growth of this species occurred on the subsurface halocline separating mPSW from PSW. A thermocline was formed in open water south of the MIZ towards the Franz Victoria Trench. A strong stratification decreases vertical nutrient fluxes, so phytoplankton biomass decreases significantly. Phytoplankton formed the maximum biomass in the thermocline. When moving south, biomass decreased and its minimum values were observed at the southernmost station where the influence of AW is minimal or completely absent. A transition from the silicon-limited state of phytoplankton (MIZ area) to nitrogen-limited (open water) was noted. [ABSTRACT FROM AUTHOR]

The marginal ice zone (MIZ) is located at the junction of ice-covered areas and open water, where waves cause ice floes to break up and change their state of motion, thus threatening the safety of ships navigating the ice. This study employs the Structured Arbitrary Lagrangian–Eulerian (S-ALE) method and the numerical wave-making method based on dynamic boundary conditions to numerically examine the motion response of ice floes in waves. The longitudinal motion of ice floes in waves can be classified into two distinct states, namely irregular and regular, depending on the wavelength. In the short-wave range, the ice floes exhibit primarily irregular motion, whereas in the long-wave range, their motion becomes regular, resembling that of isolated ice floes. The longitudinal motion response of the ice floes remains unaffected by their size. However, the longitudinal velocity, surge velocity, and displacement of the ice floes are influenced by the wavelength. Furthermore, the numerical calculations are compared to the model test conducted in a towing tank using paraffin artificial ices, revealing a qualitative agreement between the experimental and numerical results.

Primary production (PP) and the chlorophyll-a concentration (chl-a) in the European Arctic in the summer of 2020–2021, where continued climatic warming and increased “Atlantification” accelerate the sea ice losses, are discussed. The maximum integrated PP and the total chl-a content were observed in the marginal ice zone (MIZ) of the Barents Sea under weakened stratification of the water column and reached 1109 mgC m–2 day–1 and 118 mg m–2. Near the ice edge in the Nansen Basin, the main part of PP formed in the upper mixed layer and did not exceed 469 mgC m–2 day–1; the chl-a content reached 56 mg m–2. The early and late stages of phytoplankton bloom in the MIZ were characterized by the leading role of picophytoplankton in carbon fixation. Large centric diatoms, microphytoplankton, were recorded to dominate in the MIZ at the stage of peak bloom in 2020 under the dense ice cover of the Nansen Basin. A similar phenomenon was observed earlier only in the Arctic shelf seas and was not recorded in the high-latitude basins of the Arctic Ocean. With the sparse ice cover of the Nansen Basin in 2021, the main primary producers were pico- and nanophytoplankton. The low variability of assimilation numbers (1.7 ± 0.3 mgC mg chl-a–1 h–1) at all bloom stages indicates indirectly the acclimatization of different species of phytoplankton to the environmental changes. The ecological flexibility of the primary production link of the MIZ ecosystems in the studied seas of the European Arctic during the period of climate changes is confirmed. [ABSTRACT FROM AUTHOR]

Aim: Identify hotspots and areas of high species richness for Arctic marine mammals. Location: Circumpolar Arctic. Methods: A total of 2115 biologging devices were deployed on marine mammals from 13 species in the Arctic from 2005 to 2019. Getis‐Ord Gi* hotspots were calculated based on the number of individuals in grid cells for each species and for phylogenetic groups (nine pinnipeds, three cetaceans, all species) and areas with high species richness were identified for summer (Jun‐Nov), winter (Dec‐May) and the entire year. Seasonal habitat differences among species' hotspots were investigated using Principal Component Analysis. Results: Hotspots and areas with high species richness occurred within the Arctic continental‐shelf seas and within the marginal ice zone, particularly in the "Arctic gateways" of the north Atlantic and Pacific oceans. Summer hotspots were generally found further north than winter hotspots, but there were exceptions to this pattern, including bowhead whales in the Greenland‐Barents Seas and species with coastal distributions in Svalbard, Norway and East Greenland. Areas with high species richness generally overlapped high‐density hotspots. Large regional and seasonal differences in habitat features of hotspots were found among species but also within species from different regions. Gap analysis (discrepancy between hotspots and IUCN ranges) identified species and regions where more research is required. Main conclusions: This study identified important areas (and habitat types) for Arctic marine mammals using available biotelemetry data. The results herein serve as a benchmark to measure future distributional shifts. Expanded monitoring and telemetry studies are needed on Arctic species to understand the impacts of climate change and concomitant ecosystem changes (synergistic effects of multiple stressors). While efforts should be made to fill knowledge gaps, including regional gaps and more complete sex and age coverage, hotspots identified herein can inform management efforts to mitigate the impacts of human activities and ecological changes, including creation of protected areas. [ABSTRACT FROM AUTHOR]

The marginal ice zone (MIZ) connects the open ocean and the pack ice, playing significant roles in shaping the ice edge and wave–ice interaction. Spaceborne synthetic aperture radar (SAR) has been demonstrated to be one of the most advantageous sensors for MIZ exploration given its capability to collect images under all weather conditions during day and night. In this study, we take advantage of the Sentinel-1 wave mode vignettes acquired around the Antarctic to quantify the image properties over MIZ. A data set of SAR images covering the ice edge with both open water and sea ice present in the same scene was created by manual inspection. It is found that the radar return over sea ice decreases by an average of approximately 1.78 dB in comparison to its adjacent open water, which is roughly independent of the polarizations and incidence angles. The long ocean waves are barely attenuated right across the ice edge in terms of their comparable azimuth cutoff. Further inside the ice from the edge, the waves are gradually dampened out at distances associated with their wavelengths. The results obtained in this study shall help interpret the radar scattering model validation as well as the wave–ice interaction. [ABSTRACT FROM AUTHOR]

The Close-Packing model – a physically based model for wave attenuation in sea ice – is used to infer sea ice thickness from wave observations collected in the Antarctic marginal ice zone during the PIPERS experiment. The model, calibrated for Arctic conditions, predicts ice thickness in good agreement with independent satellite measurements. The calibrated Close -Packing model, which is expressed in a simple monomial form, appears to have broad validity and, therefore, can be a suitable option for operational purposes. • Physically based Closed-Packing wave-attenuation model estimates sea ice thickness. • The attenuation of the swell is sufficient to estimate the thickness of the sea ice. • Model correlation with satellite thickness increases with retrieved concentrations. [ABSTRACT FROM AUTHOR]

The analysis of ocean eddies in the marginal ice zone via remote sensing and modeling data is a challenging task. However, it is of crucial importance for various scientific applications and anthropogenic activities in the Arctic. Models often struggle to accurately represent eddies near the MIZ due to the intricate nature of sea ice-ocean interactions, unresolved small-scale processes, and coarse resolution. Nevertheless, combining the information provided from both SAR and model data offers promising results that can potentially improve eddy detection accuracy near the MIZ. Furthermore, accurate characterization of the spatial and temporal variability of eddies near the MIZ demands a holistic approach that incorporates multi-platform observations, including numerical models and remote sensing data. This study demonstrates a specific test case on the intercomparison of the eddy signatures located in the MIZ in the Fram Strait based on remote sensing SAR scenes and Lagrangian modeling data from the two global oceanographic reanalysis GOFS 3.1 and GLORYS 12 V1. The study specifically displays the strong agreement in the eddy polarity and synchronism with reality, as well as differences in spatial scales and location of eddy centers. Overall, the obtained results support the further use of the presented approach for studying the eddies in the MIZ regions in the Arctic. • The lack of climate-scale evaluation of different modeling studies in the MIZ derives from an absence of observational data. • We compare eddies in the MIZ acquired from SAR and Lagrangian modeling data based on GOFS 3.1 and GLORYS 12 V1 reanalyses. • This is the first study where such an approach is implemented for the eddy analysis in the Arctic MIZ. • Agreement in eddy structure and polarity supports further use of the presented approach for studying eddies in MIZ. [ABSTRACT FROM AUTHOR]

Accurate prediction of ocean surface wave attenuation in polar marginal ice zones remains a challenge. In this article, an alternative approach to the problem is introduced, in which the ice layer is represented with a modified version of the vegetation damping parameterization in a phase-resolved wave model. The new representation is evaluated by comparison to theory and measured data under varied wave and ice conditions. Model-estimated profiles of RMS water velocity and Reynolds stress under ice layers with different drag coefficients are found to be qualitatively comparable to a range of nondimensional profiles computed using viscous layer theory. Modeled profiles appear somewhat vertically “stretched” relative to theoretical results, and in this respect, they more closely resemble measurements obtained during a recent wave–ice laboratory experiment. Estimated values of the wave attenuation coefficient and wavenumber in ice from the adapted model align well with theory and with a range of lab and field datasets. Several additional model ice parameters are available to facilitate a more nuanced representation of surface ice effects and will be investigated further in an upcoming companion study.

The marginal ice zone (MIZ) is the dynamic interface between the open ocean and sea ice-covered ocean. It is characterized by interactions between surface gravity waves and granular ice covers consisting of relatively small, thin chunks of sea ice known as floes. This structure gives the MIZ markedly different properties to the thicker, quasi-continuous ice cover of the inner pack that waves do not reach, strongly influencing various atmosphere–ocean fluxes, especially the heat flux. The MIZ is a significant component of contemporary sea ice covers in both the Antarctic, where the ice cover is surrounded by the Southern Ocean and its fierce storms, and the Arctic, where the MIZ now occupies vast expanses in areas that were perennial only a decade or two ago. The trend towards the MIZ is set to accelerate, as it reinforces positive feedbacks weakening the ice cover. Therefore, understanding the complex, multiple-scale dynamics of the MIZ is essential to understanding how sea ice is evolving and to predicting its future. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'. [ABSTRACT FROM AUTHOR]

Sea ice in the marginal ice zone (MIZ) consists of relatively small floes with a wide size span. In response to oceanic and atmospheric forcing, it behaves as an approximately two-dimensional, highly polydisperse granular material. The established viscous-plastic rheologies used in continuum sea ice models are not suitable for the MIZ; the collisional rheology, in which sea ice is treated as a granular gas, captures only one aspect of the granular behaviour, typical for a narrow range of conditions when dynamics is dominated by binary floe collisions. This paper reviews rheology models and concepts from research on granular materials relevant for MIZ dynamics (average stress as a result of 'microscopic' interactions of grains; μ(I) and collisional rheologies). Idealized discrete-element simulations are used to illustrate granular effects and strong influence of the floe size distribution on strain–stress relationships in sheared sea ice, demonstrating the need for an MIZ rheology model capturing the whole range of 'regimes', from quasi-static/dense flow in the inner MIZ to the inertial flow in the outer MIZ. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'. [ABSTRACT FROM AUTHOR]

This study concerns wave–ice interactions in the marginal ice zone (MIZ). We compare idealized simulations using two recent three-dimensional formulations for wave–ice interactions for flexible ice floes, with selected parametrizations for the scattering of ocean surface waves due to individual ice floes. These parametrizations are implemented in a modern version of the wave model WAVEWATCH III® (hereafter, WW3) as source terms in the action balance equation. The comparisons consist of simple hypothetical experiments to identify characteristics of the wave–ice parametrizations. Comparisons show that the two new wave–ice formulations give attenuation of wave heights that can be less intense in the direction of propagation than those of other considered formulations. Within the wave energy spectrum, the one-dimensional attenuation extends over the entire frequency domain to the high-frequency limit. Within the MIZ beyond the ice edge, there is evidence for a 'roll-over' effect in the simulations of attenuation. These new formulations can potentially improve previous parametrizations in simulations of wave scattering and attenuation within the MIZ. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'. [ABSTRACT FROM AUTHOR]

For the best part of my entire career, I have focused on the marginal ice zone, abbreviated to MIZ by most sea ice scientists. Defined perfunctorily by the National Snow & Ice Data Center as the part of the seasonal ice zone where waves, swells and other open ocean processes affect the sea ice, the MIZ habitually extends from the ice edge some 100–200 km into the ice pack with morphology that varies dramatically spatially and with time. In general, the Antarctic MIZ is wider than MIZs in the Arctic, recognizing that increases in the ferocity and incidence of storms and the durability of ice due to global climate change are already affecting the physical attributes of each MIZ. I provide here a somewhat historically tailored preamble to a unique compilation of up-to-the-minute MIZ research in this theme issue that includes the nexus between contemporary theoretical, modelling and experimental projects. A prognosticative synopsis of these projects is also included later in the volume, framed in the context of the ongoing ontogenesis of the research field. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'. [ABSTRACT FROM AUTHOR]

Commentary narrated in this theme issue is recast to contextualize the diverse themes presented into a forward-looking conversation that synthesizes, debates opportunities for multidisciplinary advances and highlights topics that deserve enduring sharpened attention. Research oriented towards foundational elements of the marginal ice zone that relates to three unifying topic subclasses—namely (i) wave propagation through sea ice, (ii) floe size distributions and (iii) ice dynamics and break-up—and is encapsulated in mini-reviews provided by Thomson, Horvat and Dumont is revisited to distill it into a blueprint for the future guided by the cutting-edge, present-day knowledge documented herein by leading practitioners in the field. Six threads are signalled as imperative for prospective research, each with a bearing on Arctic and Antarctic sea-ice canopies in which the propensity for marginal ice zones to coexist with pack ice is greater as a result of global climate change reducing sea-ice resilience while increasing the prevalence and forcefulness of injurious storm winds and waves. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'. [ABSTRACT FROM AUTHOR]

Perspectives are discussed on future directions for the field of marginal ice zone (MIZ) dynamics, based on the extraordinary progress made over the past decade in its theory, modelling and observations. Research themes are proposed that would shift the field's focus towards the broader implications of MIZ dynamics in the climate system. In particular, pathways are recommended for research that highlights the impacts of trends in the MIZ on the responses of Arctic and Antarctic sea ice to climate change. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'. [ABSTRACT FROM AUTHOR]

With the increasing resolution of operational forecasting models, the marginal ice zone (MIZ), the area where waves and sea ice interact, can now be better represented. However, the proper mechanics of wave propagation and attenuation in ice, and especially their influence on sea ice dynamics, still remain poorly understood and constrained in models. Observations have shown exponential wave energy decrease with distance in sea ice, particularly strong at higher frequencies. Some of this energy is transferred to the ice, breaking it into smaller floes and weakening it, as well as exerting a stress on the ice similar to winds and currents. In this article, we present a one-dimensional, fully integrated wave and ice model that has been developed to test different parameterizations of wave–ice interactions. The response of the ice cover to the wind and wave radiative stresses is investigated for a variety of wind, wave and ice conditions at different scales. Results of sensitivity analyses reveal the complex interplay between wave attenuation and rheological parameters and suggest that the compressive strength of the MIZ may be better represented by a Mohr-Coulomb parameterization with a nonlinear dependence on thickness. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'. [ABSTRACT FROM AUTHOR]

The retreat of Arctic sea ice is enabling increased ocean wave activity at the sea ice edge, yet the interactions between surface waves and sea ice are not fully understood. Here, we examine in situ observations of wave spectra spanning 2012–2021 in the western Arctic marginal ice zone (MIZ). Swells exceeding 30 cm are rarely observed beyond 100 km inside the MIZ. However, local wind waves are observed in patches of open water amid partial ice cover during the summer. These local waves remain fetch-limited between ice floes with heights less than 1 m. To investigate these waves at climate scales, we conduct experiments varying wave attenuation and generation in ice with a global model including coupled interactions between waves and sea ice. A weak high-frequency attenuation rate is required to simulate the local waves in observations. The choices of attenuation scheme and wind input in ice have a remarkable impact on the extent of wave activity across ice-covered oceans, particularly in the Antarctic. As well as demonstrating the need for stronger constraints on wave attenuation, our results suggest that further attention should be directed towards locally generated wind waves and their role in sea ice evolution. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'. [ABSTRACT FROM AUTHOR]

Waves in the Marginal Ice Zone in the Okhotsk Sea are less studied compared to the Antarctic and Arctic. In February 2020, wave observations were conducted for the first time in the Okhotsk Sea, during the observational program by Patrol Vessel Soya. A wave buoy was deployed on the ice, and in situ wave observations were made by a ship-borne stereo imaging system and Inertial Measurement Unit. Sea ice was observed visually and by aerial photographs by drone, while satellite synthetic aperture radar provided basin-wide spatial distribution. On 12 February, a swell system propagating from east northeast was detected by both the stereo imaging system and the buoy-on-ice. The wave system attenuated from 0.34 m significant wave height to 0.25 m in about 90 km, while the wave period increased from 10 s to 15–17 s. This anomalous spectral downshifting was not reproduced by numerical hindcast and by applying conventional frequency-dependent exponential attenuation to the incoming frequency spectrum. The estimated rate of spectral downshifting, defined as a ratio of momentum and energy losses, was close to that of uni-directional wave evolution accompanied by breaking dissipation: this indicates that dissipation-driven nonlinear downshifting may be at work for waves propagating in ice. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'. [ABSTRACT FROM AUTHOR]

Despite enormous scientific and technological progress in numerical weather and climate prediction, sea ice still remains unreliably predicted by models, both in short-term forecasting and climate projection applications. The total ice extent in both hemispheres is tied to the location of the ice edge, and consequently to what happens in the portion of the ice cover immediately adjacent to the open ocean that is called the marginal ice zone (MIZ). There is mounting evidence that processes occurring in the MIZ might play an important role in the polar climate of both hemispheres, yet some key physical processes are still missing in models. As sea ice models developed for climate studies are increasingly used for operational forecasting, the missing physics also impede short-term sea ice prediction skills. This paper is a mini-review that provides a historical perspective on how MIZ research has progressed since the 1970s, with a focus on the fundamental importance of the interactions between sea ice and surface gravity waves on sea ice dynamics. Completeness is not achieved, as the body of literature is huge, scattered and rapidly growing, but the intention is to inform future collaborative research efforts to improve our understanding and predictive capabilities of sea ice dynamics in the MIZ. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'. [ABSTRACT FROM AUTHOR]

On re-examining the problem of linear gravity waves in two layers of fluids with a viscous ice layer overlaying water of deep depth, we give a detailed analysis of the fluid velocities, velocity shear, and Reynolds stress associated with wave fluctuations in both the ice layer and the wave boundary layer just beneath it. For the turbulent wave boundary layer, water eddy viscosity is used. Comprehensive discussions on various aspects of the velocity fields are made in terms of a Reynolds number based on the ice-layer thickness and viscosity, and the ice-to-water viscosity ratio. Speculation of the wave-induced steady streaming is made based on the Reynolds stress distribution, offering a preliminary insight into the mean flows in both the ice layer and wave boundary layer in the water. For wave attenuation, the results using a typical ice viscosity and a reasonable water eddy viscosity show good agreement with data over the range of frequencies for field and lab waves, significantly outperforming those assuming an inviscid water. [ABSTRACT FROM AUTHOR]

Surface waves traversing polar marginal ice zones (MIZs) generate a boundary layer immediately below the ice, similar in some respects to the wave boundary layer created at the seabed in shallow water. The wave–ice boundary layer has not yet been thoroughly measured, but it can significantly affect wave attenuation rates. In December 2021, we conducted a laboratory experiment designed to measure such a boundary layer and the associated attenuation, in which monochromatic waves propagated through broken surface ice in a salt water tank. A particle imaging velocimetry (PIV) instrument array was submerged in the tank and used to visualize the fluid motion under the moving ice. The surface was tracked at multiple locations with acoustic sensors and cameras mounted over the tank. A total of 64 trials were completed, each producing 3–6 s of highly resolved velocity time series and 30–40 s of surface elevation data. Preliminary analysis of the data has provided strong evidence of a boundary layer at the water–ice interface. The wave attenuation rates compare well with existing datasets. The vertical profiles of RMS velocities and wave-induced Reynolds stress have trends similar to the theoretical predictions, while the quantitative discrepancies in terms of numerical values are discussed. This is the first of two such experiments; the second is tentatively scheduled for early 2023. [ABSTRACT FROM AUTHOR]

In the marginal ice zone (MIZ), where ocean waves and sea ice interact, waves can produce flows of water across ice floe surfaces in a process known as wave overwash. Overwash potentially influences wave propagation characteristics, floe thermodynamics, and floe surface biological and chemical processes. However, the extent of the MIZ affected by overwash and its dependence on prevailing wave and ice conditions is unknown. In this paper, we propose a model of overwash extent caused by irregular incoming waves into a MIZ consisting of a random floe field. We validate the overwash extent model against laboratory experiments. We use the model to study mild to extreme incoming waves to floe field characteristics of the spring–summer ice retreat and autumn–winter ice advance and with compact ice edges. Overwash is typically predicted to extend a few kilometers and is generally greater for the autumn–winter advance than the spring–summer retreat. The model predictions provide a basis for improved understanding of the impacts of ocean waves on the ice cover. We also apply the model to incoming waves and a floe field with a diffuse ice edge representative of conditions during a field experiment, predicting overwash extents up to 16 km. During the field experiment, the wave and ice floe properties were intermittently monitored by a camera system, demonstrating how the sparse field data available on overwash can be advanced. Plain Language Summary: Wave overwash is the flow of water across the surface of a thin floating body due to passing waves. It is an important process in the marginal ice zone (MIZ) where sea ice floes and ocean waves interact. Overwash reduces the energy of ocean waves, removes snow from, and wets the sea ice surface, which can drive growth or melting. Water left on the sea ice surface can host organisms and affects chemical processes taking place there. Overwash is pervasive in laboratory experiments where it has been measured and studied. In contrast, there are few reports of overwash in the field and the extent of its occurrence has not been measured. We propose a model to predict the region of the MIZ in which overwash occurs. We use the model to compare overwash extents for MIZs associated with the spring–summer ice retreat and autumn–winter ice advance for calm to energetic wave conditions, including the conditions observed during a winter Antarctic icebreaker voyage. For field conditions, the model predicts that overwash typically extends at least several kilometers into the MIZ, indicating that it likely contributes to the ice edge evolution. Key Points: A mathematical model is proposed for the extent of wave overwash of ice floes in the marginal ice zone (MIZ) based on coupled floe–wave motionsFrequent overwash is predicted up to 16 km from the ice edge during a voyage into Antarctic MIZ composed of pancake iceWave overwash is predicted to be a persistent feature of the outermost MIZ, likely contributing to the evolution of the ice edge [ABSTRACT FROM AUTHOR]

Sea ice growth and consolidation play a significant role in heat and momentum exchange between the atmosphere and the ocean. However, few in situ observations of sea ice kinematics have been reported owing to difficulties of deployment of buoys in the marginal ice zone (MIZ). To investigate the characteristics of sea ice kinematics from MIZ to packed ice zone (PIZ), eight drifting buoys designed by Taiyuan University of Technology were deployed in the open water at the ice edge of the Canadian Basin. Sea ice near the buoy constantly increased as the buoy drifted, and the kinematics of the buoy changed as the buoy was frozen into the ice. This process can be determined using sea ice concentration, sea skin temperature, and drift speed of buoy together. Sea ice concentration data showed that buoys entered the PIZ in mid-October as the ice grew and consolidated around the buoys, with high amplitude, high frequency buoy motions almost ceasing. Our results confirmed that good correlation coefficient in monthly scale between buoy drift and the wind only happened in the ice zone. The correlation coefficient between buoys and wind was below 0.3 while the buoys were in open water. As buoys entered the ice zone, the buoy speed was normally distributed at wind speeds above 6 m/s. The buoy drifted mainly to the right of the wind within 45° at wind speeds above 8 m/s. During further consolidation of the ice in MIZ, the direct forcing on the ice through winds will be lessened. The correlation coefficient value increased to 0.9 in November, and gradually decreased to 0.7 in April. [ABSTRACT FROM AUTHOR]

Rapid and profound climatic and environmental changes have been predicted for the Antarctic Peninsula with so far unknown impact on the biogeochemistry of the continental shelves. In this study, we investigate benthic carbon sedimentation, remineralization and iron cycling using sediment cores retrieved on a 400 mile transect with contrasting sea ice conditions along the eastern shelf of the Antarctic Peninsula. Sediments at comparable water depths of 330–450 m showed sedimentation and remineralization rates of organic carbon, ranging from 2.5 to 13 and 1.8–7.2 mmol C m−2 d−1, respectively. Both rates were positively correlated with the occurrence of marginal sea ice conditions (5%–35% ice cover) along the transect, suggesting a favorable influence of the corresponding light regime and water column stratification on algae growth and sedimentation rates. From south to north, the burial efficiency of organic carbon decreased from 58% to 27%, while bottom water temperatures increased from −1.9 to −0.1°C. Net iron reduction rates, as estimated from pore‐water profiles of dissolved iron, were significantly correlated with carbon degradation rates and contributed 0.7%–1.2% to the total organic carbon remineralization. Tightly coupled phosphate‐iron recycling was indicated by significant covariation of dissolved iron and phosphate concentrations, which almost consistently exhibited P/Fe flux ratios of 0.26. Iron efflux into bottom waters of 0.6–4.5 μmol Fe m−2 d−1 was estimated from an empirical model. Despite the deep shelf waters, a clear bentho‐pelagic coupling is indicated, shaped by the extent and duration of marginal sea ice conditions during summer, and likely to be affected by future climate change. Plain Language Summary: The seafloor of the shallow shelf seas plays a significant role in the recycling of organic carbon and acts as a nutrient source for algae growth in the upper water layers. In Antarctic waters, the change in sea ice cover has a great impact on the growth of algae and the subsequent sinking of organic carbon to the seafloor. With global warming, profound changes in sea ice cover are expected for the Antarctic Peninsula. To better understand its imprint on the seafloor, we collected sediment samples from different locations along the eastern shelf of the Antarctic Peninsula and measured how changes in sea ice cover influence the accumulation and recycling of organic carbon. We found that moderate sea ice cover of 5%–35% increases the amount of organic carbon received by the seafloor and that the fraction that is buried in the sediments decreases from south (58%) to north (27%). We further measured that more iron, an important micro‐nutrient for algae growth, can be released from the seafloor the more organic carbon accumulates. Thus, sea ice conditions determine the organic carbon accumulation, turnover, and nutrient release at the seafloor, which are likely to be affected by future climate change. Key Points: Antarctic shelf sediments underlying marginal sea ice cover exhibit high sedimentation and remineralization rates of organic carbonA high degree of sedimentary Fe‐recycling is found which scales with organic carbon remineralization ratesCoupling between P and Fe recycling is observed with a constant P/Fe flux ratio of 0.26 for sediments with high Fe and P recycling rates [ABSTRACT FROM AUTHOR]

The automatic detection and analysis of ocean eddies in the marginal ice zone via remote sensing is a very challenging task but of critical importance for scientific applications and anthropogenic activities. Therefore, as one of the first steps toward the automation of the eddy detection process, we investigated the potential of applying YOLOv5, a deep convolutional neural network architecture, to specifically collected and labeled high-resolution synthetic aperture radar data for a very dynamic area over the Fram Strait. Our approach involved fine-tuning pre-trained YOLOv5 models on a sparse dataset and achieved accurate results with minimal training data. The performances of the models were evaluated using several metrics, and the best model was selected by visual examination. The experimental results obtained from the validation and test datasets consistently demonstrated the robustness and effectiveness of the chosen model to identify submesoscale and mesoscale eddies with different structures. Moreover, our work provides a foundation for automated eddy detection in the marginal ice zone using synthetic aperture radar imagery and contributes to advancing oceanography research.

In August 2020, during a dramatical summer retreat of sea ice in the Nansen Basin, a study of phytoplankton was conducted on the transect from two northern stations in the marginal ice zone (MIZ) (north of 83° N m and east of 38° E) through the open water to the southern station located in the Franz Victoria Trench. The presence of melted polar surface waters (mPSW), polar surface waters (PSW), and Atlantic waters (AW) were characteristic of the MIZ. There are only two water masses in open water, namely PSW and AW, at the southernmost station; the contribution of AW was minimal. In the MIZ, first-year and multiyear ice species and Atlantic species were noted; Atlantic species and first-year ice species were in open water, and only ice flora was at the southernmost station. The maximum phytoplankton biomass (30 g · m−3) was recorded at the northernmost station of the MIZ, and 99% of the phytoplankton consisted of a large diatom Porosira glacialis. Intensive growth of this species occurred on the subsurface halocline separating mPSW from PSW. A thermocline was formed in open water south of the MIZ towards the Franz Victoria Trench. A strong stratification decreases vertical nutrient fluxes, so phytoplankton biomass decreases significantly. Phytoplankton formed the maximum biomass in the thermocline. When moving south, biomass decreased and its minimum values were observed at the southernmost station where the influence of AW is minimal or completely absent. A transition from the silicon-limited state of phytoplankton (MIZ area) to nitrogen-limited (open water) was noted.

Global ocean reanalyses provide consistent and comprehensive records of ocean and sea ice variables and are therefore of pivotal significance for climate studies, particularly in data-sparse regions such as Antarctica. Here, for the first time, we present the temporal and spatial variability of sea ice area in the ensemble of global ocean reanalyses produced by the Copernicus Marine Environment Monitoring Service (CMEMS) for the period 1993–2019. The reanalysis ensemble robustly reproduces observed interannual and seasonal variability, linear trend, as well as record highs and lows. While no consensus has been reached yet on the physical source of Antarctic-wide ice changes, our study also emphasizes the importance of understanding the different responses of ice classes, marginal ice zone (MIZ) and pack ice, to climate changes. Modifications of the distribution of MIZ and pack ice have implications for the level of air/sea exchanges and for the marine ecosystem. Analysis of the spatial and temporal variability of ice classes can provide further insights on long-term trends and help to improve predictions of future changes in Antarctic sea ice. We assess the ability of the reanalysis ensemble to adequately capture variability in space and time of the MIZ and pack ice area, and conclude that it can provide consistent estimates of recent changes in the Antarctic sea ice area. Our results show that the Antarctic sea ice area agrees well with satellite estimates, and the hemispheric and regional sea ice area variability are properly reproduced on seasonal and interannual time scales. Although the ensemble reanalysis product tends to slightly overestimate MIZ in summer, results show that it properly represents the variability of MIZ minima and maxima as well as its interannual variability during the growing and melting seasons. Our results confirm that Global Reanalysis Ensemble Product is able to reproduce the observed substantial regional variability, in regions covered by marginal ice.

Theoretical estimates based on both offline calculation and an online model are made to study the wavenumber variations during wave refraction in a marginal ice zone (MIZ). Analysis of in situ observations from the MIZ of the Arctic Ocean confirms the conclusion drawn based on theoretical estimates as well as the simulation ability of our new model to describe wave evolution in the MIZ. In wave refraction, variation of wavenumber in magnitude is determined by the incident wavenumber and the ice mass. A larger incident wavenumber or a larger ice mass leads to a larger variation of wavenumber in magnitude, though during refraction, the variation of wavenumber in magnitude is more sensitive to the incident wavenumber because it is proportional to the cube of the incident wavenumber, while it is linearly proportional to the ice mass. On the other hand, both the angle of refraction and the deflection are determined by the angle of incidence, the incident wavenumber and the ice mass. A larger angle of incidence, a shorter wave or larger ice mass results in a larger angle of refraction and a larger deflection. All these conclusions are supported by offline calculations, an online model and in situ observations. The online model also suggests that the instrument should be kept at a distance from the ice edge to obtain more general information of the open ocean.

The ongoing decline in Arctic sea ice extent and thickness underscores the scientific significance of monitoring the marginal ice zone (MIZ), a transitional region between the open ocean and pack ice. In this study, we used Bootstrap sea ice concentration (SIC) to detect the trend and change point of the Arctic MIZ over 40 years (1983–2022) using two different MIZ definitions: SIC threshold-based (MIZ _t ) and SIC anomaly-based (MIZ $_{\sigma}$ ). This study marks the exploration of a SIC anomaly-based definition of the MIZ over the Arctic. While the two MIZ definitions yield comparable seasonal trends in marginal ice zone fraction (MIZF), the MIZ $_{\sigma}$ fraction values peak during the transition periods (e.g. freeze-up and break-up), while the MIZ _t fraction values peak in August. The analysis also uncovers consistently higher MIZF values for the MIZ $_{\sigma}$ than for MIZ _t across all seasons. Moreover, October and August show the fastest rate of increase in MIZ _t fraction and MIZ $_{\sigma}$ fraction, reflecting the coinciding rapid decrease in sea ice extent during those particular months. Employing the pruned exact linear time, a multiple change point detection method, highlights a significant increase in the MIZ ${_t}$ fraction in October (after 2005) and MIZ ${_\sigma}$ fraction in August (after 2007). This can be indicative of the recent climate change impacts in the Arctic region that may be linked with shifts in SIC and sea ice mobility for MIZ _t and MIZ $_\sigma$ , respectively.

The marginal ice zone (MIZ) connects the open ocean and the pack ice, playing significant roles in shaping the ice edge and wave–ice interaction. Spaceborne synthetic aperture radar (SAR) has been demonstrated to be one of the most advantageous sensors for MIZ exploration given its capability to collect images under all weather conditions during day and night. In this study, we take advantage of the Sentinel-1 wave mode vignettes acquired around the Antarctic to quantify the image properties over MIZ. A data set of SAR images covering the ice edge with both open water and sea ice present in the same scene was created by manual inspection. It is found that the radar return over sea ice decreases by an average of approximately 1.78 dB in comparison to its adjacent open water, which is roughly independent of the polarizations and incidence angles. The long ocean waves are barely attenuated right across the ice edge in terms of their comparable azimuth cutoff. Further inside the ice from the edge, the waves are gradually dampened out at distances associated with their wavelengths. The results obtained in this study shall help interpret the radar scattering model validation as well as the wave–ice interaction.