Ocean University of China

About: Ocean University of China is a education organization based out in Qingdao, China. It is known for research contribution in the topics: Population & Sea surface temperature. The organization has 27604 authors who have published 27886 publications receiving 440181 citations. The organization is also known as: Zhōngguó Hǎiyáng Dàxué & OUC.

Slowdown of the Walker circulation driven by tropical Indo-Pacific warming

Abstract: Global mean sea surface temperature (SST) has risen steadily over the past century, but the overall pattern contains extensive and often uncertain spatial variations, with potentially important effects on regional precipitation. Observations suggest a slowdown of the zonal atmospheric overturning circulation above the tropical Pacific Ocean (the Walker circulation) over the twentieth century. Although this change has been attributed to a muted hydrological cycle forced by global warming, the effect of SST warming patterns has not been explored and quantified. Here we perform experiments using an atmospheric model, and find that SST warming patterns are the main cause of the weakened Walker circulation over the past six decades (1950-2009). The SST trend reconstructed from bucket-sampled SST and night-time marine surface air temperature features a reduced zonal gradient in the tropical Indo-Pacific Ocean, a change consistent with subsurface temperature observations. Model experiments with this trend pattern robustly simulate the observed changes, including the Walker circulation slowdown and the eastward shift of atmospheric convection from the Indonesian maritime continent to the central tropical Pacific. Our results cannot establish whether the observed changes are due to natural variability or anthropogenic global warming, but they do show that the observed slowdown in the Walker circulation is presumably driven by oceanic rather than atmospheric processes.

Patterns of the seasonal response of tropical rainfall to global warming

Abstract: The response of tropical precipitation to global warming varies spatially and the factors controlling the spatial patterns of precipitation changes are unclear. An analysis of climate model simulations shows that warm regions are projected to become wetter in annual mean, whereas seasonally high rainfall anomalies are expected in regions that are currently wet.

Sources and distribution of carbon within the Yangtze River system

Abstract: Dissolved, particulate, soil and plant samples were collected from the Yangtze River (Changjiang) system in May 1997 and May 2003 to determine the sources and distribution of organic and inorganic matter within the river system. Average dissolved organic carbon (DOC) concentrations within the main stream were 105 μM C in 1997 and 108 μM C in 2003. Particulate organic carbon (POC) ranged from 0.5% to 2.5% of total suspended matter (TSM). Both dissolved inorganic carbon (DIC) and particulate inorganic carbon (PIC) concentrations decreased from upper to lower reaches of the river, within the ranges 1.2–2.7 mM and 0.08–4.3% of TSM, respectively. δ13C and δ15N values for tributaries and the main stream varied from −26.8‰ to −25.1‰ and 2.8‰ to 6.0‰, respectively. A large spatial variation in particulate organic matter (POM) is recorded along the main stream, probably due to the contributions of TSM from major tributaries and POM input from local vegetation sources. The dominance of C-3 plants throughout the entire basin is indicated by δ13C and δ15N values, which range from −28.8‰ to −24.3‰ and from −0.9‰ to 5.5‰, respectively. The δ13C and δ15N values of organic matter within surface soil from alongside tributaries and the main stream vary from −28.9‰ to −24.3‰ and 2.7‰ to 4.5‰, respectively. Although these differences are subtle, there is a slight enrichment of 15N in soils along the main stream. Various approaches, such as C/N and stable isotopes, were used to trace the sources of organic matter within the river. Riverine POM is mostly derived from soil; the contribution from phytoplankton is minor and difficult to trace via the composition of particles. POC flux has decreased from >5 × 106 t yr−1 during the period 1960–1980 to about 2 × 106 t yr−1 in 1997. This trend can be explained by decreasing sediment load within the Yangtze River. The export of TOC from the Yangtze River at the end of the 20th Century is approximately equivalent to that of the Zaire River, less than that of the Amazon River, and higher than that of other large rivers such as the Mississippi. Large amounts of DOC and POC were transported to coastal areas of the East China Sea over a short period during 1998 flood events, containing large amounts of nutrients and pollutants. Such an event could be an important trigger for coastal environmental problems and changes to the health of ecosystems.

High efficiency heterogeneous Fenton-like catalyst biochar modified CuFeO2 for the degradation of tetracycline: Economical synthesis, catalytic performance and mechanism

Abstract: The heterogeneous Fenton-like catalysts biochar modified CuFeO2 (CuFeO2/BC) were fabricated by hydrothermal method without additional chemical reducing agent. The systematic characterization demonstrated that higher CuFeO2 particles dispersion and larger BET surface area of CuFeO2/BC catalyst contributed to higher catalytic activity towards the tetracycline (TC) degradation compared to pure-phase CuFeO2. The optimum conditions for TC removal were 598.63 mg L-1 of CuFeO2/BC-1.0, 57.63 mM of H2O2 and pH = 6.27 according to the result of a response surface methodology based on the central composite design. The CuFeO2/BC-1.0 exhibited an excellent reusability and good stability by recycling degradation. The OH was evidenced to the main active radical by scavenging experiments and electron spin resonance. The XPS revealed that the high catalytic efficiency was attributed to the synergistic effect of Fe3+/Fe2+ and Cu2+/Cu+ redox cycles, and the degradation intermediates of TC and toxicity analysis were evaluated.

Increased frequency of extreme Indian Ocean Dipole events due to greenhouse warming

Abstract: Extreme positive-Indian-Ocean-dipole events cause devastating floods in eastern tropical Africa and severe droughts in Asia; increasing greenhouse gas emissions will make these dipole events about three times more frequent in the twenty-first century. Countries in the southern tropical Indian Ocean region are prone to extensive flooding and droughts in years when the Indian Ocean dipole (IOD) climate cycle is in an extreme positive phase. In these bad years, such as 1961, 1994 and 1997, warm waters appear in the western part of the basin and precipitation increases, whereas in the east cooler waters predominate and precipitation decreases. Here Wenju Cai et al. assess climate model projections in a scenario of high greenhouse gas emissions and find that the frequency of extreme positive IODs is likely to increase from one event approximately every 17.3 years through the twentieth century to one event every 6.3 years during the twenty-first century. The Indian Ocean dipole is a prominent mode of coupled ocean–atmosphere variability1,2,3,4, affecting the lives of millions of people in Indian Ocean rim countries5,6,7,8,9,10,11,12,13,14,15. In its positive phase, sea surface temperatures are lower than normal off the Sumatra–Java coast, but higher in the western tropical Indian Ocean. During the extreme positive-IOD (pIOD) events of 1961, 1994 and 1997, the eastern cooling strengthened and extended westward along the equatorial Indian Ocean through strong reversal of both the mean westerly winds and the associated eastward-flowing upper ocean currents1,2. This created anomalously dry conditions from the eastern to the central Indian Ocean along the Equator and atmospheric convergence farther west, leading to catastrophic floods in eastern tropical African countries13,14 but devastating droughts in eastern Indian Ocean rim countries8,9,10,16,17. Despite these serious consequences, the response of pIOD events to greenhouse warming is unknown. Here, using an ensemble of climate models forced by a scenario of high greenhouse gas emissions (Representative Concentration Pathway 8.5), we project that the frequency of extreme pIOD events will increase by almost a factor of three, from one event every 17.3 years over the twentieth century to one event every 6.3 years over the twenty-first century. We find that a mean state change—with weakening of both equatorial westerly winds and eastward oceanic currents in association with a faster warming in the western than the eastern equatorial Indian Ocean—facilitates more frequent occurrences of wind and oceanic current reversal. This leads to more frequent extreme pIOD events, suggesting an increasing frequency of extreme climate and weather events in regions affected by the pIOD.