Abstract: Abstract Microplastic pollution significantly threatens global marine ecosystems. Barnacles, important invertebrates that are critical to marine systems, may be more susceptible to microplastic pollution due to their stationary lifestyle. However, no studies have documented the presence of microplastics in deep-sea barnacles from the Indonesian Throughflow region. This study evaluates microplastic pollution in deep-sea barnacles at two mooring buoys located in the northern Maluku Sea and the southwestern Philippine Sea at a depth of 200 m. The following year of deployment, the barnacles were collected and analyzed for microplastic ingestion. The research indicated that nearly one-third of the deep-sea barnacles ingested microplastic particles and microscopic fibers, matching contamination levels found in surface and subsurface waters from a previous study in nearby areas. The identified microplastics are linked to sea activities and transboundary microplastics, likely from abandoned fishing gear, with nylon as the most prevalent polymer in the microfiber particles, followed by polyvinylidene fluoride and polyamide. This study emphasized the need for further research to understand the impact of microplastic ingestion on deep-sea barnacles and other organisms in these unique ecosystems, highlighting the importance of areas crucial for global ocean circulation.

Abstract: This study examines the impact of the maximum density property on the instability of thermal convection in a vertical Brinkman layer under uniform horizontal throughflow. Deviating from the classical Boussinesq approximation, the density relationship is modified to a quadratic polynomial. The Navier–Stokes equations are converted to the Orr–Sommerfeld eigenvalue problem by linear stability analysis and solved numerically by the Chebyshev collocation method. The results show that the maximum density effect will cause the buoyancy to reverse, counteract some disturbances, and enhance the stability of the system. Moreover, the presence of throughflow has a significant impact on the basic state and instability. At low Pe, increasing throughflow enhances stability; however, beyond a critical range, further increase in Pe amplifies inertial effects and vertical temperature non-uniformity, which destabilize the stability. Meanwhile, PrD also has dual effect on system stability, with low PrD promoting instability and high PrD enhancing viscous diffusion to suppress instability. Particularly, the pure and modified quadratic density models exhibit similar stability behavior in certain regions.

Abstract: ABSTRACT This study presents a comprehensive linear stability analysis of dual‐diffusivity convection in a bidispersive porous medium, embedding a uniform vertical throughflow and variable gravity within the framework of the Darcy–Brinkman model. Three distinct gravity variation profiles—linear, parabolic, and exponential—are systematically examined to understand their impact on convective stability. A high‐order Galerkin approximation is utilized to obtain solutions to the governing eigenvalue problem. The critical Darcy–Rayleigh number is evaluated as a function of key nondimensional parameters, including the Péclet number, gravity modulation parameter, solute Rayleigh number, permeability ratio, Lewis number, Darcy number, and the interphase momentum transfer parameter. Special attention is given to the role of throughflow direction and magnitude, with both upward and downward flows analyzed across varying gravity fields. The results indicate that exponential gravity variation markedly enhances system stability through intensified gravitational stratification, while higher permeability ratios and stronger interphase momentum transfer further stabilize the system by increasing viscous dissipation and drag coupling. A U‐shaped, nonmonotonic variation of the critical Rayleigh number with the throughflow parameter is observed, demonstrating the destabilizing role of moderate throughflows and the stabilizing influence of strong throughflows. Overall, the findings provide key insights into the complex interplay of hydrodynamic and buoyancy‐driven mechanisms in bidispersive porous systems, with implications for thermal management, geophysical flows, and engineered porous structures. The findings provide practical insights for optimizing geothermal reservoirs, chemical reactors, and environmental systems by controlling throughflow, interporosity exchange, and gravity variations to enhance stability and transport efficiency.

Abstract: Abstract Tridacna (giant clam) shell δ 18 O (δ 18 O Ts ) is a powerful proxy for reconstructing seasonal to interannual environmental changes before the Instrumental Era. However, the environmental controls on δ 18 O Ts in regions with significant hydrological changes are still ambiguous, and its potential for reconstructing large‐scale circulation variation has not been fully exploited. Here we present a 43‐year monthly resolution δ 18 O record of a modern Tridacna shell from the southern Timor Sea, and examined the linkages between the δ 18 O Ts and environmental parameters. The results indicate that annual δ 18 O Ts primally traces sea surface salinity variations associated with the Indonesian Throughflow (ITF). On interannual timescales, ENSO primally modulates ITF variation by altering the pressure gradient between the Western Pacific and Eastern Indian Ocean, which can be recorded in δ 18 O Ts . On decadal timescales, Pacific decadal oscillation primarily regulates the decadal variation of δ 18 O Ts by changing the ITF transport volume. Furthermore, the influence of the enhanced Walker Circulation from 1984 to 2013 on ITF transport is also imprinted in the δ 18 O Ts . Our study suggests that the δ 18 O Ts , from the areas where ITF flows, has the potential for recording past hydrological changes caused by the ITF variations.

Abstract: The Indonesian Throughflow (ITF) carries an annual average of about 15 Sv of water from the Pacific through the Indonesian Seas Into the Indian Ocean, and its year-to-year variation ranges from 1 to 4 Sv. A 10-member ensemble of 41-year integrations of a semi-global eddy-resolving oceanic general circulation model is examined to explore the intrinsic (chaotic) variability of the ITF transport and associated flow. It is found that the annual-mean ITF transport is different by about 1 Sv between the ensemble members at several years. The characteristic vertical and horizontal structures of the ensemble anomaly (deviation from the ensemble average) are described. These structures and the basin-scale spread of the anomaly suggest that the intrinsic variability of the ITF is a genuine increase or decrease of the classical ITF rather than variability due to local eddies or nonlinear currents within the Indonesian Seas. The lagged correlation of the intrinsic component of the ITF transport with sea-surface height and barotropic streamfunction suggests that the intrinsic variability may come from zonal jets in the western subtropical North Pacific.

Abstract: Abstract Next-generation aircraft with boundary layer ingesting (BLI) engines can reduce fuel consumption but pose challenges for fan and compressor operation due to inlet distortion. To optimize the design of such engines, it is essential to assess the impact of non-uniform inlet flow on stability and performance, with the final result of a distortion-tolerant machine. One of the first steps in this process is estimating the aerodynamic performance using fast but reliable mathematical models. This paper presents an extension of the existing throughflow solver that predicts the effects of the upstream distortion. The proposed method, based on the parallel compressor theory, introduces multiple planes to accurately define and track the circumferential distribution of parameters as they advance through the machine. It applies to all types of distortion: total pressure, total temperature, and swirl. The model is demonstrated for a high-pressure, low hub-to-tip diameter ratio fan with nonuniform total pressure at the inlet. Flow physics associated with distortion is analyzed using results from full annulus unsteady RANS simulations for three operating points: near stall, design, and near choke. The flow field results are compared with the CFD data at the design point. The overall performance is evaluated against a clean inlet case.

Abstract: Abstract Next-generation aircraft with boundary layer ingesting (BLI) engines can reduce fuel consumption but pose challenges for fan and compressor operation due to inlet distortion. To optimize the design of such engines, it is essential to assess the impact of nonuniform inlet flow on stability and performance, with the final result of a distortion-tolerant machine. One of the first steps in this process is estimating the aerodynamic performance using fast but reliable mathematical models. This paper presents an extension of the existing throughflow solver that predicts the effects of the upstream distortion. The proposed method, based on the parallel compressor theory, introduces multiple planes to accurately define and track the circumferential distribution of parameters as they advance through the machine. It applies to all types of distortion: total pressure, total temperature, and swirl. The model is demonstrated for a high-pressure, low hub-to-tip diameter ratio fan with nonuniform total pressure at the inlet. Flow physics associated with distortion is analyzed using results from full annulus unsteady RANS simulations for three operating points: near stall, design, and near choke. The flow field results are compared with the CFD data at the design point. The overall performance is evaluated against a clean inlet case.

Abstract: Modern compressors evolve toward higher-loading and lower-aspect-ratio designs, significantly amplifying the impact of secondary flows on flow deviation angles. However, existing secondary flow deviation models struggle to mechanistically resolve corner flow physics, which is the primary contributor to this deviation. This study develops a physics-based secondary flow deviation model for throughflow analysis that explicitly predicts both the magnitude and spanwise distribution by rigorously accounting for corner flow mechanisms. The new model decouples secondary flow deviation into two physically distinct components: (1) corner vortex-induced and (2) end wall boundary layer (EWBL) induced deviations. Each component is characterized through dedicated momentum-based submodels that respectively describe corner vortex evolution dynamics and EWBL migration processes. Comprehensive validation using numerical and experimental data from subsonic linear cascades demonstrates an over 70% reduction in root mean square error (RMSE) compared to the conventional approach. Moreover, the model successfully captures abrupt deviation increases during corner separation-to-stall transitions and reveals complex interactions between hub and shroud corner flows. This work establishes a fundamentally sound framework for secondary flow deviation prediction, substantially improving throughflow analysis accuracy in challenging corner flow regimes and providing reliable insights for preliminary compressor design optimization.

Abstract: The nonlinear stability of two-dimensional (2-D) plane Couette flow subject to a constant throughflow is analysed at finite and asymptotically large Reynolds numbers $\textit {Re}$ . The speed of this throughflow is quantified by the non-dimensional throughflow number $\eta$ . The base flow exhibits a linear instability provided $\eta \gtrsim 3.35$ , with multi-deck upper and lower branch structures developing in the limit $1\ll \eta \ll \mathit {O}(\textit {Re})$ . This instability provides a springboard for the computation of nonlinear travelling waves which bifurcate subcritically from the linear neutral curve, allowing us to map out a neutral surface at different values of $\eta$ . Using strongly nonlinear critical layer theory, we investigate the waves that bifurcate from the upper branch at asymptotically large $\textit {Re}$ . This asymptotic structure exists provided the throughflow number is larger than the critical value of $\eta _c\approx 1.20$ and is shown to give quantitatively similar results to the numerical solutions at Reynolds numbers of $\mathit {O}(10^5)$ .

Abstract: Abstract The nature and cause(s) of the Mid‐Pleistocene Transition (MPT) remain enigmatic. Notably, the role of tropical Pacific oceanographic changes during the late MPT (∼0.9–0.6 Ma) remains understudied. Here, we generated ∼1.4‐Myr‐long Mg/Ca and δ 18 O records for the planktonic foraminifer Trilobatus sacculifer from IODP Site U1490 to reconstruct sea‐surface temperature and regional seawater δ 18 O (ice‐volume‐corrected, a proxy for salinity) variation in the Western Pacific Warm Pool (WPWP). We find that the WPWP was characterized by a gradual warming and slight freshening of surface waters at ∼0.9–0.6 Ma, caused by the Indonesian Throughflow weakening and consequent accumulation of oceanic heat. These effects were likely driven by sea‐level fall due to global icesheet expansion and/or Australian monsoonal intensification. The gradual warming signal was subsequently propagated eastward via strengthened North Equatorial Countercurrent, which may have acted as a positive climatic feedback, contributing to the expansion of the North American icesheet during the late MPT.

Abstract: Abstract As a crucial component of global ocean circulation, the Indonesian Throughflow (ITF) is modulated by the El Niño‐Southern Oscillation. While multi‐year La Niña events often greatly enhance the volume transport of the ITF, the 2020–2023 La Niña caused only a modest increase in the ITF via Makassar Strait—0.3 Sv above the climatology of 12 Sv. Dominated by the 0–400 m velocity variations, the relatively weak transport is attributed to a milder Pacific easterly wind due to a weaker La Niña intensity. The strong negative Indian Ocean Dipole accompanying the third‐year La Niña induced the intensifying westerlies and anomalously elevated sea level over the eastern Indian Ocean during 2020–2023. Model experiments show that the Indian Ocean wind reduced the Pacific‐originated ITF inflow variability by 51% in 2020–2023. With the increasing frequency of multi‐year La Niña events, this study highlights the influence of Indian Ocean wind‐driven dynamics in modulating the ITF transport.

Abstract: This study aims to investigate the strength of the Indonesian Throughflow (ITF) during the Last Glacial Maximum (LGM) in comparison to the Pre-Industrial (PI) at the Makassar Strait, the Molucca Sea, and the Banda Sea, representing the pathways of the ITF. The analysis was performed based on the temperature distribution of the south (S) and north (N) thermocline gradients. Temperature data were obtained from the simulation of the Climate Community System Model, version 4 (CCSM4). The depth of the thermocline layer during the LGM and the PI period exhibits seasonal variability across the S-N stations. At Station 1, 2, and 3, the thermocline depth during the LGM ranges from 49 - 218 m (51 - 251 m), 55 - 250 m (69 - 254 m), and 48 - 238 m (48 - 218 m) in the south (north), respectively. The analysis of seasonal temperature variations in the thermocline layer in the three locations indicates that the ITF was significantly weakened both during the LGM and PI, indicated by the negative S-N Thermocline Water Temperature (TWT) gradient. The result suggests the southern part of each station is predominantly fresher compared to the northern part during these times. Additionally, it implies that the ITF is more robust in the eastern region (Banda Sea) during the LGM compared to the PI. This variation may relate to the intensity of seasonal local winds, mixing processes, and the remote influence of El Niño-like events, which could affect water transport along the pathway of the ITF.

Abstract: Abstract Next-generation aero-engine compressors will operate with overall pressure ratios exceeding 70:1. This will require shorter compressor blades, presenting a challenge to the designer when predicting tip clearance and efficiency. Buoyancy-induced flow within co-rotating compressor discs drives the heat transfer that determines rotor expansion and the resulting blade-tip clearance. This inherently unstable flow is influenced by the radial temperature distribution of the discs, rotational speed, as well as enthalpy and momentum exchange with an axial throughflow of cooled air at low radius. Due to the rotation of the engine compressor, this throughflow may become swirled, altering the temperature, mass exchange and swirl within the rotating cavity. The University of Bath Compressor Cavity Rig has been adapted to introduce pre-swirl into the axial throughflow by passing it through rotating holes. The effects of inlet swirl have been characterised in terms of Rossby and Reynolds numbers. Measurements of disc temperature, shroud heat flux and unsteady pressure in the rotating frame of reference are used to quantify the effects of ingestion (entrainment) of fluid into the cavity. The unsteady dynamics and rotation of the core relative to the disc have been measured in both the stationary and rotating frames of reference with consistent results. A single correlation between shroud Nusselt and Grashof numbers has been established, effectively capturing the impact of swirl, Rossby number and free convection.

Abstract: The Earth’s climate has many rhythms and pulses and behaves differently on longer and shorter scales depending on the changing boundary conditions. Contrasting climatic shifts on short time scales often characterise the long-term mean state of the Climate. The Tropical Pacific Mean State climate has been alternatively dominated by El Niño-like and La Niña-like conditions. Long-term El Niño-like conditions have been termed permanent El Niño, El Niño State, or El Padre (EP), spanning several thousand years. The Western Pacific Warm Pool (WPWP) responds to EP conditions by changing upper ocean hydrography. We used depth-stratified planktic foraminiferal relative abundance to characterise the changing hydrography of the WPWP over the last 6 million years and its impact on the variability of the strength of the Leeuwin Current (LC) in the Eastern Indian Ocean, which the WPWP influences via the Indonesian throughflow (ITF). Six EP events centred around 6.2-6.0 Ma, 3.6 Ma, 2.8 Ma, 2.3-2.3 Ma, 1.8 Ma and 0.4 Ma have been detected. These EP events are bridged by La Niña State-1 (6.0-4.2 Ma), La Niña State-2 (3.0 Ma), La Niña State-3 (2.6-2.0 Ma) and La Niña State-4 (1.4-1.0 Ma) events. The effect of the EP event in the Eastern Indian Ocean has been transmitted through the ITF, affecting the strength of the LC. The most influential EP events affecting the Eastern Indian Ocean have been EP-3, EP-4, EP-5 and EP-6. In general, the Eastern Indian Ocean responds to the EP events with a general reduction in the strength of the LC.

Abstract: Abstract Surface and intermediate waters flow from the Pacific to the Indian Ocean as part of the global thermohaline circulation, connected through the Indonesian Throughflow (ITF) and Tasman Leakage (TL). Modern TL likely began in the Late Miocene, but its dynamics in response to astronomical climate forcing remain unclear. To reconstruct TL history, we present new fish‐teeth neodymium (Nd) and benthic‐foraminifera δ 13 C and δ 18 O data from Ocean Drilling Program Site 752 (Broken Ridge, Indian Ocean). During the Middle Miocene, Nd‐isotopes indicate a Pacific influence on intermediate waters at Broken Ridge, likely via Indonesian Intermediate Waters from the ITF. In the Late Miocene, Antarctic Intermediate Waters (AAIW) invigorated, shifting Nd‐isotopes toward less radiogenic values. At 5.5 Ma, TL became established, restoring Pacific control over Broken Ridge waters, now sourced south of Australia. Consequently, Site 752 δ 13 C diverges from AAIW‐influenced sites at this time. An East‐West δ 13 C gradient between Sites 752 and U1506 (Lord Howe Rise) reveals ephemeral proto‐TL before 5.5 Ma, solely active during eccentricity maxima: Warmer climates and a southward‐shifted Subtropical Front (STF) allowed proto‐TL to flow westward through an open‐bottleneck configuration, with Australia in the north and the STF in the south. During eccentricity minima, the bottleneck closed, leaving Broken Ridge influenced by AAIW. After 5.5 Ma, the δ 13 C gradient loses its eccentricity modulation as the bottleneck remains constantly open, as Australia moved tectonically further north. Our findings highlight the role of orbital eccentricity in shaping Indian Ocean water‐mass exchange and reveal the dynamics of TL over astronomical timescales.

Abstract: Concentration-based internal heat sources significantly influence the stability of micropolar fluid flow, playing a vital role in biomedical engineering by accounting for metabolic heat in drug delivery and tissue engineering and in chemical reactors and polymer processing by preventing thermal instability due to exothermic reactions or ion gradients. This article analyzes the stability of a micropolar fluid-saturated porous layer with a concentration-based internal heat source and vertical throughflow. Linear stability is assessed using the normal mode technique, while nonlinear stability is investigated through an energy method. Numerical solutions are obtained using MATLAB's bvp4c routine. The effects of vertical throughflow direction (Péclet number, Pe) and parameters, such as the Darcy number (Da), Lewis number (Le), micropolar parameter (m2), coupling number (N1), and solutal Rayleigh number (Rs), are examined. A comparison of linear and nonlinear thresholds identifies regions of subcritical instability. The study reveals that the internal heat source enhances stability during upward throughflow but promotes instability during downward throughflow. Additionally, at high Péclet numbers, its effect on downward flow becomes negligible.

Abstract: Abstract This paper presents a gas turbine performance model based on streamline curvature analysis for axial flow turbomachinery. Unlike those traditional gas-turbine (GT) simulation programs used in the turbomachinery community, the present program is able to model whole GT performance at the design point and off design points where the performances of a compressor and a turbine are directly predicted using the throughflow (TF) models on the meridional plane. This feature is particularly attractive in managing secondary-air-system (SAS) for a high technology aero or industrial engine where the SAS between a compressor and a turbine is directly connected using the localized pressure and temperature predicted by the TF models, thereby ensuring more accurate predictions of the source and sink pressure driven flows. An additional benefit is the more accurate prediction in mixing between the SAS flow and the primary flow. Combustion was simplified using a relatively simple model where the combustion efficiency is derived from the combustor loading factor while the pressure loss includes the contributions from cold and hot parts. The TF treatment of component performances including a compressor and a turbine makes it feasible to remove the need for pre-generated component maps. Other advantages of this method are that the pressure loss coefficients and deviation angles in each blade row can now be easily adjusted in the TF models to match the CFD prediction or test data, thereby enabling the performance predictions to be more representative and physically meaningful to the real engine. The model can also provide the functionality of the digit-twin of a real gas turbine to simulate a virtual test, healthy operation status and performance of gas turbine. The developed program was used to predict performance at different operating conditions including part-load and part-speed. The validation of the code has been carried out using the test data at the design point (DP) and off-design-point (ODP) conditions of a production engine, indicating that a good agreement is achieved between the predictions and the test data.

Abstract: The Maritime Continent (MC) plays a critical role in regulating global atmospheric and oceanic circulation. This study explores the impact of MC topography on both regional and remote climate under preindustrial (PI) and mid-Pliocene warm period (mPWP) conditions using a lately tuned version of the HadCM3 climate model. Simulations are conducted by varying the topography of the northern MC (MCn) and southern MC (MCs), following the Pliocene Model Intercomparison Project (PlioMIP) Phase 2 experimental framework.Results indicate that changes in the MCn topography during the mPWP, compared to PI conditions, lead to cooling in the northwestern Pacific, while variations of the MCs results in cooling over the eastern Indian Ocean. The MC topography variation has a large impact on the net hydrological flux (precipitation minus evaporation) over the MC and Indian Ocean, with both MCn and MCs leading to a decrease near the Timor passage region and an increase over the northern Indian Ocean. Compared to the PI, there is a westward movement of the Walker Circulation in the mPWP, and the MCs topography contributes to this westward movement. Although MC topographical changes have a limited effect on the total volume transport of the Indonesian Throughflow (ITF), variations in MCs topography substantially affect the ITF structure above 200 meters, and variations in MCn topography affect the ITF structure at depths around 1000 meters.While the overall contribution of MC topography to global temperature changes is relatively small compared to the combination of other mPWP boundary conditions (CO2, ice sheets, soil, vegetation, lakes, and changes in topography of other regions), it plays a critical role in shaping the ITF and influencing both local and remote climate systems.

Abstract: Abstract Reanalysis data reveals that the South China Sea (SCS) experiences intensified subsurface marine heatwaves (MHWs) and marine cold spells (MCSs) near the thermocline. On the interannual scale, surface and subsurface events demonstrate an opposite correlation with ENSO, primarily due to distinct drivers at different depths. During the developing phase of El Niño, the Luzon Strait transport, indicative of the SCS throughflow (SCSTF), increases and necessitates stronger upwelling for mass balance. This upwelling, acting on large subsurface vertical temperature gradients, induces significant subsurface cooling and the occurrence of MCSs. As El Niño matures, excessive atmospheric heat flux warms the surface layer, triggering surface MHWs. This heat is then transported downward mainly by vertical turbulent mixing, diminishing subsurface cooling, and terminating subsurface MCSs. The scenario reverses during La Niña events. The SCSTF serves as a vital oceanic pathway, transmitting ENSO signals into the SCS and profoundly modulating subsurface MHWs and MCSs.

Abstract: The Indonesian Throughflow (ITF) represents the sole tropical pathway connecting Pacific and Indian Oceans, yet quantitative understanding of climate mode influences on its variability remains incomplete. We applied information-theoretic and topological frameworks to analyze 34 years (1984-2017) of observational ITF transport data alongside ENSO and IOD indices. Bootstrap analysis revealed pronounced ITF seasonality with 13.28 Sv amplitude peaking in September, contrasting with negligible climate index annual cycles, indicating scale separation in forcing mechanisms. Multi-method extrema detection identified 36-41 extreme events per variable, with 23.1% coincidence between ENSO and IOD high extrema confirming known co-occurrence patterns. Ensemble information-theoretic metrics demonstrated ENSO exerts moderately stronger influence on ITF (mean score 0.524) compared to IOD (0.500), with component-specific optimal lag relationships ranging 4-9 months. Transfer entropy quantified directional information flow with causality ratios of 0.528-0.571. Topological analysis through persistent homology identified stable second homology features (7-11 voids) across climate states, suggesting robust dynamical constraints. Two regime shifts were detected with 100% accuracy and 2.3-month average lead time during near-neutral climate conditions. Extended predictive lead times (22-33 months) indicate gradual phase space reorganization preceding transport anomalies. These findings show that nonlinear analytical frameworks can reveal climate-ocean coupling mechanisms, which are hard to detect using traditional approaches, with implications for improving ITF projections under changing climate.

Abstract: The stability of buoyancy-driven convection in a viscoelastic fluid saturating a vertical porous layer under the influence of a horizontal throughflow is studied. The viscoelastic behaviour is displayed by means of the Oldroyd-B type fluid, and its flow is represented through a suitable extension of Darcy's Law. The basic velocity and temperature fields turn out to be independent of viscoelastic rheology but are significantly influenced by throughflow. A linear stability analysis leads to a differential eigenvalue problem, which is numerically solved to obtain the neutral stability curves and the critical Darcy–Rayleigh number marking the onset of instability. The transition to instability is governed by the Péclet number and viscoelastic parameters, both of which influence the position of the neutral stability curve and the critical Darcy–Rayleigh number. The elasticity of the fluid primarily drives instability, with stress relaxation and strain retardation parameters exerting opposing effects. Though throughflow by itself does not render the system unstable, it profoundly influences the onset of instability once it arises—regardless of direction—by inducing both stabilizing and destabilizing effects.

Abstract: The flow and heat transfer in a rotating disk cavity with dual axial inlets are investigated under a range of operating conditions. A full 360° computational fluid dynamics model is employed, with 40 simulation cases varying the rotational Reynolds number (Reω= 1.9 × 106–3.1 × 106) and axial throughflow Reynolds number (Rez = 7.3 × 105–1.2 × 106). The results show that elevated rotation intensifies turbulent mixing and significantly enhances convective cooling on the upstream disk, whereas increasing throughflow improves heat transfer on the downstream disk by promoting deeper coolant penetration. However, an excessive axial flow rate can induce local thermal stratification near the upstream disk, which offsets its heat transfer gains, and strong rotation diminishes the marginal benefits of higher throughflow on downstream cooling. Overall, the study reveals distinct cooling behaviors on the upstream and downstream disk surfaces governed by the interplay between rotation and throughflow. These findings provide insight into optimizing dual-inlet cavity designs and underscore the importance of balancing rotational speed and coolant flow distribution for effective thermal management in gas turbine disk cavities.

Abstract: The transformation of water masses along the Indonesian Throughflow (ITF) pathway is evident from the disappearance of Western North Pacific Water (WNPW) south of the Makassar Strait, despite its prior presence in the Sulawesi Sea. One of the primary mechanisms driving this transformation is vertical mixing. This study investigates the characteristics of vertical mixing along the Sulawesi Sea–Makassar Strait route during the second transition season (September–November), using vertical diffusivity (Kz) as a key indicator. The temperature, density, and current velocity data were obtained from the Transport, Internal Waves, and Mixing in the Indonesian Throughflow Regions (TIMIT) cruise in October 2015. The results show spatial variability of vertical mixing both horizontally and vertically. Horizontally, the strongest vertical mixing was observed in the Makassar Strait (Kz = 8.5 × 10−3 m2 /s and Ri = 2.0−2.2), consistent with values reported for the first transition season but exceeding those typical of the southeast monsoon. Vertically, mixing was most intense in the deep layer (Kz = 9.2 × 10−3 m2/s), followed by the homogeneous layer (Kz = 3.9 × 10−3 m2/s), while the weakest is in the thermocline layer (Kz = 1.2 × 10−3 m2/s). These patterns are influenced by the complex interaction of current dynamics and bathymetric features such as sills. The findings highlight the southern Makassar Strait (Transect 4) as a hotspot of vertical mixing and water mass transformation, playing a critical role in shaping ITF structure and the downstream transport of thermohaline properties.

Abstract: The Canadian Arctic Archipelago (CAA) serves as a major conduit between the Arctic Ocean and the North Atlantic. The Nansen Sound fiord system, which encapsulates Nansen Sound, Greely Fiord, Eureka Sound and several surrounding fiords, forms the northernmost oceanographic passageway through the CAA. Due to hostile ice conditions, the area has been understudied since the original oceanographic surveys were conducted in the 1960s and 1970s. The historic data highlighted a very weak signal of the relatively fresh Pacific-derived water (PW). Here, we present new oceanographic observations, including PW tracers, and contrast them against the historic data. Salinity profiles taken in 2024 show significant freshening as compared to 1976. This freshening is attributed to enhanced presence of PW in the area. We suggest that changes in the Arctic Oscillation impact the export gateways of PW from the Arctic Ocean, with the recent switch to a positive phase enhancing the outflow of cool and less saline PW through the CAA. Overall, this provides a first glimpse into variability of the freshwater flow through the straits of the northern CAA.

Abstract: Abstract The southeast Indian Ocean (SEIO) has witnessed amplifying variability in the 0–700 m heat content during the past decades. More heat pile‐up (HPU) events have been observed than before, leading to increased occurrence of marine heatwaves and threats to local marine ecosystems. Here, we show that most of these HPU events cooccur with multi‐year La Niña (MLN) conditions, and Pacific‐origin downwelling baroclinic waves play a key role in establishing the upper‐layer convergence of the SEIO. However, model experiments and budget analysis for the recent 2020–2023 event reveal that the extra heat in the SEIO is fueled mostly by the heat redistribution over the Indian Ocean, rather than by the Pacific via the Indonesian Throughflow (ITF). Climate models project more HPU events in the SEIO in future, partly associated with the increasing MLN events in a warming climate.