The biological carbon pump, which transports particulate organic carbon (POC) from the surface to the deep ocean, plays an important role in regulating atmospheric carbon dioxide (CO ₂) ...concentrations. We know very little about geographical variability in the remineralization depth of this sinking material and less about what controls such variability. Here we present previously unpublished profiles of mesopelagic POC flux derived from neutrally buoyant sediment traps deployed in the North Atlantic, from which we calculate the remineralization length scale for each site. Combining these results with corresponding data from the North Pacific, we show that the observed variability in attenuation of vertical POC flux can largely be explained by temperature, with shallower remineralization occurring in warmer waters. This is seemingly inconsistent with conclusions drawn from earlier analyses of deep-sea sediment trap and export flux data, which suggest lowest transfer efficiency at high latitudes. However, the two patterns can be reconciled by considering relatively intense remineralization of a labile fraction of material in warm waters, followed by efficient downward transfer of the remaining refractory fraction, while in cold environments, a larger labile fraction undergoes slower remineralization that continues over a longer length scale. Based on the observed relationship, future increases in ocean temperature will likely lead to shallower remineralization of POC and hence reduced storage of CO ₂ by the ocean.
Significance A key factor regulating the air−sea balance of carbon dioxide (CO ₂) is the sinking of particles containing organic carbon from the surface to the deep ocean. The depth at which this carbon is released back into the water (remineralization) has a strong influence on atmospheric CO ₂ concentration. Here we show a significant relationship between the remineralization depth of sinking organic carbon flux in the upper ocean and water temperature, with shallower remineralization in warmer waters. Our results contrast with data from deep-sea sediment traps, highlighting the importance of upper ocean remineralization to our understanding of the ocean’s biological carbon pump. Our results suggest that predicted future increases in ocean temperature will result in reduced CO ₂ storage by the oceans.
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•An integrated system consisting of geothermal and solar power plants, an electrolyzer and a fuel cell unit is proposed.•Thermodynamic performance of the system are evaluated using ...geothermal and solar values of Afyonkarahisar.•The power plants can produce 2900 kW power and 0.0185 kg/s hydrogen could be produced, and th power output from the fuel cell is 1615 kW.•Energy and exergy efficiencies of the overall system are 5.90% and 19.0% including electrolyzer and fuel cell units.
A geothermal and solar energy-assisted multi-generation energy system supplying electricity for the residences is modeled and analyzed. The system considered is a novel configuration consisting of a binary geothermal power plant and a parabolic trough concentrating solar power plant for electricity production and water electrolysis and fuel cell unit for hydrogen storage and utilization. Thermodynamic performance evaluation of the system is performed using Afyonkarahisar's geothermal and solar energy values. In Afyonkarahisar province, geothermal water temperature ranges between 70 and 130 °C and mass flow rate between 70 and 150 kg/s. Also, solar radiation incident varies between 300 and 1000 W/m2. The geothermal and solar power plants could produce 2900 kW power. If this is used entirely for hydrogen production, 0.0185 kg/s hydrogen could be produced. One can produce 1615 kW power by using this hydrogen in the fuel cell. The overall system's energy and exergy efficiencies are calculated to be 5.90% and 18.99%, respectively. The system's parametric study is performed considering geothermal resource temperatures and solar radiation values on the power output and hydrogen production.
Loss of sea ice during winter north of Svalbard Onarheim, Ingrid H.; Smedsrud, Lars H.; Ingvaldsen, Randi B. ...
Tellus. Series A, Dynamic meteorology and oceanography,
01/2014, Letnik:
66, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Sea ice loss in the Arctic Ocean has up to now been strongest during summer. In contrast, the sea ice concentration north of Svalbard has experienced a larger decline during winter since 1979. The ...trend in winter ice area loss is close to 10% per decade, and concurrent with a 0.3°C per decade warming of the Atlantic Water entering the Arctic Ocean in this region. Simultaneously, there has been a 2°C per decade warming of winter mean surface air temperature north of Svalbard, which is 20-45% higher than observations on the west coast. Generally, the ice edge north of Svalbard has retreated towards the northeast, along the Atlantic Water pathway. By making reasonable assumptions about the Atlantic Water volume and associated heat transport, we show that the extra oceanic heat brought into the region is likely to have caused the sea ice loss. The reduced sea ice cover leads to more oceanic heat transferred to the atmosphere, suggesting that part of the atmospheric warming is driven by larger open water area. In contrast to significant trends in sea ice concentration, Atlantic Water temperature and air temperature, there is no significant temporal trend in the local winds. Thus, winds have not caused the long-term warming or sea ice loss. However, the dominant winds transport sea ice from the Arctic Ocean into the region north of Svalbard, and the local wind has influence on the year-to-year variability of the ice concentration, which correlates with surface air temperatures, ocean temperatures, as well as the local wind.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Rapid ice loss is occurring in the Amundsen Sea sector of the West Antarctic Ice Sheet. This ice loss is assumed to be a long‐term response to oceanographic forcing, but ocean conditions in the ...Amundsen Sea are unknown prior to 1994. Here we present a modeling study of Amundsen Sea conditions from 1920 to 2013, using an ensemble of ice‐ocean simulations forced by climate model experiments. We find that during the early twentieth century, the Amundsen Sea likely experienced more sustained cool periods than at present. Warm periods become more dominant over the simulations (mean trend 0.33°C/century) causing an increase in ice shelf melting. The warming is likely driven by an eastward wind trend over the continental shelf break that is partly anthropogenically forced. Our simulations suggest that the Amundsen Sea responded to historical greenhouse gas forcing, and that future changes in emissions are also likely to affect the region.
Plain Language Summary
Ice loss from the West Antarctic Ice Sheet is one of the fastest growing contributions to sea level rise. The pattern of melting suggests that the ocean has been warming in the Amundsen Sea, but we don't know what the ocean was like in this region before observations started in 1994. In this study, we model the ocean conditions over the last century, using a set of 20 ice‐ocean simulations fed with the output of larger climate models. Our simulations suggest that the Amundsen Sea used to be cooler than it is today. Over the last century, ocean temperatures have increased, but this is hard to detect in observations because the trend is obscured by frequent swings between cold and warm conditions. The main cause of the warming in our simulations is changes in the winds near the edge of the Amundsen Sea that pump more warm water from the deep ocean onto the shallower continental shelf. These wind trends are partly caused by greenhouse gas emissions from the burning of fossil fuels. Whether the Amundsen Sea continues to warm, or whether temperatures stabilize, will likely hinge on the success of future climate policies to reduce emissions.
Key Points
An ensemble of ice‐ocean simulations is used to study conditions in the Amundsen Sea over the twentieth century
The simulations show a long‐term ocean warming trend on the continental shelf, which is not yet clear in the shorter observational record
The trends are partly driven by anthropogenic forcing, suggesting the ocean and ice shelves may also be sensitive to future climate policy
In order to harness the ample solar energy resources and minimize conflicts in drip irrigation schedules, a field experiment was conducted in Xinjiang, northwest China, during 2020 and 2021. The ...study examined the combined effects of two irrigation timing (daytime - DI and nighttime - NI) and four water temperatures (15, 20, 25, and 30 °C), resulting in eight treatment combinations. The analysis focused on evaluating the impacts of these factors on soil conditions, cotton phenological period, reproductive growth, and fiber quality. Results showed that elevating the irrigation water temperature had a notable impact on soil respiration throughout the different growth stages. The treatment with an irrigation water temperature of 30 °C exhibited a substantial increase in soil respiration, ranging from 17.92% to 45.95%, when compared to conventional irrigation with water temperature at 15 °C. The elevation of irrigation water temperature resulted in notable reductions in soil nitrate and ammonium nitrogen levels. Specifically, the treatment with irrigation water temperature set at 30 °C exhibited an average decrease of 21.69% and 19.27% in soil nitrate and ammonium nitrogen content, respectively, compared to the 15 °C treatment in both years. Nighttime irrigation with increased water temperatures of 20, 25, and 30 °C advanced the onset of the boll opening stage and stimulated the reproductive growth of cotton. Conversely, irrigation with regular water temperature (15 °C) decreased the number of bolls during the early boll-forming period, as well as and the peak number of squares and flowers. However, it resulted in an increased number of bolls during the late boll-forming period. Surprisingly, despite the enhancement in fiber strength and elongation due to water-warming irrigation, it unexpectedly led to a decrease in fiber length and uniformity. Moreover, higher irrigation water temperatures (25 and 30 °C) even resulted in poor levels (> 5.0) of micronaire. Nevertheless, nighttime warming irrigation improved all other fiber qualities except for uniformity. Therefore, when considering the application of water-warming irrigation in arid regions under mulched drip systems, careful selection of irrigation timing and water temperatures is necessary, taking into account the desired fiber quality. This study serves as a valuable technical reference for such irrigation practices.
•Water warming promote soil respiration and nitrogen consumption.•Water temperature and irrigation timing significantly affect cotton phenology.•Water warming decreases the fiber quality of cotton.
To test whether gonadal development of female eels could be promoted without any exogenous hormone treatments, we observed the effect of water temperature manipulation. After 3–5 months of water ...temperature treatments, three silver eels showed higher gonadosomatic indices (GSI). In particular, one eel in the 5–15°C fluctuating temperature treatment group (5°C daytime and 15°C night‐time) had the highest GSI of 8.5 with secondary yolk globule stage oocytes of large diameter (OD; 412 μm) after 3 months, which indicated definite gonadal development compared with those in the initial states (mean GSI, 2.4; OD, 226.7 μm). The 5–15°C fluctuating temperature and constant 5°C groups had low oocyte breakdown (atretic) rates. Because daily temperature fluctuations and cold daytime water are experienced by vertically migrating silver eels in the ocean, these temperature conditions may be key maturation process components that could be useful for hormone‐free artificial maturation.
Summary
Vibrio spp. thrive in warm water and moderate salinity, and they are associated with aquatic invertebrates, notably crustaceans and zooplankton. At least 12 Vibrio spp. are known to cause ...infection in humans, and Vibrio cholerae is well documented as the etiological agent of pandemic cholera. Pathogenic non‐cholera Vibrio spp., e.g., Vibrio parahaemolyticus and Vibrio vulnificus, cause gastroenteritis, septicemia, and other extra‐intestinal infections. Incidence of vibriosis is rising globally, with evidence that anthropogenic factors, primarily emissions of carbon dioxide associated with atmospheric warming and more frequent and intense heatwaves, significantly influence environmental parameters, e.g., temperature, salinity, and nutrients, all of which can enhance growth of Vibrio spp. in aquatic ecosystems. It is not possible to eliminate Vibrio spp., as they are autochthonous to the aquatic environment and many play a critical role in carbon and nitrogen cycling. Risk prediction models provide an early warning that is essential for safeguarding public health. This is especially important for regions of the world vulnerable to infrastructure instability, including lack of ‘water, sanitation, and hygiene’ (WASH), and a less resilient infrastructure that is vulnerable to natural calamity, e.g., hurricanes, floods, and earthquakes, and/or social disruption and civil unrest, arising from war, coups, political crisis, and economic recession. Incorporating environmental, social, and behavioural parameters into such models allows improved prediction, particularly of cholera epidemics. We have reported that damage to WASH infrastructure, coupled with elevated air temperatures and followed by above average rainfall, promotes exposure of a population to contaminated water and increases the risk of an outbreak of cholera. Interestingly, global predictive risk models successful for cholera have the potential, with modification, to predict diseases caused by other clinically relevant Vibrio spp. In the research reported here, the focus was on environmental parameters associated with incidence and distribution of clinically relevant Vibrio spp. and their role in disease transmission. In addition, molecular methods designed for detection and enumeration proved useful for predictive modelling and are described, namely in the context of prediction of environmental conditions favourable to Vibrio spp., hence human health risk.
•Explored the impact of pre-1 °C influent ammonia levelson nitrifying MBBR performance at 1 °C.•Higher pre-1 °C influent ammonia levels enhanced MBBR performance, recovery speed, and nitrifier ...populations.•Identified 20 mg N/L as the optimal pre-1 °C influent ammonia concentration for the best performance at 1 °C.•Identified the dominant nitrifiers as Nitrosomonadaceae (AOB) and Nitrospiraceae (NOB).•NOB was more sensitive to varying influent ammonia levels and more resilient to free ammonia at 1 °C than AOB.
This study investigated the impact of varying total ammonia nitrogen (TAN) feed levels along with water temperature decreases on the performance of nitrifying moving bed biofilm reactor (MBBR) at 1 °C and its recovery at 3 °C. Five MBBR reactors were operated with different TAN concentrations as water temperature decreased from 20 to 3 °C: reactor R1 at 30 mg N/L, reactor R2 at 20 mg N/L, reactor R3 at 15 mg N/L, reactor R4 at 10 mg N/L and reactor R5 at 0 mg N/L. The corresponding biofilm characteristics were also analyzed to understand further nitrifying MBBR under different TAN feeding scenarios. The findings revealed that the higher TAN levels were before reaching 1 °C, the better nitrification performance and the more biomass grew. However, the highest TAN concentration (30 mg N/L) might negatively affect the nitrification performance, the activity of nitrifiers, and the growth of biofilms at 1 °C because of the toxic effects of un-ionized or free ammonia (FA). It was observed that the activities of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were affected by FA concentrations ranging from 0.2 to 0.7 mg N/L at 1 °C, but they could gradually be adapted to such inhibitory environment, with NOB recovering more quickly and robustly than AOB. The study identified 20 mg N/L (67 % of maximum influent TAN at 1 °C in R2 as the optimal TAN feeding concentration, achieving over 90 % TAN removal and a surface area removal rate (SARR) of 0.78 ± 0.02 g N/m2·d at 1 °C. Meanwhile, R2 also exhibited the highest biofilm mass, with total solids at 13.3 mg/carrier and volatile solids at 11.3 mg/carrier. As TAN was removed, nitrite accumulation was observed at 1 °C, and higher influent TAN concentrations prior to 1 °C appeared to delay the accumulation. When water temperature increased from 1 °C to 3 °C, nitrification performance improved significantly in all reactors without nitrite accumulation, and the higher TAN feeding in the previous stage led to faster recovery. Compared with 20 °C, biofilm became thinner and denser at 1 °C and 3 °C. Furthermore, this study revealed significant shifts in microbial community composition and nitrifier abundances in response to changes in water temperature and influent TAN levels. The dominant nitrifiers were identified as Nitrosomonadaceae (AOB) and Nitrospiraceae (NOB). At 1 °C, the nitrifier abundances were significantly correlated with SARRs, FA, and biofilm density. R2, which exhibited the best nitrification performance, maintained higher nitrifier abundances at 1 °C.
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•An integrated heat sink was manufactured.•The performance of three common heat sinks were compared.•The cooling water temperatures have effect on the performance of the integrated heat sink.•The ...installation angles have effect on the performance of the integrated heat sink.
To address the challenge of heat management for high-power IGBTs, a type of microchannel liquid cooling heat sinks integrated vapor chamber (VC integrated heat sink) was developed. Firstly, it compared with the VC separate heat sink and the simple microchannel heat sink under the same conditions. The experimental results showed that the VC integrated heat sink had less thermal resistance than the VC separated heat sink, and the relatively simple microchannel heat sink could significantly improve the temperature uniformity. The influence of the cooling water flow rate, temperature and inclination angle on the VC integrated heat sink was further studied. Reductions in the cooling water temperature led to decreases in the heat source temperature but did not improve temperature uniformity. The inclination angle had a significant influence on the performance of the VC integrated heat sink. The performance of the VC integrated heat sink was optimal when the inclination angle was 60°.
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