One major consequence of global warming in the Antarctic region is increased ice-free zones. Subsequent colonization of these ice-free areas by penguins alters their biogeochemistry, with one prominent example being elevation of inorganic phosphate concentrations around feces depositions. The complex soil biochemistry in the region makes it difficult to define the causal factors of these changes using common research approaches. Here, we addressed the effects of phosphate alone on microbiome structure and dynamics over time by adding external phosphate to selected soils in the Antarctic region. We then analyzed the soil bacterial community composition and diversity using 16S rRNA amplicon sequencing and compared these data with phosphate levels. Parallel geochemical analysis revealed changes in nine soil geochemical factors upon phosphate addition, all of which were relevant to microbiome structure, with soil pH showing the highest correlation. Links between geochemical factors and composition were identified, as were interactions between bacterial taxa. Additionally, Sphingobacteriia, Sphingobacteriales and Chitinophagaceae were found to be more abundant in phosphate-treated soils. Co-occurrence network analysis revealed significantly increased levels of associations in all major network properties over time after phosphate supplementation. Therefore, we conclude phosphate addition has diverse effects on Antarctic soil microbiomes.
The China Meteorological Administration recently released China Polar Climate Change Annual Report(2022)in Chinese,with the following main conclusions.Using the China Reanalysis-40 dataset(CRA-40),rapid warming has been observed in the Antarctic Peninsula and West Antarctica since 1979,with some parts of East Antarctica also experiencing warming.In 2022,the regional average temperature in Antarctica based on observational data was close to the long-term average(1991-2020).The Arctic,on the other hand,has experienced a warming trend at a rate of 0.63 ℃ per decade from 1979 to 2022 based on CRA-40,which is 3.7 times the global mean during the same period(0.17 ℃ per decade).In 2022,the overall temperature in the Arctic,using station data,was 1.10 ℃ above the long-term average(1991-2020).In recent years,both the Antarctic and Arctic regions have witnessed an increase in the frequency and intensity of extreme weather events.In 2022,based on the sea ice extent from National Snow and Ice Data Center,USA,Antarctic sea ice reached its lowest extent on record since 1979,and on 18 March,the most rapid surface warming event ever recorded on Earth occurred in the Antarctic,with a temperature increase of 49 ℃ within 3 d.This report has been integrated into China's National Climate Change Bulletin system,to contribute to raising public awareness of polar climate change and providing valuable scientific references to address climate change.
The firn aquifer beneath the Greenland Ice Sheet may play a significant role in rising sea level.Both traditional mechanical drilling and electric thermal drilling are poorly adapted for effective,low-disturbance sampling in firn aquifers.We propose using a vibrocoring technique for the undisturbed sampling of dry firn and firn aquifer layers.A remote-controlled vibrocorer is designed to obtain 1-m-long cores with a diameter of 100 mm.The depth capacity of the system is approximately 50 m.The total weight of the vibrocoring system with the surface auxiliary equipment is approximately 110 kg,and corer assembly itself weighs～60 kg.
Ice-shelf rifts are precursors of glacier calving,and thus they serve as indicators of ice shelf instability,especially under oceanic and atmospheric warming conditions.Therefore,understanding the dynamic processes underlying rift propagation and the associated damage mechanisms is essential to evaluate ice-shelf instability and to predict glacier calving.In this study,we investigated the effect of marginal weakening on rift propagation on the ice shelf of the Petermann Glacier,among the largest in Greenland,during 2016-2022.First,we analyzed satellite optical images to monitor rift growth(length and width)by tracking the tip trajectory of three large rifts identified on the Petermann Ice Shelf.Then,we estimated rift depth using ArcticDEM and ICESat-2 data.Our results indicated consistent increases of the rift widths and depths over the study period,with mean values of 133 m·a-1 and 0.3 m·a-1,respectively.We also combined remote-sensing observations with an ice-sheet numerical model to calculate the stress and damage fields on the Petermann Ice Shelf and to assess the ice shelf margin stability and strength.We determined that damage and lateral shear in the fracture zone degraded ice shelf integrity by decreasing the contact length with the fjord wall.In conclusion,marginal weakening effectively promoted rift propagation on the Petermann Ice Shelf,increasing the risk of future glacier calving.
Greenland and Antarctic ice sheets are the largest potential contributors to global sea level rise (GSLR), amounting to more than 64 m of sea level equivalence (SLE). Between the two, Greenland Ice Sheet (GrIS) alone comprises about 7 m SLE, with a much faster speed of ablation than the Antarctic Ice Sheet. The contribution of GrIS to GSLR has increased from 5％ in the early 1990s to about 25％ in the recent decade (Chen et al., 2017), with an accelerating rate of approximately 0.65 mm·a-1 (Frederikse et al., 2020).
Satellite-borne microwave radiometers provide essential measurements to study the surface melt state of ice sheets.Therefore,selecting suitable microwave radiometer data is critical to characterize the spatial distribution of surface melt.In this study,we investigated the Greenland Ice Sheet and evaluated the usefulness,as climate indicators,of data acquired by microwave radiometers onboard the F17 satellite of the United States of America Defense Meteorological Satellite Program(DMSP)and the Soil Moisture and Ocean Salinity(SMOS)satellite of the European Space Agency.First,surface melt was simulated using the DMSP dataset as input for a brightness temperature threshold algorithm,the Microwave Emission Model of Layered Snowpacks(MEMLS2),and the SMOS dataset as input for the L-band Specific MEMLS(LS-MEMLS).For accuracy evaluation,the simulation results were then compared with surface melt estimates derived from air temperature measurements at Automatic Weather Stations and from ice surface temperature measurements from the Moderate Resolution Imaging Spectroradiometer(MODIS)satellite-borne instrument.Our results show that global(over Greenland)MEMLS2 simulation performance(overall accuracy 83%)was higher than that of LS-MEMLS(overall accuracy 78%).However,in southeastern Greenland,MEMLS2 omission error was markedly higher than that of LS-MEMLS,whereas LS-MEMLS could detect longer-lasting surface melt than MEMLS2.This analysis showed that DMSP-based surface melt simulations are more accurate than SMOS-based simulations,thereby providing a data selection reference for surface melt studies of the Greenland Ice Sheet.
Rainfall was witnessed for the first time at the highest area of the Greenland Ice Sheet on 14 August,2021.The thermodynamic mechanisms supporting the rainfall are revealed by ERA5 reanalysis,in-situ and satellite data.We find that a strong southward intrusion of the polar vortex favored the maintenance of a deep cyclone over Baffin Island and an amplification of anticyclonic circulation over the southeastern ice sheet,which pumped warm and moist air toward Greenland from anomalously warm waters south of Greenland.Across a wide swath of the ice sheet,atmospheric uplift maintained above-melting and rainfall conditions via condensation and enhanced downward infrared irradiance.Without the low-level liquid clouds,the spatial extent and duration of the rainfall would have been smaller.Over the ice sheet topographic summit,the air temperature from the ground to 250 hPa level was～2 ℃ higher than the previous record set on 12 July,2012.Such events may occur more frequently with the decreased temperature contrast between the Arctic and the mid-latitude regions that drives highly amplified jet streams.Thus,this extreme event serves as a harbinger of a more likely wet surface condition across all elevations of the ice sheet.
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(GrIS).Due to the harsh climatic conditions of GrIS 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 GrIS 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 GrIS.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.
The summertime anticyclonic circulation mode(SACM)is related to recent substantial loss of sea ice in the Arctic.This review outlines the potential causes of the SACM and considers its influence on sea ice depletion.Local triggers(i.e.,sea ice loss and sea surface temperature(SST)variation)and spatiotemporal teleconnections(i.e.,extratropical cyclone intrusion,tropical and mid-latitude SST anomalies,and winter atmospheric circulation preconditions)are discussed.The influence of the SACM on the dramatic loss of sea ice is emphasized through inspection of relevant dynamic(i.e.,Ekman drift and export)and thermodynamic(i.e.,moisture content,cloudiness,and associated changes in radiation)mechanisms.Moreover,the motivation for investigation of the underlying physical mechanisms of the SACM in response to the recent substantial sea ice depletion is also clarified through an attempt to better understand the shifting ice-atmosphere interaction in the Arctic during summer.The record low extent of sea ice in September 2012 could be reset in the near future if the SACM-like scenario continues to exist during summer in the Arctic troposphere.
The melting of the West Antarctic Ice Shelf has increased since the 1990s,driven by the relatively warm Circumpolar Deep Water(CDW)that penetrates into the West Antarctic Ice Shelf cavities through submarine glacial troughs across the continental shelf.In this study,temperature,salinity,and current velocity data obtained by the Chinese National Antarctic Research Expedition in the Dotson-Getz Trough(DGT)shows clear differences in distribution of modified Circumpolar Deep Water(mCDW)in the summers of 2020 and 2022.Combined with contemporaneous wind data and additional temperature and salinity data from instrumented seals,the processes and mechanisms responsible for this variation are discussed.Compared with 2020,there is a significant increase in mCDW thickness in 2022,with a doubling of total heat content as the mCDW inflow path across the DGT shifts towards the eastern bank.We propose that a southward shift in the westerly winds in the summer of 2022 moved the upper oceanic divergence zone southward towards the continental slope,promoting the upwelling of mCDW above 500 m.Concurrently,stronger westerly winds over the continental slope strengthened the eastward undercurrent,increasing the transport of this mCDW and its associated heat content to the DGT through Ekman dynamics.These observations show there is strong interannual variability in the strength,path and extent of mCDW inflows to the DGT and that care must be taken when planning observation programs for long-term monitoring of the oceanic heat input to the ice shelves of this globally significant region.
Soil nitrogen(N)transformation processes in the High Arctic tundra are poorly understood even though nitrogen is one of the main limiting nutrients.We analyzed soil samples collected along a High Arctic tundra transect to investigate spatial variability in key nitrogen transformation processes,functional gene abundances,ammonia-oxidizing archaea(AOA)community structures,and key nitrogen transformation regulators.The potential denitrification rates were higher than the nitrification rates in the soil samples,although nitrification may still regulate N2O emissions from tundra soil.The nutrient(total carbon,total organic carbon,total nitrogen,and NH 4+-N)contents were important determinants of spatial variability in the potential denitrification rates of soil along the tundra transect.The total sulfur content was the main variable controlling potential nitrification processes,probably in association with sulfate-reducing bacteria.The nitrate content was the main variable affecting potential dissimilatory nitrate reduction to ammonium.AOA and ammonia-oxidizing bacteria amoA,nirS,and anammox 16S rRNA genes were found in all of the soil samples.AOA play more important roles than ammonia-oxidizing bacteria in soil nitrification.Anammox bacteria may utilize NO 2-produced through nitrification.Phylogenetic analysis indicated that the AOA amoA sequences could be grouped into eight unique operational taxonomic units(OTUs)with a 97%sequence similarity and were affiliated with three group 1.1b Nitrososphaera clusters.The results indicated that heterogeneous environmental factors(e.g.,the carbon and nitrogen contents of soil)along the High Arctic tundra transect strongly affected the nitrogen transformation rate and relevant functional gene abundances in soil.
On 7 October,2022,the Biden administration released an updated version of the National Strategy for the Arctic Region based on new developments in the Arctic region and global affairs.This strategy emphasizes traditional security issues in the Arctic,attaches great importance to climate governance in the region,and advocates for restoring American leadership through international cooperation.In view of the strong influence of the United States(U.S.)in the Arctic region,the changes of the U.S.Arctic strategy will inevitably have an impact on China's scientific research rights,economic interests,and governance rights in the Arctic region.To respond to the new situation brought about by the changes in the U.S.Arctic strategy,China should take the initiative to maintain positive relationships with all Arctic countries,and continue its active participation in Arctic affairs.
In recent decades,environmental changes in the Arctic have aroused widespread concern around the world.To better understand ecology issues such as ecosystem dynamics,the Arctic and the subarctic regions were integrated as the"pan-Arctic"region.In this study,mesozooplankton were sampled from the Bering Sea shelf to the northern Chukchi Sea during the 10th Chinese National Arctic Research Expedition in 2019.Based on the species composition and abundance,three geographical communities were identified:the Bering Sea shelf community(BSS),the Bering Strait transitional community(BST),and the Chukchi Sea shelf community(CSS).The BSS was characterized by Bering Sea oceanic species such as Eucalanus bungii;the BST was mainly composed of the pan-Arctic distributed Calanus glacialis,meroplankton of benthos,and neritic species such as Centropages abdominalis;copepods,especially the copepodite of C.glacialis,were predominant in the CSS community.The BSS community structure was strongly affected by the inflow of Bering Shelf Water,while those of BST and CSS were determined by the recruitment of local species.The zooplankton community structure is influenced by both advection and environmental changes such as warming and a prolonged productivity period.Here,it was difficult to distinguish the changes induced by climate change from the effects of the Bering Sea Water.The key to solving this problem is the accumulation of comparable data,which requires continuous monitoring of key species such as C.glacialis and Calanus hyperboreus.
Recent research has shown that winter warmings are phenomenally high compared to summer warmings over the poles,especially over the Arctic.Taking the current scenario into account,this paper attempts to understand the atmospheric variables causing sea ice variability over and around the region of Svalbard for seasons;winter,spring,summer and autumn for the span of 42 years(1979-2021).The variability in atmospheric and oceanic parameters namely temperature,precipitation,wind speed,and sea surface salinity are analysed over inter-spatial,inter-seasonal and inter-annual domains.Winters are characterized by inter-annual increasing trend in temperature.During 1981-1990 the rise from the decadal mean is found to be 0.39 K·a-1,during 1991-2000 it is 0.20 K·a-1,during 2001-2010 it is 0.04 K·a-1 and during 2011-2020 it is 0.23 K·a-1.Interestingly while considering inter-spatial domains,the region southwest to Svalbard seems to be wetter(0.05 mm·(10 a)-1)compared to its northeast(-0.03 mm·(10 a)-1).Across all the three domains,wind speeds are highest during autumn and then decrease subsequently through summer,spring and are least during winter.Wind is predominantly from the south,and hence it is suspected to carry hot Atlantic air.Additionally,the significant role of salinity in the ocean also plays a key role in governing the fate of sea ice conditions.The long-term forecasts of temperature over sea ice of Svalbard are alarming especially for the winter ice(r=-0.84).Correlation matrices between atmospheric and sea ice parameters are shown to gain a better understanding on their inter relation.
International cooperation is vital for the polar regions. China's past polar cooperation has tended to focus on intergovernmental and bilateral mechanisms rather than regional cooperation. However, regional and subregional cooperation is playing an increasing role in the polar regions with the rapid development of geopolitics and global climate change. Involvement in three subregional polar organizations—the Asian Forum for Polar Sciences (AFoPS), the Pacific Arctic Group (PAG), and the China-Nordic Arctic Research Center (CNARC)—in the last two decades reflects China's improved skills and flexibility in participating in international polar cooperation and represents an exercise in the "win-win" principle under China's Arctic policy. This paper presents a review of the development of polar subregional cooperation, examines China's participation in three of subregional organizations and provides feasible suggestions for China's future engagement with these organizations.
Zooplankton are critical components of the Southern Ocean ecosystems, acting as trophic links between phytoplankton and higher-level species. The composition, abundance, carbon biomass, and community structure of zooplankton were studied based on samples collected with a Norpac net (330-μm mesh, 0.5-m2 net mouth) during the austral summers of 2017/2018. Three communities in a latitudinal gradient were identified based on both a zooplankton abundance dataset and a biomass dataset. Zooplankton were mainly dominated by small copepods (e.g., Oithona similis and Ctenocalanus citer) in terms of abundance, while the total zooplankton biomass was dominated by krill (Euphausia superba and Thysanoessa macrura) and large copepods (e.g., Calanoides acutus, Calanus propinquus, and Metridia gerlachei). Redundancy analysis demonstrated that environmental factors (e.g., temperature, nitrate, dissolved oxygen, ammonium) accounted for more than 40％ of the variance in zooplankton abundance/biomass. This indicates that physical processes significantly affect the zooplankton community. Meanwhile, a significant positive correlation was found between the abundance/biomass of zooplankton and that of dominant phytoplankton and ciliates, which suggests trophic links among various plankton functional groups. Our results reveal that both physical processes and biological factors shape the community structure of zooplankton in the Amundsen Sea.
We developed a multinomial-logit-based stochastic user equilibrium (MNL SUE) model incorporating time value of cargo to investigate future proportions of cargo flow through the Northeast Passage (NEP) and the Suez Canal Route between representative ports. We studied navigation during the ice-free and ice-covered seasons using sea ice projections for 2070 based on 1991-2021 NEP ice data. Sailing distance and time between selected ports are lower via the NEP than the Suez Canal Route. Under the scenario of year-round operation of the NEP, the proportion of cargo flow through the NEP is estimated to be 68.5％, which represents considerable commercial potential. Proportions are higher for the ice-free season and for ports at high latitudes. We also assessed flow under different scenarios. Under the scenario of fuel price increase, proportion of flow through the NEP in the ice-covered season is expected to increase. If time value is ignored, flow through the NEP is expected to increase all year round. If shippers become more cost-conscious, flow through the NEP is also expected to increase.
Ice sheet collapse under a warming world poses threat to humanity as a whole since approximately 38% of global population lives within 100 km of the coast（UNEP,2014）.The West Antarctic Ice Sheet（WAIS） is grounded on bedrock currently below sea-level and therefore vulnerable to ocean warming（Mercer,1968;Hughes,1973）.
Satellite observations over the past four decades have shown that the long-term trend of Antarctic sea ice extent (SIE) is opposite to the trend of sea ice extent in the Arctic. Arctic sea ice extent continues to decline while Antarctic SIE is generally on the rise except for a dramatic decline in 2015-2016. Based on the 40-year climatology from 1981 to 2020, Antarctic SIE anomaly in December 2016 is -2.1×106 km2, reaching the minimum since 1979. There are many studies on the cause of this record decline. This present review summarizes the spatial and temporal characters of Antarctic sea ice and recaps major findings on the causes of record decline in 2015-2016 from the perspective of direct thermodynamic and dynamic process of atmosphere and ocean as well as the modulation of climate modes. Finally, the challenges and key scientific problems to be solved in the future of Antarctic sea ice research are presented.
Sea ice melt water and circumpolar deep water (CDW) intrusion have important impacts on the ecosystem of the Amundsen Sea. In this study, samples of nutrients and phytoplankton pigments from nine stations in the eastern Amundsen Sea were collected during the austral summer. Based on in-situ hydrological observations, sea ice density data from satellite remote sensing, and chemical taxonomy calculations, the relationships between environmental factors and phytoplankton biomass and community structure were studied. The results showed that with increasing latitude, the contribution of sea ice melt water (MW％) and the stability of the water body increased, and the depth of the mixed layer (MLD) decreased. The integrated concentration of chlorophyll a (Chl-a) ranged from 21.4 mg·m?2 to 148.4 mg·m?2 (the average value was 35.7±53.4 mg·m?2). Diatoms (diatoms-A [Fragilariopsis spp., Chaetoceros spp., and Proboscia spp.] and diatoms-B [Pseudonitzschia spp.]) and Phaeocystis antarctica were the two most widely distributed phytoplankton groups and contributed 32％±16％ and 28％±11％, respectively, of the total biomass. The contributions of Dinoflagellates, Chlorophytes, Cryptophytes, the high-iron group of P. antarctica, and Diatom group A were approximately 17％±8％, 15％±13％, 9％±6％, 5％±9％, and 3％±7％, respectively. The area with the highest phytoplankton biomass was located near the ice-edge region, with a short time lag (Tlag) between sampling and complete sea ice melt and a high MW％, while the area with the second-highest Chl-a concentration was located in the area affected by the upwelling of CDW, with thorough water mixing. Vertically, in the area with a short Tlag and a shallow MLD, the phytoplankton biomass and proportion of diatoms decreased rapidly with increasing water depth. In contrast, in the region with a long Tlag and limited CDW upwelling, the phytoplankton community was dominated by a relatively constant and high proportion of micro phytoplankton, and the phytoplankton biomass was low and relatively stable vertically. Generally, the phytoplankton community structure and biomass in the study area showed high spatial variation and were sensitive to environmental changes.
