Global gridded daily mean data from the NCEP/NCAR Reanalysis(1948-2012) are used to obtain the onset date,retreat date and duration time series of the South China Sea summer monsoon(SCSSM) for the past 65 years.The su...Global gridded daily mean data from the NCEP/NCAR Reanalysis(1948-2012) are used to obtain the onset date,retreat date and duration time series of the South China Sea summer monsoon(SCSSM) for the past 65 years.The summer monsoon onset(retreat) date is defined as the time when the mean zonal wind at 850 hPa shifts steadily from easterly(westerly) to westerly(easterly) and the pseudo-equivalent potential temperature at the same level remains steady at greater than 335 K(less than 335 K) in the South China Sea area[110-120°E(10-20°N)].The clockwise vortex of the equatorial Indian Ocean region,together with the cross-equatorial flow and the subtropical high,plays a decisive role in the burst of the SCSSM.The onset date of the SCSSM is closely related to its intensity.With late(early) onset of the summer monsoon,its intensity is relatively strong(weak),and the zonal wind undergoes an early(late) abrupt change in the upper troposphere.Climate warming significantly affects the onset and retreat dates of the SCSSM and its intensity.With climate warming,the number of early-onset(-retreat) years of the SCSSM is clearly greater(less),and the SCSSM is clearly weakened.展开更多
In view of the huge ice cover of 24. 5× 106 km3 in Antarctica, which accounts for over 90 % by volume of the ice body on earth, the movement of Antarctic glaciers is a major control on global sea-level change and...In view of the huge ice cover of 24. 5× 106 km3 in Antarctica, which accounts for over 90 % by volume of the ice body on earth, the movement of Antarctic glaciers is a major control on global sea-level change and climatic fluctuation. As recorded in the Quaternary deposits in King George Island, West Antarctica, three rapid ablations can be recognized at 11000, 9000 and 6100 years ago and the global climate within the past 6000 years is characterized by small-amplitude warm-cold fluctuation. Intertidal deceits at the north bank of the Shenzhen Bay suggest a periodic variation in sea level in about every 670 years over the last 6000 years with low sea levels recorded in the periods of 5500 - 4900, 3900 - 3600, 2400 2200 and 1300 - 1200 years ago. Between these periods the sea level rised for about 80 cm onaverage. The modern warming climate in the last century corresponds with a rise of sea level atthe rate of 2 - 3 mm/a.展开更多
The Arctic Oscillation(AO)has important effects on the sea ice change in terms of the dynamic and thermodynamic processes.However,while the dynamic processes of AO have been widely explored,the thermodynamic processes...The Arctic Oscillation(AO)has important effects on the sea ice change in terms of the dynamic and thermodynamic processes.However,while the dynamic processes of AO have been widely explored,the thermodynamic processes of AO need to be further discussed.In this paper,we use the fifth state-of-the-art reanalysis at European Centre for Medium-Range Weather Forecasts(ERA5)from 1979 to 2020 to investigate the relationship between AO and the surface springtime longwave(LW)cloud radiative forcing(CRF),summertime shortwave(SW)CRF in the Arctic region(65°-90°N).In addition,the contribution of CRF induced by AO to the sea ice change is also discussed.Results indicate that the positive(negative)anomalies of springtime LW CRF and summertime SW CRF are generally detected over the Arctic Ocean during the enhanced positive(negative)AO phase in spring and summer,respectively.Meanwhile,while the LW(SW)CRF generally has a positive correlation with AO index(AOI)in spring(summer)over the entire Arctic Ocean,this correlation is statistically significant over 70°-85°N and 120°W-90°E(i.e.,region of interest(ROI))in both seasons.Moreover,the response of CRF to the atmospheric conditions varies in spring and summer.We also find that the positive springtime(summertime)AOI tends to decrease(increase)the sea ice in September,and this phenomenon is especially prominent over the ROI.The sensitivity study among sea ice extent,CRF and AOI further reveals that decreases(increases)in September sea ice over the ROI are partly attributed to the springtime LW(summertime SW)CRF during the positive AOI.The present study provides a new pattern of AO affecting sea ice change via cloud radiative effects,which might benefit the sea ice forecast improvement.展开更多
Much geological research has illustrated the transition of paleoenvironmental patterns during the Cenozoic from a planetary-wind-dominant type to a monsoon-dominant type, indicating the initiation of the East Asian mo...Much geological research has illustrated the transition of paleoenvironmental patterns during the Cenozoic from a planetary-wind-dominant type to a monsoon-dominant type, indicating the initiation of the East Asian monsoon and inland-type aridity. However, there is a dispute about the causes and mechanisms of the transition, especially about the impact of the Himalayan/Tibetan Plateau uplift and the Paratethys Sea retreat, Thirty numerical sensitivity experiments under different land-sea distributions and Himalayan/Tibetan Plateau topography conditions are performed here to simulate the evolution of climate belts with emphasis on changes in the rain band, and these are compared with the changes in the paleoenvironmental patterns during the Cenozoic recovered by geological records. The consistency between simulations and the geological evidence indicates that both the Tibetan Plateau uplift and the Paratethys Sea retreat play important roles in the formation of the monsoon-dominant environmental pattern. Furthermore, the simulations show the monsoon-dominant environmental pattern comes into being when the Himalayan/Tibetan Plateau reaches 1000-2000 m high and the Paratethys Sea retreats to the Turan Plate.展开更多
Along the recently evacuated shores of the retreating Dead Sea black mud deposits have been exposed and hence subjected to head ward erosion resulting in landslides and land collapses threatening herewith the infrastr...Along the recently evacuated shores of the retreating Dead Sea black mud deposits have been exposed and hence subjected to head ward erosion resulting in landslides and land collapses threatening herewith the infrastructure in the area. The geotechnical and mineralogical characterization of the black mud show the presence of a variety of clays including smectite, kaolinite, illite, montmorollinite and muscovite with a natural water content near the liquid limit. These geotechnical and mineralogical properties indicate that the mud is prone to rapid erosion and sliding, which actually hit the area and have until now caused damages and degrading topography and geology in the area. The study also refers the origin of the black mud and its organic content to the erosion and deposition of Upper Cretaceous-Tertiary oil shale deposits formerly covering the whole surrounding areas of the Dead Sea. The study suggests engineering solutions to the geologic degradation processes in the area, before further damage to the infrastructure takes place.展开更多
利用1948—2012年NCEP/NCAR再分析全球格点日平均资料,将南海区域（110-120°E,10-20°N）850 h Pa候平均纬向风稳定地由东（西）风转为西（东）风,且同一层上稳定地有θse≥335 K（θse〈335 K）确定为南海夏季风建立（结束）...利用1948—2012年NCEP/NCAR再分析全球格点日平均资料,将南海区域（110-120°E,10-20°N）850 h Pa候平均纬向风稳定地由东（西）风转为西（东）风,且同一层上稳定地有θse≥335 K（θse〈335 K）确定为南海夏季风建立（结束）日期,得到近65 a南海夏季风建立、结束、持续日期序列。赤道印度洋地区的顺时针旋转的涡旋与越赤道气流及副高对南海夏季风的爆发起着决定性作用。南海夏季风建立日期与其强度的关系密切,夏季风建立越晚（早）其强度越强（弱）,纬向风在对流层高层先（后）发生突变。气候变暖对南海夏季风的建立和结束日期及强度的影响是显著的,气候变暖后南海夏季风建立早（晚）年明显偏多（少）,强度明显偏弱。展开更多
Arctic sea ice has significant seasonal variability. Prior to the 2000 s, it retreated about 15% in summer and fully recovered in winter. However, by the year 2007, Arctic sea ice extent experienced a catastrophic dec...Arctic sea ice has significant seasonal variability. Prior to the 2000 s, it retreated about 15% in summer and fully recovered in winter. However, by the year 2007, Arctic sea ice extent experienced a catastrophic decline to about 4.28×10^6 km^2, which was 50% lower than conditions in the 1950 s to the 1970 s(Serreze et al., 2008). That was a record low over the course of the modern satellite record, since 1979(note that the year 2012 became the new record low). This astonishing event drew wide-ranging attention in 2007-2009 during the 4 th International Polar Year. The dramatic decline of sea ice attracts many scientists’ interest and has become the focus of intense research since then. Currently, sea ice retreat is not only appearing around the marginal ice zone, but also in the pack ice inside the central Arctic(Zhao et al., 2018). In fact, premonitory signs had already been seen through other evidence. Before the disintegration of the Soviet Union, US naval submarines had been conducting an extensive survey under the sea ice and taking measurements of sea ice thickness. Their measurements revealed a gradual decrease of ice thickness to 1.8 m during winter by the end of the 20 th century, in contrast to the climatological mean of 3.1 m(Rothrock et al., 1999). However, this alarming result did not draw much attention since the Arctic was still severely cold at that time.展开更多
Nutrients and photosynthesis pigments were investigated in the western Arctic Ocean during the 3rd Chinese Arctic Research Expedition Cruise in summer 2008. The study area was divided into five provinces using the K- ...Nutrients and photosynthesis pigments were investigated in the western Arctic Ocean during the 3rd Chinese Arctic Research Expedition Cruise in summer 2008. The study area was divided into five provinces using the K- means clustering method based on the physical and chemical characteristics of the sea water, and to discuss the distribution of the phytoplankton community structure in these provinces. CHEMTAX software was performed using HPLC pigments to estimate the contributions of eight algal classes to the total chlorophyll a （TChl a）. The results showed that on the Chukchi Shelf, the Pacific Ocean inflow mainly controlled the Chl a biomass and phytoplankton communities by nutrient concentrations. The high nutrient Anadyr Water and Bering Shelf Water （AnW and BSW） controlled region have high Chl a levels and the diatom dominated community structure. In contrast, in the region occupied by low-nutrient like Alaska Coastal Water （ACW）, the Chl a biomass was low, with pico- and nano-phytoplankton as dominated species, such as prasinophytes, chrysophytes and cryptophytes. However, over the off-shelf, the ice cover condition which would affect the physical and nutrient concentrations of the water masses, in consequence had a greater impact on the phytoplankton community structure. Diatom dominated in ice cover region and its contribution to Chl a biomass was up to 75%. In the region dose to the Mendeleev Abyssal Plain （MAP）, controlled by sea-ice melt water with relatively high salinity （MW-HS）, higher nutrient and Chl a concentrations were found and the phytoplankton was dominated by pico- and nano-algae, while the diatom abundance reduced to 33%. In the southern Canada Basin, an ice-free basin （IfB） with the lowest nutrient concentrations and most freshened surface water, low Chl a biomass was a consequence of low nutrients. The ice retreating and a prolonged period of open ocean may not be beneficial to the carbon export efficiency due to reducing the Chl a biomass or intriguing smaller size algae growth.展开更多
基金National Key Basic Research and Development Planning Program of China(Program 973)(2013CB430202)Basic Research Program of Jiangsu Province,China(BK20130997)+1 种基金National Natural Science Fund of China(91337109)Project Funded by the Priority Academic program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Global gridded daily mean data from the NCEP/NCAR Reanalysis(1948-2012) are used to obtain the onset date,retreat date and duration time series of the South China Sea summer monsoon(SCSSM) for the past 65 years.The summer monsoon onset(retreat) date is defined as the time when the mean zonal wind at 850 hPa shifts steadily from easterly(westerly) to westerly(easterly) and the pseudo-equivalent potential temperature at the same level remains steady at greater than 335 K(less than 335 K) in the South China Sea area[110-120°E(10-20°N)].The clockwise vortex of the equatorial Indian Ocean region,together with the cross-equatorial flow and the subtropical high,plays a decisive role in the burst of the SCSSM.The onset date of the SCSSM is closely related to its intensity.With late(early) onset of the summer monsoon,its intensity is relatively strong(weak),and the zonal wind undergoes an early(late) abrupt change in the upper troposphere.Climate warming significantly affects the onset and retreat dates of the SCSSM and its intensity.With climate warming,the number of early-onset(-retreat) years of the SCSSM is clearly greater(less),and the SCSSM is clearly weakened.
文摘In view of the huge ice cover of 24. 5× 106 km3 in Antarctica, which accounts for over 90 % by volume of the ice body on earth, the movement of Antarctic glaciers is a major control on global sea-level change and climatic fluctuation. As recorded in the Quaternary deposits in King George Island, West Antarctica, three rapid ablations can be recognized at 11000, 9000 and 6100 years ago and the global climate within the past 6000 years is characterized by small-amplitude warm-cold fluctuation. Intertidal deceits at the north bank of the Shenzhen Bay suggest a periodic variation in sea level in about every 670 years over the last 6000 years with low sea levels recorded in the periods of 5500 - 4900, 3900 - 3600, 2400 2200 and 1300 - 1200 years ago. Between these periods the sea level rised for about 80 cm onaverage. The modern warming climate in the last century corresponds with a rise of sea level atthe rate of 2 - 3 mm/a.
基金The National Natural Science Foundation of China under contract Nos 42174016 and 42076240the Open Fund of State Key Laboratory of Satellite Ocean Environment Dynamics,Second Institute of Oceanography,Ministry of Natural Resources under contract No.QNHX2122the Shanghai Pujiang Program under contract No.19PJ1404300。
文摘The Arctic Oscillation(AO)has important effects on the sea ice change in terms of the dynamic and thermodynamic processes.However,while the dynamic processes of AO have been widely explored,the thermodynamic processes of AO need to be further discussed.In this paper,we use the fifth state-of-the-art reanalysis at European Centre for Medium-Range Weather Forecasts(ERA5)from 1979 to 2020 to investigate the relationship between AO and the surface springtime longwave(LW)cloud radiative forcing(CRF),summertime shortwave(SW)CRF in the Arctic region(65°-90°N).In addition,the contribution of CRF induced by AO to the sea ice change is also discussed.Results indicate that the positive(negative)anomalies of springtime LW CRF and summertime SW CRF are generally detected over the Arctic Ocean during the enhanced positive(negative)AO phase in spring and summer,respectively.Meanwhile,while the LW(SW)CRF generally has a positive correlation with AO index(AOI)in spring(summer)over the entire Arctic Ocean,this correlation is statistically significant over 70°-85°N and 120°W-90°E(i.e.,region of interest(ROI))in both seasons.Moreover,the response of CRF to the atmospheric conditions varies in spring and summer.We also find that the positive springtime(summertime)AOI tends to decrease(increase)the sea ice in September,and this phenomenon is especially prominent over the ROI.The sensitivity study among sea ice extent,CRF and AOI further reveals that decreases(increases)in September sea ice over the ROI are partly attributed to the springtime LW(summertime SW)CRF during the positive AOI.The present study provides a new pattern of AO affecting sea ice change via cloud radiative effects,which might benefit the sea ice forecast improvement.
基金This study was supported by the National Natural Science Foundation of China(Grant Nos.40125014 and 40231001)the Key Program of the Chinese Academy of Sciences KZCX3-SW-139.
文摘Much geological research has illustrated the transition of paleoenvironmental patterns during the Cenozoic from a planetary-wind-dominant type to a monsoon-dominant type, indicating the initiation of the East Asian monsoon and inland-type aridity. However, there is a dispute about the causes and mechanisms of the transition, especially about the impact of the Himalayan/Tibetan Plateau uplift and the Paratethys Sea retreat, Thirty numerical sensitivity experiments under different land-sea distributions and Himalayan/Tibetan Plateau topography conditions are performed here to simulate the evolution of climate belts with emphasis on changes in the rain band, and these are compared with the changes in the paleoenvironmental patterns during the Cenozoic recovered by geological records. The consistency between simulations and the geological evidence indicates that both the Tibetan Plateau uplift and the Paratethys Sea retreat play important roles in the formation of the monsoon-dominant environmental pattern. Furthermore, the simulations show the monsoon-dominant environmental pattern comes into being when the Himalayan/Tibetan Plateau reaches 1000-2000 m high and the Paratethys Sea retreats to the Turan Plate.
文摘Along the recently evacuated shores of the retreating Dead Sea black mud deposits have been exposed and hence subjected to head ward erosion resulting in landslides and land collapses threatening herewith the infrastructure in the area. The geotechnical and mineralogical characterization of the black mud show the presence of a variety of clays including smectite, kaolinite, illite, montmorollinite and muscovite with a natural water content near the liquid limit. These geotechnical and mineralogical properties indicate that the mud is prone to rapid erosion and sliding, which actually hit the area and have until now caused damages and degrading topography and geology in the area. The study also refers the origin of the black mud and its organic content to the erosion and deposition of Upper Cretaceous-Tertiary oil shale deposits formerly covering the whole surrounding areas of the Dead Sea. The study suggests engineering solutions to the geologic degradation processes in the area, before further damage to the infrastructure takes place.
基金Funding was provided by Global Change Research Program of China (No. 2015CB953900)the Key Project of the National Natural Science Foundation of China (No. 41330960)
文摘Arctic sea ice has significant seasonal variability. Prior to the 2000 s, it retreated about 15% in summer and fully recovered in winter. However, by the year 2007, Arctic sea ice extent experienced a catastrophic decline to about 4.28×10^6 km^2, which was 50% lower than conditions in the 1950 s to the 1970 s(Serreze et al., 2008). That was a record low over the course of the modern satellite record, since 1979(note that the year 2012 became the new record low). This astonishing event drew wide-ranging attention in 2007-2009 during the 4 th International Polar Year. The dramatic decline of sea ice attracts many scientists’ interest and has become the focus of intense research since then. Currently, sea ice retreat is not only appearing around the marginal ice zone, but also in the pack ice inside the central Arctic(Zhao et al., 2018). In fact, premonitory signs had already been seen through other evidence. Before the disintegration of the Soviet Union, US naval submarines had been conducting an extensive survey under the sea ice and taking measurements of sea ice thickness. Their measurements revealed a gradual decrease of ice thickness to 1.8 m during winter by the end of the 20 th century, in contrast to the climatological mean of 3.1 m(Rothrock et al., 1999). However, this alarming result did not draw much attention since the Arctic was still severely cold at that time.
基金The National Natural Science Foundation of China under contract Nos 41276198,41506222 and 41406217Chinese Polar Environment Comprehensive Investigation and Assessment Programs under contract Nos Chinare-03-04 and Chinare-04-03+2 种基金Chinese Polar Science Strategy Research Foundation under contract No.20120104the Sino-German Joint Project of"Natural variability of Arctic sea ice and its significance for global climate change and organic carbon cycle"the Foundation from the China Scholarship Council under contract No.201404180012
文摘Nutrients and photosynthesis pigments were investigated in the western Arctic Ocean during the 3rd Chinese Arctic Research Expedition Cruise in summer 2008. The study area was divided into five provinces using the K- means clustering method based on the physical and chemical characteristics of the sea water, and to discuss the distribution of the phytoplankton community structure in these provinces. CHEMTAX software was performed using HPLC pigments to estimate the contributions of eight algal classes to the total chlorophyll a （TChl a）. The results showed that on the Chukchi Shelf, the Pacific Ocean inflow mainly controlled the Chl a biomass and phytoplankton communities by nutrient concentrations. The high nutrient Anadyr Water and Bering Shelf Water （AnW and BSW） controlled region have high Chl a levels and the diatom dominated community structure. In contrast, in the region occupied by low-nutrient like Alaska Coastal Water （ACW）, the Chl a biomass was low, with pico- and nano-phytoplankton as dominated species, such as prasinophytes, chrysophytes and cryptophytes. However, over the off-shelf, the ice cover condition which would affect the physical and nutrient concentrations of the water masses, in consequence had a greater impact on the phytoplankton community structure. Diatom dominated in ice cover region and its contribution to Chl a biomass was up to 75%. In the region dose to the Mendeleev Abyssal Plain （MAP）, controlled by sea-ice melt water with relatively high salinity （MW-HS）, higher nutrient and Chl a concentrations were found and the phytoplankton was dominated by pico- and nano-algae, while the diatom abundance reduced to 33%. In the southern Canada Basin, an ice-free basin （IfB） with the lowest nutrient concentrations and most freshened surface water, low Chl a biomass was a consequence of low nutrients. The ice retreating and a prolonged period of open ocean may not be beneficial to the carbon export efficiency due to reducing the Chl a biomass or intriguing smaller size algae growth.
