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A novel phantom-imaging platform for automated and high precision imaging of the American College of Radiology (ACR) PET phantom is proposed. The platform facilitates the generation of an accurate μ-map for PET/MR systems with a robust alignment based on two-stage image registration using specifically designed PET templates. The automated analysis of PET images uses a set of granular composite volume of interest (VOI) templates in a 0.5 mm resolution grid for sampling of the system response to the insert step functions. The impact of the activity outside the field of view (FOV) was evaluated using two acquisitions of 30 minutes each, with and without the activity outside the FOV. Iterative image reconstruction was employed with and without modelled shift-invariant point spread function (PSF) and varying ordered subsets expectation maximisation (OSEM) iterations. Uncertainty analysis of all image-derived statistics was performed using bootstrap resampling of the list-mode data. We found that the activity outside the FOV can adversely affect the imaging planes close to the edge of the axial FOV, reducing the contrast, background uniformity and overall quantitative accuracy. The PSF had a positive impact on contrast recovery (although it slows convergence). The proposed platform may be helpful in a more informative evaluation of PET systems and image reconstruction methods.

NEOM (short for Neo-Mustaqbal) is a $500 billion coastal city megaproject, currently under construction in the northwestern part of the Red Sea, off the coast of Tabuk province in Saudi Arabia, and its success will rely on the preservation of biodiverse marine ecosystems. Monitoring the variability of ecological indicators, such as phytoplankton, in relation to regional environmental conditions, is the foundation for such a goal. We provide a detailed description of the phytoplankton seasonal cycle of surface waters surrounding NEOM using satellite-derived chlorophyll-a (Chla) observations, based on a regionally-tuned product of the European Space Agency’s Ocean Colour Climate Change Initiative, at 1 km resolution, from 1997 to 2018. The analysis is also supported with in situ cruise datasets and outputs of a state-of-the-art high-resolution hydrodynamic model. The open waters of NEOM follow the oligotrophic character of the Northern Red Sea (NRS), with a peak during late winter and a minimum during late summer. Coral reef-bound regions, such as Sindala and Sharma, are characterised by higher Chl-a concentrations that peak during late summer. Most of the open waters around NEOM are influenced by the general cyclonic circulation of the NRS and local circulation features, while shallow reef-bound regions are more isolated. Our analysis provides the first description of the phytoplankton seasonality and the oceanographic conditions in NEOM, which may support the development of a regional marine conservation strategy. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

The seasonal and spatial evolution of mixed layers (MLs) in the Red Sea (RS) is analyzed for the 2001-2015 period using the results of a high resolution (~1km horizontal, 50 vertical layers) ocean circulation model forced by a novel regional high resolution (5 km) atmospheric reanalysis dataset. The simulation reproduces the main features of the near-surface stratification, as described by the available observations. The seasonal evolution of the modeled mixed layer depths (MLDs) in the RS is predominantly driven by atmospheric buoyancy forcing, especially its heat flux component. Everywhere in the basin the model MLs are deepest in January and February. The deepest MLDs develop in the northern parts of the Gulf of Aqaba and in the western parts of the north RS. The MLDs gradually shoal towards the south, reflecting the meridional gradient of wintertime surface buoyancy loss. In spring and summer, the surface ocean heat gain increases the stratification and the MLs are becoming shallow everywhere in the basin. During this season wind may have a significant local impact on the MLD. Particularly important are strong winds channeled by topography, such as in the vicinity of the Strait of Bab-Al-Mandeb and the straits connecting the two gulfs in the north, and lateral jets blowing through mountain gaps, such as the Tokar jet in the central RS. The MLD distribution further suggests influence by the general and mesoscale circulation. The complex patterns of air-sea buoyancy flux, wind forcing, and the thermohaline and mesoscale circulation, are all strongly imprinted on the MLD distribution., Comment: 43 pages, 19 figures, submitted for publication in Frontiers in Marine Science

The Red Sea, home to the second-longest coral reef system in the world, is a vital resource for the Kingdom of Saudi Arabia. The Red Sea provides 90% of the Kingdom’s potable water by desalinization, supporting tourism, shipping, aquaculture, and fishing industries, which together contribute about 10%–20% of the country’s GDP. All these activities, and those elsewhere in the Red Sea region, critically depend on oceanic and atmospheric conditions. At a time of mega-development projects along the Red Sea coast, and global warming, authorities are working on optimizing the harnessing of environmental resources, including renewable energy and rainwater harvesting. All these require high-resolution weather and climate information. Toward this end, we have undertaken a multipronged research and development activity in which we are developing an integrated data-driven regional coupled modeling system. The telescopically nested components include 5-km- to 600-m-resolution atmospheric models to address weather and climate challenges, 4-km- to 50-m-resolution ocean models with regional and coastal configurations to simulate and predict the general and mesoscale circulation, 4-km- to 100-m-resolution ecosystem models to simulate the biogeochemistry, and 1-km- to 50-m-resolution wave models. In addition, a complementary probabilistic transport modeling system predicts dispersion of contaminant plumes, oil spill, and marine ecosystem connectivity. Advanced ensemble data assimilation capabilities have also been implemented for accurate forecasting. Resulting achievements include significant advancement in our understanding of the regional circulation and its connection to the global climate, development, and validation of long-term Red Sea regional atmospheric–oceanic–wave reanalyses and forecasting capacities. These products are being extensively used by academia, government, and industry in various weather and marine studies and operations, environmental policies, renewable energy applications, impact assessment, flood forecasting, and more. © 2021 American Meteorological Society

The variability of the water mass exchange between the Arabian Gulf and the Indian Ocean is investigated using a high-resolution (1/36°) ocean model. We focus on the period from December 1996 to March 1998, having as reference in situ measurements at the Strait of Hormuz. Previous studies, based on models and observations, suggested a perpetual deep outflow, mainly in the southern part of the Strait, and a variable flow in the upper layers. In the present study, we confirm that there is a permanent core of a deep outflow in the Strait at depths greater than 40 m, characterised by high-salinity waters. In addition, we show that there is a seasonal signal in the upper layers net flow in the southern part of the Strait, altering from net inflow during winter/spring to net outflow during summer/fall. The mean annual inflow through the Strait is estimated at 0.22 ± 0.01 Sv and the deep outflow at 0.147 ± 0.01 Sv. The water mass exchange through the Strait is controlled by synoptic processes with high variability net transport fields. These processes characterise the structure and the intensity of the transport patterns, exhibiting 2- to 5-day period. On synoptic time scales, winds drive an immediate baroclinic flow at the Strait of Hormuz, affecting mostly the upper layers, and a quasi-barotropic flow that peaks approximately 2 days later. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

Formation of intermediate waters in the northern Red Sea was captured by Seagliders during the winter of 2016. The analysis is based on measurements collected by consequent deployments of Seaglider autonomous underwater vehicles along a 70 km transect, which was run repeatedly from the coast to midbasin during the period from October 2015 to May 2016. The observations revealed typical open ocean convection processes including a preconditioning phase followed by deep convection and spreading of the newly formed waters through lateral exchange. Winter conditions were characterized by surface cooling and enhanced evaporation, which were observed from late October until late February. During this period, the gradual surface cooling and salinity increase resulted in the weakening of the surface stratification. Recurrent cyclonic gyres forced by strong atmospheric events led to episodic convection and the formation of intermediate seawater typical of the upper overturning circulation cell of the Red Sea. Following deep mixing, a remarkable bloom of chlorophyll was detected at the top layer of the water column in response to the nutrients delivery from the deeper layers. The end of winter was marked by the intrusion of lower salinity water presumably advected from the south and the reestablishment of the general cyclonic circulation, typical for the northernmost part of the Red Sea. To the best of our knowledge, this is the first observation study of such convection events in the northern Red Sea. ©2020. American Geophysical Union. All Rights Reserved.

The southern Red Sea is genetically distinct from the rest of the basin; yet the reasons responsible for this genetic separation remain unclear. Connectivity is a vital process for the exchange of individuals and genes among geographically separated populations, and is necessary for maintaining biodiversity and resilience in coral reef ecosystems. Here, using long-term, high-resolution, 3-D backward particle tracking simulations, we investigate the physical connectivity of coral reefs in the southern Red Sea with neighbouring regions. Overall, the simulation results reveal that the southern Red Sea coral reefs are more physically connected with regions in the Indian Ocean (e.g., the Gulf of Aden) than with the northern part of the basin. The identified connectivity exhibits a distinct monsoon-related seasonality. Though beyond the country boundaries, relatively remote regions of the Indian Ocean may have a substantial impact on the southern Red Sea coral reef regions, and this should be taken into consideration when establishing conservation strategies for these vulnerable biodiversity hot-spots. © 2019, The Author(s).

The interannual variability of the exchange flow between the Red Sea and the Gulf of Aden through the Bab-al-Mandeb strait is examined based on a high-resolution, nonhydrostatic hindcast model simulation covering a 19-year period (1995–2013), using the MITgcm (MIT general circulation model). The model is validated against moored profiles and along-strait cruise observations collected during the period from June 1995 to November 1996 and 19-year sea surface temperature satellite observations. The model well reproduces the properties of the water masses at the strait over a wide range of spatiotemporal scales, including the typical two- and three-layer seasonal patterns and the related intraseasonal-to-interannual cycles. The seasonality of the exchange flow is predominately determined by the time-varying surface winds, with a higher correlation over the Gulf of Aden, reflecting the importance of local Gulf of Aden processes for the exchanges at the strait. The alternation of the two seasonal patterns is driven by a combination of the buoyancy-driven mean circulation with the wind-induced transport. The onset/offset of the two patterns is estimated to take place one-to-two weeks after the respective monsoon-driven wind reversal. Model results indicate that the onset dates and durations of both patterns exhibit a considerable interannual variability. Additionally, the duration of the summer (winter) exchange pattern presents a significant increasing (decreasing) trend of ~1.45 day/year (~1.22 day/year) over the 19-year period. Significant interannual variabilities and trends are observed in terms of the total volume of water, salt mass, and stored heat of the exchanges. Budget analysis of these trends suggests that the duration of the two exchange patterns is more important in determining the interannual variability and the related trends than the intensity of the exchange, or the variations in mean salinity or temperature of the exchanged water masses. ©2019. American Geophysical Union. All Rights Reserved.

As the Earth's temperature continues to rise, coral bleaching events become more frequent. Some of the most affected reef ecosystems are located in poorly monitored waters, and thus, the extent of the damage is unknown. We propose the use of marine heatwaves (MHWs) as a new approach for detecting coral reef zones susceptible to bleaching, using the Red Sea as a model system. Red Sea corals are exceptionally heat-resistant, yet bleaching events have increased in frequency. By applying a strict definition of MHWs on >30 year satellite-derived sea surface temperature observations (1985–2015), we provide an atlas of MHW hotspots over the Red Sea coral reef zones, which includes all MHWs that caused major coral bleaching. We found that: (a) if tuned to a specific set of conditions, MHWs identify all areas where coral bleaching has previously been reported; (b) those conditions extended farther and occurred more often than bleaching was reported; and (c) an emergent pattern of extreme warming events is evident in the northern Red Sea (since 1998), a region until now thought to be a thermal refuge for corals. We argue that bleaching in the Red Sea may be vastly underrepresented. Additionally, although northern Red Sea corals exhibit remarkably high thermal resistance, the rapidly rising incidence of MHWs of high intensity indicates this region may not remain a thermal refuge much longer. As our regionally tuned MHW algorithm was capable of isolating all extreme warming events that have led to documented coral bleaching in the Red Sea, we propose that this approach could be used to reveal bleaching-prone regions in other data-limited tropical regions. It may thus prove a highly valuable tool for policymakers to optimize the sustainable management of coastal economic zones. © 2019 John Wiley & Sons Ltd

Recent reports of warming trends in the Red Sea raise concerns about the response of the basin's fragile ecosystem under an increasingly warming climate. Using a variety of available Sea Surface Temperature (SST) data sets, we investigate the evolution of Red Sea SST in relation to natural climate variability. Analysis of long-term SST data sets reveals a sequence of alternating positive and negative trends, with similar amplitudes and a periodicity of nearly 70 years associated with the Atlantic Multidecadal Oscillation. High warming rates reported recently appear to be a combined effect of global warming and a positive phase of natural SST oscillations. Over the next decades, the SST trend in the Red Sea purely related to global warming is expected to be counteracted by the cooling Atlantic Multidecadal Oscillation phase. Regardless of the current positive trends, projections incorporating long-term natural oscillations suggest a possible decreasing effect on SST in the near future. ©2019. The Authors.

Malanotte-Rizzoli, Paola ... et. al.-- 76 pages, The importance of the Mediterranean Sea for the world ocean has long been recognized. First, the Mediterranean sea has a profound impact on the Atlantic ocean circulation and, consequently, on the global thermohaline conveyor belt. Maps of the 5 Mediterranean salty water tongue exiting from the Gibraltar strait at intermediate depths and spreading throughout the Atlantic interior are well known since the 1950s. Through direct pathways to the Atlantic polar regions or through indirect mixing processes, the salty Mediterranean water preconditions the deep convection cells of the polar Atlantic. There the North Atlantic Deep Water is formed which successively spreads throughout 10 the world ocean constituting the core of the global thermohaline circulation. Even more importantly, the Mediterranean Sea is a laboratory basin for the investigation of processes of global importance, being much more amenable to observational surveys because of its location in mid-latitude and its dimensions. Both the western and eastern basins in fact possess closed thermohaline circulations analogous to the 15 global conveyor belt. A unique upper layer open thermohaline cell connects the eastern to the western basin and, successively, to the north Atlantic through the Gibraltar strait. In it, the Atlantic water entering into Gibraltar in the surface layer, after travelling to the easternmost Levantine basin, is transformed into one of the saltiest water masses through air–sea heat and moisture fluxes. This is the salty water which, crossing the 20 entire basin in the opposite direction below the surface Atlantic water, finally exits from the Gibraltar strait at mid-depths. Both the western and eastern basins are endowed with deep/intermediate convection cells analogous to the polar Atlantic deep convection cells or to the intermediate mode water ones. Deep and intermediate water masses are therefore formed in differ25 ent sites of the entire basin. Because of their easily accessible locations, these convection cells are much more amenable to direct observational surveys and mooring arrays

In work package 5 “Pollution and climate stress on fish” pollution and different models of fish and fish recruitment were combined. The studies were focused on oil pollution and mercury. Different regions were investigated; Aegean Sea, North Sea, Norwegian Sea, and Baltic Sea. In the Aegean Sea anchovy is a very important species and the potential effect of both continuous oil spills from ship traffic and a potential accident from a drilling platform were investigated (1). In the North Sea and Norwegian Sea, the potential impact of oil spill from a ship-accident on early life stages of cod were investigated (2). Mercury is a potentially long- term pollutant. A coupled atmosphere-ocean-biogeochemical model was formulated, tested and provided modeled fields of mercury in the North and Baltic Sea region (3). The results from this model were used as input to a model to study the potential for bioaccumulation in macrobenthos and fish in the North Sea and Baltic Sea., NERSC Technical Report no. 371. Funded by EU FP7 ERA-NET Project SEAMAN; European Regional Development Fund; and General Secretariat of Research and Technology (GSRT), Greece

In the Mediterranean sea the risk from oil spill pollution is high due to the heavy traffic of merchant vessels for transporting oil and gas, especially after the recent enlargement of the Suez canal and to the increasing coastal and offshore installations related to the oil industry in general. The basic response to major oil spills includes different measures and equipment. However, in order to strengthen the maritime safety related to oil spill pollution in the Mediterranean and to assist the response agencies, a multi-model oil spill prediction service has been set up, known as MEDESS-4MS (Mediterranean Decision Support System for Marine Safety). The concept behind the MEDESS-4MS service is the integration of the existing national ocean forecasting systems in the region with the Copernicus Marine Environmental Monitoring Service (CMEMS) and their interconnection, through a dedicated network data repository, facilitating access to all these data and to the data from the oil spill monitoring platforms, including the satellite data ones, with the well established oil spill models in the region. The MEDESS-4MS offer a range of service scenarios, multi-model data access and interactive capabilities to suite the needs of REMPEC (Regional Marine Pollution Emergency Response Centre for the Mediterranean Sea) and EMSA-CSN (European Maritime Safety Agency-CleanseaNet). © 2016 Elsevier Ltd

The Red Sea, home to the second-longest coral reef system in the world, is a vital resource for the Kingdom of Saudi Arabia. The Red Sea provides 90% of the Kingdom’s potable water by desalinization, supporting tourism, shipping, aquaculture, and fishing industries, which together contribute about 10%–20% of the country’s GDP. All these activities, and those elsewhere in the Red Sea region, critically depend on oceanic and atmospheric conditions. At a time of mega-development projects along the Red Sea coast, and global warming, authorities are working on optimizing the harnessing of environmental resources, including renewable energy and rainwater harvesting. All these require high-resolution weather and climate information. Toward this end, we have undertaken a multipronged research and development activity in which we are developing an integrated data-driven regional coupled modeling system. The telescopically nested components include 5-km- to 600-m-resolution atmospheric models to address weather and climate challenges, 4-km- to 50-m-resolution ocean models with regional and coastal configurations to simulate and predict the general and mesoscale circulation, 4-km- to 100-m-resolution ecosystem models to simulate the biogeochemistry, and 1-km- to 50-m-resolution wave models. In addition, a complementary probabilistic transport modeling system predicts dispersion of contaminant plumes, oil spill, and marine ecosystem connectivity. Advanced ensemble data assimilation capabilities have also been implemented for accurate forecasting. Resulting achievements include significant advancement in our understanding of the regional circulation and its connection to the global climate, development, and validation of long-term Red Sea regional atmospheric–oceanic–wave reanalyses and forecasting capacities. These products are being extensively used by academia, government, and industry in various weather and marine studies and operations, environmental policies, renewable energy applications, impact assessment, flood forecasting, and more.

In the Mediterranean sea the risk from oil spill pollution is high due to the heavy traffic of merchant vessels for transporting oil and gas, especially after the recent enlargement of the Suez canal and to the increasing coastal and offshore installations related to the oil industry in general. The basic response to major oil spills includes different measures and equipment. However, in order to strengthen the maritime safety related to oil spill pollution in the Mediterranean and to assist the response agencies, a multi-model oil spill prediction service has been set up, known as MEDESS-4MS (Mediterranean Decision Support System for Marine Safety). The concept behind the MEDESS-4MS service is the integration of the existing national ocean forecasting systems in the region with the Copernicus Marine Environmental Monitoring Service (CMEMS) and their interconnection, through a dedicated network data repository, facilitating access to all these data and to the data from the oil spill monitoring platforms, including the satellite data ones, with the well established oil spill models in the region. The MEDESS-4MS offer a range of service scenarios, multi-model data access and interactive capabilities to suite the needs of REMPEC (Regional Marine Pollution Emergency Response Centre for the Mediterranean Sea) and EMSA-CSN (European Maritime Safety Agency-CleanseaNet)., This paper was supported by the Med Programme project MEDESS-4MS (ref: 4175/2S-MED11-01) co-financed by the European Regional Development Funds, by the FP7 project IP-MyOCEAN-2 (contract 283367), by the H2020 project MyOCEAN-FO(grant agreement 633085).