A Global Ocean Oxygen Database and Atlas for Assessing and Predicting Deoxygenation and Ocean Health in the Open and Coastal Ocean

In this paper, we outline the need for a coordinated international effort toward the building of an open-access Global Ocean Oxygen Database and ATlas (GO2DAT) complying with the FAIR principles (Findable, Accessible, Interoperable, and Reusable). GO2DAT will combine data from the coastal and open ocean, as measured by the chemical Winkler titration method or by sensors (e.g., optodes, electrodes) from Eulerian and Lagrangian platforms (e.g., ships, moorings, profiling floats, gliders, ships of opportunities, marine mammals, cabled observatories). GO2DAT will further adopt a community-agreed, fully documented metadata format and a consistent quality control (QC) procedure and quality flagging (QF) system. GO2DAT will serve to support the development of advanced data analysis and biogeochemical models for improving our mapping, understanding and forecasting capabilities for ocean O2 changes and deoxygenation trends. It will offer the opportunity to develop quality-controlled data synthesis products with unprecedented spatial (vertical and horizontal) and temporal (sub-seasonal to multi-decadal) resolution. These products will support model assessment, improvement and evaluation as well as the development of climate and ocean health indicators. They will further support the decision-making processes associated with the emerging blue economy, the conservation of marine resources and their associated ecosystem services and the development of management tools required by a diverse community of users (e.g., environmental agencies, aquaculture, and fishing sectors). A better knowledge base of the spatial and temporal variations of marine O2 will improve our understanding of the ocean O2 budget, and allow better quantification of the Earth’s carbon and heat budgets. With the ever-increasing need to protect and sustainably manage ocean services, GO2DAT will allow scientists to fully harness the increasing volumes of O2 data already delivered by the expanding global ocean observing system and enable smooth incorporation of much higher quantities of data from autonomous platforms in the open ocean and coastal areas into comprehensive data products in the years to come. This paper aims at engaging the community (e.g., scientists, data managers, policy makers, service users) toward the development of GO2DAT within the framework of the UN Global Ocean Oxygen Decade (GOOD) program recently endorsed by IOC-UNESCO. A roadmap toward GO2DAT is proposed highlighting the efforts needed (e.g., in terms of human resources).

Preconditioning, aerosols, and radiation control the temperature of glaciation in Amazonian clouds

Glaciation in clouds is a fundamental phenomenon in determining Earth’s radiation fluxes, sensible and latent heat budgets in the atmosphere, the water cycle, cloud development and lifetime. Nevertheless, the main mechanisms that govern the temperature of glaciation in clouds have not been fully identified. Here we present an analysis of 15 years (2000-2014) of satellite, sunphotometer, and reanalysis datasets over the Amazon. We find that the temperature of glaciation in convective clouds is controlled by preconditioning dynamics, natural and anthropic aerosols, and radiation. In a moist atmospheric column, prone to deep convection, increasing the amount of aerosols leads to a delay in the onset of glaciation, reducing the glaciation temperature. For a dry column, radiative extinction by biomass burning smoke leads to atmospheric stabilization and an increase in the glaciation temperature. Our results offer observational benchmarks that can help a more precise description of glaciation in convective cloud models.

A distributed heat transfer model for thermal-hydraulic considerations in sewer networks

Thermal-hydraulic considerations in urban drainage networks are essential to utilise available heat capacities from waste- and stormwater. However, available models are either too detailed or too coarse; fully coupled thermal-hydrodynamic modelling tools are lacking.To accurately predict water-energy dynamics across an entire urban drainage network, we suggest the SWMM-HEAT model, which extends the EPA-StormWater Management Model with a heat-balance component. This enables conducting more advanced thermal-hydrodynamic simulation at full network scale than currently possible. We demonstrate the usefulness of the model by predicting temperature dynamics in two independent real-world cases under dry weather conditions. We furthermore screen the sensitivity of the model parameters to guide the choice of suitable parameters in future studies. The results of our study shows that sewer temperatures are particularly sensitive to soil temperature, sewer headspace temperature and humidity under specific conditions. Comparison with measurements suggest that the model predicts temperature dynamics adequately, with RSR values between 0.71 and 1.1. Simulation runs were generally fast; a five-day period simulation at high temporal resolution of a network with 415 nodes during dry weather was completed in a few minutes. Future work should assess the performance of the model for different applications and perform a more comprehensive sensitivity analysis under more scenarios. To facilitate the efficient estimation of available heat budgets in sewer networks and the integration in urban planning, the SWMM-HEAT code is made publicly available.

In-building heat recovery mitigates adverse temperature effects on biological wastewater treatment: a network-scale analysis of thermal-hydraulics in sewers

Heat recovery from wastewater is a robust and straightforward strategy to reduce water-related energy consumption. Its implementation, though, requires a careful assessment of its impacts across the entire wastewater system as adverse effects on the water and resource recovery facility and competition among heat recovery strategies may arise.A model-based assessment of heat recovery from wastewater therefore implies extending the current simulation spatial scope, enabling thermal-hydraulic simulations from the household tap along its entire flow path down to the wastewater resource recovery facility. With this aim in mind, we propose a new modelling framework interfacing thermal-hydraulic simulations of (i) households, (ii) private lateral connections, and (iii) the main public sewer network.Applying this framework to analyse the fate of wastewater heat budgets in a Swiss catchment, we find that heat losses in lateral connections are large and cannot be overlooked in any thermal-hydraulic analysis, due to the high-temperature, low-flow wastewater characteristics maximizing heat losses to the environment. Further, we find that implementing shower drain heat recovery devices in 50% of the catchment’s households lower the wastewater temperature at the wastewater resource recovery facility significantly less – only 0.3 K – than centralized in-sewer heat recovery, due to a significant thermal damping effect induced by lateral connections and secondary sewer lines. In-building technologies are thus less likely to adversely affect biological wastewater treatment processes. The proposed open-source modelling framework can be applied to any other catchment. We thereby hope to enable more efficient heat recovery strategies, maximizing energy harvesting while minimising impacts on biological wastewater treatment.

Absorption of Ocean Heat Along and Across Isopycnals in HadCM3

<p><span>Anthropogenic warming added to the climate system accumulates mostly in the ocean interior and discrepancies in how this is modelled contribute to uncertainties in predicting sea level rise. Temperature changes are partitioned between excess, due to perturbed surface heat fluxes, and redistribution, that arises from the changing circulation and perturbations to mixing. In a model (HadCM3) with realistic historical forcing (anthropogenic and natural) from 1960 to 2011, we firstly compare this excess-redistribution partitioning with the spice and heave decomposition, in which ocean interior temperature anomalies occur along or across isopycnals, respectively. This comparison reveals that in subtropical gyres (except in the North Atlantic) heave mostly captures excess warming in the top 2000 m, as expected from Ekman pumping, whereas spice captures redistributive cooling. At high-latitudes and in the subtropical Atlantic, however, spice predicts excess warming at the winter mixed layer whereas below this layer, spice represents redistributive warming in southern high latitudes.</span></p><p><span> </span></p><p><span>Secondly, we use Eulerian heat budgets of the ocean interior to identify the process responsible for excess and redistributive warming. In southern high latitudes, spice warming results from reduced convective cooling and increased warming by isopycnal diffusion, which account for the deep redistributive and shallow excess warming, respectively. In the North Atlantic, excess warming due to advection contains both cross-isopycnal warming (heave found in subtropical gyres) and along-isopycnal warming (spice). Finally, projections of heat budgets —coupled with salinity budgets— into thermohaline and spiciness-density coordinates inform us about how water mass formation occurs with varying T-S slopes. Such formation happens preferentially along isopycnal surfaces at high-latitudes and along isospiciness surfaces at mid-latitudes, and along both coordinates in the subtropical Atlantic. Because spice and heave depend only on temperature and salinity, our study suggests a method to detect excess warming in observations.</span></p>

How much Arctic fresh water participates in the subpolar overturning circulation?

<p><span>Fresh Arctic waters flowing into the Atlantic are thought to have two primary fates. They may be mixed into the deep ocean as part of the overturning circulation, or flow alongside regions of deep water formation without impacting overturning. Climate models suggest that as increasing amounts of fresh water enter the Atlantic, the overturning circulation will be disrupted, yet we lack an understanding of how much fresh water is mixed into the overturning circulation's deep limb in the present day. To constrain these fresh water pathways, we build steady-state volume, salt, and heat budgets east of Greenland that are initialized with observations and closed using inverse methods. Fresh water sources are split into oceanic Polar Waters from the Arctic and surface fresh water fluxes, which include net precipitation, runoff, and ice melt, to examine how they imprint the circulation differently. We find that 65 mSv of the total 110 mSv of surface fresh water fluxes that enter our domain participate in the overturning circulation, as do 0.6 Sv of the total 1.2 Sv of Polar Waters that flow through Fram Strait. Based on these results, we hypothesize that the overturning circulation is more sensitive to future changes in Arctic fresh water outflow and precipitation, while Greenland runoff and iceberg melt are more likely to stay along the coast of Greenland.</span></p>

Biological and Physical Interactions at Local Ocean Scales: Coupled Systems

Physical and biogeochemical processes that influence primary production set Earth’s carbon and heat budgets. While these processes have long been the focus of research, high resolution models to investigate local phenomena have only recently been developed, and two-way coupling between oceanic physics and biology is only recently getting attention due to computational power. With these new developments, it is possible to study the mechanisms through which these processes interact at both global and regional scales to shape Earth’s climate, which is the goal of this paper. This paper introduces oceanic physical phenomena at submesoscales to global scales –like mixed layer depth and turbulent structures–and the relationship of smaller scale events with biological factors. It discusses the implications of these relationships for primary production. After an introductory explanation of turbulence, primarily in the form of eddies and fronts, and the effects of internal instability and surface forcing, this paper emphasizes the contributions of those phenomena (turbulence, internal instability, and surface forcing)to vertical velocities and the influence of vertical transport on biology. Next, it introduces biogeochemical feedbacks, concerning both large scale population dynamics and increased absorption of radiation at the submesoscale, to consider their impacts on physical dynamics and regional climates. Finally, the paper compiles equations of irradiance and variables of significance, suggesting terms that could produce meaningful responses to variations in phytoplankton populations. The paper highlights the importance of understanding physical-biogeochemical relationships and suggests directions for future research, particularly areas related to global warming or abrupt climate change.

How much Arctic fresh water participates in the subpolar overturning circulation?

Fresh Arctic waters flowing into the Atlantic are thought to have two primary fates. They may be mixed into the deep ocean as part of the overturning circulation, or flow alongside regions of deep water formation without impacting overturning. Climate models suggest that as increasing amounts of fresh water enter the Atlantic, the overturning circulation will be disrupted, yet we lack an understanding of how much fresh water is mixed into the overturning circulation’s deep limb in the present day. To constrain these fresh water pathways, we build steady-state volume, salt, and heat budgets east of Greenland that are initialized with observations and closed using inverse methods. Fresh water sources are split into oceanic Polar Waters from the Arctic and surface fresh water fluxes, which include net precipitation, runoff, and ice melt, to examine how they imprint the circulation differently. We find that 65 mSv of the total 110 mSv of surface fresh water fluxes that enter our domain participate in the overturning circulation, as do 0.6 Sv of the total 1.2 Sv of Polar Waters that flow through Fram Strait. Based on these results, we hypothesize that the overturning circulation is more sensitive to future changes in Arctic fresh water outflow and precipitation, while Greenland runoff and iceberg melt are more likely to stay along the coast of Greenland.