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We provide high-resolution in situ observations of wave-induced sea ice breakup in the natural environment. In order to obtain such data, a drone was deployed from the Canadian Coast Guard ship Amundsen as it sailed in the vicinity of large ice floes in Baffin Bay and in the St. Lawrence Estuary, Canada. The footage recorded during these experiments was used to obtain the floe size distribution (FSD) and the temporal evolution of the breakup. Floe-area-weighted FSDs exhibit a modal shape, indicating that a preferential size is generated by wave-induced breakup. Furthermore, the increase of the mode of the distribution with greater thickness indicates that ice thickness plays a defined role in determining the preferential size. Comparison with relevant theory suggests that the maximum floe size is dictated not only by the ice rigidity but also by the incident wavelength. It was also observed that the in-ice wavelength is smaller than the estimated incident wavelength, suggesting that waves responsible for the breakup obey mass loading dispersion. The fact that the breakup advances almost as fast as the wave energy suggests that fatigue might not have been an important physical component during the experiments. Moreover, the observed breakup extents show that thicker ice can attenuate waves less than thinner ice. Overall, this dataset provides key information on wave-induced sea ice breakup and highlights the potential for better understanding the physics of natural sea ice in response to waves.

The Green Edge project was designed to investigate the onset, life, and fate of a phytoplankton spring bloom (PSB) in the Arctic Ocean. The lengthening of the ice-free period and the warming of seawater, amongst other factors, have induced major changes in Arctic Ocean biology over the last decades. Because the PSB is at the base of the Arctic Ocean food chain, it is crucial to understand how changes in the Arctic environment will affect it. Green Edge was a large multidisciplinary, collaborative project bringing researchers and technicians from 28 different institutions in seven countries together, aiming at understanding these changes and their impacts on the future. The fieldwork for the Green Edge project took place over two years (2015 and 2016) and was carried out from both an ice camp and a research vessel in Baffin Bay, in the Canadian Arctic. This paper describes the sampling strategy and the dataset obtained from the research cruise, which took place aboard the Canadian Coast Guard ship (CCGS) Amundsen in late spring and early summer 2016. The sampling strategy was designed around the repetitive, perpendicular crossing of the marginal ice zone (MIZ), using not only ship-based station discrete sampling but also high-resolution measurements from autonomous platforms (Gliders, BGC-Argo floats …) and under-way monitoring systems. The dataset is available at https://doi.org/10.17882/86417 (Bruyant et al., 2022).

Landfast ice is a common coastal feature in the Arctic Ocean and around the Antarctic continent. One contributing and stabilizing mechanism is the grounding of sea ice ridges in shallow water. Recently, a grounding scheme representing this effect on sea ice dynamics was developed in order to improve the simulation of landfast ice by continuum-based sea ice models. This parameterization assumes that the ridged keel thickness is proportional to the mean thickness. Results demonstrated that this simple parameterization notably improves the simulation of landfast ice in many regions such as in the East Siberian Sea, the Laptev Sea and along the Alaskan coast. Nevertheless, a weakness of this approach is that it is based solely on the mean properties of sea ice. Here, we extend the parameterization by taking into account subgrid-scale ice thickness distribution and bathymetry distribution, which are generally non-normal, and by computing the maximum seabed stress as a joint probability interaction between the sea ice and the seabed. The probabilistic approach shows a reasonably good agreement with observations and with the previously proposed grounding scheme while potentially offering more physical insights into the formation of landfast ice.

A simplified model, representing the dynamics of marine organic particles in a given size range experiencing coagulation and fragmentation reactions, is developed. The framework is based on a discrete size spectrum on which reactions act to exchange properties between different particle sizes. The reactions are prescribed according to triplet interactions. Coagulation combines two particle sizes to yield a third one, while fragmentation breaks a given particle size into two (i.e. the inverse of the coagulation reaction). The complete set of reactions is given by all the permutations of two particle sizes associated with a third one. Since, by design, some reactions yield particle sizes that are outside the resolved size range of the spectrum, a closure is developed to take into account this unresolved range and satisfy global constraints such as mass conservation. In order to minimize the number of tracers required to apply this model to an ocean general circulation model, focus is placed on the robustness of the model to the particle size resolution. Thus, numerical experiments were designed to study the dependence of the results on (i) the number of particle size bins used to discretize a given size range (i.e. the resolution) and (ii) the type of discretization (i.e. linear vs. nonlinear). The results demonstrate that in a linearly size-discretized configuration, the model is independent of the resolution. However, important biases are observed in a nonlinear discretization. A first attempt to mitigate the effect of nonlinearity of the size spectrum is then presented and shows significant improvement in reducing the observed biases.

A 130 km2 tabular iceberg calved from Petermann Glacier in northwestern Greenland on 5 August 2012. Subsequent fracturing generated many individual large “ice islands”, including Petermann ice island (PII)-A-1-f, which drifted between Nares Strait and the North Atlantic. Thinning caused by basal and surface ablation increases the likelihood that these ice islands will fracture and disperse further, thereby increasing the risk to marine transport and infrastructure as well as affecting the distribution of freshwater from the polar ice sheets. We use a unique stationary and mobile ice-penetrating radar dataset collected over four campaigns to PII-A-1-f to quantify and contextualize ice island surface and basal ablation rates and calibrate a forced convection basal ablation model. The ice island thinned by 4.7 m over 11 months. The majority of thinning (73 %) resulted from basal ablation, but the volume loss associated with basal ablation was ∼12 times less than that caused by areal reduction (e.g. wave erosion, calving, and fracture). However, localized thinning may have influenced a large fracture event that occurred along a section of ice that was ∼40 m thinner than the remainder of the ice island. The calibration of the basal ablation model, the first known to be conducted with field data, supports assigning the theoretically derived value of 1.2×10−5 m2∕5 s-1/5 ∘C−1 to the model's bulk heat transfer coefficient with the use of an empirically estimated ice–ocean interface temperature. Overall, this work highlights the value of systematically collecting ice island field data for analyzing deterioration processes, assessing their connections to ice island morphology, and adequately developing models for operational and research purposes.

The Green Edge initiative was developed to investigate the processes controlling the primary productivity and fate of organic matter produced during the Arctic phytoplankton spring bloom (PSB) and to determine its role in the ecosystem. Two field campaigns were conducted in 2015 and 2016 at an ice camp located on landfast sea ice southeast of Qikiqtarjuaq Island in Baffin Bay (67.4797∘ N, 63.7895∘ W). During both expeditions, a large suite of physical, chemical and biological variables was measured beneath a consolidated sea-ice cover from the surface to the bottom (at 360 m depth) to better understand the factors driving the PSB. Key variables, such as conservative temperature, absolute salinity, radiance, irradiance, nutrient concentrations, chlorophyll a concentration, bacteria, phytoplankton and zooplankton abundance and taxonomy, and carbon stocks and fluxes were routinely measured at the ice camp. Meteorological and snow-relevant variables were also monitored. Here, we present the results of a joint effort to tidy and standardize the collected datasets, which will facilitate their reuse in other Arctic studies. The dataset is available at https://doi.org/10.17882/59892 (Massicotte et al., 2019a).

Arctic sea ice is experiencing a shorter growth season and an earlier ice melt onset. The significance of spring microalgal blooms taking place prior to sea ice breakup is the subject of ongoing scientific debate. During the Green Edge project, unique time-series data were collected during two field campaigns held in spring 2015 and 2016, which documented for the first time the concomitant temporal evolution of the sea ice algal and phytoplankton blooms in and beneath the landfast sea ice in western Baffin Bay. Sea ice algal and phytoplankton blooms were negatively correlated and respectively reached 26 (6) and 152 (182) mg of chlorophyll 'a' per m2 in 2015 (2016). Here, we describe and compare the seasonal evolutions of a wide variety of physical forcings, particularly key components of the atmosphere–snow–ice–ocean system, that influenced microalgal growth during both years. Ice algal growth was observed under low-light conditions before the snow melt period and was much higher in 2015 due to less snowfall. By increasing light availability and water column stratification, the snow melt onset marked the initiation of the phytoplankton bloom and, concomitantly, the termination of the ice algal bloom. This study therefore underlines the major role of snow on the seasonal dynamics of microalgae in western Baffin Bay. The under-ice water column was dominated by Arctic Waters. Just before the sea ice broke up, phytoplankton had consumed most of the nutrients in the surface layer. A subsurface chlorophyll maximum appeared and deepened, favored by spring tide-induced mixing, reaching the best compromise between light and nutrient availability. This deepening evidenced the importance of upper ocean tidal dynamics for shaping vertical development of the under-ice phytoplankton bloom, a major biological event along the western coast of Baffin Bay, which reached similar magnitude to the offshore ice-edge bloom.

Passive flow control valves are usually intended to deliver or drain a fluid at a constant rate independently of pressure variations. Microfluidic devices made of a stack of two plates are considered here: the first plate comprises a flexible silicon membrane having through holes while the second plate is a rigid substrate with a cavity, an outlet hole and pillars aligned with the through holes of the membrane. The liquid flows through the holes etched in the membrane and through the gap between the membrane and the pillars. Each gap can be considered as a valve which progressively closes as the pressure increases. Numerical modelling of the fluid dynamics inside the device associated with FEM simulations of the membrane distortion have been performed to design a device that exhibits a constant flow rate in a specified range of pressure. To make the design more reliable, the device characteristics have been optimized using a genetic algorithm, the fitness function taking notably into account machining and alignment tolerances. This algorithm has been finally used to design flow control valves for wearable injectors dedicated to the infusion of viscous drug formulations (hyaluronic acid, adalimumab, golimumab …) at high pressure. Prototypes have been characterized using solutions of 12 and 24 cP. It has been demonstrated experimentally that this technology is suitable to passively infuse biological products at flow rates up to 1 mL/min. The numerical model has then been refined further so as to obtain a good correlation with experimental data.

Numerical simulations based on the classical Marmarou’s model have been carried out to analyse the dynamics of hydrocephalus valves. The evolution of the intracranial pressure in various case studies has been determined with a specific focus on flow control valves. It has been shown that their capability to prevent postural under- and over-drainage may be significantly altered by non-idealities of their hydrodynamic characteristics and by the inter-individual variability of the cerebrospinal fluid production rate. The use of microtechnology to improve the flow rate accuracy also enables the possibility to get original designs that are desirable to address specific restrictions of use associated with flow-control valves, in particular for patients exhibiting very high resistance to cerebrospinal fluid reabsorption. A new hybrid hydrodynamic characteristic of a hydrocephalus valve is proposed to stabilize the intracranial pressure. This new passive valve is equivalent to two pressure regulators at high and low relative pressures, corresponding respectively to upright and decubitus positions. The device is able to automatically switch from one configuration to the other as a function of the postural change. Numerical simulations suggest that this new hybrid valve should combine the advantages of both differential and flow control valves.

We consider the estimation of the grazing preferences parameters of zooplankton in ocean ecosystem models with ensemble-based Kalman filters. These parameters are introduced to model the relative diet composition of zooplankton that consists of phytoplankton, small size-classes of zooplankton and detritus. They are positive values and their sum is equal to one. However, the sum-to-one constraint cannot be guaranteed by ensemble-based Kalman filters when parameters are bounded. Therefore, a reformulation of the parameterization is proposed. We investigate two types of variable transformations for the estimation of positive sum-to-one constrained parameters that lead to the estimation of a new set of parameters with normal or bounded distributions. These transformations are illustrated and discussed with twin experiments performed with the 1-D coupled model GOTM-NORWECOM with Gaussian anamorphosis extensions of the deterministic ensemble Kalman filter (DEnKF).

Abdominal compartment syndrome (ACS) is a rare but potentially fatal complication that can occur during hip arthroscopy. This usually occurs as a result of arthroscopic fluid passing into the retroperitoneal space through the psoas tunnel. From the retroperitoneal space, the fluid can then enter the intraperitoneal space through defects in the peritoneum. Previous studies have identified female sex, iliopsoas tenotomy, pump pressure, and operative time as potential risk factors for fluid extravasation. We present a method to measure intraoperative fluid deficit during hip arthroscopy to alert surgeons to possible ACS. Our proposed technique requires diligent intraoperative monitoring of fluid output through various suction devices, including suction canisters, puddle vacuums, and suction mats. The difference is then calculated from the fluid intake from the arthroscopic fluid bags. If the difference is greater than 1500 mL, then the anesthesiologist and circulating nurse are instructed to examine the abdomen for distension every 15 minutes. This, combined with other common symptoms such as hypotension and hypothermia, should alert the surgical team to the development of ACS. Despite limitations to this technique, this approach offers an objective method to calculate intra-abdominal fluid extravasation.

Purpose: The purpose of this study was to determine if the Single-Assessment Numeric Evaluation (SANE) score correlates with existing validated hip-specific patient-reported outcome measures (PROMs), including the Modified Harris Hip Score (mHHS), the International Hip Outcome Tool (IHOT-33), the Hip Outcome Score, Activities of Daily Living subscale (HOS-ADL), and the Hip Outcome Score, Sport-Specific subscale (HOS-SS), for patients preparing to undergo hip arthroscopy for treatment of femoroacetabular impingement syndrome (FAIS). Methods: A single surgeon’s operative database was retrospectively reviewed to identify patients undergoing primary hip arthroscopy for treatment of FAIS from April 2018 to October 2019. Patient-specific factors including age, sex, body mass index (BMI), and duration of symptoms were collected. Preoperative SANE, mHHS, IHOT-33, HOS-ADL, and HOS-SS scores were analyzed. Statistical analysis using Pearson correlation was performed to identify the relationship between the SANE score and the mHHS, IHOT-33, HOS-ADL, and HOS-SS, preoperatively. Results: 154 patients were included in the study. The mean mHHS was 54.4 ± 11.7; mean IHOT-33 score was 32.7 ± 15.0; mean HOS-SS 42.9 ± 23.7; and mean HOS-ADL was 63.3 ± 1. The mean SANE score was 36.7 ± 19.9. The Simple Hip Score was directly correlated with the mHHS (P < .01), the IHOT-33 (P 1 year. Conclusion: The SANE score was strongly correlated with mHHS, IHOT-33, HOS-ADL, and HOS-SS in the preoperative setting for patients undergoing hip arthroscopy for treatment of FAIS. Given its simplicity, SANE may be a valuable tool for rapid assessment of joint function and pain in this patient population. Level of Evidence: IV, therapeutic case series.

Chronic groin pain in the athlete can be a difficult problem to manage. Adductor dysfunction is the most common cause of groin pain in athletes, with the adductor longus being the tendon most commonly involved. The most reproducible finding for adductor longus tendinopathy is tenderness along the tendon with passive abduction and resisted hip adduction in extension. Magnetic resonance imaging and injection of a corticosteroid and anesthetic into the proximal muscle-tendon junction are both helpful in confirming the diagnosis. Nonoperative treatment may consist of protected weight bearing, ice application, ultrasonography, electrical stimulation, and gentle stretching with progressive strengthening. However, nonoperative management is not always successful. In these instances, surgical treatment can be quite effective. We present the indications, surgical technique, and rehabilitation protocol of adductor tenotomy for chronic tendinopathy. This can prove a useful tool for the treatment of recalcitrant groin pain attributable to the adductor longus.