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The regime shift in the 1960s and associated atmospheric change over the southern Indian Ocean
Tianyu WANG, Yan DU, Xiaomei LIAO
2017, 36(1): 1-8. doi: 10.1007/s13131-017-0987-1
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The change of sea surface temperature (SST) in the southern Indian Ocean (SIO) during the recent six decades has been analyzed based on oceanic reanalysis and model, as well as atmospheric data. The results show that a thermal regime shift in SIO during the 1960s, which is not caught enough attentions, has been of equal magnitude to the linear warming since 1970. Empirical Orthogonal Function (EOF) analyses reveal that a thermal shift is combined with atmospheric changes such as the weakening of westerly during the period of 1960–1967. Inner dynamic connections can be defined that when the westerly winds turn weak, the anticyclonic wind circulation between westerly winds and the trade winds decreases, which further reduces the SST to a negative peak in this period. It is noted that the shifts in the 1960s are also evident for Southern Hemisphere. For example, subtropical high and the entire westerly winds belt at high latitudes both change dramatically in the 1960s. This large-scaled process maybe link to the change of southern annular mode (SAM).
Characteristics and possible causes of the seasonal sea levelanomaly along the South China Sea coast
Hui WANG, Kexiu LIU, Zhigang GAO, Wenjing FAN, Shouhua LIU, Jing LI
2017, 36(1): 9-16. doi: 10.1007/s13131-017-0988-0
Abstract(23) FullText HTML(5) FullText PDF(0)
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Based on sea level, air temperature, sea surface temperature (SST), air pressure and wind data during 1980–2014, this paper uses Morlet wavelet transform, Estuarine Coastal Ocean Model (ECOM) and so on to investigate the characteristics and possible causes of seasonal sea level anomalies along the South China Sea (SCS) coast. The research results show that: (1) Seasonal sea level anomalies often occur from January to February and from June to October. The frequency of sea level anomalies is the most in August, showing a growing trend in recent years. In addition, the occurring frequency of negative sea level anomaly accounts for 50% of the total abnormal number. (2) The seasonal sea level anomalies are closely related to ENSO events. The negative anomalies always occurred during the El Niño events, while the positive anomalies occurred during the La Niña (late El Niño) events. In addition, the seasonal sea level oscillation periods of 4–7 a associated with ENSO are the strongest in winter, with the amplitude over 2 cm. (3) Abnormal wind is an important factor to affect the seasonal sea level anomalies in the coastal region of the SCS. Wind-driven sea level height (SSH) is basically consistent with the seasonal sea level anomalies. Moreover, the influence of the tropical cyclone in the coastal region of the SCS is concentrated in summer and autumn, contributing to the seasonal sea level anomalies. (4) Seasonal variations of sea level, SST and air temperature are basically consistent along the coast of the SCS, but the seasonal sea level anomalies have no much correlation with the SST and air temperature.
Definition of water exchange zone between the Bohai Sea and Yellow Sea and the effect of winter gale on it
Jun SONG, Junru GUO, Jing LI, Lin MU, Yulong LIU, Guosong WANG, Yan LI, Huan LI
2017, 36(1): 17-25. doi: 10.1007/s13131-017-0989-z
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The marine dynamic environment of the Bohai Sea and the Yellow Sea in the winter of 2006 is simulated by the Regional Ocean Modelling System (ROMS) marine numerical model. Using the simulated temperature and salinity, the water exchange zone between the Bohai Sea and Yellow Sea is defined through the Spectral Mixture Model (SMM). The influence of winter gales on the water exchange is also discussed. It is found that the Yellow Sea water masses in winter are distributed in a " tongue” shape in the Bohai Strait region, the water exchange zone presents a zonal distribution along the margin of the " tongue”, with a tendency of running from northwest to southeast, and the water exchange is intensified at the tip of the " tongue”. Besides, the coastal area in the northernmost Yellow Sea does not participate in the water exchange between the Bohai Sea and Yellow Sea. The result shows that the winter gale events play a role in enhancing the water exchange. It is specifically shown by the facts: the Yellow Sea warm current is enhanced to intrude the Bohai Sea by the gale process; the water exchange zone extends into the Bohai Sea; the water exchange belt in the southern part becomes wider; the mixture zone of river runoff with the Bohai Sea water upon its entry is enlarged and shifts northwards. Within two days after the gale process, the exchange zone retreats toward the Yellow Sea and the exchange zone resulted from the Huanghe River (Yellow River) runoff also shrinks back shoreward.
Seasonal variation of the double diffusion processes at the Strait of Hormuz
Jafar AZIZPOUR, Vahid CHEGINI, Seyed Mostafa SIADATMOUSAVI
2017, 36(1): 26-34. doi: 10.1007/s13131-017-0990-6
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Profiles of salinity and temperature were measured in the strait of Hormuz (SH) during the winter of 2012, spring and summer of 2013. To investigate the double diffusion (DD) processes, Turner (TU) angle values are calculated in all the stations in the SH. Different TU angle values correspond to salt fingering (SF), diffusive convection (DC) and stable stratification. The distributions of the two forms of DD were plotted vertically along transects in the eastern, central and western part of the SH, and corresponding DD processes were described. The results show that both SF and DC occurred in most part of the study area. Two different water masses (the Indian Ocean surface water and the Persian Gulf water) were evident at the SH, and SF and DC were evident at the interface of two water masses. Due to evaporation, SF occurred in the surface layer of most Stations throughout the year. In the eastern part of the SH, occurrences of DC were more feasible in wintertime. SF was the main phenomenon at the end of hot season. For central part, SF occurred throughout the year in water column. In the western part, water column was stable in summer and DC happened in most part of water column in winter.
Regime shift of the dominant factor for halocline depth in the Canada Basin during 1990–2008
Longjiang MU, Jinping ZHAO, Wenli ZHONG
2017, 36(1): 35-43. doi: 10.1007/s13131-016-0883-0
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The World Ocean Database (WOD) is used to evaluate the halocline depth simulated by an ice-ocean coupled model in the Canada Basin during 1990–2008. Statistical results show that the simulated halocline is reliable. Comparing of the September sea ice extent between simulation and SSM/I dataset, a consistent interannual variability is found between them. Moreover, both the simulated and observed September sea ice extent show staircase declines in 2000–2008 compared to 1990–1999. That supports that the abrupt variations of the ocean surface stress curl anomaly in 2000–2008 are caused by rapid sea ice melting and also in favor of the realistic existence of the simulated variations. Responses to these changes can be found in the upper ocean circulation and the intermediate current variations in these two phases as well. The analysis shows that seasonal variations of the halocline are regulated by the seasonal variations of the Ekman pumping. On interannual time scale, the variations of the halocline have an inverse relationship with the ocean surface stress curl anomaly after 2000, while this relationship no longer applies in the 1990s. It is pointed out that the regime shift in the Canada Basin can be derived to illustrate this phenomenon. Specifically, the halocline variations are dominated by advection in the 1990s and Ekman pumping in the 2000s respectively. Furthermore, the regime shift is caused by changing Transpolar Drift pathway and Ekman pumping area due to spatial deformation of the center Beaufort high (BH) relative to climatology.
Arctic sea ice volume export through the Fram Strait fromcombined satellite and model data: 1979–2012
Zehua ZHANG, Haibo BI, Ke SUN, Haijun HUANG, Yanxia LIU, Liwen YAN
2017, 36(1): 44-55. doi: 10.1007/s13131-017-0992-4
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By combing satellite-derived ice motion and concentration with ice thickness fields from a popular model PIOMAS we obtain the estimates of ice volume flux passing the Fram Strait over the 1979–2012 period. Since current satellite and field observations for sea ice thickness are limited in time and space, the use of PIOMAS is expected to fill the gap by providing temporally continued ice thickness fields. Calculated monthly volume flux exhibits a prominent annual cycle with the peak record in March (roughly 145 km3/month) and the trough in August (10 km3/month). Annual ice volume flux (1 132 km3) is primarily attributable to winter (October through May) outflow (approximately 92%). Uncertainty in annual ice volume export is estimated to be 55 km3 (or 5.7%). Our results also verified the extremely large volume flux appearing between late 1980s and mid-1990s. Nevertheless, no clear trend was found in our volume flux results. Ice motion is the primary factor in the determination of behavior of volume flux. Ice thickness presented a general decline trend may partly enhance or weaken the volume flux trend. Ice concentration exerted the least influences on modulating trends and variability in volume flux. Moreover, the linkage between winter ice volume flux and three established Arctic atmospheric schemes were examined. Compared to NAO, the DA and EOF3 mechanism explains a larger part of variations of ice volume flux across the strait.
Winter sea ice albedo variations in the Bohai Sea of China
Jiajia ZHENG, Changqing KE, Zhude SHAO
2017, 36(1): 56-63. doi: 10.1007/s13131-017-0993-3
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Sea ice conditions in the Bohai Sea of China are sensitive to large-scale climatic variations. On the basis of CLARA-A1-SAL data, the albedo variations are examined in space and time in the winter (December, January and February) from 1992 to 2008 in the Bohai Sea sea ice region. Time series data of the sea ice concentration (SIC), the sea ice extent (SIE) and the sea surface temperature (SST) are used to analyze their relationship with the albedo. The sea ice albedo changed in volatility appears along with time, the trend is not obvious and increases very slightly during the study period at a rate of 0.388% per decade over the Bohai Sea sea ice region. The interannual variation is between 9.93% and 14.50%, and the average albedo is 11.79%. The sea ice albedo in years with heavy sea ice coverage, 1999, 2000 and 2005, is significantly higher than that in other years; in years with light sea ice coverage, 1994, 1998, 2001 and 2006, has low values. For the monthly albedo, the increasing trend (at a rate of 0.988% per decade) in December is distinctly higher than that in January and February. The mean albedo in January (12.90%) is also distinctly higher than that in the other two months. The albedo is significantly positively correlated with the SIC and is significantly negatively correlated with the SST (significance level 90%).
Aerial observations of sea ice and melt ponds near the North Pole during CHINARE2010
Lanyu LI, Changqing KE, Hongjie XIE, Ruibo LEI, Anqi TAO
2017, 36(1): 64-72. doi: 10.1007/s13131-017-0994-2
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An aerial photography has been used to provide validation data on sea ice near the North Pole where most polar orbiting satellites cannot cover. This kind of data can also be used as a supplement for missing data and for reducing the uncertainty of data interpolation. The aerial photos are analyzed near the North Pole collected during the Chinese national arctic research expedition in the summer of 2010 (CHINARE2010). The result shows that the average fraction of open water increases from the ice camp at approximately 87°N to the North Pole, resulting in the decrease in the sea ice. The average sea ice concentration is only 62.0% for the two flights (16 and 19 August 2010). The average albedo (0.42) estimated from the area ratios among snow-covered ice, melt pond and water is slightly lower than the 0.49 of HOTRAX 2005. The data on 19 August 2010 shows that the albedo decreases from the ice camp at approximately 87°N to the North Pole, primarily due to the decrease in the fraction of snow-covered ice and the increase in fractions of melt-pond and open-water. The ice concentration from the aerial photos and AMSR-E (The Advanced Microwave Scanning Radiometer-Earth Observing System) images at 87.0°–87.5°N exhibits similar spatial patterns, although the AMSR-E concentration is approximately 18.0% (on average) higher than aerial photos. This can be attributed to the 6.25 km resolution of AMSR-E, which cannot separate melt ponds/submerged ice from ice and cannot detect the small leads between floes. Thus, the aerial photos would play an important role in providing high-resolution independent estimates of the ice concentration and the fraction of melt pond cover to validate and/or supplement space-borne remote sensing products near the North Pole.
Characteristics of the sea ice reflectance spectrum polluted by oil spills based on field experiments in the Bohai Sea
Jinlong CHAO, Chengyu LIU, Ying LI, Xia LIN, Yu YAN
2017, 36(1): 73-79. doi: 10.1007/s13131-017-0995-1
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Oil spilled on the sea ice surface in the Bohai Sea of China is studied through the field measurements of the reflectance of a simulated sea ice-oil film mixed pixel. The reflection characteristics of sea ice and oil film are also analyzed. It is found that the mixed pixel of sea ice and oil film is a linear mixed pixel. The means of extracting sea ice pixels containing oil film is presented using a double-band ratio oil-film sea-ice index (DROSI) and a normalized difference oil-film sea-ice index (NDOSI) through the analysis of the reflectance curves of the sea ice-oil film pixel for different ratios of oil film. The area proportion of the oil film in the sea ice-oil film pixel can be accurately estimated by the average reflectance of the band of 1 610–1 630 nm, and the volume of the spilled oil can be further estimated. The method of the sea ice-oil film pixel extraction and the models to estimate the proportion of oil film area in the sea ice-oil film pixel can be applied to the oil spill monitoring of the ice-covered area in the Bohai Sea using multispectral or hyperspectral remote sensing images in the shortwave infrared band (1 500–1 780 nm).
Towards a semi-empirical model of the sea ice thickness based on hyperspectral remote sensing in the Bohai Sea
Shuai YUAN, Wei GU, Chengyu LIU, Feng XIE
2017, 36(1): 80-89. doi: 10.1007/s13131-017-0996-0
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Sea ice thickness is one of the most important input parameters for the prevention and mitigation of sea ice disasters and the prediction of local sea environments and climates. Estimating the sea ice thickness is currently the most important issue in the study of sea ice remote sensing. With the Bohai Sea as the study area, a semi-empirical model of the sea ice thickness (SEMSIT) that can be used to estimate the thickness of first-year ice based on existing water depth estimation models and hyperspectral remote sensing data according to an optical radiative transfer process in sea ice is proposed. In the model, the absorption and scattering properties of sea ice in different bands (spectral dimension information) are utilized. An integrated attenuation coefficient at the pixel level is estimated using the height of the reflectance peak at 1 088 nm. In addition, the surface reflectance of sea ice at the pixel level is estimated using the 1 550–1 750 nm band reflectance. The model is used to estimate the sea ice thickness with Hyperion images. The first validation results suggest that the proposed model and parameterization scheme can effectively reduce the estimation error associated with the sea ice thickness that is caused by temporal and spatial heterogeneities in the integrated attenuation coefficient and sea ice surface. A practical semi-empirical model and parameterization scheme that may be feasible for the sea ice thickness estimation using hyperspectral remote sensing data are potentially provided.
The phosphorus cycle in the Sanggou Bay
Wenqi XU, Ruihuan LI, Sumei LIU, Zhiming NING, Zengjie JIANG
2017, 36(1): 90-100. doi: 10.1007/s13131-017-0997-z
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The phosphorus cycle is studied during 2013–2014 in the Sanggou Bay (SGB), which is a typical aquaculture area in northern China. The forms of measured phosphorus include dissolved inorganic phosphorus (DIP), dissolved organic phosphorus (DOP), particulate inorganic phosphorus (PIP), and particulate organic phosphorus (POP). DIP and PIP are the major forms of total dissolved phosphorus (TDP) and total particulate phosphorus (TPP), representing 51%–75% and 53%–80%, respectively. The concentrations and distributions of phosphorus forms vary among seasons relative to aquaculture cycles, fluvial input, and hydrodynamic conditions. In autumn the concentration of DIP is significantly higher than in other seasons (P<0.01), and higher concentrations are found in the west of the bay. In winter and spring the phosphorus concentrations are higher in the east of the bay than in the west. In summer, the distributions of phosphorus forms are uniform. A preliminary phosphorus budget is developed, and shows that SGB is a net sink of phosphorus. A total of 1.80×107 mol/a phosphorus is transported into the bay. The Yellow Sea is the major source of net input of phosphorus (61%), followed by submarine groundwater discharge (SGD) (27%), river input (11%), and atmospheric deposition (1%). The main phosphorus sink is the harvest of seaweeds (Saccharina japonica andGracilaria lemaneiformis), bivalves (Chlamys farreri), and oysters (Crassostrea gigas), accounting for a total of 1.12×107 mol/a. Burial of phosphorus in sediment is another important sink, accounting for 7.00×106 mol/a. Biodeposition by bivalves is the major source of phosphorus in sediment, accounting for 54% of the total.
Source and nature of ore-forming fluids of the Edmond hydrothermal field, Central Indian Ridge: evidence from He-Arisotope composition and fluid inclusion study
Yejian WANG, Xiqiu HAN, Zhongyan QIU
2017, 36(1): 101-108. doi: 10.1007/s13131-016-0963-1
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To understand the source and nature of the ore-forming fluids of the Edmond hydrothermal field on the Central Indian Ridge, we studied the He-Ar isotope composition and fluid inclusions of the hydrothermal precipitates. Our results show that the sulfide samples contain noble gases He, Ne, Kr, and Xe with their abundances in between those of air-saturated water (ASW) and mid-ocean ridge basalt (MORB). The3He/4He ratio varies from 1.3 to 8.7 Ra (n=10, average: 5.1 Ra), whereas the40Ar/36Ar ratio is from 285.3 to 314.7 (n=10, average: 294.8). These results suggest that the He was derived from a mixture of MORB with variable amounts of seawater, but the Ar in the ore-forming fluids trapped in the sulfides is predominantly derived from seawater. The fluid inclusions of barite have a wide range of homogenization temperatures and salinities varying from 163°C to 260°C and 2.6 wt% to 8.5 wt% NaCl equiv., respectively. It is suggested that the ore-forming fluids were produced by phase separation, which agreed with the present-day vent fluid study.
The determination of 52 elements in marine geological samples by an inductively coupled plasma optical emission spectrometry and an inductively coupled plasma mass spectrometry with a high-pressure closed digestion method
Jingjing GAO, Jihua LIU, Xianguo LI, Quanshu YAN, Xiaojing WANG, Hongmin WANG
2017, 36(1): 109-117. doi: 10.1007/s13131-017-0991-5
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An improved analytical method to determine the content of 52 major, minor and trace elements in marine geological samples, using a HF-HCl-HNO3 acid system with a high-pressure closed digestion method (HPCD), is studied by an inductively coupled plasma optical emission spectrometry (ICP-OES) and an inductively coupled plasma mass spectrometry (ICP-MS). The operating parameters of the instruments are optimized, and the optimal analytical parameters are determined. The influences of optical spectrum and mass spectrum interferences, digestion methods and acid systems on the analytical results are investigated. The optimal spectral lines and isotopes are chosen, and internal standard element of rhodium is selected to compensate for matrix effects and analytical signals drifting. Compared with the methods of an electric heating plate digestion and a microwave digestion, a high-pressure closed digestion method is optimized with less acid, complete digestion, less damage for digestion process. The marine geological samples are dissolved completely by a HF-HCl-HNO3 system, the relative error (RE) for the analytical results are all less than 6.0%. The method detection limits are 2–40 μg/g by the ICP-OES, and 6–80 ng/g by ICP-MS. The methods are used to determine the marine sediment reference materials (GBW07309, GBW07311, GBW07313), rock reference materials (GBW07103, GBW07104, GBW07105), and cobalt-rich crust reference materials (GBW07337, GBW07338, GBW07339), the obtained analytical results are in agreement with the certified values, and both of the relative standard deviation (RSD) and the relative error (RE) are less than 6.0%. The analytical method meets the requirements for determining 52 elements contents of bulk marine geological samples.