To comprehensively understand the Arctic and Antarctic upper atmosphere, it is often crucial to analyze various data that are obtained from many regions. Infrastructure that promotes such interdisciplinary studies on ...To comprehensively understand the Arctic and Antarctic upper atmosphere, it is often crucial to analyze various data that are obtained from many regions. Infrastructure that promotes such interdisciplinary studies on the upper atmosphere has been developed by a Japanese inter-university project called the Inter-university Upper atmosphere Global Observation Network (1UGONET). The objective of this paper is to describe the infrastructure and tools developed by IUGONET. We focus on the data analysis software. It is written in Interactive Data Language (IDL) and is a plug-in for the THEMIS Data Analysis Software suite (TDAS), which is a set of IDL libraries used to visualize and analyze satellite- and ground-based data. We present plots of upper atmospheric data provided by IUGONET as examples of applications, and verify the usefulness of the software in the study of polar science. We discuss IUGONET's new and unique developments, i.e., an executable file of TDAS that can run on the IDL Virtual Machine, IDL routines to retrieve metadata from the IUGONET database, and an archive of 3-D simulation data that uses the Common Data Format so that it can easily be used with TDAS.展开更多
Majority areas of Antarctica and Greenland are under the thick ice sheet and characterized by evolving cryosphere surroundings. In the polar region, associated with the recent trend on climate change such as global wa...Majority areas of Antarctica and Greenland are under the thick ice sheet and characterized by evolving cryosphere surroundings. In the polar region, associated with the recent trend on climate change such as global warming, glacier relating earthquakes are increasing during this 21</span><sup><span style="font-family:Verdana;">st</span></sup><span style="font-family:Verdana;"> century. In this paper, a decade of progress in “Cryoseismology” at bi-polar regions is re-viewed by focusing on the contribution from Japanese researchers. In particular, the specific cryoseismic events are treated, which occurred in the coastal area of East Antarctica, around the L</span><span style="color:#4F4F4F;font-family:Verdana;">ü</span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;">tzow-Holm Bay, together with the coast and whole inland area of Greenland. As the major scientific results, frequency-overtone signals in the harmonic cryoseismic tremors were analyzed by assuming constant sources, suggesting inter-glacial asperities that generate characteristic tremors. Infrasound source locations were also determined by using the array deployment at the coastal regions in the Antarctic. In contrast, characteristics of glacial earthquakes and seismic interferometry approach have been conducted so as to achieve the fine structure of the Greenland Ice Sheet (GrIS) in particular the basal condition beneath the ice sheet.展开更多
Atmospheric rivers(ARs)are an important component of the hydrological cycle linking moisture sources in lower latitudes to the Antarctic surface mass balance.We investigate AR signatures in the atmospheric vertical pr...Atmospheric rivers(ARs)are an important component of the hydrological cycle linking moisture sources in lower latitudes to the Antarctic surface mass balance.We investigate AR signatures in the atmospheric vertical profiles at the Dronning Maud Land coast,East Antarctica,using regular and extra radiosonde measurements conducted during the Year of Polar Prediction Special Observing Period November 2018 to February 2019.Prominent AR events affecting the locations of Neumayer and Syowa cause a strong increase in specific humidity extending through the mid-troposphere and a strong low-level jet(LLJ).At Neumayer,the peak in the moisture inversion(up to 4 g kg^?1)is observed between 800 and 900 hPa,while the LLJ(up to 32 m s^?1)is concentrated below 900 hPa.At Syowa the increase in humidity is less pronounced and peaks near the surface,while there is a substantial increase in wind speed(up to 40 m s?1)between 825 and 925 hPa.Moisture transport(MT)within the vertical profile during the ARs attains a maximum of 100 g kg?1 m s?1 at both locations,and is captured by both ERA-Interim and ERA5 reanalysis data at Neumayer,but is strongly underestimated at Syowa.Composites of the enhanced MT events during 2009?19 show that these events represent an extreme state of the lower-tropospheric profile compared to its median values with respect to temperature,humidity,wind speed and,consequently,MT.High temporal-and vertical-resolution radiosonde observations are important for understanding the contribution of these rare events to the total MT towards Antarctica and improving their representation in models.展开更多
We present observations of a duskside shock aurora occurred on 21 April 2001 by the SuperDARN radar at Syowa Station and the all-sky camera at Zhongshan Station (ZHS) in Antarctica when the radar was operated in fas...We present observations of a duskside shock aurora occurred on 21 April 2001 by the SuperDARN radar at Syowa Station and the all-sky camera at Zhongshan Station (ZHS) in Antarctica when the radar was operated in fast-scan mode covering the ZHS region. With the two independent data sets, we examine ionospheric plasma convection and aurora arising from a sudden impulse (SI) event associated with an interplanetary shock. During the transient shock compression, the aurora was quiescent without any optical emission at the preliminary impulse of the SI. About 7 min later, a new thin auroral arc with brighter emissions and a lifetime of -14 rain expanded westward from the region above ZHS during the main impulse of the SI. SuperDARN radar line-of-sight measurements showed periodical oscillation in the flow direction with ultra-low-frequency waves having a period of -8 min during the shock compression. We suggest that downward field-aligned current during the preliminary impulse stage of the SI was the main driver of the first plasma flow reversal, and the subsequent new discrete auroral arc may be associated with field-aligned acceleration in the region of the main impulse related upward field-aligned currents. The ground magnetometer observations suggest that the oscillation of the ionospheric convection on the duskside was associated with field line resonance activity.展开更多
We report new petrological data and geochronological measurements of granulites from Vesleknausen in the highest-grade section of the L&#252;tzow-Holm Complex, part of the Gondwana-assembling collisional orogen in Ea...We report new petrological data and geochronological measurements of granulites from Vesleknausen in the highest-grade section of the L&#252;tzow-Holm Complex, part of the Gondwana-assembling collisional orogen in East Antarctica. The locality is dominated by felsic to intermediate orthogneiss (charnockite and minor biotite gneiss), mafic orthogneiss, and hornblende-pyroxene granulite, with deformed and undeformed dykes of metagranite and felsic pegmatite. Pseudosection analysis of charnockite in the system NCKFMASHTO, supported by geothermometry of mafic orthogneiss, was used to infer peak metamorphic temperatures of 750e850 ?C, approximately 150 ?C lower than those estimated for met-asedimentary gneisses from Rundv?gshetta, 6 km to the northeast. SHRIMP U-Pb analysis of zircons from feldspar-pyroxene gneiss, which corresponds to a partially molten patch around mafic orthogneiss, yielded a Concordia upper intercept ages of 2507.9 ? 7.4 Ma, corresponding to the time of formation of the magmatic protolith to the orthogneiss. Partial melting during peak metamorphism probably took place between 591 and 548 Ma, as recorded in rims overgrew around magmatic zircon. Our results suggest that Rundv?gshetta-Vesleknausen-Strandnibba region in southwestern L&#252;tzow-Holm Bay, where orthogneisses are dominant, consists of a single crustal block, possibly formed by ca. 2.5 Ga arc mag-matism. The Neoarchean magmatic terrane was tectonically mingled with other fragments (such as metasedimentary units in northern L&#252;tzow-Holm Bay) by subduction/collision events during the as-sembly of Gondwana supercontinent, and subsequently underwent w850 ?C granulite-facies meta-morphosed during Neoproterozoic to Cambrian final collisional event.展开更多
Characteristic infrasound waves observed at Antarctic stations demonstrate physical interaction involving environmental changes in the Antarctic continent and the surrounding oceans. A Chaparraltype infrasound sensor ...Characteristic infrasound waves observed at Antarctic stations demonstrate physical interaction involving environmental changes in the Antarctic continent and the surrounding oceans. A Chaparraltype infrasound sensor was installed at Syowa Station (SYO; 39°E, 69°S), East Antarctica, as one of the projects of the International Polar Year (IPY2007-2008). Data continuously recorded during the three seasons in 2008-2010 clearly indicate a contamination of the background oceanic signals (microbaroms) with peaks between 4 and 10 s observed during a whole season. The peak amplitudes of the microbaroms have relatively lower values during austral winters, caused by a larger amount of sea-ice extending around the Lutzow-Holm Bay near SYO, with decreasing ocean wave loading effects. Micro- baroms measurements are useful tool for characterizing ocean wave climate, complementing other oceanographic and geophysical data. A continuous monitoring by infrasound sensors in the Antarctic firmly contributes to the Comprehensive Nuclear-Test-Ban Treaty (CTBT) in the southern high latitude, together with the Pan-Antarctic Observations System (PAntOS) under the Scientific Committee on Antarctic Research (SCAR). Detailed measurements of the infrasound waves in Antarctica, consequently, could be a new proxy for monitoring regional environmental change as well as the temporal climate variations in the polar regions.展开更多
During the period from October 2014 to March 2015, a total number of 82 seismic tremors and 66 ice-quakes were identified in both three-component short-period seismographs (HES) and broadband seismographs (STS-1) at S...During the period from October 2014 to March 2015, a total number of 82 seismic tremors and 66 ice-quakes were identified in both three-component short-period seismographs (HES) and broadband seismographs (STS-1) at Syowa Station (SYO), Antarctica. Statistics of the number of these tremors indicated that many tremors were likely to occur when large increases in temperature and/or wind speed during the period. This implied that the rapid increase in temperature enhanced a melting speed of cryosphere environment with generating seismic energy;the tremors were also excited by stormy conditions, associated with interactive resonance between sea-ices and oceanic swells. The characteristic tremors of harmonic overtones with strong amplitudes were explained by repetitive sources, suggesting inter-glacial asperities such as the collision of icebergs and fast sea-ice, calving of glaciers/ice-streams at the coastal environment of Antarctica. These high amplitude tremors occurred independently from other majority types of events, characterized by non-linear, small amplitude and weak signals at the stormy condition and rapid increase in temperature.展开更多
A quantitative analysis of the total concentrations of Al and Na in the Antarctic ice sheet during the past 340 kyr was performed by applying the acid digestion method to the Dome Fuji ice core. Atmospheric fluxes of ...A quantitative analysis of the total concentrations of Al and Na in the Antarctic ice sheet during the past 340 kyr was performed by applying the acid digestion method to the Dome Fuji ice core. Atmospheric fluxes of mineral and sea-salt aerosol to Dome Fuji were calculated from the total concentration. The average fluxes of mineral aerosol to Dome Fuji in the periods of glacial maximum, 18.6 ± 10.1 mg·m–2·yr–1, were larger than the value in the interglacial periods, 3.77 ± 2.20 mg·m–2·yr–1. Conversely, the fluxes of sea-salt have no significant difference between the average value of glacial maximum, 130 ± 55 mg·m–2·yr–1, and that of interglacial, 111 ± 54 mg·m–2·yr–1. The results obtained in this study suggest that the variation of mineral aerosol flux in Dome Fuji, together with climate change, was much larger than that of sea-salt aerosol flux. This result may have occurred because the variety in the intensity of the source and transport during the glacial-interglacial cycle is more significant for mineral aerosol than that for sea-salt aerosol.展开更多
On the basis of the analysis of atmospheric carbon dioxide concentration variations and the annual mean air temperature at Syowa Station, Antarctica in the period of 1984-1988, the following results are easily obtaine...On the basis of the analysis of atmospheric carbon dioxide concentration variations and the annual mean air temperature at Syowa Station, Antarctica in the period of 1984-1988, the following results are easily obtained:(1) The annual mean values of the atmospheric carbon dioxide concentration are gradually increased and equal to 342.59, 343.80, 345.15, 346.83 and 348.82 ppmv for 1984, 1985, 1986, 1987 and 1988, respectively. Its annual increase rates are 1.21, 1.35, 1.68 and 1.99 ppmv/yr. For 1984-1985, 1985-1986, 1986-1987 and 1987-1988, respectively and are raised year by year.The seasonal variations are observed and the maximum concentration is in spring and the minimum one is in late-summer or early-autumn.(2)The increasing tendency of the concentration of the atmospheric carbon dioxide is consistent with that of the a.ir temperature.展开更多
A study on the effect of the solar ultra-violet radiation on the human skin fibroblast cells revealed that the production of matrix metalloproteinase-2 was inhibited by the radiation.A CO2 incubator connected by optic...A study on the effect of the solar ultra-violet radiation on the human skin fibroblast cells revealed that the production of matrix metalloproteinase-2 was inhibited by the radiation.A CO2 incubator connected by optical fibers to a reflector telescope for collecting the solar light was built at Syowa station by the 49th Japanese Antarctica Research Expedition.The direction of the telescope was continuously controlled by a sun-tracker to follow the movement of the Sun automatically.The intensity of the collected light was monitored by a portable spectrophotometer housed inside.The human skin fibroblast cells were incubated in the CO2 chamber to investigate the effect of the solar radiation at Syowa station and were compared with those reference experiments at a laboratory in Japan.The results showed cell damage by strong UV radiation.The production of matrix metalloproteinase-2 was prompted by the moderate UV-B,but was inhibited by the strong UV-B radiation,as studied under laboratory conditions in Japan.The effect of strong solar radiation at Syowa station involving the radiation of UV-B region was estimated to be of the same extent of the radiation caused by an artificial UV-B light with the intensity more than 50 mJ/cm2.展开更多
Fluids (fluorine, chlorine, and OH) in accessory minerals (apatite, titanite and allanite) of Pan-African granitoids (Group-I granitoids, Group-II granitoids and Mefjell Plutonic Complex) from the Sor Rondane Mo...Fluids (fluorine, chlorine, and OH) in accessory minerals (apatite, titanite and allanite) of Pan-African granitoids (Group-I granitoids, Group-II granitoids and Mefjell Plutonic Complex) from the Sor Rondane Mountains, East Antarctica were precisely measured by an electronic microprobe analyzer in this study. Apatites in the granites have commonly high fluorine contents. However, fluorine contents from the Group-Ⅰ, Group-Ⅱ granitoids and Mefjell Plutonic Complex (MPC) are of important variation, which F contents (3.21-7.20 wt%) in apatite from the Group-Ⅱ granitoids are much higher than those from the Group-Ⅰ granitoids (1.22-3.60 wt%) and the MPC (3.21-4.11 wt%). Titanite in the MPC has a low fluorine content (0.23-0.50 wt%), being less than those in the Group-Ⅰ granitoids (2.28 wt%) and Group-Ⅱ granitoids (1.85-2.78 wt%). Fluorine in allanite in the Group-Ⅱ granitoids seems to have much lower contents than those from the Group-Ⅰ granitoids and the MPC. Higher fluorine contents in the titanite from the Group-Ⅱ granitoids may be mainly controlled by late-magmatic fluid-rock interaction processes associated with melt, but may not be indicative of original magma contents based on its petrographic feature, Due to very lower chlorine contents from all of accessory minerals, the authors suggest that titanite and apatite with higher fluorine contents in the Group-Ⅱ granitoids have much lower H2O (OH) contents compared with those in the Group-Ⅰ granitoids according to the partition among (F, Cl, OH). Fluorine contents in whole-rock samples show a variation from the higher in the Group-Ⅰ granitoids to the lower in the Group-Ⅱ granitoids and the MPC, which are consistent with the changes of those from the biotite and hornblende as well as fluorite occurred in the Group-Ⅰ granitoids reported previously. Based on the above study of fluorine in accessory minerals and combined with the previous fluorine contents from biotites and hornblendes, the authors suggest that apatites and titanites with higher F contents in the Group-Ⅱ granitoids and the MPC may not be an indicator of higher fluorine contents in whole-rock, which reflect fluorine contents in magma sources and/or late-thermal activity. Higher fluorine contents in apatite, titanite and allanite may be an additional evidence of A-type affinity.展开更多
This paper reports the results of field-based absolute gravity measurements aimed at detecting gravity change and crustal displacement caused by glacial isostatic adjustment. The project was initiated within the frame...This paper reports the results of field-based absolute gravity measurements aimed at detecting gravity change and crustal displacement caused by glacial isostatic adjustment. The project was initiated within the framework of the 53rd Japanese Antarctic Research Expedition (JARE53). Absolute gravity measurements, together with GPS measurements, were planned at several outcrops along the Prince Olav Coast and S6ya Coast of East Antarctica, including at Syowa Station. Since the icebreaker Shirase (AGB 5003) was unable to moor alongside Syowa Station, operations were somewhat restricted during JARE53. However, despite this setback, we were able to complete measurements at two sites: Syowa Station and Langhovde. The absolute gravity value at the Syowa Station IAGBN (A) site, observed using an FG-5 absolute gravimeter (serial number 210; FG-5 #210), was 982 524 322.7+0.1 ktGal, and the gravity change rate at the beginning of 2012 was -0.26 gGal.a-1. An absolute gravity value of 982 535 584.2~0.7 ktGal was obtained using a portable A-10 absolute gravimeter (serial number 017; A-10 #017) at the newly located site AGS01 in Langhovde.展开更多
The Soya Coast in East Antarctica has several ice-free areas where many small (〈1 km2) and shallow (〈50 m depth) glacial lakes display various limnological features. Geological, biological, and ecological studie...The Soya Coast in East Antarctica has several ice-free areas where many small (〈1 km2) and shallow (〈50 m depth) glacial lakes display various limnological features. Geological, biological, and ecological studies conducted by the Japanese Antarctic Research Expeditions since 1957 are reviewed herein. Most of the lakes along the coast are oligotrophic; however, water quality is highly variable depending on differences in lake morphology and history. Geophysical and paleolimnological studies suggest that most of the lakes appeared after the Last Glacial Maximum (LGM) and have since maintained a lacustrine condition. The ubiquitous occurrence of benthic microbial assemblages with low phytoplankton biomasses is a common feature of other Antarctic lakes. However, diverse benthic assemblages such as moss pillars and large pinnacle microbial structures are found in the lake basins. Frequent and continuous limnological studies have revealed three typical water circulation patterns, underwater light climate features (too much light, which includes UV radiation during the ice free season), and the structure of benthic assemblages based on their photosynthetic physiology. The phenomenon of mass floatation of benthic assemblages was observed in a lake during the ice-covered season; this was explained by seasonal environmental conditions. Thus, a hypothesis was formulated based on ecological matter cycling, eutrophication, and lake succession processes.展开更多
Biogeochemical feedback processes between soil organic carbon (SOC) in high-latitude organic soils and climate change is of great concern for projecting future climate. More accurate models of the SOC stock and its dy...Biogeochemical feedback processes between soil organic carbon (SOC) in high-latitude organic soils and climate change is of great concern for projecting future climate. More accurate models of the SOC stock and its dynamics in organic soil are of increasing importance. As a first step toward creating a soil model that accurately represents SOC dynamics, we have created the Physical and Biogeochemical Soil Dynamics Model (PB-SDM) that couples a land surface model with a SOC dynamics model to simulate the feedback cycle of SOC accumulation and thermal hydrological dynamics of high-latitude soils. The model successfully simulated soil temperatures for observed data from a boreal forest near Fairbanks, and 2000 year simulations indicated that the effect of the feedback cycle of SOC accumulation on soil thickness would result in a significant differences in the amount of SOC.展开更多
We measured the spatial variability of Cl -, Na +, SO 2- 4, NO - 3 and 7Be concentrations in snow cover along the traverse route from S16 to Dome Fuji station in east Dronning Maud Land, Antarctica. T...We measured the spatial variability of Cl -, Na +, SO 2- 4, NO - 3 and 7Be concentrations in snow cover along the traverse route from S16 to Dome Fuji station in east Dronning Maud Land, Antarctica. The concentrations of Cl - and Na + at the coast exponentially decreased with distance from the coast up to 200 km inland. Between 200 1000 km inland, the concentrations of Na + were nearly constant. On the other hand, the concentrations of Cl - increased with distance beyond 750 km inland. Furthermore, the contribution factors between Cl - and Na + decreased and the Cl -/Na + ratio and the nssCl -/Cl - ratio increased toward the interior of the continent. These results indicate that sea salt aerosols are transported from the coastal region toward the inland region of the Antarctic continent, and that a source of Cl - other than sea salt exists in the inland plateau of Antarctica. The concentrations of SO 2- 4, NO - 3 and 7Be in snow were relatively high in the coastal region and the inland plateau region compared with those in the katabatic wind region.展开更多
The shallow reflection surveys were carried out in 2007 and 2010 austral summers in East Ongul Island, the Lützow-Holm Complex (LHC), East Antarctica. LHC is identified by geologically as one of the Pan-African t...The shallow reflection surveys were carried out in 2007 and 2010 austral summers in East Ongul Island, the Lützow-Holm Complex (LHC), East Antarctica. LHC is identified by geologically as one of the Pan-African terrains of Eastern Dronning Maud Land. The multi-channel reflection surveys targeted to achieve the image of laminated layering of metamorphic rocks near the surface (the depths down to a few hundreds of meters) of the crystalline crust. Two surveys were conducted in total length of the profiles about 500 m along a main traffic load across the East Ongul Island. The multi-channel acquisition systems were utilized with combining the dense geophones along the profiles. Seismic sources were adopted by combining the boom of a power shovel, a weight drop and hammer shots with their intervals in a few tens of meters. The obtained data include clear first P-arrivals in far offset distance. The energy of P-S converted waves was enhanced because of the characteristics of the seismic sources. Pre-stacked images could be expected to the information on metamorphic layering for several lithological structure composed by hornblende gneiss, garnet gneiss and pyroxene gneiss appearing as the surface bedrocks. The conducted shallow reflection surveys would give rise to one step for understanding tectonic formation of LHC, as one of the Pan-African mobile belts in Gondwana super-continent.展开更多
To investigate temporal and spatial evolution of global geomagnetic field variations from high-latitude to the equator during geomagnetic storms, we analyzed ground geomagnetic field disturbances from high latitudes t...To investigate temporal and spatial evolution of global geomagnetic field variations from high-latitude to the equator during geomagnetic storms, we analyzed ground geomagnetic field disturbances from high latitudes to the magnetic equator. The daytime ionospheric equivalent current during the storm main phase showed that twin-vortex ionospheric currents driven by the Region 1 field-aligned currents (R1 FACs) are intensified significantly and expand to the low-latitude region of-30~ magnetic latitude. Centers of the currents were located around 70~ and 65~ in the morning and afternoon, respectively. Corresponding to intensification of the R1 FACs, an enhancement of the eastward/westward equatorial electrojet occurred at the daytime/nighttime dip equator. This signature suggests that the enhanced convection electric field penetrates to both the daytime and nighttime equa- tor. During the recovery phase, the daytime equivalent current showed that two new pairs of twin vortices, which are different from two-cell ionospheric currents driven by the R1 FACs, appear in the polar cap and mid latitude. The former led to enhanced north- ward Bz (NBZ) FACs driven by lobe reconnection tailward of the cusps, owing to the northward interplanetary magnetic field (IMF). The latter was generated by enhanced Region 2 field-aligned currents (R2 FACs). Associated with these magnetic field variations in the mid-latitudes and polar cap, the equatorial magnetic field variation showed a strongly negative signature, produced by the westward equatorial electrojet current caused by the dusk-to-dawn electric field.展开更多
Deployments of seismic stations in Antarctica are an ambitious project to improve the spatial resolution of the Antarctic Plate and surrounding regions. Several international programs had been conducted in wide area o...Deployments of seismic stations in Antarctica are an ambitious project to improve the spatial resolution of the Antarctic Plate and surrounding regions. Several international programs had been conducted in wide area of the Antarctic continent during the International Polar Year (IPY 2007-2008). The “Antarctica’s GAmburtsev Province (AGAP)”, the “GAmburtsev Mountain SEISmic experiment (GAMSEIS)” as a part of AGAP, and the “Polar Earth Observing Network (POLENET)” were major contributions to the IPY. The AGAP/GAMSEIS was an internationally coordinated deployments of more than few tens of broadband seismographs over the wide area of East Antarctica. Detailed information on crustal thickness and mantle structure provides key constraints on an origin of the Gamburtsev Mountains;and more broad structure and evolution of the East Antarctic craton and sub-glacial environment. From POLENET data obtained, local and regional signals associated with ice movements were recorded together with a significant number of teleseismic events. Moreover, seismic deployments have been carried out in the Lützow-Holm Bay (LHB), East Antarctica, by Japanese activities. The recorded teleseismic and local events are of sufficient quality to image the structure and dynamics of the crust and mantle, such as the studies by receiver functions suggesting a heterogeneous upper mantle. In addition to studies on the shallow part of the Earth, we place emphasis on these seismic deployments’ ability to image the Earth’s deep interior, as viewed from Antarctica, as a large aperture array in the southern high latitude.展开更多
In this paper we use the high speed multi channel meridian scanning photometer data and all sky TV camera images to analyze the intensity variations of the postnoon auroral bright sports of 557.7 nm and 630.0 nm em...In this paper we use the high speed multi channel meridian scanning photometer data and all sky TV camera images to analyze the intensity variations of the postnoon auroral bright sports of 557.7 nm and 630.0 nm emissions. Several results can be obtained from this paper. (1) Bright spots are rather transient features lasting typically for only a few minutes. (2) The intensity of the postnoon bright spots of 557.7 nm emissions can surpass 11 kR. The occurrence of the bright spots seems rather frequent. (3) The ratios of I(427.8)/I(630.0) and I(427.8)/I(557.7) during the bright spots occurring time show a positive peak and negative peak respectively. It qualitatively indicates that the average precipitating electron energies along the meridianal scan above Zhongshan Station increased as the bright spot appeared. And the intensification of the spot mainly was caused by the increasing of high energy (3 10 keV) flux. (4) Usually the bright spots are accompanied with the magnetic pulsation and the occurrence of multi band arcs.展开更多
Characteristic infrasound waves are clearly recorded at Syowa Station (SYO), East Antarctica, involving physical interaction in surrounding environments at the continent and SouthernOcean. A Chaparral microphone type ...Characteristic infrasound waves are clearly recorded at Syowa Station (SYO), East Antarctica, involving physical interaction in surrounding environments at the continent and SouthernOcean. A Chaparral microphone type infrasound sensor is deployed at SYO during the International Polar Year (IPY2007-2008), the most diverse international science program held recently. Continuous recorded data in 2008-2010 indicate a contamination of background oceanic signals (microbaroms). The characteristic signals are identified as the “microbaroms” with peaks between 4 and 10 s in the records. The peak amplitudes of microbaroms may be enhanced by the extratropical cyclonic storms and wind noises in Southern Ocean. The microbaroms has relatively lower amplitudes during austral winters, which may be caused by the larger amount of the sea-ice extent around theLützow-HolmBaynear SYO, with decreasing the ocean wave loading effects. In addition, the large energy with intrinsic periods between 12 and 30 s are observable under excellent storm conditions, particularly in local winter. The oceanic effects appearing on infrasound data are modulated by the presence of sea-ice and explained by a relationship between the atmosphere-ocean-cryosphere systems. Microbaroms measurements could be a useful tool for characterizing ocean wave climate, as well as a new proxy for monitoring a regional environmental variation inAntarctica.展开更多
基金supported by the Special Edu-cational Research Budget(Research Promotion)[FY2009]the Special Budget(Project)[FY2010 and later years]from the Ministry of Education,Culture,Sports,Science and Technology(MEXT),Japansupported by the GRENE Arctic Climate Change Research Project,Japan
文摘To comprehensively understand the Arctic and Antarctic upper atmosphere, it is often crucial to analyze various data that are obtained from many regions. Infrastructure that promotes such interdisciplinary studies on the upper atmosphere has been developed by a Japanese inter-university project called the Inter-university Upper atmosphere Global Observation Network (1UGONET). The objective of this paper is to describe the infrastructure and tools developed by IUGONET. We focus on the data analysis software. It is written in Interactive Data Language (IDL) and is a plug-in for the THEMIS Data Analysis Software suite (TDAS), which is a set of IDL libraries used to visualize and analyze satellite- and ground-based data. We present plots of upper atmospheric data provided by IUGONET as examples of applications, and verify the usefulness of the software in the study of polar science. We discuss IUGONET's new and unique developments, i.e., an executable file of TDAS that can run on the IDL Virtual Machine, IDL routines to retrieve metadata from the IUGONET database, and an archive of 3-D simulation data that uses the Common Data Format so that it can easily be used with TDAS.
文摘Majority areas of Antarctica and Greenland are under the thick ice sheet and characterized by evolving cryosphere surroundings. In the polar region, associated with the recent trend on climate change such as global warming, glacier relating earthquakes are increasing during this 21</span><sup><span style="font-family:Verdana;">st</span></sup><span style="font-family:Verdana;"> century. In this paper, a decade of progress in “Cryoseismology” at bi-polar regions is re-viewed by focusing on the contribution from Japanese researchers. In particular, the specific cryoseismic events are treated, which occurred in the coastal area of East Antarctica, around the L</span><span style="color:#4F4F4F;font-family:Verdana;">ü</span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;">tzow-Holm Bay, together with the coast and whole inland area of Greenland. As the major scientific results, frequency-overtone signals in the harmonic cryoseismic tremors were analyzed by assuming constant sources, suggesting inter-glacial asperities that generate characteristic tremors. Infrasound source locations were also determined by using the array deployment at the coastal regions in the Antarctic. In contrast, characteristics of glacial earthquakes and seismic interferometry approach have been conducted so as to achieve the fine structure of the Greenland Ice Sheet (GrIS) in particular the basal condition beneath the ice sheet.
基金the financial support to CESAM (UID/AMB/ 50017/2019) through national funds and FCT grant CIRCNA/CAC/ 0273/2019National Institute of Polar Research (NIPR) Project Research No. KP302
文摘Atmospheric rivers(ARs)are an important component of the hydrological cycle linking moisture sources in lower latitudes to the Antarctic surface mass balance.We investigate AR signatures in the atmospheric vertical profiles at the Dronning Maud Land coast,East Antarctica,using regular and extra radiosonde measurements conducted during the Year of Polar Prediction Special Observing Period November 2018 to February 2019.Prominent AR events affecting the locations of Neumayer and Syowa cause a strong increase in specific humidity extending through the mid-troposphere and a strong low-level jet(LLJ).At Neumayer,the peak in the moisture inversion(up to 4 g kg^?1)is observed between 800 and 900 hPa,while the LLJ(up to 32 m s^?1)is concentrated below 900 hPa.At Syowa the increase in humidity is less pronounced and peaks near the surface,while there is a substantial increase in wind speed(up to 40 m s?1)between 825 and 925 hPa.Moisture transport(MT)within the vertical profile during the ARs attains a maximum of 100 g kg?1 m s?1 at both locations,and is captured by both ERA-Interim and ERA5 reanalysis data at Neumayer,but is strongly underestimated at Syowa.Composites of the enhanced MT events during 2009?19 show that these events represent an extreme state of the lower-tropospheric profile compared to its median values with respect to temperature,humidity,wind speed and,consequently,MT.High temporal-and vertical-resolution radiosonde observations are important for understanding the contribution of these rare events to the total MT towards Antarctica and improving their representation in models.
基金supported by the Polar Strategic Research Foundation of China(Grant no.20100203)the National Natural Science Foundation of China(Grant nos.40974083,41031064,40904041)+2 种基金the Ocean Public Welfare Scientific Research Project of China(Grant no.201005017)the International Collaboration Supporting Project,Chinese Arctic and Antarctic Administration(Grant no.IC201303)the National Basic Research Program of China(Grant no.2010CB950503-06)
文摘We present observations of a duskside shock aurora occurred on 21 April 2001 by the SuperDARN radar at Syowa Station and the all-sky camera at Zhongshan Station (ZHS) in Antarctica when the radar was operated in fast-scan mode covering the ZHS region. With the two independent data sets, we examine ionospheric plasma convection and aurora arising from a sudden impulse (SI) event associated with an interplanetary shock. During the transient shock compression, the aurora was quiescent without any optical emission at the preliminary impulse of the SI. About 7 min later, a new thin auroral arc with brighter emissions and a lifetime of -14 rain expanded westward from the region above ZHS during the main impulse of the SI. SuperDARN radar line-of-sight measurements showed periodical oscillation in the flow direction with ultra-low-frequency waves having a period of -8 min during the shock compression. We suggest that downward field-aligned current during the preliminary impulse stage of the SI was the main driver of the first plasma flow reversal, and the subsequent new discrete auroral arc may be associated with field-aligned acceleration in the region of the main impulse related upward field-aligned currents. The ground magnetometer observations suggest that the oscillation of the ionospheric convection on the duskside was associated with field line resonance activity.
基金partly supported by a Grant-in-Aid for Scientific Research (B) from Japan Society for the Promotion of Science (JSPS) to Tsunogae (Nos. 20340148, 22403017)
文摘We report new petrological data and geochronological measurements of granulites from Vesleknausen in the highest-grade section of the L&#252;tzow-Holm Complex, part of the Gondwana-assembling collisional orogen in East Antarctica. The locality is dominated by felsic to intermediate orthogneiss (charnockite and minor biotite gneiss), mafic orthogneiss, and hornblende-pyroxene granulite, with deformed and undeformed dykes of metagranite and felsic pegmatite. Pseudosection analysis of charnockite in the system NCKFMASHTO, supported by geothermometry of mafic orthogneiss, was used to infer peak metamorphic temperatures of 750e850 ?C, approximately 150 ?C lower than those estimated for met-asedimentary gneisses from Rundv?gshetta, 6 km to the northeast. SHRIMP U-Pb analysis of zircons from feldspar-pyroxene gneiss, which corresponds to a partially molten patch around mafic orthogneiss, yielded a Concordia upper intercept ages of 2507.9 ? 7.4 Ma, corresponding to the time of formation of the magmatic protolith to the orthogneiss. Partial melting during peak metamorphism probably took place between 591 and 548 Ma, as recorded in rims overgrew around magmatic zircon. Our results suggest that Rundv?gshetta-Vesleknausen-Strandnibba region in southwestern L&#252;tzow-Holm Bay, where orthogneisses are dominant, consists of a single crustal block, possibly formed by ca. 2.5 Ga arc mag-matism. The Neoarchean magmatic terrane was tectonically mingled with other fragments (such as metasedimentary units in northern L&#252;tzow-Holm Bay) by subduction/collision events during the as-sembly of Gondwana supercontinent, and subsequently underwent w850 ?C granulite-facies meta-morphosed during Neoproterozoic to Cambrian final collisional event.
基金supported by the Ministry of Education,Science,Sports and Culture, Grant-in-Aid for Young Scientists(B) 19740265,2007(P.I.for Dr. Yoshiaki Ishihara)
文摘Characteristic infrasound waves observed at Antarctic stations demonstrate physical interaction involving environmental changes in the Antarctic continent and the surrounding oceans. A Chaparraltype infrasound sensor was installed at Syowa Station (SYO; 39°E, 69°S), East Antarctica, as one of the projects of the International Polar Year (IPY2007-2008). Data continuously recorded during the three seasons in 2008-2010 clearly indicate a contamination of the background oceanic signals (microbaroms) with peaks between 4 and 10 s observed during a whole season. The peak amplitudes of the microbaroms have relatively lower values during austral winters, caused by a larger amount of sea-ice extending around the Lutzow-Holm Bay near SYO, with decreasing ocean wave loading effects. Micro- baroms measurements are useful tool for characterizing ocean wave climate, complementing other oceanographic and geophysical data. A continuous monitoring by infrasound sensors in the Antarctic firmly contributes to the Comprehensive Nuclear-Test-Ban Treaty (CTBT) in the southern high latitude, together with the Pan-Antarctic Observations System (PAntOS) under the Scientific Committee on Antarctic Research (SCAR). Detailed measurements of the infrasound waves in Antarctica, consequently, could be a new proxy for monitoring regional environmental change as well as the temporal climate variations in the polar regions.
文摘During the period from October 2014 to March 2015, a total number of 82 seismic tremors and 66 ice-quakes were identified in both three-component short-period seismographs (HES) and broadband seismographs (STS-1) at Syowa Station (SYO), Antarctica. Statistics of the number of these tremors indicated that many tremors were likely to occur when large increases in temperature and/or wind speed during the period. This implied that the rapid increase in temperature enhanced a melting speed of cryosphere environment with generating seismic energy;the tremors were also excited by stormy conditions, associated with interactive resonance between sea-ices and oceanic swells. The characteristic tremors of harmonic overtones with strong amplitudes were explained by repetitive sources, suggesting inter-glacial asperities such as the collision of icebergs and fast sea-ice, calving of glaciers/ice-streams at the coastal environment of Antarctica. These high amplitude tremors occurred independently from other majority types of events, characterized by non-linear, small amplitude and weak signals at the stormy condition and rapid increase in temperature.
文摘A quantitative analysis of the total concentrations of Al and Na in the Antarctic ice sheet during the past 340 kyr was performed by applying the acid digestion method to the Dome Fuji ice core. Atmospheric fluxes of mineral and sea-salt aerosol to Dome Fuji were calculated from the total concentration. The average fluxes of mineral aerosol to Dome Fuji in the periods of glacial maximum, 18.6 ± 10.1 mg·m–2·yr–1, were larger than the value in the interglacial periods, 3.77 ± 2.20 mg·m–2·yr–1. Conversely, the fluxes of sea-salt have no significant difference between the average value of glacial maximum, 130 ± 55 mg·m–2·yr–1, and that of interglacial, 111 ± 54 mg·m–2·yr–1. The results obtained in this study suggest that the variation of mineral aerosol flux in Dome Fuji, together with climate change, was much larger than that of sea-salt aerosol flux. This result may have occurred because the variety in the intensity of the source and transport during the glacial-interglacial cycle is more significant for mineral aerosol than that for sea-salt aerosol.
文摘On the basis of the analysis of atmospheric carbon dioxide concentration variations and the annual mean air temperature at Syowa Station, Antarctica in the period of 1984-1988, the following results are easily obtained:(1) The annual mean values of the atmospheric carbon dioxide concentration are gradually increased and equal to 342.59, 343.80, 345.15, 346.83 and 348.82 ppmv for 1984, 1985, 1986, 1987 and 1988, respectively. Its annual increase rates are 1.21, 1.35, 1.68 and 1.99 ppmv/yr. For 1984-1985, 1985-1986, 1986-1987 and 1987-1988, respectively and are raised year by year.The seasonal variations are observed and the maximum concentration is in spring and the minimum one is in late-summer or early-autumn.(2)The increasing tendency of the concentration of the atmospheric carbon dioxide is consistent with that of the a.ir temperature.
基金fnancially supported partly by the Grand-In-Aid for Scientifc Research(C)18510022 and (C)21510032 of Japan Society for the promotion of Science
文摘A study on the effect of the solar ultra-violet radiation on the human skin fibroblast cells revealed that the production of matrix metalloproteinase-2 was inhibited by the radiation.A CO2 incubator connected by optical fibers to a reflector telescope for collecting the solar light was built at Syowa station by the 49th Japanese Antarctica Research Expedition.The direction of the telescope was continuously controlled by a sun-tracker to follow the movement of the Sun automatically.The intensity of the collected light was monitored by a portable spectrophotometer housed inside.The human skin fibroblast cells were incubated in the CO2 chamber to investigate the effect of the solar radiation at Syowa station and were compared with those reference experiments at a laboratory in Japan.The results showed cell damage by strong UV radiation.The production of matrix metalloproteinase-2 was prompted by the moderate UV-B,but was inhibited by the strong UV-B radiation,as studied under laboratory conditions in Japan.The effect of strong solar radiation at Syowa station involving the radiation of UV-B region was estimated to be of the same extent of the radiation caused by an artificial UV-B light with the intensity more than 50 mJ/cm2.
基金Project (Nos. 40472040 and 40472120) supported by the National Natural Science Foundation of China
文摘Fluids (fluorine, chlorine, and OH) in accessory minerals (apatite, titanite and allanite) of Pan-African granitoids (Group-I granitoids, Group-II granitoids and Mefjell Plutonic Complex) from the Sor Rondane Mountains, East Antarctica were precisely measured by an electronic microprobe analyzer in this study. Apatites in the granites have commonly high fluorine contents. However, fluorine contents from the Group-Ⅰ, Group-Ⅱ granitoids and Mefjell Plutonic Complex (MPC) are of important variation, which F contents (3.21-7.20 wt%) in apatite from the Group-Ⅱ granitoids are much higher than those from the Group-Ⅰ granitoids (1.22-3.60 wt%) and the MPC (3.21-4.11 wt%). Titanite in the MPC has a low fluorine content (0.23-0.50 wt%), being less than those in the Group-Ⅰ granitoids (2.28 wt%) and Group-Ⅱ granitoids (1.85-2.78 wt%). Fluorine in allanite in the Group-Ⅱ granitoids seems to have much lower contents than those from the Group-Ⅰ granitoids and the MPC. Higher fluorine contents in the titanite from the Group-Ⅱ granitoids may be mainly controlled by late-magmatic fluid-rock interaction processes associated with melt, but may not be indicative of original magma contents based on its petrographic feature, Due to very lower chlorine contents from all of accessory minerals, the authors suggest that titanite and apatite with higher fluorine contents in the Group-Ⅱ granitoids have much lower H2O (OH) contents compared with those in the Group-Ⅰ granitoids according to the partition among (F, Cl, OH). Fluorine contents in whole-rock samples show a variation from the higher in the Group-Ⅰ granitoids to the lower in the Group-Ⅱ granitoids and the MPC, which are consistent with the changes of those from the biotite and hornblende as well as fluorite occurred in the Group-Ⅰ granitoids reported previously. Based on the above study of fluorine in accessory minerals and combined with the previous fluorine contents from biotites and hornblendes, the authors suggest that apatites and titanites with higher F contents in the Group-Ⅱ granitoids and the MPC may not be an indicator of higher fluorine contents in whole-rock, which reflect fluorine contents in magma sources and/or late-thermal activity. Higher fluorine contents in apatite, titanite and allanite may be an additional evidence of A-type affinity.
文摘This paper reports the results of field-based absolute gravity measurements aimed at detecting gravity change and crustal displacement caused by glacial isostatic adjustment. The project was initiated within the framework of the 53rd Japanese Antarctic Research Expedition (JARE53). Absolute gravity measurements, together with GPS measurements, were planned at several outcrops along the Prince Olav Coast and S6ya Coast of East Antarctica, including at Syowa Station. Since the icebreaker Shirase (AGB 5003) was unable to moor alongside Syowa Station, operations were somewhat restricted during JARE53. However, despite this setback, we were able to complete measurements at two sites: Syowa Station and Langhovde. The absolute gravity value at the Syowa Station IAGBN (A) site, observed using an FG-5 absolute gravimeter (serial number 210; FG-5 #210), was 982 524 322.7+0.1 ktGal, and the gravity change rate at the beginning of 2012 was -0.26 gGal.a-1. An absolute gravity value of 982 535 584.2~0.7 ktGal was obtained using a portable A-10 absolute gravimeter (serial number 017; A-10 #017) at the newly located site AGS01 in Langhovde.
基金partly supported by a grant from the Center for the Promotion of Integrated Sciences,the Graduate University for Advanced Studies(SOKENDAI),Japan and an NIPR publication subsidy
文摘The Soya Coast in East Antarctica has several ice-free areas where many small (〈1 km2) and shallow (〈50 m depth) glacial lakes display various limnological features. Geological, biological, and ecological studies conducted by the Japanese Antarctic Research Expeditions since 1957 are reviewed herein. Most of the lakes along the coast are oligotrophic; however, water quality is highly variable depending on differences in lake morphology and history. Geophysical and paleolimnological studies suggest that most of the lakes appeared after the Last Glacial Maximum (LGM) and have since maintained a lacustrine condition. The ubiquitous occurrence of benthic microbial assemblages with low phytoplankton biomasses is a common feature of other Antarctic lakes. However, diverse benthic assemblages such as moss pillars and large pinnacle microbial structures are found in the lake basins. Frequent and continuous limnological studies have revealed three typical water circulation patterns, underwater light climate features (too much light, which includes UV radiation during the ice free season), and the structure of benthic assemblages based on their photosynthetic physiology. The phenomenon of mass floatation of benthic assemblages was observed in a lake during the ice-covered season; this was explained by seasonal environmental conditions. Thus, a hypothesis was formulated based on ecological matter cycling, eutrophication, and lake succession processes.
文摘Biogeochemical feedback processes between soil organic carbon (SOC) in high-latitude organic soils and climate change is of great concern for projecting future climate. More accurate models of the SOC stock and its dynamics in organic soil are of increasing importance. As a first step toward creating a soil model that accurately represents SOC dynamics, we have created the Physical and Biogeochemical Soil Dynamics Model (PB-SDM) that couples a land surface model with a SOC dynamics model to simulate the feedback cycle of SOC accumulation and thermal hydrological dynamics of high-latitude soils. The model successfully simulated soil temperatures for observed data from a boreal forest near Fairbanks, and 2000 year simulations indicated that the effect of the feedback cycle of SOC accumulation on soil thickness would result in a significant differences in the amount of SOC.
文摘We measured the spatial variability of Cl -, Na +, SO 2- 4, NO - 3 and 7Be concentrations in snow cover along the traverse route from S16 to Dome Fuji station in east Dronning Maud Land, Antarctica. The concentrations of Cl - and Na + at the coast exponentially decreased with distance from the coast up to 200 km inland. Between 200 1000 km inland, the concentrations of Na + were nearly constant. On the other hand, the concentrations of Cl - increased with distance beyond 750 km inland. Furthermore, the contribution factors between Cl - and Na + decreased and the Cl -/Na + ratio and the nssCl -/Cl - ratio increased toward the interior of the continent. These results indicate that sea salt aerosols are transported from the coastal region toward the inland region of the Antarctic continent, and that a source of Cl - other than sea salt exists in the inland plateau of Antarctica. The concentrations of SO 2- 4, NO - 3 and 7Be in snow were relatively high in the coastal region and the inland plateau region compared with those in the katabatic wind region.
文摘The shallow reflection surveys were carried out in 2007 and 2010 austral summers in East Ongul Island, the Lützow-Holm Complex (LHC), East Antarctica. LHC is identified by geologically as one of the Pan-African terrains of Eastern Dronning Maud Land. The multi-channel reflection surveys targeted to achieve the image of laminated layering of metamorphic rocks near the surface (the depths down to a few hundreds of meters) of the crystalline crust. Two surveys were conducted in total length of the profiles about 500 m along a main traffic load across the East Ongul Island. The multi-channel acquisition systems were utilized with combining the dense geophones along the profiles. Seismic sources were adopted by combining the boom of a power shovel, a weight drop and hammer shots with their intervals in a few tens of meters. The obtained data include clear first P-arrivals in far offset distance. The energy of P-S converted waves was enhanced because of the characteristics of the seismic sources. Pre-stacked images could be expected to the information on metamorphic layering for several lithological structure composed by hornblende gneiss, garnet gneiss and pyroxene gneiss appearing as the surface bedrocks. The conducted shallow reflection surveys would give rise to one step for understanding tectonic formation of LHC, as one of the Pan-African mobile belts in Gondwana super-continent.
基金supported by the Inter-university Upper atmosphere Global Observation NETwork(IUGONET)projectfunded by the Ministry of Education,Culture,Sports,Science and Technology(MEXT),Japan,the National Institute of Polar Research through General Collaboration Projects(Grant no.23-14)JSPS KAKENHI(Grant no.11020535)
文摘To investigate temporal and spatial evolution of global geomagnetic field variations from high-latitude to the equator during geomagnetic storms, we analyzed ground geomagnetic field disturbances from high latitudes to the magnetic equator. The daytime ionospheric equivalent current during the storm main phase showed that twin-vortex ionospheric currents driven by the Region 1 field-aligned currents (R1 FACs) are intensified significantly and expand to the low-latitude region of-30~ magnetic latitude. Centers of the currents were located around 70~ and 65~ in the morning and afternoon, respectively. Corresponding to intensification of the R1 FACs, an enhancement of the eastward/westward equatorial electrojet occurred at the daytime/nighttime dip equator. This signature suggests that the enhanced convection electric field penetrates to both the daytime and nighttime equa- tor. During the recovery phase, the daytime equivalent current showed that two new pairs of twin vortices, which are different from two-cell ionospheric currents driven by the R1 FACs, appear in the polar cap and mid latitude. The former led to enhanced north- ward Bz (NBZ) FACs driven by lobe reconnection tailward of the cusps, owing to the northward interplanetary magnetic field (IMF). The latter was generated by enhanced Region 2 field-aligned currents (R2 FACs). Associated with these magnetic field variations in the mid-latitudes and polar cap, the equatorial magnetic field variation showed a strongly negative signature, produced by the westward equatorial electrojet current caused by the dusk-to-dawn electric field.
文摘Deployments of seismic stations in Antarctica are an ambitious project to improve the spatial resolution of the Antarctic Plate and surrounding regions. Several international programs had been conducted in wide area of the Antarctic continent during the International Polar Year (IPY 2007-2008). The “Antarctica’s GAmburtsev Province (AGAP)”, the “GAmburtsev Mountain SEISmic experiment (GAMSEIS)” as a part of AGAP, and the “Polar Earth Observing Network (POLENET)” were major contributions to the IPY. The AGAP/GAMSEIS was an internationally coordinated deployments of more than few tens of broadband seismographs over the wide area of East Antarctica. Detailed information on crustal thickness and mantle structure provides key constraints on an origin of the Gamburtsev Mountains;and more broad structure and evolution of the East Antarctic craton and sub-glacial environment. From POLENET data obtained, local and regional signals associated with ice movements were recorded together with a significant number of teleseismic events. Moreover, seismic deployments have been carried out in the Lützow-Holm Bay (LHB), East Antarctica, by Japanese activities. The recorded teleseismic and local events are of sufficient quality to image the structure and dynamics of the crust and mantle, such as the studies by receiver functions suggesting a heterogeneous upper mantle. In addition to studies on the shallow part of the Earth, we place emphasis on these seismic deployments’ ability to image the Earth’s deep interior, as viewed from Antarctica, as a large aperture array in the southern high latitude.
文摘In this paper we use the high speed multi channel meridian scanning photometer data and all sky TV camera images to analyze the intensity variations of the postnoon auroral bright sports of 557.7 nm and 630.0 nm emissions. Several results can be obtained from this paper. (1) Bright spots are rather transient features lasting typically for only a few minutes. (2) The intensity of the postnoon bright spots of 557.7 nm emissions can surpass 11 kR. The occurrence of the bright spots seems rather frequent. (3) The ratios of I(427.8)/I(630.0) and I(427.8)/I(557.7) during the bright spots occurring time show a positive peak and negative peak respectively. It qualitatively indicates that the average precipitating electron energies along the meridianal scan above Zhongshan Station increased as the bright spot appeared. And the intensification of the spot mainly was caused by the increasing of high energy (3 10 keV) flux. (4) Usually the bright spots are accompanied with the magnetic pulsation and the occurrence of multi band arcs.
文摘Characteristic infrasound waves are clearly recorded at Syowa Station (SYO), East Antarctica, involving physical interaction in surrounding environments at the continent and SouthernOcean. A Chaparral microphone type infrasound sensor is deployed at SYO during the International Polar Year (IPY2007-2008), the most diverse international science program held recently. Continuous recorded data in 2008-2010 indicate a contamination of background oceanic signals (microbaroms). The characteristic signals are identified as the “microbaroms” with peaks between 4 and 10 s in the records. The peak amplitudes of microbaroms may be enhanced by the extratropical cyclonic storms and wind noises in Southern Ocean. The microbaroms has relatively lower amplitudes during austral winters, which may be caused by the larger amount of the sea-ice extent around theLützow-HolmBaynear SYO, with decreasing the ocean wave loading effects. In addition, the large energy with intrinsic periods between 12 and 30 s are observable under excellent storm conditions, particularly in local winter. The oceanic effects appearing on infrasound data are modulated by the presence of sea-ice and explained by a relationship between the atmosphere-ocean-cryosphere systems. Microbaroms measurements could be a useful tool for characterizing ocean wave climate, as well as a new proxy for monitoring a regional environmental variation inAntarctica.