Recent progress in Chinese polar upper-atmospheric physics research: review of research advances supported by the Chinese Arctic and Antarctic expeditions

It has been more than 30 years since the first Chinese Antarctic Expedition took place. Polar upper atmospheric observations started at this time. First began at Great Wall Station and then at Zhongshan Station in Antarctica, and later in the Arctic at Yellow River Station, Kjell Henriksen Observatory on Svalbard, and at the China-Iceland Joint Aurora Observatory in Iceland. In this paper, we reviewed the advances in polar upper atmosphere physics(UAP) based on the Chinese national Arctic and Antarctic research over the last five years. These included newly deployed observatories and research instruments in the Arctic and Antarctic; and new research findings, from ground-based observations, about polar ionosphere dynamics, aurora and particle precipitation, polar plasma convection, geomagnetic pulsations and space plasma waves, space weather in the polar regions, simulations of the polar ionosphere-magnetosphere. In conclusion, suggestions were made for future polar upper atmosphere physics research in China.

A conjugate study of the polar ionospheric F2-layer and IRI-2007 at 75 ° magnetic latitude for solar minimum

Long-duration conjugate observations by the EISCAT Svalbard Radar (ESR) and the ionosonde at Zhongshan station from the International Polar Year (IPY) during solar minimum conditions are analyzed, with respect to variability in the F 2-layer peak parameters. A comparison between International Reference Ionosphere2007 (IRI-2007) and observation data clearly demonstrates good agreement in summer, but greater deviations in winter. The IRI model reproduces the F 2 peak parameters dominated by solar photoionization reasonably well, but it does not address the effect of electron precipitation. Hence, the discrepancies become large in the winter auroral ionosphere.

Overview of China's Antarctic research progress 1984–2016

It is more than 30 years since the first Chinese National Antarctic Research Expedition(CHINARE) landed in Antarctica in 1984, representing China's initiation in polar research. This review briefly summarizes the Chinese Antarctic scientific research and output accomplished over the past 30 years. The developments and progress in Antarctic research and the enhancement of international scientific cooperation achieved through the implementation of the CHINARE program have been remarkable. Since the 1980 s, four permanent Chinese Antarctic research stations have been established successively and 33 CHINAREs have been completed. The research results have been derived from a series of spatiotemporal observations in association with various projects and multidisciplinary studies in the fields of oceanography, glaciology, geology, geophysics, geochemistry, atmospheric science, upper atmospheric physics, Antarctic astronomy, biology and ecology, human medicine, polar environment observation, and polar engineering.

Meteorological observations and weather forecasting services of the CHINARE

By 2018, China had conducted 34 scientific explorations in Antarctica spearheaded by the Chinese National Antarctic Research Expedition(CHINARE). Since the first CHINARE over 30 years ago, considerable work has been undertaken to promote the development of techniques for the observation of surface and upper-air meteorological elements, and satellite image and data reception systems at Chinese Antarctic stations and onboard Chinese icebreakers have played critical roles in this endeavor. The upgrade of in situ and remote sensing measurement methods and the improvement of weather forecasting skill have enabled forecasters to achieve reliable on-site weather forecasting for the CHINARE. Nowadays, the routing of icebreakers, navigation of aircraft, and activities at Chinese Antarctic stations all benefit from the accurate weather forecasting service. In this paper, a review of the conventional meteorological measurement and operational weather forecasting services of the CHINARE is presented.

Phylogenetic diversity of dinoflagellates in polar regions

Because of the limitations of sampling and seasonal study in polar regions,knowledge of dinoflagellate diversity,distribution and ecology are limited.Dinoflagellates have been incidentally reported from polar regions during some seasons and some populations have been reported as components of microalgae.Surveys of molecular diversity link the genotype of dinoflagellates from polar regions with environmental adaptation.In this study,37 positive clones of dinoflagellates collected from different sites were used for genotype analysis,providing new insights into the biodiversity and distribution of these species based on 18S rRNA sequencing.Diverse genotypes were recorded for the summer season in Kongsfjorden (high Arctic) whilst a single novel genotype of dinoflagellate was recorded from winter samples from the Antarctic Ocean.Data from ice cores suggests that this single dinoflagellate genotype was adapted to extreme cold and clone library screening found that it was occasionally the only microbial eukaryotic genotype found in winter ice cores.The findings of this study could improve our understanding of the diverse dinoflagellate genotypes occurring in these perennially cold microbial ecosystems.

Review of research on Arctic sea ice physics based on the Chinese National Arctic Research Expedition

China launched its Arctic research program and organized the first Chinese National Arctic Research Expedition(CHINARE-Arctic) in 1999. By 2016, six further expeditions had been conducted using the R/V Xuelong. The main region of the expeditions has focused on the Pacific sector of the Arctic Ocean for sea ice observations. The expeditions have used icebreaker, helicopter, boat, floe, and buoy platforms to perform these observations. Some new technologies have been developed, in particular, the underway auto-observing system for sea ice thickness using an electromagnetic instrument. The long-term measurement systems, e.g., the sea ice mass balance buoy, allow observations to extend from summer to winter. Some international cooperation projects have been involved in CHINARE-Arctic, especially the "Developing Arctic Modeling and Observing Capabilities for Long-Term Environmental Studies" project funded by the European Union during the International Polar Year. Arctic sea ice observations have been used to verify remote sensing products, identify changes in Arctic sea ice, optimize the parameterizations of sea ice physical processes, and assess the accessibility of ice-covered waters, especially around the Northeast Passage. Recommendations are provided as guidance to future CHINARE-Arctic projects. For example, a standardized operation system of sea ice observations should be contracted, and the observations of sea ice dynamics should be enhanced. The upcoming launch of a new Chinese icebreaker will allow increased ship time in support of future CHINARE Arctic oceanographic investigations.

Meteorite classification for building the Chinese Antarctic Meteorite Depository Introduction of the classification of 500 Grove Mountains meteorites

Meteorites provide an important window into the origins and evolution of the solar system. Since the first four meteorites were recovered in Grove Mountains, Antarctica, in 1998, a further total of 12665 meteorites have been collected over seven polar seasons in the Grove Mountains. All of these meteorites are owned and managed by the Chinese Antarctic Meteorite Depository(CAMD) at the Polar Research Institute of China(PRIC). In recent years, another 500 Antarctic meteorites have been classified and characterized based on mineralogy and petrology. In this work we examine four samples that have been identified as terrestrial, and a further 496 samples that have been confirmed as meteorites. These meteorites are further divided into different types:488 ordinary chondrites, one eucrite, one ureilite, one CM2 carbonaceous chondrite, one EH4 enstatite chondrite, one mesosiderite and three iron meteorites. The classification of meteorites not only provides an abundance of fundamental scientific data, but is also significant for introducing meteorites and related scientific knowledge to the public, particularly via the website of Chinese Resource-sharing Platform of Polar Samples for scientific research and education.

Simultaneous optical and radar observations of poleward moving auroral forms under different IMF conditions

Using high temporal resolution optical data obtained from three-wavelength all-sky imagers at Chinese Yellow River Station in the Arctic, together with the EISCAT Svalbard radar (ESR) and SuperDARN radars, we investigated the dayside poleward moving auroral forms (PMAFs) and the associated plasma features in the polar ionosphere under different interplanetary magnetic field (IMF) conditions, between 0900 and 1010 UT on 22 December 2003. Simultaneous optical and ESR observations revealed that all PMAFs were clearly associated with pulsed particle precipitations. During northward IMF, particles can precipitate into lower altitudes and reach the ionospheric E-region, and there is a reverse convection cell associated with these PMAFs. This cell is one of the typical signatures of the dayside high-latitude (lobe) reconnection in the polar ionosphere. These results indicate that the PMAFs were associated with the high-latitude reconnection. During southward IMF, the PMAFs show larger latitudinal motion, indicating a longer mean lifetime, and the associated ionospheric features indicate that the PMAFs were generated by the dayside low-latitude reconnection.

Prospect of China's Auroral Fine-structure Imaging System(CAFIS) at Zhongshan station in Antarctica

A new auroral imaging system is reported which is planned to be deployed at Zhongshan Station in Antarctica in the end of 2009.The system will focus on study of optical auroras in small scales and be called China' s Auroral Fine-structure Imaging System(CAFIS).The project of CAFIS is carried out by support of 'the tenth five-year plan for capacity building' of China.CAFIS will be a powerful ground-based platform for aurora observational experiments.Composing and advantages of CAFIS are introduced in this brief report.Some potential study topics involved CAFIS are also considered.

The properties of solar active regions responsible for ground level enhancements during solar cycles 22 and 23

This is a study designed to analyze the relationship between ground level enhancements(GLEs)and their associated solar active regions during solar cycles 22and 23.Results show that 90.3%of the GLE events that are investigated are accompanied by X-class flares,and that 77.4%of the GLE events originate from super active regions.It is found that the intensity of a GLE event is strongly associated with the specific position of an active region where the GLE event occurs.As a consequence,the GLE events having a peak increase rate exceeding 50%occur in a longitudinal range from W20 to W100.Moreover,the largest GLE events occur in a heliographic longitude at roughly W60.Additionally,an analysis is made to understand the distributional pattern of the Carrington longitude of the active regions that have generated the GLE events.

Heavy metal exposure reduces hatching success of Acartia pacifica resting eggs in the sediment

The potential effects of three heavy metals(Cu,Pb,and Cd)on hatching success of Acartia pacifica resting eggs in the sediment ofXiamen Bay were experimentally investigated.The number of A.pacifica nauplii hatched from the sediment sharply decreased with theincrease of metal concentration and exposure time from 3 to 30 d.An increase of the Cu concentration from 34.8 to 348 mg/kg,reducedthe number of hatched nauplii by 46.6%-100%.An increase of the Pb concentration from 75.2 to 752 mg/kg,reduced the number ofhatched nauplii by 21.4%-78.9%.An increase of the Cd concentration from 0.68 to 6.8 mg/kg,reduced the number of hatched naupliiby 31.6%-94.7%.The number of nauplii also significantly decreased with the increase of mixed-metal concentration and exposure timein the mixed-metal test.Trimmed Spearman-Karber analysis gave sediment metal 72-h LC50 values of 1.25 mmol Cu/kg,1.73 mmolPb/kg,and 0.054 mmol Cd/kg,which suggested that Cd was the most toxic to A.pacifica resting eggs in the three tested metals.Theresults indicate that heavy metals with higher concentrations can reduce recruitment of A.pacifica nauplii from benthic resting eggs toplanktonic population.

Reduction of recruitment of Acartia pacifica nauplii from benthic resting eggs due to organochlorine pesticides

Many estuarine and coastal planktonic copepods depend on the hatching of benthic resting eggs for recruitment of nauplii to the water column populatio n. The potential effects of two organochlorine pesticides, hexchloriobinzene (HC H) and dichlorodiphenyltrichloroethane (DDT), on the recruitment of Acartia paci fica nauplii from benthic resting eggs in the seabed of Xiamen Bay were experime ntally investigated. The abundance of A. pacifica nauplii hatched from the sedim ent significantly decreased with the increase of pesticide concentration. Trimme d Spearman-Karber analysis gave sediment 96-h LC50 values were 84.81 ng/g for HC H, and 157.94 ng/g for DDT. The median AI (AI50) was -0.77, which suggested that the combined effect of HCH and DDT showed a weak effect than individual effects . There was a positive relationship between mortality and exposure time in DDT t reatment, while the relationship was not significant in HCH treatment. The resul ts suggest that organochlorine pesticides can reduce recruitment of A. pacifica nauplii from benthic resting eggs to planktonic population.

Biodiversity of the Symbiotic Bacteria Associated with Toxic Marine Dinoflagellate Alexandrium tamarense

Paralytic shellfish poisoning (PSP) toxins are potent neurotoxins mainly produced by dinoflagellates and being concentrated in bivalves through food web transfer. Increasing number of findings of toxin-producing bacteria in the cells of dinoflagellate such as Alexandriumtamarense supports the hypothesis of the bacterial origin of PSP toxins. Evidence that there are specific symbiosis bacterial taxa associated with the phytoplankton indicates the presence of specific selective mechanisms between them, and implies that the symbiosis bacteria have some vital function to the benefit of the dinoflagellates. Studies on the role of toxin-producing symbiosis bacteria in the marine ecosystem are considered to be becoming more important. Although toxigenic bacteria could be isolated from toxic dinoflagellates, it was not clearly proven whether the isolated bacterial strains based on culture-dependent manner and the corresponding intracellular bacteria were the same because of microbial unculturability. This paper aims to demonstrate the biodiversity of the symbiotic bacteria associated with toxic dinoflagellate A. tamarense using the culture-indepen- dent high-throughput pyrosequencing method, as well as the phylogenetic analysis based on 16S rDNA sequences of the symbiotic cultivable bacteria strains isolated from toxic Alexander tamarense.

Statistical characteristics of ionospheric backscatter observed by SuperDARN Zhongshan radar in Antarctica

Zhongshan HF radar, as one component of SuperDARN, has been established and in operation since April, 2010. Using data from the first two years of its operation, this paper investigates the radar's performance, the diurnal and seasonal variations of ionospheric echoes, and their dependence on geomagnetic activity. Statistical studies show that the occurrence of echoes in different beams varies at different frequencies, which arises from the direction of the beam and the area over which the beam can achieve the orthogonality condition between the wave vector and the Earth's magnetic field. The diurnal variation is obvious with double peak structures both in the occurrence rate and average power at 04-08 UT and 16-17 UT. The line-of-sight velocities are mainly positive on the dayside and negative on the nightside for Beam 0, which is the opposite of the trend for Beam 15. The spectral widths on the dayside are often higher than those on the nightside owing to the high energy particle precipitation in the cusp region. The seasonal variations are more obvious for those beams with larger numbers. The occurrence, the average power, the line-of-sight velocity, and the spectral widths are generally larger in the winter months than in the summer months. The influence of geomagnetic activity on radar echoes is significant. The peak echo occurrence appears on the dayside during geomagnetically quiet times, and shifts toward the nightside and exhibits an obvious decrease with increasing Kp. With increasing geomagnetic activity, the line-of-sight velocities increase, whereas the spectral widths decrease. The frequency dependence is investigated and it is found that in the operating frequency bands in 2010, 9-10 MHz is the most appropriate band for the SuperDARN Zhongshan radar.

Extraction of auroral oval boundaries from UVI images: A new FLICM clustering-based method and its evaluation

Based on the fuzzy local information c-means (FLICM) clustering algorithm, a new method is developed for extracting the equatorward and poleward boundaries of the auroral oval from images acquired by the Ultraviolet Imager (UVI) aboard the POLAR satellite. First, the method iteratively segments the UVI image with the FLICM clustering algorithm, according to an integrity criterion for the segmented auroral oval. Then, possible gaps in the extracted auroral oval are filled, based on prior knowledge of its shape. To evaluate the method objectively, the extracted boundaries are compared with the precipitating electron boundaries determined from DMSP satellite precipitation particle data. The evaluation results demonstrate that the proposed method generates more accurate auroral boundaries than traditional methods.

Advances in Chinese Arctic and subarctic research in marine biology and ecology with emphasis on the Pacific Arctic sector

The Arctic is one of the most sensitive regions that respond through feedback to global climate changes. Climatic, hydrological and ecological changes in the Arctic are clear evidence of global warming. In 2012 and 2014, the 5 th and 6 th Chinese National Arctic Research Expeditions undertook studies in the Bering Sea, the Arctic Ocean(including the Chukchi Sea), and the Norwegian Sea. These studies provided us with a better understanding of the marine biology and ecology in the Arctic and subarctic regions, particularly in the Pacific Arctic sector. Rapid changes observed in the Arctic environment include the shrinking of cold-water masses in the Bering Sea in the summer, and elevated water temperatures promoting phytoplankton blooms, leading to an increase in phytoplankton transferred to higher trophic levels. As a result, the transfer efficiency of organic matter toward the bottom weakened, leading to a reduction in benthic biomass. This is consistent with expectations that the overall carbon and energy flux will ultimately switch from the dominant mode of sea ice–algae–benthos to one of phytoplankton–zooplankton. Influenced by Pacific water inflow, fluvial runoff and melting sea ice, the Chukchi Sea exhibited different responses to various environmental changes. Interactions between water masses led to other interannual ecological shifts. With the increase in sea ice melt and sunlight in the central region of the Arctic Ocean, the relative abundance of heterotrophic bacteria is expected to increase, and play a vital role in the Arctic microbial loop.

Optical and SuperDARN radar observations of duskside shock aurora over Zhongshan Station

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 min 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.

Spatial heterogeneity of a microbial community in Kongsfjorden,Svalbard during late summer 2006 and its relationship to biotic and abiotic factors

The 16S and 18S ribosomal ribonucleic acid genes of microbial organisms collected from the contrasting environments (temperature,salinity,silicate,phosphate and nitrate,p <0.05) of the inner and outer basins of Kongsfjorden (Spitsbergen,Arctic) were studied using polymerase chain reaction-denaturing gradient gel electrophoresis(DGGE) fingerprinting.Comparison of the microbial fingerprints and the physicochemical parameters revealed that molecular methodology exhibited a greater sensitivity.Sequences obtained from bacterial DGGE were affiliated with four main phylogenetic groups of bacteria:Proteobacteria(Alpha,Beta and Gamma),Bacteroidetes,Verrucomicrobia and Cyanobacteria.The relationships between the genotype distribution of these microbes and associated biotic/abiotic factors,revealed by canonical correspondence analysis,showed that Station 1 at 30 m (outer fjord) was grouped separately from the other sites.This difference could be a consequence of the thermocline and base of the euphotic layer at this depth where the Atlantic and Arctic-type waters overlapped.

Ice concentration assimilation in a regional ice-ocean coupled model and its application in sea ice forecasting

A reasonable initial state of ice concentration is essential for accurate short-term forecasts of sea ice using ice-ocean coupled models.In this study,sea ice concentration data are assimilated into an operational ice forecast system based on a combined optimal interpolation and nudging scheme.The scheme produces a modeled sea ice concentration at every time step,based on the difference between observational and forecast data and on the ratio of observational error to modeled error.The impact and the effectiveness of data assimilation are investigated.Significant improvements to predictions of sea ice extent were obtained through the assimilation of ice concentration,and minor improvements through the adjustment of the upper ocean properties.The assimilation of ice thickness data did not significantly improve predictions.Forecast experiments show that the forecast accuracy is higher in summer,and that the errors on five-day forecasts occur mainly around the marginal ice zone.

Auroral event detection using spatiotemporal statistics of local motion vectors

The analysis and exploration of auroral dynamics are very significant for studying auroral mechanisms.This paper proposes a method based on auroral dynamic processes for detecting auroral events automatically.We first obtained the motion fields using the multiscale fluid flow estimator.Then,the auroral video frame sequence was represented by the spatiotemporal statistics of local motion vectors.Finally,automatic auroral event detection was achieved.The experimental results show that our methods could detect the required auroral events effectively and accurately,and that the detections were independent on any specific auroral event.The proposed method makes it feasible to statistically analyze a large number of continuous observations based on the auroral dynamic process.