2021 Vol. 40, No. 12
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2021, 40(12): .
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2021, 40(12): 0-1.
Abstract:
2021, 40(12): 1-11.
doi: 10.1007/s13131-021-1872-5
Abstract:
Seamounts are ubiquitous topographic units in global oceans, and their influences on local oceanic circulation have attracted great attention in physical oceanography; however, previous efforts were less made in paleoclimatology and paleoceanography. The Caiwei Guyot in the Magellan Seamounts of the western Pacific is a typical seamount, and in this study, we investigate a well-dated sediment core by magnetic properties to reveal the relationship between deep-sea sedimentary processes and global climate changes. The principal results are as follows: (1) the dominant magnetic minerals in the sediments are low-coercivity magnetite in pseudo-single domain range, probably including a biogenic contribution; (2) the variabilities of magnetic parameters can be clustered into two sections at ~500 ka, and the differences between the two units are evident in amplitudes and means; (3) changes in the grainsize-dependent magnetic parameters can be well correlated to records of global ice volume and atmospheric CO2 in the middle Pleistocene. Based on these results, a close linkage was proposed between deep-sea sedimentary processes in the Caiwei Guyot and global climate changes. This linkage likely involves different roles of biogenic magnetite in the sediments between interglacial and glacial intervals, responding to changes in marine productivity and deep-sea circulation and displaying a major change in the Mid-Brunhes climate event. Therefore, we proposed that the sedimentary archives at the bottom of the Caiwei Guyot record some key signals of global climate changes, providing a unique window to observe interactions between various environmental systems on glacial-interglacial timescales.
Seamounts are ubiquitous topographic units in global oceans, and their influences on local oceanic circulation have attracted great attention in physical oceanography; however, previous efforts were less made in paleoclimatology and paleoceanography. The Caiwei Guyot in the Magellan Seamounts of the western Pacific is a typical seamount, and in this study, we investigate a well-dated sediment core by magnetic properties to reveal the relationship between deep-sea sedimentary processes and global climate changes. The principal results are as follows: (1) the dominant magnetic minerals in the sediments are low-coercivity magnetite in pseudo-single domain range, probably including a biogenic contribution; (2) the variabilities of magnetic parameters can be clustered into two sections at ~500 ka, and the differences between the two units are evident in amplitudes and means; (3) changes in the grainsize-dependent magnetic parameters can be well correlated to records of global ice volume and atmospheric CO2 in the middle Pleistocene. Based on these results, a close linkage was proposed between deep-sea sedimentary processes in the Caiwei Guyot and global climate changes. This linkage likely involves different roles of biogenic magnetite in the sediments between interglacial and glacial intervals, responding to changes in marine productivity and deep-sea circulation and displaying a major change in the Mid-Brunhes climate event. Therefore, we proposed that the sedimentary archives at the bottom of the Caiwei Guyot record some key signals of global climate changes, providing a unique window to observe interactions between various environmental systems on glacial-interglacial timescales.
Alentiana palinpoda, a new commensal polynoid species from a seamount in the Northwest Pacific Ocean
2021, 40(12): 12-19.
doi: 10.1007/s13131-021-1888-x
Abstract:
Alentiana has only one member, A. aurantiaca (Verrill, 1885 ), commensal with sea anemone (Bolocera tuediae). Here, Alentiana palinpoda sp. nov., a second member in the genus Alentiana (subfamily Lepidastheniinae), a new commensal polynoid is described, based on a specimen collected from a deep-water seamount in the Northwest Pacific Ocean. The new species is characterized by large elytra that completely cover the dorsum and are present in every third segment in the posterior regions. Neuropodia are truncated, with two types of neurochaetae; supraacicular chaetae toothed on one side with a slightly inflated end, and subacicular chaetae that are heavy and smooth; the prechaetal lobe is larger than the postchaetal lobe, with the ventral part rolling upward and backward.
Alentiana has only one member, A. aurantiaca (
2021, 40(12): 20-26.
doi: 10.1007/s13131-021-1886-z
Abstract:
A new species of the nereidid annelid, genus Nicon Kinberg, 1866, from KIOST Seamount, Northwest Pacific deep water is described. Nicon is a genus characterized by lacking paragnaths or papillae on the pharynx and composed of nine species worldwide, distributed from shallow water to deep sea. Nicon ablepsia sp. nov. here described is characterized by the lack of eyes on the prostomium, prolonged tentacular cirri reaching to chaetiger 6, notochaetae homogomph spinigers, neurochaetae homogomph spinigers and heterogomph falcigers. Phylogenetic relationships of Nicon remain undetermined based on molecular data. In this study, we constructed molecular Maximum-Likelihood phylogenetic tree from 29 nereidid species based on four marker genes: mitochondrial 16S rRNA gene and cytochrome c oxidase subunit I (COI) gene; nuclear 18S rRNA gene and 28S rRNA gene. Our analysis suggest the Nicon is clustered within Nereidinae, and nereidinae is not recovered as monophyletic. A key to species of Nicon is provided.
A new species of the nereidid annelid, genus Nicon Kinberg, 1866, from KIOST Seamount, Northwest Pacific deep water is described. Nicon is a genus characterized by lacking paragnaths or papillae on the pharynx and composed of nine species worldwide, distributed from shallow water to deep sea. Nicon ablepsia sp. nov. here described is characterized by the lack of eyes on the prostomium, prolonged tentacular cirri reaching to chaetiger 6, notochaetae homogomph spinigers, neurochaetae homogomph spinigers and heterogomph falcigers. Phylogenetic relationships of Nicon remain undetermined based on molecular data. In this study, we constructed molecular Maximum-Likelihood phylogenetic tree from 29 nereidid species based on four marker genes: mitochondrial 16S rRNA gene and cytochrome c oxidase subunit I (COI) gene; nuclear 18S rRNA gene and 28S rRNA gene. Our analysis suggest the Nicon is clustered within Nereidinae, and nereidinae is not recovered as monophyletic. A key to species of Nicon is provided.
2021, 40(12): 27-38.
doi: 10.1007/s13131-021-1901-4
Abstract:
The compositional variability of ocean island basalts (OIBs) is thought to reflect partial melting of a lithologically-heterogeneous mantle source dominated by either pyroxenite or peridotite. The Pohnpei Island in Micronesia, which is associated with the Caroline hotspot, is suggested to have been generated from partial melting of a pyroxenite-rich mantle. To examine this hypothesis, we present new major- and trace-element compositions of olivine phenocrysts in basalts from the island. The olivines exhibit large systematic inter- and intra-crystalline compositional variability. In Sample DS1, olivines record compositional zonation, in which cores have relatively high Fo (77–85), Ni (550×10−6–2 392×10−6), and Fe/Mn ratios (66–82), whereas rims have lower Fo (71–78), Ni (526×10−6–1 537×10−6), and Fe/Mn ratios (51–62). By contrast, olivines within other samples preserve no clear compositional zonation, exhibiting similar or slightly lower Fo values (66–78), Ni contents (401×10−6–1 268×10−6), and Fe/Mn ratios (53–69) as the rims of zoned crystals. The distinct chemical contrast between the two different types of olivine suggests they formed in magma chambers at different depths. Analysis using forward petrological modeling and multi-element indicators (Fe/Mn, Zn/Fe, FC3MS (FeOT/CaO−(3×MgO/SiO2)), Mn/Zn, and Ni/(Mg/Fe)) of whole-rock samples and high-Fo olivines is inconsistent with a pyroxenite-rich mantle source. We suggest these inconsistencies reflect an influence on the partition coefficients of Ni and Mn between olivine and liquid during melting at variable pressures and temperatures. In addition, magma recharge and mixing within the magmatic plumbing system can change the composition of olivine. We suggest that identification of the mantle source of OIBs in volcanic islands such as the Pohnpei Island using olivine geochemistry should be treated with caution.
The compositional variability of ocean island basalts (OIBs) is thought to reflect partial melting of a lithologically-heterogeneous mantle source dominated by either pyroxenite or peridotite. The Pohnpei Island in Micronesia, which is associated with the Caroline hotspot, is suggested to have been generated from partial melting of a pyroxenite-rich mantle. To examine this hypothesis, we present new major- and trace-element compositions of olivine phenocrysts in basalts from the island. The olivines exhibit large systematic inter- and intra-crystalline compositional variability. In Sample DS1, olivines record compositional zonation, in which cores have relatively high Fo (77–85), Ni (550×10−6–2 392×10−6), and Fe/Mn ratios (66–82), whereas rims have lower Fo (71–78), Ni (526×10−6–1 537×10−6), and Fe/Mn ratios (51–62). By contrast, olivines within other samples preserve no clear compositional zonation, exhibiting similar or slightly lower Fo values (66–78), Ni contents (401×10−6–1 268×10−6), and Fe/Mn ratios (53–69) as the rims of zoned crystals. The distinct chemical contrast between the two different types of olivine suggests they formed in magma chambers at different depths. Analysis using forward petrological modeling and multi-element indicators (Fe/Mn, Zn/Fe, FC3MS (FeOT/CaO−(3×MgO/SiO2)), Mn/Zn, and Ni/(Mg/Fe)) of whole-rock samples and high-Fo olivines is inconsistent with a pyroxenite-rich mantle source. We suggest these inconsistencies reflect an influence on the partition coefficients of Ni and Mn between olivine and liquid during melting at variable pressures and temperatures. In addition, magma recharge and mixing within the magmatic plumbing system can change the composition of olivine. We suggest that identification of the mantle source of OIBs in volcanic islands such as the Pohnpei Island using olivine geochemistry should be treated with caution.
2021, 40(12): 39-49.
doi: 10.1007/s13131-021-1939-3
Abstract:
We report on a hexactinellid sponge new to science, Walteria demeterae sp. nov. , which was collected from the northwestern Pacific seamounts at depths of 1 271–1 703 m. Its tubular and basiphytous body, extensive lateral processes, numerous oval lateral oscula which are irregularly situated in the body wall, the presence of microscleres with oxyoidal, discoidal and onychoidal outer ends, and the absence of anchorate discohexasters, indicate it belongs to the genus Walteria of family Euplectellidae, which is also supported by molecular phylogenetic evidence from 18S, 28S, 16S rRNA and cytochrome c oxidase subunit I (COI) gene sequences. The unique morphotype, which is structured by a thin and rigid framework of body wall and lateral processes consisting of diactins, characterizes it as a new species. Local aggregations of individuals of this new species coupled with their associated macrofauna in the Suda Seamount are reported, highlighting its functional significance in providing biogenic microhabitats in the deep sea.
We report on a hexactinellid sponge new to science, Walteria demeterae sp. nov. , which was collected from the northwestern Pacific seamounts at depths of 1 271–1 703 m. Its tubular and basiphytous body, extensive lateral processes, numerous oval lateral oscula which are irregularly situated in the body wall, the presence of microscleres with oxyoidal, discoidal and onychoidal outer ends, and the absence of anchorate discohexasters, indicate it belongs to the genus Walteria of family Euplectellidae, which is also supported by molecular phylogenetic evidence from 18S, 28S, 16S rRNA and cytochrome c oxidase subunit I (COI) gene sequences. The unique morphotype, which is structured by a thin and rigid framework of body wall and lateral processes consisting of diactins, characterizes it as a new species. Local aggregations of individuals of this new species coupled with their associated macrofauna in the Suda Seamount are reported, highlighting its functional significance in providing biogenic microhabitats in the deep sea.
2021, 40(12): 50-54.
doi: 10.1007/s13131-021-1937-5
Abstract:
A new species of Psychropotidae holothuroid, Benthodytes palauta sp. nov., was collected from the Kyushu-Palau Ridge at a depth of 2 666 m. This new species is characterized by a leathery body wall, red-violet skin, five pairs of dorsal papillae, nineteen pairs of tube feet, and a narrow brim. The internal organs include one Polian vesicle, two tufts of gonads, and no respiratory trees. Ventral ossicles are large and spinous, with crosses of four arms with central bipartite apophyses. Papillae ossicles are crosses with four arms with bipartite apophyses. The dorsal ossicles were few and large, and cross-shaped with four arms and central bipartite apophyses. Tentacle ossicles were large and rod-shaped or slender rods. Gonad ossicles were primary crosses of four arms and brim ossicles were cross-shaped with spines. The phylogenetic analyses of this species support that B. palauta sp. nov. belongs to Benthodytes. Furthermore, the paraphyletic relationships were confirmed; however, a revision of the genus Benthodytes is needed to resolve its phylogenetic relationship.
A new species of Psychropotidae holothuroid, Benthodytes palauta sp. nov., was collected from the Kyushu-Palau Ridge at a depth of 2 666 m. This new species is characterized by a leathery body wall, red-violet skin, five pairs of dorsal papillae, nineteen pairs of tube feet, and a narrow brim. The internal organs include one Polian vesicle, two tufts of gonads, and no respiratory trees. Ventral ossicles are large and spinous, with crosses of four arms with central bipartite apophyses. Papillae ossicles are crosses with four arms with bipartite apophyses. The dorsal ossicles were few and large, and cross-shaped with four arms and central bipartite apophyses. Tentacle ossicles were large and rod-shaped or slender rods. Gonad ossicles were primary crosses of four arms and brim ossicles were cross-shaped with spines. The phylogenetic analyses of this species support that B. palauta sp. nov. belongs to Benthodytes. Furthermore, the paraphyletic relationships were confirmed; however, a revision of the genus Benthodytes is needed to resolve its phylogenetic relationship.
2021, 40(12): 55-78.
doi: 10.1007/s13131-021-1887-y
Abstract:
Seamounts are vulnerable ecosystems in the deep sea and can be heavily impacted by human activities, such as bottom fishing and deep-sea mining. The species composition and distribution patterns of benthic fauna is key information for the designation of marine protected areas and environmental management plans. Three contracts for cobalt-rich crust exploration have been granted to China, Japan and Korea in the Northwest Pacific Ocean by the International Seabed Authority. However, our knowledge of benthic biodiversity in this area is extremely insufficient. During 2013–2020, eight Chinese Ocean Mineral Resources R&D Association (COMRA) cruises were conducted to investigate the benthic assemblages of nine seamounts in this region. In this study, 191 ophiuroids collected from seamounts in the Northwest Pacific were identified into 29 species in 11 families. Ophiacanthidae and Euryalidae were the two most dominant families with 12 and 6 species, respectively. Ophiotomidae and Ophiopyrgidae were represented by two species each, while seven families were represented by only one species. Four species were widely distributed among 4–5 seamounts, and 17 species were found only at a single site. An integrated regional taxonomic dataset of Ophiuroidea was generated and analyzed. A total of 23 and 14 species were obtained from the Magellan Seamount Chain (MSC) and the Marcus-Wake seamounts (MWS), respectively, with 8 species shared between the two seamount groups. The individual-based rarefaction curves did not reach an asymptote, suggesting that the sampling effort was inadequate for either the entire region or each single seamount. Most species distributed in a narrow depth range, and the species composition was different between water depths above and below 2 000 m. Our results greatly improve the understanding of megafaunal biodiversity from seamounts in the Northwest Pacific Ocean, and highlight the necessity of further surveys to provide more robust information for environmental protection and management in this region.
Seamounts are vulnerable ecosystems in the deep sea and can be heavily impacted by human activities, such as bottom fishing and deep-sea mining. The species composition and distribution patterns of benthic fauna is key information for the designation of marine protected areas and environmental management plans. Three contracts for cobalt-rich crust exploration have been granted to China, Japan and Korea in the Northwest Pacific Ocean by the International Seabed Authority. However, our knowledge of benthic biodiversity in this area is extremely insufficient. During 2013–2020, eight Chinese Ocean Mineral Resources R&D Association (COMRA) cruises were conducted to investigate the benthic assemblages of nine seamounts in this region. In this study, 191 ophiuroids collected from seamounts in the Northwest Pacific were identified into 29 species in 11 families. Ophiacanthidae and Euryalidae were the two most dominant families with 12 and 6 species, respectively. Ophiotomidae and Ophiopyrgidae were represented by two species each, while seven families were represented by only one species. Four species were widely distributed among 4–5 seamounts, and 17 species were found only at a single site. An integrated regional taxonomic dataset of Ophiuroidea was generated and analyzed. A total of 23 and 14 species were obtained from the Magellan Seamount Chain (MSC) and the Marcus-Wake seamounts (MWS), respectively, with 8 species shared between the two seamount groups. The individual-based rarefaction curves did not reach an asymptote, suggesting that the sampling effort was inadequate for either the entire region or each single seamount. Most species distributed in a narrow depth range, and the species composition was different between water depths above and below 2 000 m. Our results greatly improve the understanding of megafaunal biodiversity from seamounts in the Northwest Pacific Ocean, and highlight the necessity of further surveys to provide more robust information for environmental protection and management in this region.
2021, 40(12): 79-89.
doi: 10.1007/s13131-020-1666-1
Abstract:
Many seamounts are covered with cobalt-rich ferromanganese crusts, and are increasingly attracting interest for the potential extraction of valuable mineral resources from deep seabed environments. However, the impacts of potential mining activities on the vulnerable seamount ecosystem remain unclear. To enhance the understanding of connectivity in benthic invertebrate populations in the Northwest Pacific, several seamounts were surveyed and biological samples collected. In the present study, the ophiuroid species Ophioplinthaca defensor is reported for the first time from four deep seamounts in the Northwest Pacific, and described, providing more detailed morphological diagnosis characters. To assess the population structure of the species between and within seamounts, two mitochondrial markers (COI and 16S) were sequenced. In total, 20 haplotypes from 32 COI sequences and 8 haplotypes from 37 16S sequences were recovered. The star-shaped TCS networks and non-significant pairwise population differences reveal the absence of distinct population structures between and within seamounts. In addition, the O. defensor population seemed to have undergone a demographic expansion in history. This is the first study on the genetic population structure of a benthic invertebrate from seamounts in the Northwest Pacific, and this results suggest a potentially high, long distance dispersal capacity in O. defensor between seamounts, which could inform the development of the Regional Environmental Management Plans for the cobalt-rich crust seamounts in the area.
Many seamounts are covered with cobalt-rich ferromanganese crusts, and are increasingly attracting interest for the potential extraction of valuable mineral resources from deep seabed environments. However, the impacts of potential mining activities on the vulnerable seamount ecosystem remain unclear. To enhance the understanding of connectivity in benthic invertebrate populations in the Northwest Pacific, several seamounts were surveyed and biological samples collected. In the present study, the ophiuroid species Ophioplinthaca defensor is reported for the first time from four deep seamounts in the Northwest Pacific, and described, providing more detailed morphological diagnosis characters. To assess the population structure of the species between and within seamounts, two mitochondrial markers (COI and 16S) were sequenced. In total, 20 haplotypes from 32 COI sequences and 8 haplotypes from 37 16S sequences were recovered. The star-shaped TCS networks and non-significant pairwise population differences reveal the absence of distinct population structures between and within seamounts. In addition, the O. defensor population seemed to have undergone a demographic expansion in history. This is the first study on the genetic population structure of a benthic invertebrate from seamounts in the Northwest Pacific, and this results suggest a potentially high, long distance dispersal capacity in O. defensor between seamounts, which could inform the development of the Regional Environmental Management Plans for the cobalt-rich crust seamounts in the area.
2021, 40(12): 90-103.
doi: 10.1007/s13131-021-1885-0
Abstract:
Ceuthonoe, a new genus with type species C. nezhai sp. n. commensal with euplectellid glass sponge (Hexactinellida: Euplectellidae), is described and illustrated, based on the material collected from Weijia Guyot, western Pacific. The new genus is distinguished by a combination of characters: body with 32 segments; 14 pairs of elytra; prostomium with prominent cephalic peaks and facial tubercle; aciculae and chaetae on tentaculophores; biramous parapodium, each ramus with a long aciculum penetrating epidermis, without supra- or subacicular process; and noto- and neurochaetae with unidentate tips. Ceuthonoe gen. n. is mostly silimar to genera of Polynoinae in morphology. However the phylogenetic analysis based on cytochrome c oxidase subunit I, 16S, 18S, and 28S genes suggested that this new genus was separated from the main branch of Polynoinae. The study also discussed the genera related to the new genus.
Ceuthonoe, a new genus with type species C. nezhai sp. n. commensal with euplectellid glass sponge (Hexactinellida: Euplectellidae), is described and illustrated, based on the material collected from Weijia Guyot, western Pacific. The new genus is distinguished by a combination of characters: body with 32 segments; 14 pairs of elytra; prostomium with prominent cephalic peaks and facial tubercle; aciculae and chaetae on tentaculophores; biramous parapodium, each ramus with a long aciculum penetrating epidermis, without supra- or subacicular process; and noto- and neurochaetae with unidentate tips. Ceuthonoe gen. n. is mostly silimar to genera of Polynoinae in morphology. However the phylogenetic analysis based on cytochrome c oxidase subunit I, 16S, 18S, and 28S genes suggested that this new genus was separated from the main branch of Polynoinae. The study also discussed the genera related to the new genus.
2021, (12): 1-10.
Abstract:
2021, 40(12): 104-113.
doi: 10.1007/s13131-021-1877-0
Abstract:
The present climate simulation and future projection of the mixed layer depth (MLD) and subduction process in the subtropical Southeast Pacific are investigated based on the geophysical fluid dynamics laboratory earth system model (GFDL-ESM2M). The MLD deepens from May and reaches its maximum (>160 m) near (24°S, 104°W) in September in the historical simulation. The MLD spatial pattern in September is non-uniform in the present climate, which shows three characteristics: (1) the deep MLD extends from the Southeast Pacific to the West Pacific and leads to a “deep tongue” until 135°W; (2) the northern boundary of the MLD maximum is smoothly near 18°S, and MLD shallows sharply to the northeast; (3) there is a relatively shallow MLD zone inserted into the MLD maximum eastern boundary near (26°S, 80°W) as a weak “shallow tongue”. The MLD non-uniform spatial pattern generates three strong MLD fronts respectively in the three key regions, promoting the subduction rate. After global warming, the variability of MLD spatial patterns is remarkably diverse, rather than deepening consistently. In all the key regions, the MLD deepens in the south but shoals in the north, strengthing the MLD front. As a result, the subduction rate enhances in these areas. This MLD antisymmetric variability is mainly influenced by various factors, especially the potential-density horizontal advection non-uniform changes. Notice that the freshwater flux change helps to deepen the MLD uniformly in the whole basin, so it hardly works on the regional MLD variability. The study highlights that there are regional differences in the mechanisms of the MLD change, and the MLD front change caused by MLD non-uniform variability is the crucial factor in the subduction response to global warming.
The present climate simulation and future projection of the mixed layer depth (MLD) and subduction process in the subtropical Southeast Pacific are investigated based on the geophysical fluid dynamics laboratory earth system model (GFDL-ESM2M). The MLD deepens from May and reaches its maximum (>160 m) near (24°S, 104°W) in September in the historical simulation. The MLD spatial pattern in September is non-uniform in the present climate, which shows three characteristics: (1) the deep MLD extends from the Southeast Pacific to the West Pacific and leads to a “deep tongue” until 135°W; (2) the northern boundary of the MLD maximum is smoothly near 18°S, and MLD shallows sharply to the northeast; (3) there is a relatively shallow MLD zone inserted into the MLD maximum eastern boundary near (26°S, 80°W) as a weak “shallow tongue”. The MLD non-uniform spatial pattern generates three strong MLD fronts respectively in the three key regions, promoting the subduction rate. After global warming, the variability of MLD spatial patterns is remarkably diverse, rather than deepening consistently. In all the key regions, the MLD deepens in the south but shoals in the north, strengthing the MLD front. As a result, the subduction rate enhances in these areas. This MLD antisymmetric variability is mainly influenced by various factors, especially the potential-density horizontal advection non-uniform changes. Notice that the freshwater flux change helps to deepen the MLD uniformly in the whole basin, so it hardly works on the regional MLD variability. The study highlights that there are regional differences in the mechanisms of the MLD change, and the MLD front change caused by MLD non-uniform variability is the crucial factor in the subduction response to global warming.
2021, 40(12): 114-124.
doi: 10.1007/s13131-021-1869-0
Abstract:
Authigenic carbonate samples were collected from the northern Okinawa Trough. Based on their carbon and oxygen isotopes, these samples were found to be methane-related carbonates precipitated by the anaerobic oxidation of methane (AOM). Petrological analysis revealed numerous framboidal pyrites that had been partly oxidized. In order to trace the variation and diagenetic information of these framboidal pyrites, their diameters and geochemical components were studied using an electron probe. The results showed that their diameters varied from 4 µm to 17 µm (n = 60; geometric mean of 9.9 µm) and were of a normal distribution. The diameters of single pyrite that formed the framboidal pyrites varied from 1 µm to 2 µm. The framboidal pyrites with diameters of 6–14 µm accounted for ~80% of the total. The geometric mean of 9.9 µm indicates that they are probably diagenetic pyrites that were precipitated in a lower dysoxic environment (weakly oxygenated bottom waters). The S/Fe ratio of the framboidal minerals ranged from 0 to 1.67, and the pyrite content of single framboid varied between 0% and 86.4%. Therefore, numerous pyrites were oxygenated to iron oxides or oxyhydroxides, and were retained as pseudomorphism pyrites. The size of framboidal pyrites precipitated in cold seeps can be used to trace the redox environment; however, acquisition of additional data via investigation of different cold seeps is necessary to obtain more persuasive results.
Authigenic carbonate samples were collected from the northern Okinawa Trough. Based on their carbon and oxygen isotopes, these samples were found to be methane-related carbonates precipitated by the anaerobic oxidation of methane (AOM). Petrological analysis revealed numerous framboidal pyrites that had been partly oxidized. In order to trace the variation and diagenetic information of these framboidal pyrites, their diameters and geochemical components were studied using an electron probe. The results showed that their diameters varied from 4 µm to 17 µm (n = 60; geometric mean of 9.9 µm) and were of a normal distribution. The diameters of single pyrite that formed the framboidal pyrites varied from 1 µm to 2 µm. The framboidal pyrites with diameters of 6–14 µm accounted for ~80% of the total. The geometric mean of 9.9 µm indicates that they are probably diagenetic pyrites that were precipitated in a lower dysoxic environment (weakly oxygenated bottom waters). The S/Fe ratio of the framboidal minerals ranged from 0 to 1.67, and the pyrite content of single framboid varied between 0% and 86.4%. Therefore, numerous pyrites were oxygenated to iron oxides or oxyhydroxides, and were retained as pseudomorphism pyrites. The size of framboidal pyrites precipitated in cold seeps can be used to trace the redox environment; however, acquisition of additional data via investigation of different cold seeps is necessary to obtain more persuasive results.
2021, 40(12): 125-134.
doi: 10.1007/s13131-021-1868-1
Abstract:
The influences of the three types of reanalysis wind fields on the simulation of three typhoon waves occurred in 2015 in offshore China were numerically investigated. The typhoon wave model was based on the simulating waves nearshore model (SWAN), in which the wind fields for driving waves were derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis-Interim (ERA-interim), the National Centers for Environmental Prediction climate forecast system version 2 (CFSv2) and cross-calibrated multi-platform (CCMP) datasets. Firstly, the typhoon waves generated during the occurrence of typhoons Chan-hom (1509), Linfa (1510) and Nangka (1511) in 2015 were simulated by using the wave model driven by ERA-interim, CFSv2 and CCMP datasets. The numerical results were validated using buoy data and satellite observation data, and the simulation results under the three types of wind fields were in good agreement with the observed data. The numerical results showed that the CCMP wind data was the best in simulating waves overall, and the wind speeds pertaining to ERA-Interim and CCMP were notably smaller than those observed near the typhoon centre. To correct the accuracy of the wind fields, the Holland theoretical wind model was used to revise and optimize the wind speed pertaining to the CCMP near the typhoon centre. The results indicated that the CCMP wind-driven SWAN model could appropriately simulate the typhoon waves generated by three typhoons in offshore China, and the use of the CCMP/Holland blended wind field could effectively improve the accuracy of typhoon wave simulations.
The influences of the three types of reanalysis wind fields on the simulation of three typhoon waves occurred in 2015 in offshore China were numerically investigated. The typhoon wave model was based on the simulating waves nearshore model (SWAN), in which the wind fields for driving waves were derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis-Interim (ERA-interim), the National Centers for Environmental Prediction climate forecast system version 2 (CFSv2) and cross-calibrated multi-platform (CCMP) datasets. Firstly, the typhoon waves generated during the occurrence of typhoons Chan-hom (1509), Linfa (1510) and Nangka (1511) in 2015 were simulated by using the wave model driven by ERA-interim, CFSv2 and CCMP datasets. The numerical results were validated using buoy data and satellite observation data, and the simulation results under the three types of wind fields were in good agreement with the observed data. The numerical results showed that the CCMP wind data was the best in simulating waves overall, and the wind speeds pertaining to ERA-Interim and CCMP were notably smaller than those observed near the typhoon centre. To correct the accuracy of the wind fields, the Holland theoretical wind model was used to revise and optimize the wind speed pertaining to the CCMP near the typhoon centre. The results indicated that the CCMP wind-driven SWAN model could appropriately simulate the typhoon waves generated by three typhoons in offshore China, and the use of the CCMP/Holland blended wind field could effectively improve the accuracy of typhoon wave simulations.
2021, 40(12): 135-147.
doi: 10.1007/s13131-021-1883-2
Abstract:
Ocean currents are a key element in ocean processes and in meteorology, affecting material transport and modulating climate change patterns. The Doppler frequency shift information of the synthetic aperture radar (SAR) echo signal can reflect the dynamic characteristics of the sea surface, and has become an essential sea surface dynamic remote sensing parameter. Studies have verified that the instantaneous Doppler frequency shift can realize the SAR detection of the sea surface current. However, the validation of SAR-derived ocean current data and a thorough analysis of the errors associated with them remain lacking. In this study, we derive high spatial resolution flow measurements for the Kuroshio in the East China Sea from SAR data using a theoretical model of shifts in Doppler frequency driven by ocean surface current. Global ocean multi observation (MOB) products and global surface Lagrangian drifter (GLD) data are used to validate the Kuroshio flow retrieved from the SAR data. Results show that the central flow velocity for the Kuroshio derived from the SAR is 0.4–1.5 m/s. The error distribution between SAR ocean currents and MOB products is an approximate standard normal distribution, with the 90% confidence interval concentrated between –0.1 m/s and 0.1 m/s. Comparative analysis of SAR ocean current and GLD products, the correlation coefficient is 0.803, which shows to be significant at a confidence level of 99%. The cross-validation of different ocean current dataset illustrate that the SAR radial current captures the positions and dynamics of the Kuroshio central flow and the Kuroshio Counter Current, and has the capability to monitor current velocity over a wide range of values.
Ocean currents are a key element in ocean processes and in meteorology, affecting material transport and modulating climate change patterns. The Doppler frequency shift information of the synthetic aperture radar (SAR) echo signal can reflect the dynamic characteristics of the sea surface, and has become an essential sea surface dynamic remote sensing parameter. Studies have verified that the instantaneous Doppler frequency shift can realize the SAR detection of the sea surface current. However, the validation of SAR-derived ocean current data and a thorough analysis of the errors associated with them remain lacking. In this study, we derive high spatial resolution flow measurements for the Kuroshio in the East China Sea from SAR data using a theoretical model of shifts in Doppler frequency driven by ocean surface current. Global ocean multi observation (MOB) products and global surface Lagrangian drifter (GLD) data are used to validate the Kuroshio flow retrieved from the SAR data. Results show that the central flow velocity for the Kuroshio derived from the SAR is 0.4–1.5 m/s. The error distribution between SAR ocean currents and MOB products is an approximate standard normal distribution, with the 90% confidence interval concentrated between –0.1 m/s and 0.1 m/s. Comparative analysis of SAR ocean current and GLD products, the correlation coefficient is 0.803, which shows to be significant at a confidence level of 99%. The cross-validation of different ocean current dataset illustrate that the SAR radial current captures the positions and dynamics of the Kuroshio central flow and the Kuroshio Counter Current, and has the capability to monitor current velocity over a wide range of values.
2021, 40(12): 148-160.
doi: 10.1007/s13131-021-1867-2
Abstract:
Sea ice velocity impacts the distribution of sea ice, and the flux of exported sea ice through the Fram Strait increases with increasing ice velocity. Therefore, improving the accuracy of estimates of the sea ice velocity is important. We introduce a pyramid algorithm into the Horn-Schunck optical flow (HS-OF) method (to develop the PHS-OF method). Before calculating the sea ice velocity, we generate multilayer pyramid images from an original brightness temperature image. Then, the sea ice velocity of the pyramid layer is calculated, and the ice velocity in the original image is calculated by layer iteration. Winter Arctic sea ice velocities from 2014 to 2016 are obtained and used to discuss the accuracy of the HS-OF method and PHS-OF (specifically the 2-layer PHS-OF (2LPHS-OF) and 4-layer PHS-OF (4LPHS-OF)) methods. The results prove that the PHS-OF method indeed improves the accuracy of sea ice velocity estimates, and the 2LPHS-OF scheme is more appropriate for estimating ice velocity. The error is smaller for the 2LPHS-OF velocity estimates than values from the Ocean and Sea Ice Satellite Application Facility and the Copernicus Marine Environment Monitoring Service, and estimates of changes in velocity by the 2LPHS-OF method are consistent with those from the National Snow and Ice Data Center. Sea ice undergoes two main motion patterns, i.e., transpolar drift and the Beaufort Gyre. In addition, cyclonic and anticyclonic ice drift occurred during winter 2016. Variations in sea ice velocity are related to the open water area, sea ice retreat time and length of the open water season.
Sea ice velocity impacts the distribution of sea ice, and the flux of exported sea ice through the Fram Strait increases with increasing ice velocity. Therefore, improving the accuracy of estimates of the sea ice velocity is important. We introduce a pyramid algorithm into the Horn-Schunck optical flow (HS-OF) method (to develop the PHS-OF method). Before calculating the sea ice velocity, we generate multilayer pyramid images from an original brightness temperature image. Then, the sea ice velocity of the pyramid layer is calculated, and the ice velocity in the original image is calculated by layer iteration. Winter Arctic sea ice velocities from 2014 to 2016 are obtained and used to discuss the accuracy of the HS-OF method and PHS-OF (specifically the 2-layer PHS-OF (2LPHS-OF) and 4-layer PHS-OF (4LPHS-OF)) methods. The results prove that the PHS-OF method indeed improves the accuracy of sea ice velocity estimates, and the 2LPHS-OF scheme is more appropriate for estimating ice velocity. The error is smaller for the 2LPHS-OF velocity estimates than values from the Ocean and Sea Ice Satellite Application Facility and the Copernicus Marine Environment Monitoring Service, and estimates of changes in velocity by the 2LPHS-OF method are consistent with those from the National Snow and Ice Data Center. Sea ice undergoes two main motion patterns, i.e., transpolar drift and the Beaufort Gyre. In addition, cyclonic and anticyclonic ice drift occurred during winter 2016. Variations in sea ice velocity are related to the open water area, sea ice retreat time and length of the open water season.
