Physical Oceanography Research Articles (Page 1)

Pelagic iodine cycling over the Western Indian margin: Impact of anoxic events and benthic flux.

Dispersion, nonlinearity, and waves-wave interactions are some of the important aspects of two-dimensional wave behaviour that are captured by the mathematical model known as the ion sound and Langmuir wave system. This study uses the truncated Painlevé technique to examine the (1+1) dimensional integrable ion Sound and Langmuir wave system. Various localised solutions, such as rogue or irregular waves, dromion-pair, and dromions can be produced via applying random functions to the findings. The collisional interaction of these solutions are produced, investigated, and visually displayed as a result of selecting suitable starting values for the arbitrary functions. We discover that dromions interact inelastically, exchanging both energy and phase, but rogue waves are inherently erratic. These findings advance our understanding of complex wave dynamics and have important implications for the study of non-linear occurrences in a variety of disciplines such as physical mechanisms, fluid dynamics, oceanography and nonlinear optics. It’s crucial to remember that all computations and visualisations are generated and their reliability and accuracy verified using Mathematica software. All things taken into account this work enhances our knowledge of complexities nonlinear systems and how their behaviour is influenced by their initial conditions. The study’s findings will aid in our comprehension of how waves behave in higher dimensional controlling models.

Abstract The detailed knowledge of bathymetry pattern represents a key factor in the deep understanding of ocean processes, physical oceanography, biology, ecohydraulics, and marine geology. However, the accuracy of bathymetry modeling is still low from satellite altimetry, gravity model, and shipborne gravity data. In this paper, a novel scheme is proposed based on black-box theory for regional bathymetry modeling in the Persian Gulf and the Oman Sea via geodetic data sources such as satellite altimetry, gravity model, and shipborne gravity data. Multi-Layer Perceptron (MLP), Adaptive Neuro-Fuzzy Inference System (ANFIS), and Local Linear Model Tree (LOLIMOT) algorithms are used as nonlinear black-box tools to identify the basic mathematical model. The geoid height, gravity gradient, and gravity anomaly are used as inputs to these artificial intelligence models, with the GEBCO bathymetry model as the output. The derived basic model is further improved by assimilating with the shipborne bathymetry measurements using the 3D variational optimization method to determine the final bathymetry model. The model is validated by the shipborne bathymetry in control tracks of regions Chabahar, Genaveh, and Alamshah, and the results show high accuracy and reliability with root mean square errors (RMSEs) of about 4, 0.8, and 0.92 m, respectively. The proposed approach is valuable for various uses in marine science.

Abstract The Strait of Gibraltar is a region characterized by intricate oceanic submesoscale features arising from the interplay of topography, tidal forcing, hydrodynamic instabilities, and strongly nonlinear internal hydraulic processes, all governed by the nonlinear equations of fluid motion. In this study, we aim to uncover the underlying physics of these phenomena as represented in the 3D Massachusetts Institute of Technology (MIT) General Circulation Model simulations, including simulated waves, eddies, and gyres. To achieve this, we employ dynamic mode decomposition (DMD) to break down simulation snapshots into Koopman modes, with distinct exponential growth/decay rates and oscillation frequencies. Our objectives encompass evaluating DMD’s efficacy in capturing known features, unveiling new elements, ranking modes, and exploring order reduction. We also introduce modifications to enhance DMD’s numerical accuracy and the robustness of its eigenvalues. DMD analysis yields a comprehensive understanding of flow patterns, internal wave formation, and the dynamics and meandering behaviors within the Strait of Gibraltar, the formation of the secondary western Alboran Gyre, and the propagation of Kelvin and coastal-trapped waves along the African coast. In doing so, it significantly advances our comprehension of intricate oceanographic phenomena and underscores the immense utility of DMD as an analytical tool for such complex datasets, suggesting that DMD could serve as a valuable addition to the toolkit of oceanographers. Significance Statement A challenge arising in all branches of geophysics is making sense of increasingly large datasets describing complex processes. In physical oceanography, these data usually come from high-resolution models and observations. Reduced-order models such as dynamic mode decomposition (DMD) have the potential to identify key processes and interactions through the synthesis of a data-based model with relatively few degrees of freedom. Because of its connection with Koopman operator theory, DMD is also able, in principle, to deal with data describing nonlinear processes. In this work, we test the ability of DMD to describe the essential physics exhibited in a complicated dataset produced by a model of the ocean circulation in the Strait of Gibraltar and western Mediterranean, a region that contains striking, time-dependent, and often nonlinear features, mostly driven or modulated by tides. We carefully describe the connection to Koopman theory and the step-by-step DMD algorithm, and we present a procedure for singling out the most robust of the DMD modes. We then show how particular modes contain information about specific physical processes including modulation of the two-layer exchange flow in the strait, the generation of internal waves, meandering of the Atlantic jet, and the generation of coastal-trapped waves. Some of these features are already well known, but others such as the jet meandering have received little attention.

Abstract We present the GFDL‐CM4X (Geophysical Fluid Dynamics Laboratory Climate Model version 4X) coupled climate model hierarchy. The primary application for CM4X is to investigate ocean and sea ice physics as part of a realistic coupled Earth climate model. CM4X utilizes an updated MOM6 (Modular Ocean Model version 6) ocean physics package relative to CM4.0, and there are two members of the hierarchy: one that uses a horizontal grid spacing of (referred to as CM4X‐p25) and the other that uses a grid (CM4X‐p125). CM4X also refines its atmospheric grid from the nominally 100 km (cubed sphere C96) of CM4.0–50 km (C192). Finally, CM4X simplifies the land model to allow for a more focused study of the role of ocean changes to global mean climate. CM4X‐p125 reaches a global ocean area mean heat flux imbalance of within years in a pre‐industrial simulation, and retains that thermally equilibrated state over the subsequent centuries. This 1850 thermal equilibrium is characterized by roughly less ocean heat than present‐day, which corresponds to estimates for anthropogenic ocean heat uptake between 1870 and present‐day. CM4X‐p25 approaches its thermal equilibrium only after more than 1000 years, at which time its ocean has roughly more heat than its early 21st century ocean initial state. Furthermore, the root‐mean‐square sea surface temperature bias for historical simulations is roughly 20% smaller in CM4X‐p125 relative to CM4X‐p25 (and CM4.0). We offer the mesoscale dominance hypothesis for why CM4X‐p125 shows such favorable thermal equilibration properties.

Eutrophication poses a significant challenge in Indonesian waters, largely due to a lack of data for effective mitigation. This complex issue, characterized by a time lag and multi-phase progression, is triggered by an influx of nutrients like nitrate and phosphate, leading to harmful algal blooms (HABs) that degrade water quality. This study proposes a more comprehensive approach using the Trophic Index (TRIX), which integrates multiple parameters from the PISCES global biogeochemical model data. The PISCES model accurately captures seasonal TRIX trends, with high values in the southern islands during the southeast monsoon and in northern areas during the northwest monsoon. The model's reliability is confirmed by RMSE and Bias data to be quite low, respectively, for Chl-a (0.065, -0.005), Nitrate (0.144, -0.080), Phosphate (0.084, -0.059), and DO (3.109, 0.919), from the World Ocean Database. The highest TRIX values (8-10) were found in Jakarta Bay, while the Lombok Strait had values (5-7), a difference attributed to varying oceanographic conditions. However, it is crucial to consider physical oceanography and boundary conditions when using the TRIX model. So then, model TRIX data is more valuable for informing policy and mitigation plans for the various Indonesian waters, taking into account their unique characteristics. These findings underscore the importance of considering both monsoon cycles and local conditions when assessing eutrophication risk. The TRIX data is therefore a valuable tool for developing informed policies and mitigation plans for Indonesia's diverse coastal areas.

This study investigates soliton solutions and dynamic wave structures in the complex Ginzburg-Landau (CGL) equation, which is crucial for understanding wave propagation in various physical systems. We employ three analytical methods: the Kumar-Malik method, the generalized Arnous method, and the energy balance method to derive novel closed-form solutions. These solutions exhibit diverse solitonic phenomena, including multi-wave solitons, complex solitons, singular solitons, periodic oscillating waves, dark-wave, and bright-wave profiles. Our results reveal new families of exact solitary waves via the generalized Arnous method and diverse soliton solutions through the Kumar-Malik method, including hyperbolic, trigonometric, and Jacobi elliptic functions. Verification is ensured through back-substitution to the considered model using Mathematica software. Additionally, we plot the various graphs with the appropriate parametric values under the influence of the M-truncated fractional derivative to visualize the solution behaviors with varying parameter values. This research contributes significantly to understanding wave dynamics in physical oceanography, and the unique outcomes explored in this research will play a vital role for the forthcoming investigation of nonlinear equations.

Acoustic particle motion is the primary cue for fish hearing and a vector quantity that contains polarization information (including directionality) relevant to the directional hearing abilities of fishes. Polarization metrics, including ellipse orientation angle, ellipticity angle, and degree of polarization, have been recently applied to describe particle motion polarization in physical acoustical oceanography studies and have yet to be applied to in situ biological signals. This study harnessed data from a compact orthogonal hydrophone array deployed on the seafloor offshore of Florida (part of the Atlantic Deepwater Ecosystem Observatory Network) to investigate particle motion polarization properties of unidentified acoustic fish signals relative to ambient and ship noise. These properties described bivariate particle motion in a vertical plane formed by a source-receiver axis and orthogonal vertical axis. Particle motion of fish signals had more horizontal orientation than ambient noise and ship noise at the closest point of approach, which were more vertically oriented. Fish signals had narrower (small ellipticity) and more temporally stable (high degree of polarization) particle motion ellipses than ship and ambient noise. Applications of this analysis framework to fish bioacoustics studies and relevance of polarization properties to fish directional hearing and sound localization capacity are discussed.

This investigation studies the newly created (3+1)-D Kadomtsev-Petviashvili-Sawada-Kotera-Ramani equation with the effect of the conformable fractional derivative. The modified extended direct algebraic approach is used to investigate novel solitons and various other exact solutions. Furthermore, several kinds of analytical solutions are created, including bright, dark, and singular solitons. Additionally, singular periodic, hyperbolic solutions, Weierstrass elliptic doubly periodic solutions, and exponential solutions are derived. This study provides a framework for explaining various nonlinear phenomena that emerge in a variety of scientific fields, including fluid mechanics, ocean physics, and marine physics. Different types of acquired solutions are visually displayed to assist them with a physical understanding of the results in the sense of the conformable fractional derivative. Our findings shed light on the intricate dynamics of fluid waves and give vital new insights into the behavior of traveling waves and their many forms.

Erratum to: Double Anniversary: Sixtieth Anniversary of the Journal Atmospheric and Oceanic Physics and the Ninetieth Anniversary of Academician G.S. Golitsyn

Marine heatwaves are increasing in frequency, intensity, and duration as a result of climate change, and their biological impacts can in turn influence coastal communities. Despite advances in our knowledge of the physical drivers of marine heatwaves and their biological impacts, there has been limited work linking these extreme events to subsequent impacts on social systems. Describing risk to well-being in coastal communities from marine heatwaves requires the consideration of the severity of marine heatwaves, impacted systems, and social vulnerability. We compared potential risk to well-being, or quality of life, from 2012 to 2016 in coastal communities in the United States and Australia by considering marine heatwave total cumulative intensity, fishing dependence, and vulnerability indices. We extended a social indicators framework for the United States to develop vulnerability indices for coastal communities in Australia. Our approach revealed different spatial patterns in risk to well-being and its drivers between the two countries. Marine heatwaves as the hazard were a key driver of risk in both countries, and vulnerability for the United States and fishing employment for Australia were also influential. Our study demonstrates that risk does not necessarily equal the hazard, and there is non-transferability of risk results between countries despite similar physical oceanography and socioeconomic status. Identifying regions of high risk with our broad approach can help prioritize higher resolution community-level work to mitigate risk and develop adaptation pathways.

We utilize Surface Water and Ocean Topography (SWOT) satellite data to derive a complete longitudinal profile of water surface elevations for tidal waves and capture a tidal bore within the Bristol Channel and Severn River system, marking the first such observation from satellite data. We demonstrate that SWOT high-rate data is highly accurate, even in intertidal zones with significant wetting and drying and extreme tidal amplitude, emphasizing the importance of minimal data smoothing to preserve critical details. By examining the tidal bore and associated tidal waves over three days (April 19–21, 2023), we gain novel insights into tidal bore dynamics and tidal wave interactions with inland waters. SWOT’s high-resolution altimetry data bridges the coastal knowledge gap, enabling unprecedented integration of hydrology and physical oceanography. Tidal bores are crucial for ecological processes and hold cultural significance globally. Despite ongoing research, many hydrodynamic aspects of tidal bores remain unresolved, and our findings enhance the understanding of these phenomena.

Abstract. The Northwest Pacific is characterized by the presence of the warm and nutrient-depleted Kuroshio Current and the cold and nutrient-enriched Oyashio Current. In this region, surface primary production leads to increased nutrient consumption and CO2 exchange. The Yellow and East China Seas (YECS) are predominantly influenced by freshwater input. A high resolution regional numerical model tailored to the specific features of each area is required to reproduce the different characteristics of each region. Therefore, to accurately analyze the physical and biogeochemical system, this study developed a new coupled physical–biogeochemical model combining the three-dimensional Regional Ocean Modeling System (ROMS) and the Generic Ocean Turbulence Model Tracers of Phytoplankton with Allometric Zooplankton (TOPAZ) for the Northwest Pacific, including the YECS. The simulated physical and biogeochemical variables in the ROMS–TOPAZ (NPRT) were evaluated by comparing them with available observational data. NPRT successfully simulated the seasonal variability of chlorophyll and nutrients, capturing two peaks in spring and autumn that were not captured by the CMIP6 data. Particularly in the YECS, NPRT effectively represented the high phytoplankton biomass driven by the riverine effect, which is difficult to reproduce in global biogeochemical models with low-resolution. However, NPRT still exhibits significant biases in the subarctic region and marginal seas. To minimize the uncertainties in biogeochemical variables, it is necessary to refine the initial and boundary conditions, adjust parameters, and apply discharge forcing based on observational data. Despite these limitations, NPRT is an important tool for studying the interaction between ocean physics and biogeochemistry at a high resolution.

Sea Surface Salinity is a crucial climatic variable due to its twofold role as both a passive and an active tracer of oceanic processes. Despite its relevance, however, it could not be measured from space, mainly because of technological limitations, until 2009. Since then, the generation and assessment of satellite salinity has become a game-changer in physical and biogeochemical oceanography, as well as in climate science. Three satellite sensors with salinity-measuring capabilities (SMOS-Soil Moisture and Ocean Salinity, Aquarius, and SMAP-Soil Moisture Active Passive) have been launched in the previous decade, each characterized by specific measurement concepts and features and ad hoc validation approaches. The increasing usage of spaceborne salinity products has produced a variety of results and applications, which are here summarized under three specific domains: climate, scientific, and operational. Finally, short-to-mid-term perspectives, indicating both the expected improvements in terms of algorithms and also looking at novel mission concepts (that will provide continuation of these measurements in the decade to come) have been described.

Abstract This research article examines the influence of the local M-derivative on wave propagation in the fractional generalized (3+1)-dimensional P-type equation, a model with significant applications in plasma physics. The modified extended direct algebraic approach (MEDAA) is employed to derive a variety of exact solutions, including Jacobi elliptic function solutions, soliton solutions (bright, dark, and singular), Weierstrass elliptic function solutions, as well as hyperbolic, exponential, and singular periodic solutions. A comparative analysis with existing literature highlights the novelty and significance of the obtained wave solutions. Additionally, 3D, 2D, and contour plots are presented to visually illustrate the physical behavior of the extracted solutions. These solutions have a wide range of applications, including physics, engineering, plasma physics, ocean physics, nonlinear dynamics, and so on.

In marine ecosystems, cetaceans are large mobile predators that depend on maximizing foraging efficiency. Their presence within a habitat can therefore be strongly related to the modulation of local prey by oceanographic conditions. Understanding how cetaceans are impacted by prey responses to the physical environment is challenging due to the difficulty of collecting presence data of cetaceans and their prey over long, comparable time periods. We used passive and active acoustic recordings collected from moorings within the San Diego Trough, along with physical oceanographic sampling (i.e. in situ, satellite-derived, and ocean general circulation model measurements), to elucidate relationships between cetaceans, their prey, and the physical environment. Our results show that the predator-prey dynamics of some cetaceans within the San Diego Trough are influenced by seasonal changes in the physical oceanographic conditions and processes that shape their prey resources. Specifically, common dolphin Delphinus delphis foraging activity increased during conditions associated with increased presence of diel vertically migrating fish prey. Blue whale Balaenoptera musculus foraging-associated acoustic activity increased during periods with increased presence of mid-water crustacean zooplankton and was replaced with breeding-associated acoustic activity during conditions associated with the waning of mid-water crustacean zooplankton. Fin whale B. physalus foraging-associated calling activity was more complex to model, most likely because these animals have a generalist diet and occupy this area year-round. Our results highlight environmental conditions and features relevant to cetaceans inhabiting this region and may aid in developing better spatially explicit management actions.

Atmospheric interactions have led to a consistent rise in ocean temperatures in the Indonesian seas, exacerbated by the emergence of marine heatwaves (MHWs) that extend over thousands of kilometers. MHWs are defined as temperature anomalies above the 90th percentile of the sea surface temperature (SST) baseline for at least five consecutive days. The Savu Sea, influenced by the Indonesian throughflow that transports warm water from the Pacific to the Indian Ocean, experiences significant temperature anomalies. This study employs OSTIA L4 Marine Copernicus Global Ocean Physics Reanalysis SST data from 1982 to 2021 to analyze the frequency, duration, and intensity of MHW events in this region. Using Hobday's hierarchical approach, the study finds that MHWs in the Savu Sea lasted up to 1,170 days over 40 years, with 117 recorded events. The worst MHW event occurred in 2016, lasting 194 days with a maximum cumulative intensity of 2.0°C/year, particularly affecting the northern Savu Sea. These heatwaves significantly impact marine ecosystems, leading to coral bleaching that affects about 50% of coral colonies and threatens marine biodiversity and fisheries recovery.

The concept of a long-term (20-30 year) systematic, international effort to map the entire world seafloor from beach to trench (GOMaP = Global Ocean Mapping Program) has been developing at a series of informal and formal meetings over the last 2 years. The goal of GOMaP is to systematically map the ocean floors with at least 100 per cent coverage sidescan and swath bathymetry, and to perform whatever other data collection could be carried out simultaneously (e.g., subbot­tom profiling, magnetics, gravity, physical oceanography and meteorology). Minimum standards for data accuracy, pixel navigation, and resolution have been recommended. Spatial resolutions for GOMaP sidescan sonar imagery should be 100 m or better in the deep sea. This is comparable to what has been achieved by the Shuttle Imaging Radar over the terrestrial earth, the MAGELLAN radar mapping of Venus, the MARS GLOBAL SURVEYOR and other probes on Mars, and the GALILEO mis­sion to the moons of Jupiter. Although spatial resolution for swath bathymetry is slightly less than for sidescan, the resolution of both systems improves sharply with decreasing water depths, particularly for the 10 per cent of the world ocean less than 500 m deep. The decrease of swath width with water depth implies that over 600 ship years are required to map waters 25-500 m deep, compared to just approximately 200 ship years for the deep ocean (500 m and greater). Better pixel navigation accuracy suggests hull-mounted systems (9-16 kHz for deep water, and 30 kHz or higher for shelf waters) may be superior to towed systems, although improvements in towed system navigation instrumentation and techniques may mitigate this difference in the future. Seafloor mapping with air-deployed hyper- spectral and laser bathymetric scanning may be required to replace or supplement shipborne mapping in clear waters less than 50 m deep.

Abstract Marine mesoscale eddies are a common marine ocean phenomenon and they can affect the heat, salinity and water currents in the ocean. Identifying mesoscale eddies can play an important role in shipping, military, and ocean resource development. Compared to traditional recognition algorithms, artificial intelligence methods can identify mesoscale eddies more accurately and efficiently, but they lack physical interpretability due to their training process are driven by data. In this paper, an intelligent detection algorithm with physical constraints was used to realize identification of mesoscale eddies. Firstly, the mesoscale eddy dataset was built from the global ocean physics reanalysis data provided by the Copernicus Marine Environment Monitoring Service (CMEMS), and the PET method was applied to generate labels for the dataset which would be used in intelligent models. Then, the classic EddyNet model was realized and an attention mechanism was added to optimize model performance. Finally, a physical constraint was introduced to make the model more consistent with the physical characteristics of mesoscale eddies: the divergence of the vorticity field was added into the total loss function of the optimized model. By introducing 30% physical constraint weights in the model, the accuracy can be improved from 92.68% to 93.57%. The result illustrated that combining data and physical constraints significantly improves the ability of artificial intelligence methods to recognize mesoscale eddies.

Abstract During summer, the southern South China Sea (SCS) is continuously freshened by the propagation of an anticyclonic gyre driven by monsoon, which transports low‐salinity water from the Gulf of Thailand and Karimata Strait. This study examines the propagation, structure, and dynamics of summer SCS surface salinity and its response to the monsoon variability. Analysis using Global Ocean Physics Reanalysis product and salinity budget indicates that advection from the Gulf of Thailand serves as the primary source of low‐salinity water, whereas transport from the Karimata Strait plays a secondary role. The summer surface salinity in the SCS experiences significant interannual changes driven by the summer monsoon associated with the El Niño‐Southern Oscillation. Strong summer monsoons during the developing phase of El Niño reduce salinity in the interior region of the southern SCS (SSCS) but create high‐salinity regions off the Vietnamese coast (∼11–15˚N); the former is caused by the increased influx of low‐salinity water into the interior region of the SSCS along an anticyclonic pathway, whereas the latter results from a combined effect of enhanced Ekman suction and reduced horizontal advection. In contrast, weak summer monsoons during the decaying phase of El Niño disrupt the low‐salinity anticyclonic pathway, increasing salinity in the interior region of the SSCS and forming a low‐salinity tongue along the Vietnamese coast.