Dense Water Research Articles

Connection and disconnection

Rania Plain lies on the eastern side of Iraqi Kurdistan, at the foot of the seemingly impenetrable Zagros Mountains. During the Early Modern Period, this microregion was on the fringe of the two major powers of the Middle East, the Ottoman and Persian Empires, but it was also part of the Soran Emirate, one of the semi-autonomous vassal states that existed for hundreds of years. The Rania Plain was close to the main trade route linking Baghdad with the major Kurdish cities of Erbil and Mosul. In addition, the Lower Zab River, which flows through this valley to reach the Mesopotamian Plain, provided a natural trade and information route between the inner parts of the Zagros Mountains, the Iranian Plateau, and the fertile plains crossed by the Tigris River. Despite this, the Rania region and its cities do not appear on Ottoman Period maps, and written sources are silent about the function of the area between the 16th and 20th centuries. Field survey and excavation data from the last fifty years have provided a complex and varied picture of the valley’s topography, which, combined with the dense water network in the area, defines possible lines of population movement. One of the key questions to be addressed in examining the historical significance and complex use of the area is how to reconstruct the historical road use in the microregion using historical, archaeological, topographical, ethnographic, and GIS data and whether the area played a connecting or separating role in relation to the eastern frontier of the Ottoman Empire.

Physical drivers of bio-optical properties in the Guangdong-Hong Kong-Macao Greater Bay Area during the winter dry season

Understanding the variability of bio-optical properties in coastal seas is essential to assessing the impact of natural and anthropogenic activities on the quality of the coastal environments and their resources. This study investigated the vertical distribution of bio-optical properties and their potential driving forces in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) using a bio-optical dataset collected during the winter dry season. The hydrographic and biogeochemical properties observed across the GBA exhibited significant spatial variability, allowing the classification of the waters into three distinct regions: estuarine diluted water (EDW), Guangdong coastal current water (GCCW), and dense shelf water (DSW). Our findings show that EDW exhibited beam attenuation and optical backscatter coefficients an order of magnitude greater compared to the other two regions, which was attributed to factors such as higher concentrations of suspended particulate matter and organic material from estuarine sources. In contrast, the GCCW was characterized by lower salinity, temperature, and suspended particulate matter and displayed reduced turbidity near the coast, whereas nutrient-rich GCCW waters transported to the mid-shelf region supported increased phytoplankton biomass and a greater abundance of micro-phytoplankton. By exploring the bio-optical characteristics and their underlying processes in the GBA, this study enhances our understanding of the complex dynamics shaping the optical properties of coastal waters in this heavily urbanized region.

A new vision of the Adriatic Dense Water future under extreme warming

Abstract. We use the Adriatic Sea and Coast (AdriSC) kilometer-scale atmosphere–ocean model to assess the impact of a far-future extreme-warming scenario on the formation, spreading, and accumulation of North Adriatic Dense Water (NAddW) over the entire basin, including the Jabuka Pit accumulation site, and Adriatic Deep Water (AdDW) over the Southern Adriatic Pit (SAP). Our key findings differ from previous studies that used coarser Mediterranean climate models and did not update the thresholds for dense-water and deep-water definitions to account for the far-future background density changes caused by warmer sea surface temperatures. We show that surface buoyancy losses at NAddW generation sites, driven by evaporation, are expected to increase by 15 % under extreme warming, despite a 25 % reduction in the intensity and spatial extent of Bora winds. As a result, future NAddW formation will remain similar to present conditions. However, the volume of dense water in the Jabuka Pit will decrease due to the increased far-future stratification. Additionally, dense-water transport between the Jabuka Pit and the deepest part of the SAP will stop, as future NAddW will be lighter than the AdDW. Regarding Ionian–Adriatic exchanges, extreme warming will not affect the impact of the bimodal oscillation system on the Adriatic salinity variability, but future AdDW dynamics will be determined by density changes in the northern Ionian Sea. Our findings highlight the complexity of climate change impacts on Adriatic atmosphere–ocean processes and the importance of high-resolution models for more accurate far-future projections in the Adriatic Sea.

Representation of Dense Shelf Water formation by global oceanic reanalyses

This study evaluates the representation of Dense Shelf Water (DSW) formation in the Southern Ocean by two global oceanic reanalyses: GLORYS2v4 and ORAS5. We found that GLORYS2v4 generally represents larger areas and more consistent temporal patterns of DSW compared to ORAS5. This latter reanalysis significantly underestimates the extent and frequency of DSW formation. Although both reanalyses show good statistical agreement with the World Ocean Circulation Experiment data set, with a root mean squared error of approximately 0.7, a mean absolute percentage error of 1.16% and an r value of 0.99, ORAS5 fails to reproduce the expected sea-surface salinity trend, exhibiting a negative trend across most of the Southern Ocean. This may lead to a weak representation of the water-mass formation processes in the region, thereby affecting its ability to satisfactorily represent the Meridional Overturning Circulation and the global thermohaline circulation. These discrepancies are attributed to the nudging process used for the sea-surface temperature in the ORAS5 model. This study highlights the importance of oceanic reanalyses to validate climate modelling results, in particular in high-latitude regions, where observations are scarce and crucial for understanding global climatic changes.

Development and Validation of a Global Thin Ice Thickness Algorithm for SMMR

Abstract Thin ice thickness algorithms using satellite passive microwave radiometers are frequently used to quantify sea ice production in coastal polynyas. The objective of this paper is to develop and validate a thin ice thickness algorithm using only low-frequency (LF) data (19- and 37-GHz channels), applicable back to 1978 when the Scanning Multichannel Microwave Radiometer (SMMR) observations started. We compared several recent satellite observations for 22 cases of typical polynya events in the Southern Ocean and developed a new method to discriminate three types of thin ice (active frazil, thin solid ice, and a mixture of the two) using only LF data. Combined with ice-type discrimination, the obtained LF ice thickness (20 cm or less) has a bias of less than 1 cm and an RMSD of about 5 cm, as shown by validation data from 24 cases of typical polynya events that occurred prior to 1992 in the Southern Ocean and the Bering Sea. Although the error in ice-type discrimination with LF data is relatively large in comparison with previous studies, these results still suggest that the LF ice thickness could be a continuous global data since 1978. We also developed a false thin ice detection algorithm using only LF data and created daily false thin ice masks from 1978 to the present, which are also essential for estimating global sea ice production. The use of our new LF algorithm will allow quantification of the global sea ice production over nearly half a century since 1978. Significance Statement Sea ice production is a key element for dense water formation and thus deep/intermediate overturning circulation. Global estimation of sea ice production will be achieved through a heat budget analysis incorporating a thin ice thickness algorithm of satellite passive microwave radiometers. The previous algorithms use high-frequency channel data that only became available after 1992. In this study, we have developed an algorithm of ice type and thin ice thickness using only low-frequency channels (19 and 37 GHz) data, which allows us to obtain the thin ice thickness distribution on a global scale from 1978 to the present. This will further lead to a unified global estimate of sea ice production over a time scale of nearly half a century.

Record-low Antarctic sea ice in 2023 increased ocean heat loss and storms

Recent Antarctic sea-ice decline is a substantial source of concern, notably the record low in 2023 (ref. 1). Progress has been made towards establishing the causes of ice loss1, 2, 3, 4–5 but uncertainty remains about its consequences for ocean–atmosphere interaction. Resolution of this uncertainty is important as ice decline can substantially alter surface heat loss and thus the ocean and atmosphere6. Here we show that the strongest winter 2023 ice-retraction regions provide an important new source of turbulent ocean heat loss to the atmosphere in wintertime. Ice concentration in these regions (located primarily in the Weddell, Bellingshausen and Ross seas) is reduced by up to 80% and is accompanied by an unprecedented doubling of mid-winter ocean heat loss. Also, there is a phase shift in the time of peak heat loss from late April to mid-June, with weaker than normal heat loss in austral autumn. The winter surface-heat-loss intensification is accompanied by substantial changes on both sides of the ocean–atmosphere interface. These include increases in atmospheric-storm frequency and surface-heat-loss-driven dense water formation, although the implications of the densification for broader processes such as Antarctic bottom water formation remain unclear. Our results reveal that the 2023 Antarctic sea-ice loss has substantially modified air–sea interaction in the Southern Ocean and motivate in-depth analysis of the wider climate-system impacts.

Acceleration of Warming, Deoxygenation, and Acidification in the Arabian Gulf Driven by Weakening of Summer Winds

AbstractThe Arabian Gulf (AG) exports hypersaline, dense waters into the Sea of Oman (SOO), replaced by fresher inflowing surface waters from the Indian Ocean. We investigate the impact of recent AG warming on its exchange with the SOO and the implications this has on the AG biogeochemistry. Using an eddy‐resolving hindcast model simulation, we analyze the hydrography and biogeochemistry of the AG and the SOO from 1980 to 2018. Our study reveals that changes in summer surface winds have accelerated AG warming and weakened it in the SOO, reducing the density gradient and water exchange between the two seas during late summer. This has led to nutrient buildup, increased productivity, and heightened deoxygenation and acidification in the AG. These findings underscore how subtle wind changes can exacerbate the vulnerability of marginal seas to climate change and stress the need to properly represent regional winds in global climate models.

Improvement of the urban microclimate with aromatic and medicinal plants

The paper examines the bioclimatic contribution of urban gardening through the use of aromatic and medicinal plants, proposing an innovative approach to urban design. The research aims to evaluate the role of these plants in improving the urban microclimate, focusing on their ability to reduce temperature, increase relative humidity, and contribute to the creation of a synergistic ecosystem that attracts beneficial insects. The methodology involved experimental research at eight sites in Thessaloniki, where temperature, humidity, and solar radiation were recorded. At the sites with aromatic and medicinal plants, a temperature reduction of 10-15% was observed compared to the non-planted areas. Significant improvement was recorded in areas simulating balconies, where potted plants led to a temperature reduction of 5-10%. Furthermore, areas with dense vegetation and water features showed greater humidity, while air circulation was limited, creating adverse thermal comfort conditions. In locations with small arrangements of aromatic plants, a reduction in discomfort perception of up to 26% was observed. The study highlights the innovative potential of integrating aromatic and medicinal plants into urban design for improving the microclimate. Replacing grass in public spaces and using these plants on vertical and horizontal surfaces can improve thermal comfort, aesthetic value, and attract beneficial insects, such as bees.

Detecting the role of urban green parks in thermal comfort and public health for sustainable urban planning in Delhi

Urbanization has significantly impacted the environment and urban life, with urban green spaces playing a crucial role in enhancing sustainability and public health. Urban Green Spaces (UGS) offer benefits such as temperature regulation, ecological services, and improved thermal comfort, while providing entertainment, culture, disaster avoidance, and ecological services. This study evaluates the cooling effects of UGS in mitigating the Urban Heat Islands (UHIs) phenomenon in Delhi, India, using satellite imagery to assess the Land Surface Temperature (LST) of 24 parks. We calculated the Park Cooling Intensity (PCI) by applying the mono-window algorithm. We found that parks larger than 1.55 hectares with dense vegetation and water bodies significantly reduced surrounding temperatures by up to 8.28 °C. The PCI effect was significantly influenced by park size, vegetation density, and the presence of water bodies, with larger parks and denser vegetation and water bodies demonstrating enhanced cooling capacity. These findings highlight the importance of integrating green spaces into urban planning as vital infrastructure for enhancing urban resilience, reducing heat-related health risks, and ensuring equitable access to public health benefits. The study also highlights the importance of addressing socio-economic disparities in park accessibility, which have significant implications for equitable urban development. This study emphasized the importance of formulating a strategic urban planning approach that focuses on green spaces' growth, conservation, and equitable allocation, thereby fostering eco-friendly, habitable, and robust urban environments.

Water Mass Transformation and Its Relationship With the Overturning Circulation in the Eastern Subpolar North Atlantic

AbstractA recent study using the first 21 months of the OSNAP time series revealed that the export of dense waters in the eastern subpolar North Atlantic―as part of the Atlantic Meridional Overturning Circulation (MOC)―can be almost wholly attributed to surface‐forced water mass transformation (SFWMT) in the Irminger and Iceland basins, thus suggesting a minor role for other means of transformation, such as diapycnal mixing. To understand whether this result is valid over a period that exceeds the current observational record, we use four different ocean reanalysis products to investigate the relationship between surface buoyancy forcing and dense water production in this region. We also reexplore this relationship with the now available 6‐year OSNAP time series. Our analysis finds that although surface transformation in the eastern subpolar gyre dominates the production of deep waters, mixing processes downstream of the Greenland Scotland Ridge are also responsible for the production of waters carried within the AMOC's lower limb both in the observations and reanalyses. Further analysis of the reanalyses shows that SFWMT partly explains MOC interannual variability, the remaining portion can be attributed to basin storage and mixing. Compared to the observations, the reanalyses exhibit stronger MOC variance but comparable SFWMT variance on interannual timescales.

Competition Between Advected and Local Variability Determines Coherent Propagation of Labrador Sea Water Along the DWBC

AbstractThe Deep Western Boundary Current (DWBC) is a major conduit for the equatorward export of dense waters formed in the subpolar North Atlantic and Nordic Seas that constitute the lower limb of the Atlantic Meridional Overturning Circulation. Here, we investigate the extent to which there is coherent propagation of property anomalies along the DWBC from the Labrador Sea exit to 26.5°N. Past studies have focused on relationships between DWBC anomalies at selected sites. Here we use a hydrographic data set (EN4) that covers the time period of 1970–2020 to examine coherence continuously along the boundary current. Our findings reveal sharp differences between the upper and deep Labrador Sea Water (uLSW, dLSW). Specifically, dLSW property anomalies are highly correlated at all points downstream to the Labrador Sea exit. Furthermore, the lags that yield maximum correlations uniformly increase with distance along the boundary. uLSW, however, shows a sharp decline in coherence along the boundary such that the anomalies downstream are poorly correlated with those at the Labrador Sea exit and the lag times are not monotonic. Most of the decline in uLSW coherence occurs from the Labrador Sea exit to Flemish Cap, where local variability at uLSW densities is large. Our study sheds light on the competition between advected property variability and local property variability that impacts the identification of anomalies downstream. The uLSW and dLSW differences expressed along the DWBC are also evident offshore, consistent with past Lagrangian studies.

Does Cabbeling Shape the Thermohaline Structure of High-Latitude Oceans?

Abstract Vertical exchange of heat and carbon in the ocean regulates Earth’s climate. Convection, a driver of near-surface exchange, occurs when dense water overlies light water. In a 1957 study, N. Fofonoff pointed out that when lighter overlying cold-fresh water mixes with denser underlying warm-salty water, the mixture can become denser than the underlying water due to a nonlinear process known as cabbeling. He suggested that such profiles, despite being gravitationally stable, could be classed as being unstable to cabbeling. Fofonoff hypothesized that, by mixing away such profiles, cabbeling may be shaping the thermohaline structure of polar oceans. We investigate this hypothesis here. In a one-dimensional model, we find that convective mixing occurs in temperature inverted profiles that are unstable to cabbeling even when they are initially gravitationally stable. In data from an observationally constrained global circulation model, we find profiles with a temperature inversion larger than −0.5°C are unstable to cabbeling less than 0.02% of the time, and in high-quality in situ observations, they are unstable less than 12% of the time. We find that due to cabbeling, larger temperature inversions, which should weaken stratification, make profiles more stable. Our results suggest that cabbeling limits the stability behavior of temperature inverted profiles and influences the thermohaline structure in parts of the ocean where cold-fresh water overlays warm-salty water.

Thermohaline Intrusions as Seen by Argo Floats: The Case of the Black Sea

AbstractUnderstanding the dynamics of thermohaline intrusions is crucial for predicting changes in water masses and their impact on marine ecosystems, especially in highly stratified semi‐enclosed seas and other coastal environments. We use high‐resolution (up to 1–2 m) Argo profiling float data collected over 15 years in the Black Sea, an excellent test area for studying thermohaline intrusions. Our analysis challenges the conventional view of stagnant intermediate and deep waters, revealing active mixing processes that reshape the thermohaline structure. We identified two main mechanisms driving these intrusions, related to dense water inflows from the Marmara Sea and boundary mixing enhanced by frontal instabilities. Argo data also allowed us to identify areas with favorable conditions for double‐diffusive processes. The variability of intrusions is due to changes in the thermohaline state of the upper ocean as well as to quasi‐periodic changes in the inflow caused by local conditions. Trends in the intensity and frequency of intrusions indicate shifts in water mass properties that are likely to be associated with climate variability and extreme weather events. Such trends can affect nutrient cycling, oxygen distribution and the overall stability of the water column, thereby affecting biogeochemical cycles and the resilience of marine ecosystems. Similar ventilation mechanisms may operate in other highly stratified marine systems, such as the Baltic Sea and the Arctic Ocean, so our findings may have wider implications for understanding climate‐induced changes in water masses at regional and global scales.

Risk assessment of flash flood under climate and land use and land cover change in Tianshan Mountains, China

Tianshan Mountains in China (CTM) is one of the flash flood-prone areas worldwide, constraining economic development and threatening human safety. We assessed the short-term and long-term future flash flood risk in CTM using a multi-criteria model combined with future climate and Land use and land cover (LULC). The short-term risk assessment results indicated that moderate, high, and extremely high risk areas were mainly located in the northern foothills of the Tianshan Mountain, the southern Junggar Basin, and the northern Tarim Basin, accounting for about 10 % of the total area. The areas classified as high and extremely high risk were distributed in Ili (10,100 km2), Changji (4838 km2), Bortala (1783 km2), and Urumqi (1505 km2). The spatial distributions of future long-term and short-term flash flood risk are similar. There will be an increase in the flash flood risk from 2020 to 2030, mainly in Ili, Changji, and Hami. The flash flood risk in the CTM will decrease under different scenarios from 2030 to 2070. Historical flash flood data from the 1940s to the 2010s indicated that the results of the risk assessment are reasonable. Abundant precipitation from the westerly circulation and the trumpet-shaped topography drove the flash floods in Bortala-shuanghe(BS), Ili, Changji (west), and Urumqi-wujiaqv(UW). Snowmelt flash floods are another important flash flood type in Changji (West) and UW. The dense water system and the undulating terrain led to rainstorm flash floods in high mountainous areas of Aksu and Kashgar, Hami, Kizilsu, and Changji (east). Cultivated land, population, and roads are important risk receptors. The oases, water resource constraints, and the urban scale discontinuity led to the spatial displacement between hazard and risk. The flash flood risk change in the future is more closely related to LUCC than climate change. This study provides support for flash flood risk assessment and management in CTM and other arid inland areas under changed climate and LULC.

Spatial Distribution and Decadal Variability of 129I and 236U in the Western Mediterranean Sea

This study investigates the spatial and temporal distribution of the artificial radionuclides 129I and 236U in the Western Mediterranean Sea, focusing on their connection to radionuclide sources and circulation dynamics. Taking advantage of unprecedented precision of accelerator mass spectrometry, both tracers were firstly investigated in 2013. Here, we examine tracer observations obtained along four stations (re-)visited during the TAlPro2022 expedition in May 2022. Distributions of both 129I and 236U were related to water masses and clearly linked to local circulation patterns: a tracer-poor surface Atlantic inflow, a thining of the tracer minimum at intermediate depths, and a higher tracer signal in Western Mediterranean Deep Waters due to dense water formation in the Algero-Provençal basin. The comparison to 2013 tracer data indicated recent deep ventilation of the Tyrrhenian Sea, the mixing of deep waters and enhanced stratification in intermediate waters in the Algero-Provençal basin due to a temperature and salinity increase between 2013 and 2022. We estimate an overall 129I increase of 20% at all depths between 0 and 500m with respect to 2013, which is not accompanied by 236U. This suggests either the lateral transport of 129I from the Eastern Mediterranean Sea, or an additional source of this tracer. The inventories of 129I calculated for each water mass at the four stations point to the deposition of airborne releases from the nuclear reprocessing plants (La Hague and Sellafield) on the surface Mediterranean waters as the more likely explanation for the 129I increase. This work demonstrates the great potential of including measurements of anthropogenic radionuclides as tracers of ocean circulation. However, a refinement of the anthropogenic inputs is necessary to improve their use in understanding ventilation changes in the Mediterranean Sea.

Turbulent Vertical Velocities in Labrador Sea Convection

AbstractTurbulent vertical velocity measurements are scarce in regions prone to convection such as the Labrador Sea, which hinders our understanding of deep convection dynamics. Vertical velocity, , is retrieved from wintertime glider deployments in the convective region. From , downward convective plumes of dense waters are identified. These plumes only cover a small fraction of the convective area. Throughout the convective area, the standard deviation of agrees with scaling relations for the atmospheric surface and boundary layers. It initially depends on surface buoyancy loss in winter, and later, on wind stress after mid‐March. Both periods are characterized by positive turbulent vertical buoyancy flux. During convective periods in winter, the positive buoyancy flux is mostly forced by surface heat loss. After mid‐March, when buoyancy loss to the atmosphere is reduced, the positive buoyancy flux results from a restratifying upward freshwater flux, potentially of lateral origins and without much atmospheric influence.

Application of Rubber-Wheeled directional drilling rig for probing and draining holes in coal mine

Abstract In view of the requirements of dense underground water exploration and drainage holes, high hole forming accuracy, rapid drilling rig relocation and reduced labor intensity in coal mines with trackless transportation conditions, the application of rubber wheel directional drilling rigs can well meet the requirements and complete the drilling construction. Taking the representative ZDY3500JD rubber wheel directional drilling rig as an example, the composition and basic parameters of the drilling rig are introduced, and the field application is carried out in the Shendong coal mine of the National Energy Group. The completion of the relocation greatly reduces the labor intensity of workers and improves work efficiency. It has stable performance and high hit rate in the construction of water exploration and drainage holes, and various parameters meet the design requirements, which lays a good foundation for the construction of similar mine drilling.

Do interspecific differences in morphology influence foraging efficiency of juvenile crappie?

Sympatric black crappie ( Pomoxis nigromaculatus Lesueur in Cuvier and Valenciennes, 1829) and white crappie ( Pomoxis annularis Rafinesque, 1818) often differ in ecological performance, such that white crappie outnumber black crappie in turbid waterbodies and black crappie predominate in clear waters with abundant cover. Recent work suggests that this performance difference is driven by juvenile white crappie having a limnetic body form and juvenile black crappie having a littoral body form, resulting in differential predation mortality between the species within open-water and vegetated environments. We tested whether these morphologies also lead to interspecific differences in foraging efficiency between the congeners in structure and open water. Juvenile black crappie spent more time pursuing fish prey than white crappie across all trials, suggesting that energetic gains of piscivory may differ between species. However, both species had similar capture efficiencies when attacking fathead minnows ( Pimephales promelas Rafinesque, 1820) within vegetated and open-water habitats. We conclude that variation in morphology between juvenile black crappie and white crappie does not have a large influence on foraging efficiency, at least on fish prey, in dense cover or open water, and suggest their performance in sympatry is likely not driven by predatory capabilities at the onset of piscivory within these different environmental contexts. Instead, the relationship between morphology and predator evasion may drive the distribution and relative abundance of crappie species within sympatric populations.

Knowledge graph-driven mountain railway alignment optimization integrating karst hazard assessment

Karst hazard is a considerable threat that should be considered in railway alignment design for mountainous regions with dense water systems. Nevertheless, alignment design principles in karst regions have not been systematically studied. Moreover, a quantitative karst hazard assessment model is currently lacking for automated alignment optimization. To solve the above problems, based on the analyses of karst inducing factors and hazard representation, the railway alignment design principles in karst regions are summarized through an event tree. A highly-coupled knowledge graph (called KaRAD-KG) modeling method is proposed. Then, a bi-objective alignment optimization model considering railway construction cost and karst hazard (mainly including hazard components of synclinal karst, anticlinal karst and karst depression) is constructed. To solve the optimization model, a knowledge-driven distance transform algorithm incorporating a karst hazard assessment method and a multicriteria tournament decision method is customized. Finally, the application in a real-world case indicates that the proposed method can generate an alignment which reduces construction cost by 3.39 % and karst hazard by 18.73 % compared to the best manually-designed alternative, which verifies the effectiveness of this method for assisting actual railway alignment design in a karst-dense mountainous region.

A simulation study of deepwater ventilation in fjords through artificial downwelling

The pumping of less dense surface water into a deep layer, also termed artificial downwelling (AD), has demonstrated its effectiveness in ventilating basin water in a few fjords. Building on a previous experiment in By Fjord, we established a well-calibrated far-field hydrodynamic model to simulate bottom water circulation caused by AD implementation. Our simulations suggest that (1) laterally closed boundaries are crucial for AD to cause spatially uniform compensatory downwelling in the bottom water and that (2) dissolved oxygen delivered through downwelling can be sourced from both surface waters and below the pycnocline to enhance oxygen levels effectively. We propose a physical oxygen budget model to predict the temporal variability of deep-water oxygen levels, offering guidelines on the number of pipes and flow rates required for large-scale oxygenation. For small fjords (∼1 km2), a few pipes (each has a flow rate of 1 m3 s−1) may suffice, while medium-sized basins like Chesapeake Bay (∼1000 km2) may require several hundred pipes.