Frontal Features Research Articles

Revisiting circulation and water masses over the East Antarctic margin (80–150°E)

Full-depth hydrographic sections of the BROKE experiment in 1996 (across the Antarctic margin from 80 to 150°E; Bindoff et al., 2000) were revisited for the first time during the 2018/2019 austral summer. We describe the subsurface physical oceanography in 2019 and the hydrographic changes between 1996 and 2019 not documented in earlier studies. The survey captured decadal changes in ocean structure from the southern flank of the Antarctic Circumpolar Current (ACC) to the continental shelves. In five cross-slope meridional sections, where 1996 and 2019 measurements are comparable (112, 120, 128, 140, and 150°E), the poleward shift of the southern boundary of the ACC (50–120 km) prevailed near the continental rise. The simultaneous displacement of barotropic ACC fronts and poleward migration of deep water contributed to full-depth warming (0.1–1.6 °C) and potentially to a reduction in the bottom water volume. Freshening was widely observed from the deep to bottom layers (∼0.02 g/kg), with the signal extending from the upper continental slope. Bottom-intensified freshening was accompanied by an oxygenation of 10–20 μmol/kg, indicating that freshening-driven oxygenation of bottom layers counteracted the deoxygenation effect of the poleward barotropic frontal shift. Westward transport of the Antarctic Slope Current decreased by more than 10 Sv from 1996 to 2019 in the five cross-slope sections; its frontal features and current axis shifted offshore by more than 20 km in 112–140°E. Additionally, subsurface warming along modified Circumpolar Deep Water by up to 0.4 °C was commonly detected across the upper continental slope. For the 2019 hydrography, shelf water sufficiently dense to form bottom water (>28.35 kg/m3) was found to the east of Mertz Polynya (142–148°E), implying a pathway for dense shelf water export from the eastern margin of Mertz Polynya. Our findings underscore the importance of sustained efforts for in-situ observations that widely cover the East Antarctic margin.

Masked face age and gender identification using CAFFE-modified MobileNetV2 on photo and real-time video images by transfer learning and deep learning techniques

One of the most challenging factors related to masked face age and gender identification (MFAGI) is developing a technique to quickly carry out identification and maintain accuracy without needing people to remove their masks. The eyes, forehead and important frontal features including the ears were the main focus of this investigation. In this study, we evaluated and compared ten (10) different MFAGI techniques, which include traditional methods such as MobileNet, MobileNetV2, ResNet101, DenseNet169, DenseNet201, EfficientNetB0, ResNet152V2, InceptionV3, Xception and our one proposed approach. These 10 models were used to classify masked faces of people among sixteen (16) classes. Combining the convolutional architecture of fast feature embedding (CAFFE) with the modified MobileNetV2 (MNV2) model developed a novel method known as the “CMNV2” model. To achieve the goal of model performance and classification accuracy for MFAGI of people’s faces, this work introduces a unique CMNV2 model by developing a pre-trained model with eight (8) different layers. Using deep learning (DL) and a transfer learning approach, we developed a unique novel approach to image feature extraction that outperforms the nine (9) traditional methods for masked face classification (MFC), masked face age identification (MFAI) and masked face gender identification (MFGI). This approach developed a Python model that was trained and evaluated on 12,160 masked face images. This study demonstrates that an efficient CMNV2 method can be achieved by combining transfer learning with deep neural network (DNN) development. This proposed CMNV2 model achieved 96.54% accuracy and 3.46% error rate with less parameters and computational time exceeding the other 9 different traditional masked identification methods. It also shows that our proposed CMNV2 strategy is more successful than the other 9 models and can identify masked people’s faces age and gender in photo and real-time video images. Overall, the results of this research indicate that DL methods have the capability to improve the accuracy and speed with which masked face classification and identification is performed. The artificially masked faces of images dataset created by us utilized in this work is publicly made available on the Kaggle website https://www.kaggle.com/datasets/banilkumar20phd7071/masked-face-age-and-gender-identify-artificial-masking.

The influence of the angle of the trunk flexion and extension in the sagittal plane and flexion in the frontal plane on the value of features describing the spine and pelvis among 7 to 15-year-old youth of both sexes

The aim of the study was to demonstrate the significant effect of the value of the angle of trunk flexion and extension in the sagittal plane and the flexion to the left and right in the frontal plane on the value of selected features describing the spine. Material and methodology. The research was conducted in a group of 2,361 people aged 7 to 15, in 6 semi-annual successive editions. This made it possible to record 16,608 observations using the photogrammetric method: 29 features describing spatially body posture. Results. Four features influencing the value of features describing the posture were selected for the analysis like an angle of trunk flexion and extension in the sagittal plane, an angle of flexion to the left and right in the frontal plane on selected sagittal and frontal features. Conclusions. (1) The influence of trunk flexion and extension angles in the sagittal plane and left and right flexion in the frontal oplane on the spine features is multidirectional and differential. (2) Spine characteristics are significantly and positively affected in particular by the value of the trunk extension angle in the sagittal plane and the value of the left flexion angle in the frontal plane, and negatively the value of the flexion angle in the sagittal plane. (3) None of the examined angles affect the characteristics of the pelvis.

Bipolar disorder progression to dementia with frontal features. A scoping review protocol

Background: A subset of patients with bipolar disorder (BD) develop a midlife cognitive/behavioral decline that overlaps with the clinical features of behavioral variant Frontotemporal Dementia (bvFTD). Several case reports and case series have described different clinical features and outcomes of a frontal cognitive/behavioral decline in patients with history of BD. Given that this presentation is scarcely reported, a first step to better characterize this specific condition is to perform an evidence synthesis report. Objective: This scoping review protocol aims to describe and characterize the different patterns of frontal cognitive/behavioral decline in patients with history of BD. Information sources: Studies will be retrieved from MEDLINE (PubMed), PsychINFO, EMBASE and Google Scholar, no other sources will be considered. Inclusion criteria: Studies describing patients with an established diagnosis of BD preceding a later development of dementia with frontal cognitive/behavioral decline. Exclusion criteria: Studies written in languages different than Spanish or English or French that could not be appropriately translated, or whose full text files could not be retrieved, and studies describing manic or BD symptoms, but not an antecedent history consistent with bipolar disorder, as a clear prodrome of bvFTD diagnosis. Data will be extracted by two researchers and verified by agreement. This protocol complies with the PRISMA-P, PRISMA ScR and JBI manual for evidence synthesis scoping review guidelines.

P.026 Frontal cognitive-behavioural deficits in patients with anti-leucine-rich glioma-inactivated protein 1 antibody encephalitis

Background: Cognitive impairment is a common manifestation of anti-LGI1 encephalitis and is typically defined as prominent memory deficits. We frequently encounter frontal cognitive-behavioural deficits when evaluating these patients, but this has yet to be well described in the literature. Methods: Patients with anti-LGI1 encephalitis were retrospectively identified from three tertiary centres in Toronto, Ontario between 2013 and 2022. Their medical records were evaluated and frontal features were categorized based on diagnostic criteria for behavioural variant frontotemporal dementia (bvFTD). Results: Nineteen patients were identified (median age 60 years [range 18–84]; 10 [52.6%] male). Eighteen (94.7%) had frontal cognitive-behavioural symptoms. Two developed these symptoms during treatment with steroids and were excluded from further analysis. The remaining 16 presented with behavioural disinhibition (n=13), apathy or inertia (n=6), perseverative, stereotyped or compulsive/ritualistic behaviours (n=6), hyperorality and dietary changes (n=4), a neuropsychological profile with predominant deficits in executive tasks (n=4), and loss of sympathy or empathy (n=4). Nine (47.3%) met diagnostic criteria for possible bvFTD. Anterograde memory impairment was common (n=14). Of the 16 patients with frontal features, 6 had faciobrachial dystonic seizures. Conclusions: Patients with anti-LGI1 encephalitis exhibit frontal cognitive-behavioural symptoms in addition to memory impairment. Clinicians should consider anti-LGI1 encephalitis in the differential diagnosis of bvFTD.

Frontal cognitive-behavioural deficits in patients with anti-leucine-rich glioma-inactivated protein 1 antibody encephalitis (S22.004)

<h3>Objective:</h3> To determine the prevalence of a frontal cognitive-behavioural phenotype in patients with anti-leucine-rich glioma-inactivated protein 1 (LGI1) encephalitis. <h3>Background:</h3> Cognitive impairment is a common manifestation of anti-LGI1 encephalitis and is typically defined as prominent memory deficits. We frequently encounter frontal cognitive-behavioural deficits when evaluating these patients, but this has yet to be well described in the literature. <h3>Design/Methods:</h3> We retrospectively identified patients from three tertiary centres in Toronto, Ontario who were diagnosed with anti-LGI1 encephalitis between October 2013 and September 2022. Patient electronic medical records were evaluated for cognitive features and frontal features were categorized based on the diagnostic criteria for behavioural variant frontotemporal dementia (bvFTD). <h3>Results:</h3> Fifteen patients were identified (median age 65 years [range 18–84]; 8 [53.3%] male). Fourteen (93.3%) patients had cognitive symptoms that localized to the frontal lobe. Two developed these symptoms during treatment with steroids and were therefore excluded from further analysis. The remaining 12 patients presented with behavioural disinhibition (n=11), apathy or inertia (n=5), perseverative, stereotyped or compulsive/ritualistic behaviours (n=4), hyperorality and dietary changes (n=4), a neuropsychological profile with predominant deficits in executive tasks (n=4), and loss of sympathy or empathy (n=1). Seven (46.7%) met diagnostic criteria for possible bvFTD. Of these, 3 had significant functional decline and none had neuroimaging findings consistent with bvFTD. Anterograde memory impairment was common (n=11), and patients also presented with language deficits (n=3) and difficulties with spatial navigation (n=3). Of the 12 patients with frontal symptoms, only 5 had faciobrachial dystonic seizures. <h3>Conclusions:</h3> Patients with anti-LGI1 encephalitis can exhibit frontal cognitive-behavioural symptoms in addition to memory impairment, and screening for these features on clinical assessment may help to identify the diagnosis. Clinicians should also consider anti-LGI1 encephalitis in the differential diagnosis of bvFTD. <b>Disclosure:</b> Dr. Lee has nothing to disclose. Dr. Climans has nothing to disclose. Dr. Day has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Parabon Nanolabs. The institution of Dr. Day has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Eli Lilly. Dr. Day has received personal compensation in the range of $500-$4,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for DynaMed (EBSCO Health). Dr. Day has received personal compensation in the range of $10,000-$49,999 for serving as an Expert Witness for Barrow Law. Dr. Day has stock in ANI Pharmaceuticals. The institution of Dr. Day has received research support from National Institutes of Health / NIA. The institution of Dr. Day has received research support from Chan Zuckerberg Initiative. The institution of Dr. Day has received research support from Alzheimer’s Association. The institution of Dr. Day has received research support from National Institutes of Health / NINDS. The institution of Dr. Day has received research support from Horizon Therapeutics. Dr. Day has received personal compensation in the range of $500-$4,999 for serving as a Presenter at Annual Meeting (CME) with American Academy of Neurology. Dr. Day has received personal compensation in the range of $500-$4,999 for serving as a Content Development (CME) with PeerView, Inc. Dr. Day has received personal compensation in the range of $5,000-$9,999 for serving as a Content Development (CME) with Continuing Education, Inc. Dr. Day has a non-compensated relationship as a Clinical Director with AntiNMDA Receptor Encephalitis Foundation that is relevant to AAN interests or activities. Dr. Hebert has nothing to disclose. Dr. Lapointe has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Alexion. Dr. Ramos has nothing to disclose. The institution of Dr. Steriade has received research support from NIH. The institution of Dr. Steriade has received research support from Dorris Duke Fund to Retain Clinician Scientists. Dr. Wennberg has nothing to disclose. Dr. Muccilli has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Biogen. Dr. Muccilli has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Novartis. Dr. Muccilli has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for EMD Serono. Dr. Tang-Wai has nothing to disclose.

Vertically Resolved Pelagic Particle Biomass and Size Structure Across a Continental Shelf Under the Influence of a Western Boundary Current

AbstractContinental shelves are key to societal interactions with the oceans, supporting &gt;90% of the world's fisheries through highly productive ecosystems. Previous research has shown that phytoplankton biomass is generally higher on the inner continental shelves, often due to increased nutrient inputs from upwelling or coastal run‐off. However, consistency in observed vertical and horizontal gradients (in abundance, biomass or size) of larger particulates, including zooplankton, on continental shelves has not been established. Using an optical plankton counter and CTD mounted on an undulating towed body, we present high‐resolution vertically resolved profiles of pelagic particle size structure across a continental shelf. Biomass was highest inshore, declining with distance from shore and with depth in the top 100 m of the water column, although the presence of frontal zones can alter this pattern. In the region adjacent to the East Australian Current (EAC), uplift generated by either the EAC interacting with the continental slope or upwelling‐favorable winds, correlated with smaller geometric mean sizes and steeper size spectrum slopes, particularly in the presence of frontal features. South of the EAC separation, the continental shelf water mass was more homogenous but still displayed the same horizontal and vertical patterns in particulate biomass and mean size. By combining our observations in a global comparison, we demonstrate consistent particulate distributions on continental shelves where the inner shelf has higher biomass with a steeper size spectrum slope compared to offshore. The highly productive inner shelf supports zooplankton communities vital to temperate ecosystems and coastal fisheries, through their consistently high biomass.

Identification of Sea Surface Temperature and Sea Surface Salinity Fronts along the California Coast: Application Using Saildrone and Satellite Derived Products

Coastal upwelling regions are one of the most dynamic areas of the world’s oceans. The California and Baja California Coasts are impacted by both coastal upwelling and the California Current, leading to frontal activity that is captured by gradients in both Sea Surface Temperature (SST) and Sea Surface Salinity (SSS). Satellite data are a great source of spatial data to study fronts. However, biases near coastal areas and coarse resolutions can impair its usefulness in upwelling areas. In this work gradients in SST from NASA Multi-Scale Ultra-High Resolution (MUR) and in two SSS products derived from the Soil Moisture Active Passive (SMAP) NASA mission are compared directly with gradients derived from the Saildrone uncrewed vehicles to validate the gradients as well as to assess their ability to detect known frontal features. The three remotely sensed data sets (MURSST/JPL, SMAP SSS/RSS, SMAP SSS) were co-located with the Saildrone data prior to the calculation of the gradients. Wavelet analysis is used to determine how well the satellite derived SST and SSS products are reproducing the Saildrone derived gradients. Overall results indicate the remote sensing products are reproducing features of known areas of coastal upwelling. Differences between the SST and SSS gradients are mainly associated with the limitations of the microwave derived SSS coverage near land and its reduced spatial resolution. The results are promising for using remote sensing data sets to monitor frontal structure along the California Coast and the application to long term changes in coastal upwelling and dynamics.

The stability of inviscid Beltrami flow between parallel free-slip impermeable boundaries

We present a family of exact inviscid three-dimensional Beltrami flows in a horizontally periodic domain lying between two parallel free-slip boundaries. Significantly, these flows are not stress free: the horizontal vorticity varies on each boundary. Using direct numerical simulations (employing horizontal hyperdiffusion only for numerical stability), we find that the largest-scale member of the family is unstable and breaks down into anisotropic turbulence, with relatively large horizontal vorticity at and near each boundary, and associated surface frontal features. We conjecture that all members of the family are similarly unstable. The free-slip boundaries play an important role in the late stages of the instability by constraining the deformation of vortex lines near the boundaries. This study appears to be the first to consider the role of boundary horizontal vorticity in an inviscid context.

Seasonal Cycle of the Confluence of the Tsugaru Warm, Oyashio, and Kuroshio Currents East of Japan

AbstractThe Sanriku Confluence east of Japan is the region of confluence of the Tsugaru Warm Current from the Sea of Japan, the Oyashio Current from the western subarctic gyre and the Sea of Okhotsk, and Kuroshio water that has detached from the subtropical gyre. It is a field of vigorous stirring driven by variability in current systems, but transition processes between water masses have yet to be clarified. High‐resolution underwater conductivity‐temperature‐depth observations were undertaken during each of the four seasons to test a hypothesis that the water‐mass gradient in the Sanriku Confluence is set without full stirring. Analyses in isopycnal coordinates indicate the seasonal occurrence of prominent fronts of both salinity and displacement, related to the emergence of various water masses. After fitting error functions to frontal features, the seasonally emerging isopycnal salinity fronts often became extremely sharp with widths typically narrower than 3 km, supporting the hypothesis. Disturbances distinguished from frontal structures indicate variance peaks with ranges similar to or slightly greater than the baroclinic Rossby radius, likely stirring the large‐scale tracer gradient at this scale. Elevated variances in isopycnal salinity were often observed around the fronts, and variances caused by isolated patches with salinity anomalies were also large. By determining the horizontal scales at which the effects of internal wave heaving becomes dominant, we were able to calculate the potential vorticity (PV) of the balanced flow field. As the PV becomes negative or near zero around the fronts, symmetric instability might have developed.

Variability and Intensity of the Sea Surface Temperature Front Associated With the Kuroshio Extension

Seventeen years of satellite observational data are used to describe the variability in sea surface temperature (SST) fronts and associated features, e.g., frontal intensity and probability, in the northwestern Pacific Ocean. Compared with the SST gradient and frontal probability, the frontal intensity is less impacted by background noise in satellite observations and precisely represents the variability in frontal patterns. The seasonal variability in frontal intensity is prominent, and the corresponding seasonality varies spatially. Fronts are more common during winter in the northern region around the Oyashio Current but are most common during spring in the Kuroshio Current and to the south of the Kuroshio Extension. The meridional migration of fronts is associated with the seasonal movement of the North Pacific subtropical gyre. Though overall averaged frontal intensity along the Kuroshio Extension is most prominent in the northwestern Pacific Ocean, the associated variability in fronts is highly complex. The current study reveals that seasonality itself cannot capture the whole picture of frontal features because eddy-induced intraseasonal variability and basin-scale signal-induced interannual variability can modulate frontal dynamics. In particular, the monthly frontal intensity in regions where the seasonal cycle is not significant depends on the Pacific Decadal Oscillation and North Pacific Gyre Oscillation. Furthermore, the oscillation of the Kuroshio Extension and associated mesoscale eddies can impact its intraseasonal variability. The comprehensive analysis of frontal intensity in the Kuroshio Extension is helpful for delineating regional dynamics and has the potential to improve our understanding of controls on marine primary production.

Ocean Temperature and Color Frontal Zones in the Gulf of Mexico: Where, When, and Why

AbstractThe spatial and temporal patterns of ocean frontal zones in the Gulf of Mexico (GoM) are studied using ocean color and sea surface temperature (SST) imagery collected by the Moderate Resolution Imaging Spectroradiometer/Aqua (MODIS/A) over an 18‐year (2002–2019) period. A gradient‐based front detection algorithm is applied to each daily image to detect frontal features, from which a comprehensive data set of ocean frontal zones (both climatology and time series) is established. Prominent seasonality is found in both ocean color and SST frontal zones while their seasonal variations differ. Major persistent frontal zones are mainly distributed in coastal waters within the 130‐m isobath, and they are often associated with wind forcing, wind‐driven Ekman transport, upwelling/downwelling, river discharge, ocean currents, and topography. The seasonal and interannual variations in frontal distributions are also revealed in the dominant spatial and temporal modes derived from an empirical orthogonal function (EOF) decomposition analysis. These findings may have significant implications on fisheries and ocean ecology research. For example, both ocean color and SST frontal features in certain months are found to coincide with a well‐known fishing ground in the eastern GoM, and surface macroalgae features are found to align well with the identified ocean frontal features.

Mesoscale productivity fronts and local fishing opportunities in the European Seas

AbstractThis study evaluates the relationship between both commercial and scientific spatial fisheries data and a new satellite‐based estimate of potential fish production (Ocean Productivity available to Fish, OPFish) in the European Seas. To construct OPFish, we used productivity frontal features derived from chlorophyll‐ahorizontal gradients, which characterize 10%–20% of the global phytoplankton production that effectively fuels higher trophic levels. OPFish is relatively consistent with the spatial distribution of both pelagic and demersal fish landings and catches per unit of effort (LPUEs and CPUEs, respectively). An index of harvest relative to ocean productivity (HPindex) is calculated by dividing these LPUEs or CPUEs with OPFish. The HPindex reflects the intensity of fishing by gear type with regard to local fish production. Low HPlevels indicate lower LPUEs or CPUEs than expected from oceanic production, suggesting over‐exploitation, while high HPlevels imply more sustainable fishing. HPallows comparing the production‐dependent suitability of local fishing intensities. Our results from bottom trawl data highlight that over‐exploitation of demersal species from the shelves is twice as high in the Mediterranean Sea than in the North‐East Atlantic. The estimate of HPindex by dominant pelagic and demersal gears suggests that midwater and bottom otter trawls are associated with the lowest and highest overfishing, respectively. The contrasts of fishing intensity at local scales captured by the HPindex suggest that accounting for the local potential fish production can promote fisheries sustainability in the context of ecosystem‐based fisheries management as required by international marine policies.

Ocean Fronts detection over the Bay of Bengal using changepoint algorithms – A non-parametric approach

Oceanic fronts are regions over the oceans where a significant change in the characteristics of the water masses is observed. Advanced Very High Resolution Radiometer (AVHRR) satellite imagery over the Bay of Bengal shows regions that are populated by frontal structures. Over the Bay of Bengal, some of the strongest gradients in temperature and salinity are observed. In recent years, there has been a tremendous growth in the availability of satellite imagery and the necessity of automated fast detection of the frontal features is needed for services like potential fishing zones over open oceans. In this article, an algorithm to infer oceanic fronts over the Bay of Bengal is described using changepoint analysis. The changepoint algorithm is combined in a novel way with a contextual median filter to detect frontal features in AVHRR imagery. The changepoint analysis is a non-parametric technique that does not put thresholds on the gradients of brightness temperatures of the satellite imagery. In the open oceans, the gradients of temperature and salinity are not sharp and changepoint analysis is found to be a useful complementary technique to the existing front detecting methods when combined with contextual median filters.

Detailed Feature Guided Generative Adversarial Pose Reconstruction Network

Face frontalization is a critical and difficult task on face pose reconstruction. Previous researches use simple posture information as guidance, such as pose coding and facial landmarks. To explore the guidance effect of profile faces, we propose detailed features that provide much detailed information. In this paper, a D etailed Feature G uided Generative Adversarial P ose R econstruction Network (DGPR) is proposed. Firstly, frontal pose coding and profile detailed features are fed into DGPR to generate detailed features of front face. Then, the second generator combines frontal detailed features and profile face to reconstruct front face. Besides, we propose a conditional enhancement loss to strengthen the guiding role of detailed features, and a smoothing loss to reduce edge sharpness in generated faces. Experimental results show that our method generates photorealistic front faces and outperforms state-of-the-art methods on M2FPA and CAS-PEAL. Specifically, DGPR improves the face recognition accuracy under pose angles of ±60°, ±75°, ±90° by 2%, 1%, and 6% respectively over the state-of-the-art methods on M2FPA, achieves the average rank-1 recognition rate to 99.95% and improves it by 0.05% on CAS-PEAL. These results demonstrate the effects of detailed features and corresponding modules.

Adaptive Sampling of Surface Fronts in the Arctic Using an Autonomous Underwater Vehicle

Fronts between Arctic- and Atlantic-origin waters are characterized by strong lateral gradients in temperature and salinity. Ocean processes associated with fronts are complex with considerable space and time variability. Therefore, resolving the processes in frontal zones by observation is challenging but important for understanding the associated physical–biological interactions and their impact on the marine ecosystem. The use of autonomous robotic vehicles and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> data-driven sampling can help improve and augment the traditional sampling practices, such as ships and profiling instruments. Here, we present the development and results of using an autonomous agent for detection and sampling of an Arctic front, integrated on board an autonomous underwater vehicle. The agent is based on a subsumption architecture implemented as behaviors in a finite-state machine. Once a front is detected, the front tracking behavior uses observations to continuously adapt the path of the vehicle to perform transects across the front interface. Following successful sea trials in the Trondheimsfjord, the front-tracking agent was deployed to perform a full-scale mission near 82 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ}$</tex-math></inline-formula> N north of Svalbard, close to the sea ice edge. The agent was able to detect and track an Arctic frontal feature, performing a total of six crossings while collecting vertical profiles in the upper 90 m of the water column. Measurements yield a detailed volumetric description of the frontal feature with high resolution along the frontal zone, augmenting ship-based sampling that was run in parallel.

Barrier Layers in a High‐Resolution Model in the Eastern Tropical Pacific

AbstractThis study examines salinity barrier layers (BLs) in the eastern tropical North Pacific in the region of the Salinity Processes in the Upper ocean Regional Studies‐2 field campaign. We utilize a high‐resolution numerical model to study BLs and their relationship to frontal features and small‐scale ocean variability, focusing on two specific events. One is associated with a large outbreak of BL presence near 7°N along 125°W. The other is a relatively isolated but persistent BL that forms near 13°N, again along 125°W. In both cases we find that the BL is proximate to a salinity frontal feature in which isohalines tilt toward the fresh side of the front at its base. The BLs studied are associated with divergent flow at the surface on the fresh side of the front and convergent flow on the salty side. Tilting of the front is invoked to explain this, with an additional mechanism involving a vertical circulation which causes the base of the front to tilt preferentially.

Satellite-derived sea surface temperature fronts in a river-influenced coastal upwelling area off central–southern Chile

The variability of thermal fronts in eastern ocean boundaries has received increased attention because of being active regions of vertical fluxes of tracers and biological activity. Sea Surface Temperature (SST) images from three distinct satellite products are used to identify areas with enhanced surface thermal gradients (i.e. SST fronts) in the coastal ocean off central–southern Chile. The main objective is to evaluate their use in the study of SST frontal variability in a river-influenced continental shelf. In contrast with previous studies focused on the mesoscale structure of the upwelling front, this study highlights the importance of using high spatial resolution (i.e. 1 km) satellite products to resolve the small-scale surface thermal gradients on a relatively narrow continental shelf impacted by freshwater river outflows. An improved approach, merging Moderate Resolution Imaging Spectroradiometer (MODIS) imagery from Aqua and Terra satellites (MODIS-AT), increases the percentage of available SST data for the computation of SST gradients and frontal probability over these shelf waters. Overall, SST data from all three sources (Pathfinder, Geostationary Operational Environmental Satellite (GOES), and MODIS) resolve the major mesoscale frontal features along the offshore limit of the continental shelf. However, MODIS-AT considerably improves the detection of SST fronts over the continental shelf, especially during winter and spring when river outflows are important on the dynamics of coastal flows. A case study off the Itata River mouth reveals high spatio-temporal variability of thermal fronts over the continental shelf, which is not well detected from GOES and Pathfinder data. The analysis of MODIS-AT images is highly recommended for studies of thermal fronts over shelf waters. In contrast, the use of GOES imagery improves the monitoring of the mesoscale frontal activity farther offshore.

Meroplankton community structure across oceanographic fronts along the South Brazil Shelf

The influence of oceanographic fronts on the abundance and community composition of invertebrate larvae, mostly of benthic species, along nearly 2000 km of the southwestern Atlantic shelf (21–34°S) was investigated. Meroplankton was sampled through vertical hauls at 89 stations, distributed along 14 cross-shelf transects, during late spring 2010 and early summer 2011. Salinity and temperature were registered with a CTD/rosette system, which provided seawater for chlorophyll-a and nutrient concentrations estimations. Vertical profiles of temperature, salinity, chlorophyll-a and nutrients were used as proxies of the fronts. In addition, high-resolution thermosalinograph data were used to detect surface frontal features. Meroplankton abundance peaks were found at several fronts intersected by the ship, including upwelling zones, estuarine and plume fronts, a shelf-break front, and two cyclonic eddies. Furthermore, meroplankton abundance was also relatively higher at small-scale thermal and/or saline surface fronts observed along the shelf. Such increases in meroplankton abundance are likely to be ascribed to high nutrient input and primary production. Distinct taxa of invertebrate larvae occurred at different types of fronts, besides the coastal realm, which was virtually dominated by decapod, cirripede and bivalve larvae. Small-scale shelf fronts presented high abundances of decapod and gastropod larvae, for instance, while larvae of polychaetes were the most frequent in the estuarine front of Patos Lagoon section.

Suppression of winter heavy precipitation in Southeastern China by the Kuroshio warm current

The possible effects of the Kuroshio current and associated sea surface temperature (SST) fronts on Southeastern China winter precipitation are examined using twin simulations of a regional atmospheric model. When the SST frontal features in the forcing data are artificially weakened, the simulated rainfall over Southeastern China, particularly heavy rainfall, is found to increase by a statistically significant amount, compared to the simulations with the observed SST fronts. This difference is attributed to an anomalous regional overturning circulation that interferes with the onshore moisture transport. With the presence of stronger frontal SSTs, an anomalous ascending motion is anchored along the warm current, with a descending branch to its western side, forming a circulation cell that strides across the coasts of Southern China. In days of heavy rainfall over the Southeastern China, the regional atmospheric circulation tunnels oceanic moisture onto land across the coasts, serving as the primary water vapor source for the precipitation. This process is weakened by the anomalous regional overturning circulation in that the imbalance between low-level offshore and upper-level onshore flux drains the land of moisture, and the up-lifted moisture import aloft creates unfavorable condition for land precipitation.