Search Results (9)

This study presents a global assessment of the climatological seasonal variability of river discharge into the oceans, based on an expanded dataset comprising 958 gauging stations across 136 countries. Monthly discharges were compiled for 145 major rivers and tributaries, with a focus on improving the accuracy and spatial coverage of global freshwater flux estimates. Compared to previous datasets, this updated compilation includes a broader set of rivers, explicitly integrates tributary inflows, and quantifies both the absolute and relative seasonal amplitudes of discharge variability. The results reveal substantial differences among ocean basins. The Atlantic Ocean, although receiving the highest total runoff, shows relatively weak seasonal variability, with a coefficient of variation of CV = 12.6% due to asynchronous peak discharge from its major rivers (Amazon, Congo, Orinoco). In contrast, the Indian Ocean exhibits the most pronounced seasonal cycle (CV = 88.3%), driven by monsoonal rivers. The Pacific Ocean shows intermediate variability (CV = 62.1%), influenced by a combination of monsoon rains and snowmelt. At the river scale, Orinoco and Changjiang display high seasonal amplitudes, exceeding 89% of their mean flows, whereas more stable regimes are found in equatorial and temperate rivers like the Amazon and Saint Lawrence. In addition, the critical role of tributaries in altering discharge magnitude and seasonal variability is well established. This study provides high-resolution monthly discharge climatologies at global and basin scales, enhancing freshwater forcing in OGCMs. By improving the representation of land–ocean exchanges, it enables more accurate simulations of salinity, circulation, biogeochemical cycles, and climate-sensitive processes in coastal and open-ocean regions. Full article

Background: The global number of operatively treated proximal femoral fractures is steadily growing, driven by the demographic shift toward an increasingly elderly, frail, and comorbid population. This clinical condition profoundly impacts not only patient health but also the finances of healthcare systems. The aim of this economic analysis was to investigate the impact on direct costs of orthogeriatric co-management (OGCM) compared to standard of care (SOC). Methods: A retrospective analysis was conducted investigating two comparable cohorts of patients aged 75 and above, originating from the exact same geographic area, who underwent surgical treatment for proximal femoral fractures in 2023. The two cohorts differed in their perioperative care protocols: one followed an OGCM (n = 143) protocol, while the other adhered to a SOC protocol (n = 141). Economic data were retrieved from the centralised finance department managing the two hospital sites under investigation. Results: The findings revealed that the OGCM protocol was associated with direct costs that were not higher (CHF 16,019 vs. CHF 16,713, p = 0.78) compared to SOC, despite higher daily costs in the OGCM cohort (CHF 2504 vs. CHF 2202, p < 0.0001). This difference was largely driven by a significantly shorter length of stay in the OGCM group (6 days vs. 7 days, p = 0.002). Conclusions: Optimising resource allocation through tailored geriatric care protocols suggests not only an improvement in clinical outcomes but also a reduction in economic burden, thereby alleviating pressure on the healthcare system. Full article

Oceanic general circulation models (OGCMs) are important tools used to investigate mechanisms for ocean climate variability and predict the ocean change in the future. However, in most current ocean models, the impact of sea surface waves as one of the most significant dynamic processes in the upper ocean is absent. In this study, the Stokes drift and the vertical mixing induced by nonbreaking surface waves derived from the wave model (WAVEWATCH III) are incorporated into a Climate System Ocean Model, and their effects on an ocean climate simulation are analyzed. Numerical experiments show that both physical processes can improve the simulation of sea surface temperature (SST) and mixed layer depth (MLD) in the Southern Hemisphere. The introduction of Stokes drift effectively reduces the subsurface warm bias in the equatorial tropics, which is caused by the weakening of vertical mixing in the equatorial region. The nonbreaking surface wave mainly reduces the temperature bias in the Southern Ocean by enhancing mixing in the upper ocean. For the MLD, the Stokes drift mainly improves the simulation of the winter MLD, and the nonbreaking surface wave improves the summer MLD. For MLD south of 40° S in summer, the introduction of nonbreaking surface waves resulted in a reduction of 11.86 m in MLD bias and 7.8 m in root mean square errors (RMSEs), respectively. For winter subtropical MLD in the Southern Hemisphere, considering the Stokes drift, the MLD bias and RMSEs were reduced by 2.49 and 5.39 m, respectively. Adding these two physical processes simultaneously provides the best simulation performance for the structure of the upper layer. The introduction of sea surface waves effectively modulates the vertical mixing of the upper ocean and then improves the simulation of the MLD. Thus, sea surface waves are very important for ocean simulation, so we will further couple a sea waves model in the Chinese Academy of Sciences Earth System Model (CAS-ESM) as part of their default model component. Full article

Background and Objectives: The implementation of orthogeriatric co-management (OGCM) reflects the demand for interdisciplinary collaborations due to the increasing comorbidities of geriatric trauma patients. This study aimed to assess clinical in-hospital outcomes in lumbar spine, thoracic spine, and pelvic ring fragility fracture patients before and after the implementation of a Geriatric Trauma Centre (GTC) certified by the German Trauma Society (DGU^®). Materials and Methods: In this observational, retrospective cohort study, geriatric trauma patients (>70 years of age) were stratified into either a pre-GTC group (hospital admission between 1 January 2012 and 31 December 2013) or a post-GTC group (hospital admission between 1 January 2017 and 31 December 2018). Patients’ pre-injury medical complexity was measured by ASA class (American Society of Anaesthesiologists classification), the use of anticoagulant medication, and the ACCI (Age-adjusted Charlson Comorbidity Index). Outcome parameters were patients’ in-hospital length of stay (LOS) and mortality rates, as well as new in-hospital findings and diagnoses. Further, the necessity of deviation from initial management plans due to complications was assessed using the Adapted Clavien–Dindo Scoring System in Trauma (ACDiT score of ≥1). Results: Patients in the post-GTC group (n = 111) were older (median age 82.0 years) compared to the pre-GTC group (n = 108, median age 80.0 years, p = 0.016). No differences were found in sex, body mass index, ASA class, or ACCI (all p > 0.05). Patients in the post-GTC group used vitamin K antagonists or direct oral anticoagulants more frequently (21.3% versus 10.8%). The incidence of non-surgical treatment and mortality was comparable between groups, while LOS tended to be shorter in the post-GTC group (7.0 days versus 9.0 days, p = 0.076). In the post-GTC group, the detection of urinary tract infections (UTI) increased (35.2% versus 16.2%, p = 0.001), and the delirium diagnoses tended to increase (13.0% versus 6.3%, p = 0.094), while an ACDiT score of ≥1 was comparable between groups (p = 0.169). Conclusions: In this study including lumbar spine, thoracic spine, and pelvic ring geriatric fragility fractures, patients in the post-GTC group were more medically complex. More UTIs and the tendency for increased delirium detection was observed in the post-GTC group, likely due to improved diagnostic testing. Nonetheless, the necessity of deviation from initial management plans (ACDiT score of ≥1) was comparable between groups, potentially a positive result of OGCM. Full article

The tropical Atlantic Warm Pool is one of the main drivers of the marine intertropical convergence zone and the associated coastal Northeast Brazilian and West-African monsoons. Its meridional displacement is driven by the solar cycle, modulated by the atmosphere and ocean interactions, whose nature and respective proportions are still poorly understood. This paper presents a climatological study of the upper ocean and lower atmosphere contributions to the warm pool seasonal migration, using an Ocean General Circulation Model (OGCM). First, we provide quantitative, albeit simple, pieces of evidence on how the large amplitude of migration in the west, compared to the east, is mainly due to the strong east–west contrast of the background meridional SST gradient intensities, which is maintained by equatorial and eastern tropical upwellings. Our main results consist first in identifying a diagnostic equation for the migration speed of the two meridional boundary isotherms of the Warm Pool, expressed in terms of the various mixed-layer heat fluxes. We then evidence and quantify how, in general, the migration is forced by air–sea fluxes, and damped by ocean circulation. However, remarkable controls by the ocean are identified in some specific regions. In particular, in the northwestern part of the Warm Pool, characterized by a large temperature inversion area, the boreal spring northward movement speed depends on the restitution of the solar heating by the thermocline. Additionally, over the southern part of the Warm Pool, our study quantifies the key role of the equatorial upwelling, which, depending on the longitude, significantly accelerates or slows down the summer poleward migration. Full article

High-resolution global ocean general circulation models (OGCMs) play a key role in accurate ocean forecasting. However, the models of the operational forecasting systems are still not in high resolution due to the subsequent high demand for large computation, as well as the low parallel efficiency barrier. Good scalability is an important index of parallel efficiency and is still a challenge for OGCMs. We found that the communication cost in a barotropic solver, namely, the preconditioned conjugate gradient (PCG) method, is the key bottleneck for scalability due to the high frequency of the global reductions. In this work, we developed a new algorithm—a communication-avoiding Krylov subspace method with a PCG (CA-PCG)—to improve scalability and then applied it to the Nucleus for European Modelling of the Ocean (NEMO) as an example. For PCG, inner product operations with global communication were needed in every iteration, while for CA-PCG, inner product operations were only needed every eight iterations. Therefore, the global communication cost decreased from more than 94.5% of the total execution time with PCG to less than 63.4% with CA-PCG. As a result, the execution time of the barotropic modes decreased from more than 17,000 s with PCG to less than 6000 s with CA-PCG, and the total execution time decreased from more than 18,000 s with PCG to less than 6200 s with CA-PCG. Besides, the ratio of the speedup can also be increased from 3.7 to 4.6. In summary, the high process count scalability when using CA-PCG was effectively improved from that using the PCG method, providing a highly effective solution for accurate ocean simulation. Full article

This paper describes the near-surface transport properties and Lagrangian statistics in the Adriatic semi-enclosed basin using synthetic drifters. Lagrangian transport models were used to simulate synthetic trajectories from the mean flow fields obtained by the Massachusetts Institute of Technology general circulation model (MITgcm), implemented in the Adriatic from October 2006 until December 2008. In particular, the surface circulation properties in two contrasting years (2007 had a mild winter and cold fall, while 2008 had a normal winter and hot summer) are compared here. In addition, the Lagrangian statistics for the entire Adriatic Basin after removing the Eulerian mean circulation for numerical particles were calculated. The results indicate that the numerical particles were slower in this simulation when compared with the real drifters. This is because of the reduced energetic flow field generated by the MIT general circulation model during the selected years. The numerical results showed that the balanced effects of the wind-driven recirculation in the northernmost area(which would be a sea response to the Bora wind field) and the Po River discharge cause the residence times to be similar during the two selected years (182 and 185 days in 2007 and 2008, respectively). Furthermore, the mean angular momentum, diffusivity, and Lagrangian velocity covariance values are smaller than in the real drifter observations, while the maximum Lagrangian integral time scale is the same. Full article

The aim of this study is to assess the capacity of the Surface Water Ocean Topography (SWOT) satellite to resolve fine scale oceanic surface features in the western Mediterranean. Using as input the Sea Surface Height (SSH) fields from a high-resolution Ocean General Circulation Model (OGCM), the SWOT Simulator for Ocean Science generates SWOT-like outputs along a swath and the nadir following the orbit ground tracks. Given the characteristic temporal and spatial scales of fine scale features in the region, we examine temporal and spatial resolution of the SWOT outputs by comparing them with the original model data which are interpolated onto the SWOT grid. To further assess the satellite’s performance, we derive the absolute geostrophic velocity and relative vorticity. We find that instrument noise and geophysical error mask the whole signal of the pseudo-SWOT derived dynamical variables. We therefore address the impact of removal of satellite noise from the pseudo-SWOT data using a Laplacian diffusion filter, and then focus on the spatial scales that are resolved within a swath after this filtering. To investigate sensitivity to different filtering parameters, we calculate spatial spectra and root mean square errors. Our numerical experiments show that noise patterns dominate the spectral content of the pseudo-SWOT fields at wavelengths below 60 km. Application of the Laplacian diffusion filter allows recovery of the spectral signature within a swath down to the 40–60 km wavelength range. Consequently, with the help of this filter, we are able to improve the observation of fine scale oceanic features in pseudo-SWOT data, and in the estimation of associated derived variables such as velocity and vorticity. Full article

Recent satellite data and modeling studies indicate a pronounced role Tropical Instability Waves (TIW)-induced wind feedback plays in the tropical Pacific climate system. Previously, remotely sensed data were used to derive a diagnostic model for TIW-induced wind stress perturbations (τ_TIW), which was embedded into an ocean general circulation model (OGCM) to take into account TIW-induced ocean-atmosphere coupling in the tropical Pacific. While the previous paper by Zhang (2013) is concerned with the effect on the mean ocean state, the present paper is devoted to using the embedded system to examine the effects on TIW activity in the ocean, with τ_TIW being interactively determined from TIW-scale sea surface temperature (SST_TIW) fields generated in the OGCM, written as τ_TIW = α_TIW·F(SST_TIW), where α_TIW is a scalar parameter introduced to represent the τ_TIW forcing intensity. Sensitivity experiments with varying α_TIW (representing TIW-scale wind feedback strength) are performed to illustrate a negative feedback induced by TIW-scale air-sea coupling and its relationship with TIW variability in the ocean. Consistent with previous modeling studies, TIW wind feedback tends to have a damping effect on TIWs in the ocean, with a general inverse relationship between the τ_TIW intensity and TIWs. It is further shown that TIW-scale coupling does not vary linearly with α_TIW: the coupling increases linearly with intensifying τ_TIW forcing at low values of α_TIW (in a weak τ_TIW forcing regime); it becomes saturated at a certain value of α_TIW; it decreases when α_TIW goes above a threshold value as the τ_TIW forcing increases further. This work presents a clear demonstration of using satellite data to effectively represent TIW-scale wind feedback and its multi-scale interactions with large-scale ocean processes in the tropical Pacific. Full article