Performance of surface radiation products of Greenland Ice Sheet using in-situ measurements

Radiation is the direct energy source of the surface natural environment and the main driving force of climate change.It has increasingly become an important meteorological factor affecting the surface heat exchange and glacier mass balance,especially in the glacier changes of the Greenland Ice Sheet(Gr IS).Due to the harsh climatic conditions of Gr IS and sparse observed data,it has become an important way to obtain radiation data from reanalysis datasets.However,the applicability of these radiation data on Gr IS is uncertain and worth exploring.In this work,we evaluate five reanalysis datasets(the fifth generation of European Centre for Medium-Range Weather Forecasts(ERA5),European Centre for Medium-Range Weather Forecasts Interim Reanalysis(ERA-Interim),Japanese 55-year Reanalysis(JRA55),National Centers for Environmental Prediction Reanalysis II(NCEP2)and Modern-Era Retrospective analysis for Research and Applications,Version 2(MERRA-2))during 1997-2022 using observations from 26 Program for Monitoring the Greenland Ice Sheet(PROMICE)automatic weather stations(AWSs)and 3 K-transect AWSs on Gr IS.The conclusions are as follows:ERA5 has the best performances in downward shortwave radiation(SWD)as well as downward and upward longwave radiation(LWD and LWU),but the performance is not the best in upward shortwave radiation(SWU).Based on the radiation budget analysis with ERA5 during 1979-2022,the fluctuation of longwave radiation is greater than that of shortwave radiation.The seasonal variation of shortwave radiation is obvious,while that of longwave radiation is small.The increasing trend of longwave radiation may result from global warming,in which ice sheets absorb more solar radiation and the surface heats up significantly,emitting more LWU.

Editorial

Advances in Polar Science(APS),published since 1990 as a peer-reviewed English-language journal,is dedicated to the presentation of polar research(both Arctic and Antarctic)and of the accomplishments of Arctic and Antarctic expeditions.The international character of the journal improved greatly over the years from 24%of the published papers with a non-Chinese submitting author in 2015 to 63%in 2020.

Late Maastrichtian–Paleocene chronostratigraphy from Seymour Island,James Ross Basin,Antarctic Peninsula:Eustatic controls on sedimentation

The Paleocene(66–56 Ma)was a critical time interval for understanding the geological history in high palaeolatitudes after the end of Cretaceous event(recovery from mass extinction,palaeoclimate,global sea level changes,among others).The sedimentary succession from Seymour Island(Antarctic Peninsula)provides key reference material from this important phase of the early Cenozoic.A detailed age model is proposed for the López de Bertodano Formation(LBF),Sobral Formation(SF)and Cross Valley–Wiman Formation(CVWF)based on a new magnetostratigraphic section which integrates previous dinoflagellate cyst biostratigraphy,Iridium anomaly(K-Pg boundary),U-Pb zircon dating(airfall tuff)and strontium isotope values from macrofossils.The new composite magnetostratigraphic section,which includes the Cretaceous–Paleogene boundary,has been correlated to the GPTS from C29r up to C24r.The top of the LBF is confirmed as latest Maastrichtian to earliest Danian(~65.4 Ma)in age.The overlying SF is mostly Danian in age(~65.2–~63 Ma)and CVWF is Selandian–Thatenian(~61.3–56.9 Ma).LBF,SF and CVWF are unconformity-bounded units(alloformations)that record the geological evolution of the James Ross Basin during a period of relative decreasing tectonism but coeval with volcanic activity.Unconformity based internal units have been recognized,dividing each formation into allomembers(LBF:Molluscan and Cenozoic;SF:A,B and C;CVWF:Díaz,Ara?ado,Bahía Pingüino).The new age model allows correlation of base-level changes with eustatic sea-level fluctuations.The bases of the SF and CVWF are correlated with the 65.3 and 61.5 Ma sea level lowstands.

Seasonal variations in aerosol compositions at Great Wall Station in Antarctica

High volume aerosol samplers at Great Wall Station in Antarctica were used to collect 73 aerosol samples between January 2012 and November 2013. The main ions in these aerosol samples, Cl^-, NO3-, SO4^2-, Na＋, K＋, Ca2＋, Mg2＋, NH4＋, as well as methane sulfonic acid, were analyzed using ion chromatography. Trace metals in these samples, including Pb, Cu, Cd, V, Zn, Fe, and Al, were determined by inductively-coupled plasma mass spectrometry. Results showed that sea salt was the main component in aerosols at Great Wall Station. Most ions exhibited significant seasonal variations, with higher concentrations in summer and autumn than in winter and spring. Variations in ions and trace metals were related to several processes（or sources）, including sea salt emission, secondary aerosol formation, and anthropogenic pollution from both local and distant sources. The sources of ions and trace metals were identified using enrichment factor, correlation, and factor analyses. Clearly, Na＋, K＋, Ca2＋, and Mg2＋were from marine sources, while Cu, Pb, Zn, and Cd were from anthropogenic pollution, and Al and V were mainly from crustal sources.

Evaluation of reanalysis and satellite-based sea surface winds using in situ measurements from Chinese Antarctic Expeditions

Sea surface winds from reanalysis （NCEP-2 and ERA-40 datasets） and satellite-based products （QuikSCAT and NCDC blended sea winds） are evaluated using in situ ship measurements from the Chinese National Antarctic Research Expeditions （CH1NAREs） from 1989 through 2006, with emphasis on the Southern Ocean （south of 45°S）. Compared with ship observations, the reanalysis winds have a positive mean bias （0.32 m·s-1 for NCEP-2 and 0.13 m·s-1 for ERA-40）, and this bias is more pronounced in the Southern Ocean （0.57 m·s-1 and 0.45 m·s-1, respectively）. However, mean biases are negative in the tropics and subtropics. The satellite-based winds also show positive mean biases, larger than those of the reanalysis data. All four wind products overestimate ship wind speed for weak winds （〈4 m·s-1） but underestimate for strong winds （〉10 m·s-1）. Differences between the reanalysis and satellite winds are examined to identify regions with large discrepancies.

The global Antarctic Research event,SCAR 2024

We are pleased to announce that“The 11th SCAR Open Science Conference”will take place in Pucón,Chile from 19-23 August 2024,hosted by the Chilean Antarctic Institute.Detailed information at https://www.scar2024.org/.The 11th SCAR Open Science Conference theme“Antarctic Science:Crossroads for a New Hope”,recognizes the importance of Antarctica as a unique and fragile ecosystem.With increasing concerns about climate change and its impact on the polar regions,this theme aims to highlight the significance of Antarctic research in shaping our understanding of global environmental challenges.By fostering collaboration and knowledge exchange,the SCAR Open Science conference hopes to inspire new solutions and a renewed sense of hope for the future of our planet.

Assessment on India’s involvement and capacity-building in Arctic Science

India became an observer in Arctic Council in 2013 and has three research stations operational in the poles,including“Maitri”commissioned in 1989 and“Bharati”commissioned in 2012 at Antarctic and“Himadri”at Arctic.Though the Government of India has consistently been extending full support to the research endeavours yet the same is bogged by inadequate research output,lack of dedicated polar research vessel and other bureaucratic bottlenecks.A massive void in the Indian scientific pursuits is that India does not possess a polar research vessel or an icebreaker and has to rely on chartered vessels,seriously limiting its research timeframe as well as huge economic drain and thus compromising the scientific research.This cleft in the professed research narrative despite having a physical presence for over 3 decades in the polar regions and the proposal for acquisition of a polar research vessel having been approved in June 2010 yet the same is yet to be operationalised which is seriously impinging the scientific research as well as the professed commitment to Arctic research.Recently,India has released its draft Arctic Policy and had sought public comments thereon till 26 January 21 before its finalisation.India’s draft policy reiterates the oft stated goals of scientific research,connectivity,global governance and international cooperation,and human development with emphasis on Indian human resource pool.The inspiration of a delayed Indian policy on the High North appears to be the Chinese white paper of 2018.The scientific pursuits can propel the strategic engagement in the region to greater levels by extensive collaboration and cooperation with several other nations present there.Indian attempts so far have remained acutely short of the promise and India should build on its strengths for obtaining a leadership position in this strategically vital and economically lucrative region.

Considerable increase in bowhead,blue,humpback and fin whales numbers in the Greenland Sea and Fram Strait between 1979 and 2014

In the frame of our long-term study of cetacean abundance and distribution in polar marine ecosystems begun in 1979, a drastic increase in the bowbead Balaena mysticetus North Atlantic ＂stock＂ was observed from 2005 on, by a factor 30 and more： from 0.0002 per count between 1979 and 2003 （one individual, n=5430 cotmts） to 0.06 per count from 2005 to 2014 （34 individuals, n=6000 counts）; the most significant part of the increase occurred from 2007 on. Other large whale species （Mysticeti） showed a similar pattern, mainly blue Balaenoptera musculus, humpback Megaptera novaeangliae and fin whales Balaenoptera physalus. This large and abrupt increase cannot logically be due to population growth, nor to survival of a hidden ＂relic＂ population, nor to a changing geographical distribution within the European Arctic, taking into account the importance of the coverage during this study. Our interpretation is that individuals passed through the Northwest and/or Northeast Passages from the larger Pacific stock into the almost depleted North Atlantic populations coinciding with a period of very low ice coverage -- at the time the lowest ever recorded. In contrast, no clear evolution was detected neither for sperm whale Physeter macrocephalus nor for Minke whale Balaenoptera acusrostrata.

Self-organization: the governance of CAO fisheries from perspective of the global commons

The Central Arctic Ocean （CAO） is a global commons, and fishes in the CAO are common property resources. If humanity does not manage this region well, then this will lead to a ＂Tragedy of the Commons,＂ an old problem in human society. However, the two existing means of commons governance, privatization and government control, are not appropriate for the CAO. This study＇s findings indicate that CAO fisheries management will most likely result from a process of self-organization. The openness of the CAO and the imbalance of powers, interests and responsibilities among the states that are involved will lead to a process of self-organized governance of CAO fisheries. There are four stages in this process： competition, synergy, establishment of governing principles and mechanisms, and expansion and evolution of influence. The outcome of CAO fisheries governance will be the result of compromise among the parties as no one actor is in a dominant position.

Long-term study of at-sea distribution of seabirds and marine mammals in the Scotia Sea, Antarctica

The Scotia Sea is one of the most biologically rich regions of Antarctica, and it hosts a large community of upper trophic-level predators. Long-term at-sea monitoring provides valuable information on the Antarctic marine ecosystem and relationships among top predators. This paper presents the results of at-sea monitoring of seabirds and cetaceans over five consecutive summer seasons （2010--2014） in the Scotia Sea, Antarctica. A total of 11 656 flying birds belonging to 24 species were recorded in 884 ten-minute counts. Six Procellariiformes species were abundant： Black-browed Albatross, Cape Petrel, Southern Fulmar, Antarctic Prion, Wilson＇s Storm-petrel, and Black-bellied Storm-petrel. Only three of these species accounted for 82% of the total abundance： Antarctic Prion （40%）, Southern Fulmar （22%）, and Cape Petrel （20%）. A total of 678 baleen whales belonging to five species were recorded along a sampling effort of 2 351 nautical miles： Humpback, Sei, Southern Right, Fin, and Minke whales, which had different abundances during the study. The Fin Whale had the highest mean encounter rate for the 5 years （0.29 whales per nautical mile）, followed by the Humpback Whale （0.09 whales per nautical mile）. Annual dissimilarity in abundance of both seabirds and cetaceans occurred in conjunction with changes in the sea surface temperature and ice cover, showing the dependence of top predators on environmental changes. The largest aggregations of all top predators （seabirds and cetaceans） were recorded in two regions, west and south of the South Orkney Islands, suggesting important prey availability （especially krill） in those areas.

Linkages between Arctic sea ice cover,large-scale atmospheric circulation,and weather and ice conditions in the Gulf of Bothnia,Baltic Sea

During years 1980/1981-2012/2013, inter-annual variations in sea ice and snow thickness in Kemi, in the northern coast of the Gulf of Bothnia, Baltic Sea, depended on the air temperature, snow fall, and rain. Inter-annual variations in the November--April mean air temperature, accumulated total precipitation, snow fall, and rain, as well as ice and snow thickness in Kemi and ice concentration in the Gulf of Bothnia correlated with inter-annual variations of the Pacific Decadal Oscillation （PDO）, Arctic Oscillation （AO）, North Atlantic Oscillation （NAO）, Scandinavian Pattern （SCA）, and Polar / Eurasian Pattern （PEU）. The strong role of PDO is a new finding. In general, the relationships with PDO were approximately equally strong as those with AO, but rain and sea ice concentration were better correlated with PDO. The correlations with PDO were, however, not persistent; for a study period since 1950 the correlations were much lower. During 1980/1981--2012/2013, also the Pacific / North American Pattern （PNA） and E1 Nino-Southern Oscillation （ENSO） had statistical connections with the conditions in the Gulf of Bothnia, revealed by analyzing their effects combined with those of PDO and AO. A reduced autumn sea ice area in the Arctic was related to increased rain and total precipitation in the following winter in Kemi. This correlation was significant for the Pan-Arctic sea ice area in September, October, and November, and for the November sea ice area in the Barents / Kara seas.

Features and influencing mechanisms of gaseous elemental mercury over the equatorial Pacific and their differences with the Southern Ocean

Due to the harmful impacts on the ecosystem and even human health,mercury(Hg)compounds in the environment deserve serious concern.Atmospheric mobilization and exchange at the air-sea interface are important processes in biogeochemical cycling of Hg.Relying on the 30th(2013/2014),31st(2014/2015),and 33rd(2016/2017)Chinese National Antarctic Research Expedition aboard R/V Xuelong,we found significant rising gaseous elemental mercury(GEM)concentrations over the equatorial Central Indo-Pacific region.Excluding the contribution of anthropogenic,volcanic and biomass burning emissions,the enhanced GEM in marine boundary layer was likely due to the combined actions of two driving factors drove by the Inter-Tropical Conversion Zone(ITCZ):(1)intense wet deposition of Hg,followed by subsequent rapid photoreduction and vast evasion from the surface sea;and(2)the regional low-level convergence of airflow that caused the mass accumulation of GEM in air.In addition,apparently higher GEM concentration level in the equatorial Central Indo-Pacific than in the Southern Ocean was observed in one cruise.Further investigation suggests that apart from the ITCZ corresponded mechanisms,the effects of spatial differences in anthropogenic emissions and more significant GEM oxidation in Antarctic sea should play roles in this phenomenon.

Marine biogenic aerosols and their effects on aerosol-cloud interactions over the Southern Ocean:a review

The Southern Ocean(SO)plays an important role in the global climate system.Changes in SO biogeochemistry and marine ecosystems may influence the distribution of atmospheric aerosols and clouds and impact the climate system.We reviewed current knowledge on the interactions between marine aerosols and clouds over the SO.We focused on marine primary and secondary organic aerosols and summarized their characteristics,processes and roles as cloud condensation nuclei and ice nuclei.We described in detail the interactions between the marine ecosystem,aerosols and clouds.We discussed marine productivity,formation of marine biogenic aerosols and interactions between aerosols,clouds and climate.We explored the impact of climate change on SO marine ecosystem productivity and aerosol-cloud-climate feedback.Marine biogenic aerosols could impact the radiation budget and oceanic low-level clouds over the SO.This study contributes towards an improved understanding of marine productivity,aerosol-cloud interactions and climate change in the SO.The SO may respond to climate change in varying degrees.More studies are urgently needed to support accurate forecasts of future changes in the SO.

Interplanetary shock-associated aurora

Interplanetary shocks or solar wind pressure pulses have prompted impacts on Earth's magnetospheric and ionospheric environment, especially in causing dynamic changes to the bright aurora in the polar ionosphere. The auroral phenomenon associated with shock impingements, referred to as shock aurora, exhibits distinct signatures differing from other geophysical features on the dayside polar ionosphere. Shock aurora provides a direct manifestation of the solar wind–magnetosphere–ionosphere interaction. Imagers onboard satellites can obtain the associated large-scale auroral characteristics during shock impingement on the magnetopause. Therefore, auroral data from satellites are very useful for surveying the comprehensive features of shock aurora and their general evolution. Nonetheless, the ground-based high temporal-spatial resolution all-sky imagers installed at scientific stations play an essential role in revealing medium-and small-scale characteristics of shock aurora. Here, we focus on shock aurora imaging signatures measured by imagers onboard satellites and ground-based all-sky imagers.

The importance of long-term research and monitoring in the Ross Sea

The Ross Sea region is a biologically rich and dynamic environment and,although protected under various instruments of the Antarctic Treaty System,is threatened by a changing climate and increasing human activities locally and globally.This opinion editorial describes the importance of research and monitoring in the Ross Sea and identifies opportunities and barriers to enhance them.

Newly established autonomous adaptive low-power instrument platform(AAL-PIP) chain on East Antarctic Plateau and operation

An autonomous adaptive low-power instrument platform(AAL-PIP)chain of six stations has been newly established on East Antarctic Plateau along the 40°geomagnetic meridian,to investigate interhemispheric geomagnetically conjugate current systems,waves,and other space weather phenomena in Polar Regions.These six stations,PG0 to PG5,which host low-power magnetometers(Fluxgate and Searchcoil),dual frequency GPS receivers,HF radio experiment,and run autonomously with solar power and two-way satellite communication,are designated at the geomagnetically conjugate(based on the International Geomagnetic Reference Field)locations of the West Greenland geomagnetic chain covering magnetic latitudes from 70°to 80°.We present the development,deployment,and operation of this chain,as well as the data collected by the chain and some preliminary scientific results showing evidence of interhemispheric asymmetries,which are important to better understand Solar Wind–Magnetosphere–Ionosphere(SWMI)coupling in Polar Regions.Recent investigations focus on magnetic impulse(MI)events,traveling convection vortices(TCVs),and ultra-low frequency(ULF)waves in the coupled southern and northern hemispheres.

Hotspots of seabirds and marine mammals between New Zealand and the Ross Gyre:importance of hydrographic features

This article is part of our long-term study on the quantitative at-sea distribution of the marine "upper trophic levels"—seabirds and marine mammals—in polar ecosystems, aiming at quantifying the factors influencing their distribution as well as detecting possible spatial and temporal changes, with special attention to hydrography and to global climate changes. During an expedition of icebreaking RV Polarstern in February 2010, along the North–South transect between New Zealand and the Ross Gyre, off the Ross Sea, 3200 seabirds belonging to 22 identified pelagic species were recorded during 338 half-hour transect counts. Four major hotspots were identified. These were in Sub-tropical Water off New Zealand(up to 300 birds per count), and at the main Southern Ocean fronts: the Sub-Antarctic Front(up to 240 per count), the Antarctic Front(up to 150 per count) and the Polar Front(up to 200 per count), representing the vast majority of recorded seabirds. The most numerous species in the three frontal zones were: prions—mainly slender-billed Pachyptila belcheri—and Salvin’s albatross Thalassarche [cauta]salvini. The eight more abundant species represented 2650 birds, i.e. more than 80% of the total. A random forest clustering method identified four groups of seabird species occupying similar oceanographic niches.

Middle Eocene chondrichthyan fauna from Antarctic Peninsula housed in the Museo de La Plata,Argentina

In recent years,the taxonomy and systematics of the cartilaginous fish taxa from the Eocene La Meseta Formation of Seymour(Marambio)Island,Antarctica have been extensively discussed in a series of papers,resulting in a complete revision of the Antarctic Eocene ichthyofauna housed in the Vertebrate Paleontology collection of the Museo de La Plata,Argentina.This collection constitutes one of the largest and taxonomically most diverse in the world,with approximately 20000 specimens,which provides a solid database used for the analysis of qualitative and quantitative chondrichthyan taxonomic composition.The information provided herein might be useful to understand the sudden decline in chondrichthyan taxonomic diversity towards the top of La Meseta Formation as well as its potential relationship with environmental changes during the Eocene.

Leveraging the UAV to support Chinese Antarctic expeditions:a new perspective

Recent developments in Unmanned Aerial Vehicles(UAVs)and their applications in various subjects are of interest to polar communities.Due to the harsh climate and dangerous environment,these regions pose challenges for the expedition teams.Several countries have tested the UAV technology to support Antarctic research and logistics.In this trend paper,we provide insightful reviews and discussions on such a prospective topic.Based on a comprehensive literature survey,we firstly summarize the key research progress of UAV in Antarctic studies.Then the examples of risk scenarios during the field exploration are given,after which several promising applications of the UAVs in safety guarantee are illustrated.In particular,we present a case of site-selection for the Chinese first ice sheet airfield,using the data collected in the 34th Chinese National Antarctic Research Expedition(CHINARE).In the end,we highlight the unique value of the UAVs in the popularization of polar science before concluding the advantages and limitations.Considering their excellent performance,we expect more innovations for UAV’s applications in the following Antarctic expeditions.