2019 Vol. 41, No. 9
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2019, 41(9): 1-12.
doi: 10.3969/j.issn.0253-4193.2019.09.001
Abstract:
Coupled ocean and sea-ice models, developed based on Version 3.6 of the Nucleus for European Modelling of the Ocean (NEMO), with the sea-ice component being Version 3 of Louvain-la-Neuve Sea Ice Model (LIM), are applied for hindcast simulations covering the North Atlantic-North Pacific-Arctic Oceans (NAPA). The two model configurations, NAPA1/4 and NAPA1/12, have nominal horizontal resolutions of (1/4)° and (1/12)° in latitude/longitude, respectively. The model domains cover the Pacific Ocean north of 45°N, the whole Arctic, and the North Atlantic north of 26°N for NAPA1/4 and 7°N for NAPA1/12. A decade-long hindcast from 1993 to 2015 using NAPA1/4 has been completed. The hindcast results of sea-ice, circulation and hydrography variations in the Arctic Ocean are evaluated with available observational data and previously published results. The evaluation suggests that NAPA1/4 possesses reasonable skills in reproducing the key thermal and dynamic processes, and can be applied to study the seasonal and inter-annual variations of sea-ice, water masses, and Atlantic/Pacific inflows/outflows. Preliminary analysis of the NAPA1/12 hindcast during 1993-1996 suggests that increasing horizontal resolution simulates more details of the spatial structures of sea-ice, water-mass properties, and ocean circulation.
Coupled ocean and sea-ice models, developed based on Version 3.6 of the Nucleus for European Modelling of the Ocean (NEMO), with the sea-ice component being Version 3 of Louvain-la-Neuve Sea Ice Model (LIM), are applied for hindcast simulations covering the North Atlantic-North Pacific-Arctic Oceans (NAPA). The two model configurations, NAPA1/4 and NAPA1/12, have nominal horizontal resolutions of (1/4)° and (1/12)° in latitude/longitude, respectively. The model domains cover the Pacific Ocean north of 45°N, the whole Arctic, and the North Atlantic north of 26°N for NAPA1/4 and 7°N for NAPA1/12. A decade-long hindcast from 1993 to 2015 using NAPA1/4 has been completed. The hindcast results of sea-ice, circulation and hydrography variations in the Arctic Ocean are evaluated with available observational data and previously published results. The evaluation suggests that NAPA1/4 possesses reasonable skills in reproducing the key thermal and dynamic processes, and can be applied to study the seasonal and inter-annual variations of sea-ice, water masses, and Atlantic/Pacific inflows/outflows. Preliminary analysis of the NAPA1/12 hindcast during 1993-1996 suggests that increasing horizontal resolution simulates more details of the spatial structures of sea-ice, water-mass properties, and ocean circulation.
2019, 41(9): 13-25.
doi: 10.3969/j.issn.0253-4193.2019.09.002
Abstract:
Based on the 34th Chinese Antarctic scientific expedition "Xiangyanghong 01" cruise around the Antarctic Peninsula from January to February 2018, the properties and exchanges of water masses in the region of Antarctic Peninsula were analyzed. The main water masses are Antarctic Surface Water, Circumpolar Deep Water, Warm Deep Water, Antarctic Bottom Water, Bransfield Srait Bottom Water. Weddell Sea Warm Deep Water and Weddell Sea Deep Water flow into Scotia Sea through the Orkney Passage, the Bruce Passage on the east of the South Orkney Plateau and the Hesperides Gap on the west of the South Orkney Plateau. Among them, the deepest current velocity is 0.25 m/s in Orkney Passage, which allow denser Weddell Sea Deep Water to flow to Scotia Sea; the current velocity is 0.13 m/s in Bruce Passage, which allow warmer Warm Deep Water flows and the temperature of Warm Deep Water passing through this gap is the lowest, and the current velocity is 0.10 m/s in Hesperides Gap, only colder Warm Deep Water and lighter Weddell Sea Deep Water can pass. Southward currents and northward currents were observed on both sides of the South Orkney Plateau, but northward currents and water exchange are stronger. Water flow westward along the north side of the South Scotia Ridge after entering the Scotia Sea through the Passages on both sides of the South Orkney Plateau, with a velocity of 0.21 m/s. A branch of Antarctic Circumpolar Current in Drake Passage flow eastward to Scotia Sea, and influenced by Warm Deep Water and Weddell Sea Deep Water flowing westward, Circumpolar Deep Water in the Scotia Sea is obviously weaker than that in the Drake Passage. Affected by the eastward Antarctic Circumpolar Current, Weddell Sea Deep Water on the north side of the South Scotia Ridge is warmer than that on the south side. The water on the South Scotia Ridge may be affected by the Circumpolar Deep Water and Warm Deep Water in the north, Shelf Water in the West and Winter Water in the east, so the structure of the water on the South Scotia Ridge is much complex.
Based on the 34th Chinese Antarctic scientific expedition "Xiangyanghong 01" cruise around the Antarctic Peninsula from January to February 2018, the properties and exchanges of water masses in the region of Antarctic Peninsula were analyzed. The main water masses are Antarctic Surface Water, Circumpolar Deep Water, Warm Deep Water, Antarctic Bottom Water, Bransfield Srait Bottom Water. Weddell Sea Warm Deep Water and Weddell Sea Deep Water flow into Scotia Sea through the Orkney Passage, the Bruce Passage on the east of the South Orkney Plateau and the Hesperides Gap on the west of the South Orkney Plateau. Among them, the deepest current velocity is 0.25 m/s in Orkney Passage, which allow denser Weddell Sea Deep Water to flow to Scotia Sea; the current velocity is 0.13 m/s in Bruce Passage, which allow warmer Warm Deep Water flows and the temperature of Warm Deep Water passing through this gap is the lowest, and the current velocity is 0.10 m/s in Hesperides Gap, only colder Warm Deep Water and lighter Weddell Sea Deep Water can pass. Southward currents and northward currents were observed on both sides of the South Orkney Plateau, but northward currents and water exchange are stronger. Water flow westward along the north side of the South Scotia Ridge after entering the Scotia Sea through the Passages on both sides of the South Orkney Plateau, with a velocity of 0.21 m/s. A branch of Antarctic Circumpolar Current in Drake Passage flow eastward to Scotia Sea, and influenced by Warm Deep Water and Weddell Sea Deep Water flowing westward, Circumpolar Deep Water in the Scotia Sea is obviously weaker than that in the Drake Passage. Affected by the eastward Antarctic Circumpolar Current, Weddell Sea Deep Water on the north side of the South Scotia Ridge is warmer than that on the south side. The water on the South Scotia Ridge may be affected by the Circumpolar Deep Water and Warm Deep Water in the north, Shelf Water in the West and Winter Water in the east, so the structure of the water on the South Scotia Ridge is much complex.
2019, 41(9): 26-39.
doi: 10.3969/j.issn.0253-4193.2019.09.003
Abstract:
Sea ice is an important part of the global climate system. Landfast ice is commonly found in the Antarctic coastal area, which reached the thickest in the middle and late November around Zhongshan Station. Sea ice thickness is one of the important parameters of the sea ice. We presented measurements by taken 1 SIMBA (Snow and Ice Mass Balance Array) buoy and 3 TY buoys to monitor ice thickness based on the bias of different linear temperature gradient in air, snow, ice and sea water in three different landfast ice stations (S1, S2 and S3) in the Prydz Bay outside Zhongshan Station in 2016. The SIMBA measures vertical temperature profiles 4 times a day and TY measures vertical temperature per hour. Both SIMBA and TY buoys were set up in S3 station. Compared with borehole in situ measurements, the ice thickness derived by TY buoys had a mean bias and RMSE of 3.3 cm and 14.7 cm in S1 Station, 6.6 cm and 6.9 cm in S2 Station and 4.0 cm and 4.8 cm in S3 Station. And the mean bias and RMSE for the SIMBA buoys in S3 Station compared with borehole in situ measurements were 8.2 cm and 9.7 cm. The sea ice thickness derived by TY buoys were more agreement with the borehole in situ measurements compared with the sea ice thickness derives from SIMBA buoys in S3 Station. The result of Stefan’s law of ice growth model shows the sea ice growth process and the ice growth rate varied between 0.1 cm/d to 0.8 cm/d, which is faster than the result of TY buoys and is affected by the snow thickness. While compare with limited borehole in situ sea ice thickness measurements and the great uncertain in the sea ice thickness derived by remote sense data, the error for both the TY and SIMBA buoys are reasonable, which will benefit to the future sea ice thickness monitor near Zhongshan Station.
Sea ice is an important part of the global climate system. Landfast ice is commonly found in the Antarctic coastal area, which reached the thickest in the middle and late November around Zhongshan Station. Sea ice thickness is one of the important parameters of the sea ice. We presented measurements by taken 1 SIMBA (Snow and Ice Mass Balance Array) buoy and 3 TY buoys to monitor ice thickness based on the bias of different linear temperature gradient in air, snow, ice and sea water in three different landfast ice stations (S1, S2 and S3) in the Prydz Bay outside Zhongshan Station in 2016. The SIMBA measures vertical temperature profiles 4 times a day and TY measures vertical temperature per hour. Both SIMBA and TY buoys were set up in S3 station. Compared with borehole in situ measurements, the ice thickness derived by TY buoys had a mean bias and RMSE of 3.3 cm and 14.7 cm in S1 Station, 6.6 cm and 6.9 cm in S2 Station and 4.0 cm and 4.8 cm in S3 Station. And the mean bias and RMSE for the SIMBA buoys in S3 Station compared with borehole in situ measurements were 8.2 cm and 9.7 cm. The sea ice thickness derived by TY buoys were more agreement with the borehole in situ measurements compared with the sea ice thickness derives from SIMBA buoys in S3 Station. The result of Stefan’s law of ice growth model shows the sea ice growth process and the ice growth rate varied between 0.1 cm/d to 0.8 cm/d, which is faster than the result of TY buoys and is affected by the snow thickness. While compare with limited borehole in situ sea ice thickness measurements and the great uncertain in the sea ice thickness derived by remote sense data, the error for both the TY and SIMBA buoys are reasonable, which will benefit to the future sea ice thickness monitor near Zhongshan Station.
2019, 41(9): 40-51.
doi: 10.3969/j.issn.0253-4193.2019.09.004
Abstract:
Core AMS01 dredged on the northwestern continental rise of the Amundsen Sea was used to reconstruct the history of ice sheet and paleoproductivity since MIS9 (about 34 ka BP) based on the analyses of color reflectance, grain size and geochemical proxies. The results show that: (1) Grain size and paleoproductivity proxies of the core exhibits evident glacial–interglacial cycles of Quaternary; (2) The interglacials such as MIS9, MIS7 and MIS5 have low sedimentation rates, brown sediments, low ice-rafted detritus (IRD) contents and high paleoproductivity, indicating warm climate, limited sea ice and large-scale retreat of the ice sheet in the Amundsen Sea sector; (3) Glacial ages such as MIS8c, MIS8a, MIS6 and MIS2 have relatively high sedimentation rates, gray sediments, high IRD and low biological components, which indicate the ice sheet expanded greatly to the edge of the continental shelf, and the continental rise became a proximal environment close to the grounded ice sheet and/or floating ice shelf with dense sea ice and icebergs, and significantly lowered marine productivity; (4) In the glacials and interglacials, ice sheet and paleoproductivity also have certain fluctuations, especially in MIS8b interstadial, the light brown sediments with low IRD and elevated marine productivity make it be like the environment of interglacial period, which indicates that the ice sheet and ocean in the Amundsen Sea sector are more sensitive to climate change than those in the East Antarctica.
Core AMS01 dredged on the northwestern continental rise of the Amundsen Sea was used to reconstruct the history of ice sheet and paleoproductivity since MIS9 (about 34 ka BP) based on the analyses of color reflectance, grain size and geochemical proxies. The results show that: (1) Grain size and paleoproductivity proxies of the core exhibits evident glacial–interglacial cycles of Quaternary; (2) The interglacials such as MIS9, MIS7 and MIS5 have low sedimentation rates, brown sediments, low ice-rafted detritus (IRD) contents and high paleoproductivity, indicating warm climate, limited sea ice and large-scale retreat of the ice sheet in the Amundsen Sea sector; (3) Glacial ages such as MIS8c, MIS8a, MIS6 and MIS2 have relatively high sedimentation rates, gray sediments, high IRD and low biological components, which indicate the ice sheet expanded greatly to the edge of the continental shelf, and the continental rise became a proximal environment close to the grounded ice sheet and/or floating ice shelf with dense sea ice and icebergs, and significantly lowered marine productivity; (4) In the glacials and interglacials, ice sheet and paleoproductivity also have certain fluctuations, especially in MIS8b interstadial, the light brown sediments with low IRD and elevated marine productivity make it be like the environment of interglacial period, which indicates that the ice sheet and ocean in the Amundsen Sea sector are more sensitive to climate change than those in the East Antarctica.
2019, 41(9): 52-64.
doi: 10.3969/j.issn.0253-4193.2019.09.005
Abstract:
Analyses of grain size, organic carbon and biomarker have been carried out for the core ANT32-RB16C, in order to identify the source of organic matter and reconstruct the sedimentary environment since the Last Glacial Maximum in the western Ross Sea. From the bottom to the top within the core, sub-ice-shelf, pre-ice-shelf and open-marine sedimentary environments can be differentiated. The combined parameters of biomarker indicate that organic matter is mainly a mixed input of terrigenous and marine origin. During the Last Glacial Maximum (24.8–20 ka BP), under the influence of ice sheet and the current condition, the organic matter content was low and its source was associated mainly with a marine origin, with a relatively low plankton productivity. During the Last Deglaciation (20–11.7 ka BP), the organic matter released by the dissolution of the glaciers in the retreat process of the Ross Ice Shelf, caused the increase of terrestrial organic matter. During the Holocene, the content of organic matter increased significantly, together with the proportion of marine origin input. The number of prokaryotes such as bacteria increased, resulting in a greater degree of degradation of short-chain n-alkanes. The redox condition in the study area is mainly affected by the ice shelf and sea ice limitation, and has little relationship with the organic matter content and the high-oxygen Antarctic Bottom Water. In general, from the Last Glacial Maximum to the Last Deglaciation, the study area sedimentary environment was affected by the Ross Ice Shelf, and by the climate since the Holocene.
Analyses of grain size, organic carbon and biomarker have been carried out for the core ANT32-RB16C, in order to identify the source of organic matter and reconstruct the sedimentary environment since the Last Glacial Maximum in the western Ross Sea. From the bottom to the top within the core, sub-ice-shelf, pre-ice-shelf and open-marine sedimentary environments can be differentiated. The combined parameters of biomarker indicate that organic matter is mainly a mixed input of terrigenous and marine origin. During the Last Glacial Maximum (24.8–20 ka BP), under the influence of ice sheet and the current condition, the organic matter content was low and its source was associated mainly with a marine origin, with a relatively low plankton productivity. During the Last Deglaciation (20–11.7 ka BP), the organic matter released by the dissolution of the glaciers in the retreat process of the Ross Ice Shelf, caused the increase of terrestrial organic matter. During the Holocene, the content of organic matter increased significantly, together with the proportion of marine origin input. The number of prokaryotes such as bacteria increased, resulting in a greater degree of degradation of short-chain n-alkanes. The redox condition in the study area is mainly affected by the ice shelf and sea ice limitation, and has little relationship with the organic matter content and the high-oxygen Antarctic Bottom Water. In general, from the Last Glacial Maximum to the Last Deglaciation, the study area sedimentary environment was affected by the Ross Ice Shelf, and by the climate since the Holocene.
2019, 41(9): 65-79.
doi: 10.3969/j.issn.0253-4193.2019.09.006
Abstract:
Eco-dynamics of marine plankton are remarkably sensitive to changes in their environments. The Arctic Ocean is undergoing rapid environmental changes as the global climate change intensifies. Understanding the seasonal distribution and variation of low-trophic plankton is a prerequisite for exploring the response of ecosystem to changing environment in the Arctic Ocean, and is also an important basis for assessing the carbon sequestration capacity of the Arctic Ocean. Based on above, a coupled ocean-sea ice-biogeochemical cycling model was developed and applied to evaluate the temporal-spatial variations of chlorophyll a concentration and planktonic structures in the Arctic Ocean. The results suggested that: (1) surface chlorophyll a concentration mainly peaks in May, with the higher values on the Pacific side than the Atlantic; since stratification occurs, subsurface chlorophyll a maximums are found in areas having limited nutrients at surface, and the depth of subsurface chlorophyll a maximums gradually deepens from the shelf towards the basin; in September, the high chlorophyll a concentration returns to the upper layer from the subsurface, presenting a sub-peak of surface chlorophyll a concentration on the Pacific side. (2) Substantial regional differences in surface plankton communities exist in the Arctic Ocean due to the influences of the Pacific and Atlantic inflows with variations in nutrients concentrations and structures. Diatom and mesozooplankton are dominant species on the Pacific side where diatom biomass exhibits two peaks in May and September, meanwhile nanophytoplankton maintains relatively high biomass in March, May and June. Atlantic side experiences a seasonal succession from nanophytoplankton to diatom then to nanophytoplankton corresponding to early spring, late spring-early summer, and summer-autumn, respectively. Over the entire growth season, nanophytoplankton and microzooplankton dominate on the Atlantic side. Generally, the peak biomass of zooplankton has a lag for half a month to the peak of phytoplankton biomass in the Arctic Ocean.
Eco-dynamics of marine plankton are remarkably sensitive to changes in their environments. The Arctic Ocean is undergoing rapid environmental changes as the global climate change intensifies. Understanding the seasonal distribution and variation of low-trophic plankton is a prerequisite for exploring the response of ecosystem to changing environment in the Arctic Ocean, and is also an important basis for assessing the carbon sequestration capacity of the Arctic Ocean. Based on above, a coupled ocean-sea ice-biogeochemical cycling model was developed and applied to evaluate the temporal-spatial variations of chlorophyll a concentration and planktonic structures in the Arctic Ocean. The results suggested that: (1) surface chlorophyll a concentration mainly peaks in May, with the higher values on the Pacific side than the Atlantic; since stratification occurs, subsurface chlorophyll a maximums are found in areas having limited nutrients at surface, and the depth of subsurface chlorophyll a maximums gradually deepens from the shelf towards the basin; in September, the high chlorophyll a concentration returns to the upper layer from the subsurface, presenting a sub-peak of surface chlorophyll a concentration on the Pacific side. (2) Substantial regional differences in surface plankton communities exist in the Arctic Ocean due to the influences of the Pacific and Atlantic inflows with variations in nutrients concentrations and structures. Diatom and mesozooplankton are dominant species on the Pacific side where diatom biomass exhibits two peaks in May and September, meanwhile nanophytoplankton maintains relatively high biomass in March, May and June. Atlantic side experiences a seasonal succession from nanophytoplankton to diatom then to nanophytoplankton corresponding to early spring, late spring-early summer, and summer-autumn, respectively. Over the entire growth season, nanophytoplankton and microzooplankton dominate on the Atlantic side. Generally, the peak biomass of zooplankton has a lag for half a month to the peak of phytoplankton biomass in the Arctic Ocean.
2019, 41(9): 80-85.
doi: 10.3969/j.issn.0253-4193.2019.09.007
Abstract:
To investigate the heat stress responding strategies of Antarctic ice algae, the characteristics of a catalase gene CiCAT from the transcriptome of Antarctic ice alga Chlamydomonas sp. ICE-L were analyzed. The length of CiCAT is 2 066 bp encoding a catalase of 492 amino acids. In the phylogenetic tree of catalase amino acid sequences, Antarctic ice alga is clustered with green algae. The amino acid sequence identities of CiCAT are about 80.5% and 78.9% to the catalase from Dunaliella salina and Haematococcus lacustris, respectively. The changes of CiCAT gene expression and catalase activity in Antarctic ice alga were also investigated. Under heat stress, both the relative expression state of CiCAT gene and catalase activity changed from up-regulation to down-regulation over time. After heat stress treatment for 24 h, the expression of CiCAT gene was almost unchanged, while the enzyme activity in the heat treatment group was significantly higher than that in the control group. After 72 h's heat stress treatment, both gene expression and enzyme activity reached the highest level. Our preliminary results show that antioxidase system plays an important role in Antarctic ice algae responding to heat stress, which is similar to that in temperate algae and higher plants.
To investigate the heat stress responding strategies of Antarctic ice algae, the characteristics of a catalase gene CiCAT from the transcriptome of Antarctic ice alga Chlamydomonas sp. ICE-L were analyzed. The length of CiCAT is 2 066 bp encoding a catalase of 492 amino acids. In the phylogenetic tree of catalase amino acid sequences, Antarctic ice alga is clustered with green algae. The amino acid sequence identities of CiCAT are about 80.5% and 78.9% to the catalase from Dunaliella salina and Haematococcus lacustris, respectively. The changes of CiCAT gene expression and catalase activity in Antarctic ice alga were also investigated. Under heat stress, both the relative expression state of CiCAT gene and catalase activity changed from up-regulation to down-regulation over time. After heat stress treatment for 24 h, the expression of CiCAT gene was almost unchanged, while the enzyme activity in the heat treatment group was significantly higher than that in the control group. After 72 h's heat stress treatment, both gene expression and enzyme activity reached the highest level. Our preliminary results show that antioxidase system plays an important role in Antarctic ice algae responding to heat stress, which is similar to that in temperate algae and higher plants.
2019, 41(9): 86-93.
doi: 10.3969/j.issn.0253-4193.2019.09.008
Abstract:
The Brazil-Malvinas Confluence (BMC) may have a southward shift in a long time trend and many marine factors’ change may cause this drift. We analysis this phenomenon from two aspects: the changes of currents’ volume transport, and the winds’ alternation. Using the monthly mean flow field between 1993 and 2016 to calculate the cross-sectional water transport volume, the results show that the transport change trend of the Malvinas Current (MC) is decreasing and the transport change trend of the Brazil Current (BC) is increasing. The trajectory of the Argo buoy during 2014–2016 indicates that the MC’s water mainly comes from one of the three polar fronts of ACC (Antarctic Circumpolar Current) when passing through the Drake Passage: SAF (the Subantactic Front). Calculating and analyzing the transport of SAF, we find that the transport’s trend of SAF is lessened, which is an important reason caused the reduce of MC’s transport. We also find that the PF’s transport on the south SAF has incremental trend. Based on the monthly mean wind field data during year 1993–2016, we find that the prevailing westerly wind stress in the Southern Hemisphere is growing and moves toward to Antarctic which will make ACC contract to Antarctica. So we can explain that the transport of SAF reduces while the transport of PF increases. Therefore, it is found that the southward movement of the prevailing westerly winds in the Southern Hemisphere and the increase of BC transport are the reasons for the southward drift of BMC.
The Brazil-Malvinas Confluence (BMC) may have a southward shift in a long time trend and many marine factors’ change may cause this drift. We analysis this phenomenon from two aspects: the changes of currents’ volume transport, and the winds’ alternation. Using the monthly mean flow field between 1993 and 2016 to calculate the cross-sectional water transport volume, the results show that the transport change trend of the Malvinas Current (MC) is decreasing and the transport change trend of the Brazil Current (BC) is increasing. The trajectory of the Argo buoy during 2014–2016 indicates that the MC’s water mainly comes from one of the three polar fronts of ACC (Antarctic Circumpolar Current) when passing through the Drake Passage: SAF (the Subantactic Front). Calculating and analyzing the transport of SAF, we find that the transport’s trend of SAF is lessened, which is an important reason caused the reduce of MC’s transport. We also find that the PF’s transport on the south SAF has incremental trend. Based on the monthly mean wind field data during year 1993–2016, we find that the prevailing westerly wind stress in the Southern Hemisphere is growing and moves toward to Antarctic which will make ACC contract to Antarctica. So we can explain that the transport of SAF reduces while the transport of PF increases. Therefore, it is found that the southward movement of the prevailing westerly winds in the Southern Hemisphere and the increase of BC transport are the reasons for the southward drift of BMC.
2019, 41(9): 94-104.
doi: 10.3969/j.issn.0253-4193.2019.09.009
Abstract:
Mesoscale eddies are widely distributed in the ocean and play a significant role in the mixing and transporting of momentum and nutrients. Statistics suggest that more than 80% eddies’ lifetime are less than 1 month, belonging to the defined “short-life eddies” in this paper. This design adopt statistics and comparison, commit to having a earlier reasearch of global scale, short-life eddies. Results show that short-life eddies have a close correlation with ocean current. The most productive places for short-life eddies are those where warm and cold currents or two currents with opposite directions meet, and except in tropical areas of 30°S–30°N, the short-life eddies in other areas have a slight preference for cyclonic. Seasons with low temperature are favorable for short-life eddies in low latitudes, while seasons with high temperature are favorable in high latitudes. Short-life eddies tend to propagate westward in most of areas, however, they notable propagate eastward in eastward currents areas. Meridional deflection is quite messy, but with a tiny preference for equatorward and poleward deflections of cyclones and anticyclones, respectively. The distribution of average displacement and propagation velocity have similar regulation.
Mesoscale eddies are widely distributed in the ocean and play a significant role in the mixing and transporting of momentum and nutrients. Statistics suggest that more than 80% eddies’ lifetime are less than 1 month, belonging to the defined “short-life eddies” in this paper. This design adopt statistics and comparison, commit to having a earlier reasearch of global scale, short-life eddies. Results show that short-life eddies have a close correlation with ocean current. The most productive places for short-life eddies are those where warm and cold currents or two currents with opposite directions meet, and except in tropical areas of 30°S–30°N, the short-life eddies in other areas have a slight preference for cyclonic. Seasons with low temperature are favorable for short-life eddies in low latitudes, while seasons with high temperature are favorable in high latitudes. Short-life eddies tend to propagate westward in most of areas, however, they notable propagate eastward in eastward currents areas. Meridional deflection is quite messy, but with a tiny preference for equatorward and poleward deflections of cyclones and anticyclones, respectively. The distribution of average displacement and propagation velocity have similar regulation.
2019, 41(9): 105-113.
doi: 10.3969/j.issn.0253-4193.2019.09.010
Abstract:
This thesis aimed to analyze the stable multimodal (3-peaked) particle size distributions (PSDs) of flocs in the Zhujiang River Estuary with the field observation data getting by LISST and the bottom boundary layer observation system during the dry season in 2010. The results show that the mean diameter of the basic building blocks of flocs, so-called primary particle, is about 8.3–9.0 μm; the mean diameter of microflocs in a range of 36–100 μm, and macroflocs have a size range of 180 μm to thousands of micrometers. In the neap tidal periods, the suspension sediment of halocline is dominated by the macroflocs with strong flocculation process; the mean diameter of flocs is increases and is controlled by flocs during the moderate and spring tide. The dynamic change of the tide has little impact on the multimodal PSDs and morphological parameters, with aggregation and breakage of the flocculation in the dynamic equilibrium. Study results further demonstrate the turbulent dynamic mechanism of flocculation by combining the turbulence data collected by the bottom tripod and the simplified Population Balance Equation (PBE). It is that, the high shear of the peak flow would enhance breakage of macroflocs to microflocs and decrease the mean diameter of flocs, on the contrary, aggregation is much stronger than breakage. It also shows that PSDs are in according with observation by solving PBE based on gaussian moment integral method. It turns out that PBE which containes the turbulent dynamic mechanism can be used to study the flocculation of cohesive sediment with turbulence and PSDs data.
This thesis aimed to analyze the stable multimodal (3-peaked) particle size distributions (PSDs) of flocs in the Zhujiang River Estuary with the field observation data getting by LISST and the bottom boundary layer observation system during the dry season in 2010. The results show that the mean diameter of the basic building blocks of flocs, so-called primary particle, is about 8.3–9.0 μm; the mean diameter of microflocs in a range of 36–100 μm, and macroflocs have a size range of 180 μm to thousands of micrometers. In the neap tidal periods, the suspension sediment of halocline is dominated by the macroflocs with strong flocculation process; the mean diameter of flocs is increases and is controlled by flocs during the moderate and spring tide. The dynamic change of the tide has little impact on the multimodal PSDs and morphological parameters, with aggregation and breakage of the flocculation in the dynamic equilibrium. Study results further demonstrate the turbulent dynamic mechanism of flocculation by combining the turbulence data collected by the bottom tripod and the simplified Population Balance Equation (PBE). It is that, the high shear of the peak flow would enhance breakage of macroflocs to microflocs and decrease the mean diameter of flocs, on the contrary, aggregation is much stronger than breakage. It also shows that PSDs are in according with observation by solving PBE based on gaussian moment integral method. It turns out that PBE which containes the turbulent dynamic mechanism can be used to study the flocculation of cohesive sediment with turbulence and PSDs data.
2019, 41(9): 114-125.
doi: 10.3969/j.issn.0253-4193.2019.09.011
Abstract:
Winter-to-winter recurrence (WWR) is an important persistence characteristic of large-scale sea surface temperature anomalies (SSTAs) in middle-high latitude, which is a unique phenomenon of the extratropical ocean. Its influence on extratropical climate change can not be ignored. WWR also exist in the atmosphere in the North Pacific Ocean, which could induce SSTAs WWR. In this paper, the WWRs of the air-sea system in the North Pacific are evaluated using the model output of 23 coupled models of CMIP in IPCC 4th assessment. Observational results show that, SSTAs WWR occurs over most of the basin of North Pacific, but the recurrence timing is in winter in the central and in fall in other regions. The atmospheric WWR is mainly located in central North Pacific, which is essential for the occurrence of the SSTAs WWR. Most of models can simulate the basinwide SSTAs WWR, but they can’t reproduce the geographical distribution of recurrence timing well. Compared with the SSTAs, little skill is shown in the WWR of the atmospheric circulation in most models. Moreover, the possible effect of the atmospheric WWR on the SSTAs WWR is not reflected in these coupled models. The coupling model has yet to be improved for simulating the atmospheric WWR in the North Pacific.
Winter-to-winter recurrence (WWR) is an important persistence characteristic of large-scale sea surface temperature anomalies (SSTAs) in middle-high latitude, which is a unique phenomenon of the extratropical ocean. Its influence on extratropical climate change can not be ignored. WWR also exist in the atmosphere in the North Pacific Ocean, which could induce SSTAs WWR. In this paper, the WWRs of the air-sea system in the North Pacific are evaluated using the model output of 23 coupled models of CMIP in IPCC 4th assessment. Observational results show that, SSTAs WWR occurs over most of the basin of North Pacific, but the recurrence timing is in winter in the central and in fall in other regions. The atmospheric WWR is mainly located in central North Pacific, which is essential for the occurrence of the SSTAs WWR. Most of models can simulate the basinwide SSTAs WWR, but they can’t reproduce the geographical distribution of recurrence timing well. Compared with the SSTAs, little skill is shown in the WWR of the atmospheric circulation in most models. Moreover, the possible effect of the atmospheric WWR on the SSTAs WWR is not reflected in these coupled models. The coupling model has yet to be improved for simulating the atmospheric WWR in the North Pacific.
2019, 41(9): 126-135.
doi: 10.3969/j.issn.0253-4193.2019.09.012
Abstract:
The statistical characteristics of rapid changes of different grade tropical cyclone intensity and path in the South China Sea are analyzed by the best track data set of tropical cyclones for 69 years from 1949 to 2017 compiled by Shanghai Typhoon Institute of China Meteorological Administrator. The results show that: (1) The change from a severe tropical storm to a typhoon, and from a typhoon to a severe typhoon, are the most frequent events of rapid intensity changes. Most tropical cyclones experience intensity change no more than twice. However, most of the rapid intensifying tropical cyclones occur mainly outside the South China Sea in the western Pacific, and the probability of rapid intensifying over the South China Sea is only 9.8%. (2) The duration of intensity maintenance has an important effect on rapid intensity changes for different grade tropical cyclones. It is the highest rapid change stage during the first 24 hours. Rapid intensity change to typhoon or above grade is easily to occur when the decreasing velocity of central pressure exceeds –12.0 hPa/(6 h). Moreover, the rapid intensifying of tropical cyclones is easily to occur in areas with high sea surface temperature. (3) The deflection of the tropical cyclone path in the South China Sea is mainly in the westbound path, in which the deflection of 5°–30° is the most common, accounting for 48.65% of the total number of tropical cyclones. However, According to the defined path mutation criterion, the probability of path sharp turning is only 15.13%. With the increase of tropical cyclone intensity, the frequency of path sharp turning in the South China Sea decreases rapidly, and the path sharp turning occurs mainly in the coastal area and the east-central region of the South China Sea. This work further refines and enriches the understanding of the intensity and path rapid changes of tropical cyclones in the South China Sea.
The statistical characteristics of rapid changes of different grade tropical cyclone intensity and path in the South China Sea are analyzed by the best track data set of tropical cyclones for 69 years from 1949 to 2017 compiled by Shanghai Typhoon Institute of China Meteorological Administrator. The results show that: (1) The change from a severe tropical storm to a typhoon, and from a typhoon to a severe typhoon, are the most frequent events of rapid intensity changes. Most tropical cyclones experience intensity change no more than twice. However, most of the rapid intensifying tropical cyclones occur mainly outside the South China Sea in the western Pacific, and the probability of rapid intensifying over the South China Sea is only 9.8%. (2) The duration of intensity maintenance has an important effect on rapid intensity changes for different grade tropical cyclones. It is the highest rapid change stage during the first 24 hours. Rapid intensity change to typhoon or above grade is easily to occur when the decreasing velocity of central pressure exceeds –12.0 hPa/(6 h). Moreover, the rapid intensifying of tropical cyclones is easily to occur in areas with high sea surface temperature. (3) The deflection of the tropical cyclone path in the South China Sea is mainly in the westbound path, in which the deflection of 5°–30° is the most common, accounting for 48.65% of the total number of tropical cyclones. However, According to the defined path mutation criterion, the probability of path sharp turning is only 15.13%. With the increase of tropical cyclone intensity, the frequency of path sharp turning in the South China Sea decreases rapidly, and the path sharp turning occurs mainly in the coastal area and the east-central region of the South China Sea. This work further refines and enriches the understanding of the intensity and path rapid changes of tropical cyclones in the South China Sea.
2019, 41(9): 136-144.
doi: 10.3969/j.issn.0253-4193.2019.09.013
Abstract:
Sand waves are widely distributed in the world and have complex genesis. And multi-scale complex sand waves often overlap to form a complex sand wave geomorphology system, which makes it difficult to conduct quantitative research. To solve this problem, a practical Fourier analysis method is proposed in this paper, and Butterworth filter is designed to transform water depth data into frequency domain, and then decompose complex sand wave geomorphology into a series of single types of sand waves in different frequencies. Taking the complex sand wave geomorphology system of Taiwan Banks as an example, three spatial scales of sand waves are quantitatively decomposed, which are: giant sand waves (over 100 m in length, over 5 m in height), medium sand waves (wavelength of 5–100 m, wave height of 0.4–5 m) and sand ripples (wavelength less than 5 m, wave height less than 0.4 m). The quantitative analysis method of sand waves proposed in this paper is helpful to study the genesis and mechanism of sand waves in different scales, and is also of practical value to the safety assessment of marine engineering in sand wave fields.
Sand waves are widely distributed in the world and have complex genesis. And multi-scale complex sand waves often overlap to form a complex sand wave geomorphology system, which makes it difficult to conduct quantitative research. To solve this problem, a practical Fourier analysis method is proposed in this paper, and Butterworth filter is designed to transform water depth data into frequency domain, and then decompose complex sand wave geomorphology into a series of single types of sand waves in different frequencies. Taking the complex sand wave geomorphology system of Taiwan Banks as an example, three spatial scales of sand waves are quantitatively decomposed, which are: giant sand waves (over 100 m in length, over 5 m in height), medium sand waves (wavelength of 5–100 m, wave height of 0.4–5 m) and sand ripples (wavelength less than 5 m, wave height less than 0.4 m). The quantitative analysis method of sand waves proposed in this paper is helpful to study the genesis and mechanism of sand waves in different scales, and is also of practical value to the safety assessment of marine engineering in sand wave fields.
2019, 41(9): 145-155.
doi: 10.3969/j.issn.0253-4193.2019.09.014
Abstract:
Based on the Okada model, nonlinear shallow water equation, and nested grid with high resolution, a real-time tsunami warning system of transoceanic-offshore-local is built for Wenzhou and Taizhou’s coastal region of Zhejiang Province. The grid resolution of the refined layer is 900 m. The tsunami warning system includes parallel numerical calculation module, visualization module based on Python 2D library (matplotlib), and product integration module which integrates all numerical graphical products on a web page by Python. Once an earthquake occurs, the system could complete the numerical calculation, visualization processing and graphic product integration within 10 minutes. Firstly, the system has been validated by the 2011 Japan tsunami with the magnitude of Mw 9.0. Then, the extreme potential tsunami from Nankai Trough and Okinawa Trough is simulated by the system in terms of tsunami amplitude and currents. The results show that the tsunami warning system can improve the efficiency and accuracy of tsunami early warning in the coastal region, and provide a scientific basis for tsunami early warning, disaster reduction and decision supporting.
Based on the Okada model, nonlinear shallow water equation, and nested grid with high resolution, a real-time tsunami warning system of transoceanic-offshore-local is built for Wenzhou and Taizhou’s coastal region of Zhejiang Province. The grid resolution of the refined layer is 900 m. The tsunami warning system includes parallel numerical calculation module, visualization module based on Python 2D library (matplotlib), and product integration module which integrates all numerical graphical products on a web page by Python. Once an earthquake occurs, the system could complete the numerical calculation, visualization processing and graphic product integration within 10 minutes. Firstly, the system has been validated by the 2011 Japan tsunami with the magnitude of Mw 9.0. Then, the extreme potential tsunami from Nankai Trough and Okinawa Trough is simulated by the system in terms of tsunami amplitude and currents. The results show that the tsunami warning system can improve the efficiency and accuracy of tsunami early warning in the coastal region, and provide a scientific basis for tsunami early warning, disaster reduction and decision supporting.
2019, 41(9): 156-169.
doi: 10.3969/j.issn.0253-4193.2019.09.015
Abstract:
As a main carrier of nutrients and pollutants, total suspended matter (TSM) has a significant influence on water environment, especially on estuary water environment. The Ocean and Land Colour Instrument (OLCI) was onboard ESA Sentinel-3A satellite and launched in February 16, 2016, with fine spatial, temporal and spectral resolution. To find the best atmospheric correction method and TSM retrieval model for the application of OLCI in Hangzhou Bay (HZB), six atmospheric correction methods and eight TSM retrieval models were test based on in situ water color data collected from HZB on July 2017. In addition, the OLCI Level 2 product (e.g. TSM and inherent optical properties (IOP) data) was compared with in situ data to evaluate the accuracy and applicability of OLCI Level 2 product. The results show that the method of atmospheric correction based on ultraviolet wavelength (UVAC) and the TSM retrieval model based on band ratio have best performance. Specifically, the mean absolute percentage error (MAPE) of atmospheric correction in four match-up sites is 34.21%, 13.11%, 5.92% and 20.28%, respectively. In addition, the averaged MAPE of atmospheric correction in band Oa2 to Oa12 and Oa16 to Oa18 is 15.23%, and in band Oa4 to Oa10 is less than 8%. The band ratio (Oa16/Oa5) model has the best performance, with a MAPE of 16.49% and root mean square error (RMSE) of 50.92 mg/L in calibration stage, and a MAPE of 19.08% and RMSE of 19.29 mg/L in validation stage. However, the TSM and IOP product derived from C2RCC (case 2 regional coast colour) algorithm and the TSM product derived from OLCI Level 2 product has no linear relationship with in situ data. These results indicate that the above Level 2 product is unsuitable for HZB TSM and IOP remote estimation. Finally, the UVAC method and band ratio model are applied to OLCI imagery that is collected on July 23, 2017. Spatially, TSM shows a relative low value in the center of HZB and relative high value in the south and east part of HZB.
As a main carrier of nutrients and pollutants, total suspended matter (TSM) has a significant influence on water environment, especially on estuary water environment. The Ocean and Land Colour Instrument (OLCI) was onboard ESA Sentinel-3A satellite and launched in February 16, 2016, with fine spatial, temporal and spectral resolution. To find the best atmospheric correction method and TSM retrieval model for the application of OLCI in Hangzhou Bay (HZB), six atmospheric correction methods and eight TSM retrieval models were test based on in situ water color data collected from HZB on July 2017. In addition, the OLCI Level 2 product (e.g. TSM and inherent optical properties (IOP) data) was compared with in situ data to evaluate the accuracy and applicability of OLCI Level 2 product. The results show that the method of atmospheric correction based on ultraviolet wavelength (UVAC) and the TSM retrieval model based on band ratio have best performance. Specifically, the mean absolute percentage error (MAPE) of atmospheric correction in four match-up sites is 34.21%, 13.11%, 5.92% and 20.28%, respectively. In addition, the averaged MAPE of atmospheric correction in band Oa2 to Oa12 and Oa16 to Oa18 is 15.23%, and in band Oa4 to Oa10 is less than 8%. The band ratio (Oa16/Oa5) model has the best performance, with a MAPE of 16.49% and root mean square error (RMSE) of 50.92 mg/L in calibration stage, and a MAPE of 19.08% and RMSE of 19.29 mg/L in validation stage. However, the TSM and IOP product derived from C2RCC (case 2 regional coast colour) algorithm and the TSM product derived from OLCI Level 2 product has no linear relationship with in situ data. These results indicate that the above Level 2 product is unsuitable for HZB TSM and IOP remote estimation. Finally, the UVAC method and band ratio model are applied to OLCI imagery that is collected on July 23, 2017. Spatially, TSM shows a relative low value in the center of HZB and relative high value in the south and east part of HZB.
2019, 41(9): 170-180.
doi: 10.3969/j.issn.0253-4193.2019.09.016
Abstract:
The muddy coast has a large change in scouring and silting, and the beach profile is diverse. Firstly, according to the tidal range relationship between muti-temporal remote sensing watelines, the shape of the shoreline is automatically judged, and then the different functions are used to fit the profile. A new method of coastline remote sensing prediction based on self-adaptive profile morphology is constructed. The central muddy coast in Jiangsu has been empirically applied. The research shows that the concave-shaped erosion shore section, the slope-shaped gentle bank section and the upper convex-shaped siltation section use a three-exponential decay function, a linear function and a second-order polynomial function respectively to have a good profile fitting effect, using three waterlines. The absolute slope error of the profile obtained by data fitting is 0.20‰, –0.17‰, and 0.13‰, respectively, which is less than an order of magnitude than the measured average slope. When using the five waterlines data fitting to calculate the coastline, the error of the coastline plane position of the erosion shore section and gentle shore section are 6.5 m and –91.96 m, respectively, and the error is reduced by about 82.4% compared with the average slope method. Further consideration of seasonal changes in the beach, using the waterline data of the winter to calculate the coastline, has little effect on the erosion of the shore and the long section of the silt, but for the slope-shaped smooth section, the error is reduced by about 63.65%, so the use of winter waterline data has a higher shoreline projection accuracy than the season without distinction.
The muddy coast has a large change in scouring and silting, and the beach profile is diverse. Firstly, according to the tidal range relationship between muti-temporal remote sensing watelines, the shape of the shoreline is automatically judged, and then the different functions are used to fit the profile. A new method of coastline remote sensing prediction based on self-adaptive profile morphology is constructed. The central muddy coast in Jiangsu has been empirically applied. The research shows that the concave-shaped erosion shore section, the slope-shaped gentle bank section and the upper convex-shaped siltation section use a three-exponential decay function, a linear function and a second-order polynomial function respectively to have a good profile fitting effect, using three waterlines. The absolute slope error of the profile obtained by data fitting is 0.20‰, –0.17‰, and 0.13‰, respectively, which is less than an order of magnitude than the measured average slope. When using the five waterlines data fitting to calculate the coastline, the error of the coastline plane position of the erosion shore section and gentle shore section are 6.5 m and –91.96 m, respectively, and the error is reduced by about 82.4% compared with the average slope method. Further consideration of seasonal changes in the beach, using the waterline data of the winter to calculate the coastline, has little effect on the erosion of the shore and the long section of the silt, but for the slope-shaped smooth section, the error is reduced by about 63.65%, so the use of winter waterline data has a higher shoreline projection accuracy than the season without distinction.
2019, 41(9): 181-190.
doi: 10.3969/j.issn.0253-4193.2019.09.017
Abstract:
Aiming at the characteristics of SAR images on the ocean surface, the texture feature method based on gray level co-occurrence matrix is a common method for extracting oil spill information from the sea surface, but the complex information on the actual ocean surface makes the SAR image produce a dark spot area similar to the oil spill phenomenon. The false alarm rate is obtained when the oil feature information is extracted by the texture feature method, and the extraction precision of the oil spill information is reduced. Based on the RADARSAT-2 SAR quadratic polarization image, this paper proposes a texture feature recognition method based on SAR polarization ratio image to identify and extract the oil film on the sea surface. The results show that the texture feature recognition method based on SAR polarization ratio image can effectively and accurately extract the oil spill information on the sea surface. Compared with the texture feature recognition method of VV polarization image, the false alarm rate in the oil spill monitoring process is reduced by 17.96 %, the overall accuracy of oil spill monitoring reached 96.83%.
Aiming at the characteristics of SAR images on the ocean surface, the texture feature method based on gray level co-occurrence matrix is a common method for extracting oil spill information from the sea surface, but the complex information on the actual ocean surface makes the SAR image produce a dark spot area similar to the oil spill phenomenon. The false alarm rate is obtained when the oil feature information is extracted by the texture feature method, and the extraction precision of the oil spill information is reduced. Based on the RADARSAT-2 SAR quadratic polarization image, this paper proposes a texture feature recognition method based on SAR polarization ratio image to identify and extract the oil film on the sea surface. The results show that the texture feature recognition method based on SAR polarization ratio image can effectively and accurately extract the oil spill information on the sea surface. Compared with the texture feature recognition method of VV polarization image, the false alarm rate in the oil spill monitoring process is reduced by 17.96 %, the overall accuracy of oil spill monitoring reached 96.83%.
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