Migration and role of zinc in biogeochemical cycles in the Antarctic Ice Sheet and the Southern Ocean

Zinc(Zn),a widespread metal in the Earth’s crust,serves as a crucial nutrient in the Southern Ocean’s primary production.Studies on Zn in Antarctic snow and ice offer insights into the origins of this metal and its transport routes,as well as its impact on the biogeochemical processes within the Antarctic atmosphere–land–ocean system.This review examines research on the spatial and temporal distribution of Zn in Antarctic snow and ice,as well as in Southern Ocean waters.It includes an overview of advanced methods for sampling and analyzing Zn,along with explanations for the observed variations.The review also discusses various sources of Zn as a nutrient to the Southern Ocean.Finally,it addresses prospective issues related to the use of Zn isotopes in identifying atmospheric sources and their biogeochemical effects on the development of the Southern Ocean ecosystem.

Some recent advances in remote sensing-based monitoring of changes in the Greenland Ice Sheet

The mass balance of the Greenland Ice Sheet(GrIS)plays a crucial role in global sea level change.Since the 1960s,remote sensing missions have been providing extensive and continuous observation data for change monitoring of the GrIS.In this paper,we present our recent research results from remote sensing-based GrIS change monitoring.First,historical satellite data are processed and used to fill data gaps and are combined with existing partial maps,completing an ice velocity map of the GrIS from the 1960s to 1980s.This map provides valuable data for estimating the historical mass balance of Greenland.Second,the monthly gravimetry-based mass balance of the GrIS from 2002 to 2020 is estimated by combining Gravity Recovery and Climate Experiment(GRACE)and GRACE Follow On(GRACE-FO)data.It is found that the GrIS has lost a total mass of approximately 4443±75 Gt during this period.Third,based on Global Land Ice Measurements from Space(GLIMS),an updated Greenland glacier inventory is achieved utilizing data collected between 2006 and 2020.This inventory provides more detailed and up-to-data glacier boundaries of Greenland.Overall,these advances provide essential data support for estimating the mass balance of the GrIS,contributing to the advancement of research on global sea level change.

Persistently explore new understandings of Greenland Ice Sheet ablation

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 mSLE,with a much faster speed of ablation than the Antarctic Ice Sheet.

Research progress in geophysical exploration of the Antarctic ice sheet

The Antarctic ice sheet is an important target of Antarctic research.Thickness and structure,including intraice and subice,are closely related to the mass balance of the ice sheet,and play an important role in the study of global sea level and climate change.Subglacial topography is an important basis for studying ice sheet dynamics and ice sheet evolution.This paper briefly reviews the geophysical detection methods and research status of the Antarctic ice sheet:(1)Conventional methods such as ice radar are the main methods for studying the ice sheet today,and passive source seismic methods such as the receiver function method,H/V method and P-wave coda autocorrelation method have good development prospects;(2)the high-resolution(1 km)ice thickness and subglacial topographic database BEDMAP2 established based on various data has greatly improved the ability to detect internal isochronous layers,anisotropic layers,and temperature changes within ice and has advanced research on ice sheet evolution;and(3)ice radar,numerical simulation and core drilling are the main methods to study subglacial lakes and sediments.More than 400 subglacial lakes have been confirmed,and more than 12000 simulation results have been obtained.Research on the Antarctic ice sheet faces enormous challenges and is of great urgency.Aiming at hot issues,such as Antarctic geological evolution,glacial retreat,ice sheet melting and their relationships with global climate change,it is the frontier and trend of future Antarctic ice sheet research to carry out multidisciplinary and multicountry comprehensive geophysical exploration based on the traditional ice radar method combined with passive seismic methods,especially new technologies such as short-period dense array technology,unmanned aerial vehicles and artificial intelligence.This is expected to further promote Antarctic research.

Analysis of the record-breaking August 2021 rainfall over 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.

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.

Greenland Ice Sheet Contribution to Future Global Sea Level Rise based on CMIP5 Models

Sea level rise （SLR） is one of the major socioeconomic risks associated with global warming. Mass losses from the Greenland ice sheet （GrIS） will be partially responsible for future SLR, although there are large uncertainties in modeled climate and ice sheet behavior. We used the ice sheet model SICOPOLIS （Simulation COde for POLythermal Ice Sheets） driven by climate projections from 20 models in the fifth phase of the Coupled Model Intercomparison Project （CMIP5） to estimate the GrlS contribution to global SLR. Based on the outputs of the 20 models, it is estimated that the GrIS will contribute 0-16 （0-27） cm to global SLR by 2100 under the Representative Concentration Pathways （RCP） 4.5 （RCP 8.5） scenarios. The projected SLR increases further to 7-22 （7-33） cm with 2~basal sliding included. In response to the results of the multimodel ensemble mean, the ice sheet model projects a global SLR of 3 cm and 7 cm （10 cm and 13 cm with 2~basal sliding） under the RCP 4.5 and RCP 8.5 scenarios, respectively. In addition, our results suggest that the uncertainty in future sea level projection caused by the large spread in climate projections could be reduced with model-evaluation and the selective use of model outputs.

Accumulation over the Greenland Ice Sheet as Represented in Reanalysis Data

Annual precipitation,evaporation,and calculated accumulation from reanalysis model outputs have been investigated for the Greenland Ice Sheet （GrIS）,based on the common period of 1989-2001.The ERA-40 and ERA-interim reanalysis data showed better agreement with observations than do NCEP-1 and NCEP-2 reanalyses.Further,ERA-interim showed the closest spatial distribution of accumulation to the observation.Concerning temporal variations,ERA-interim showed the best correlation with precipitation observations at five synoptic stations,and the best correlation with in situ measurements of accumulation at nine ice core sites.The mean annual precipitation averaged over the whole GrIS from ERA-interim （363 mm yr 1） and mean annual accumulation （319 mm yr 1） are very close to the observations.The validation of accumulation calculated from reanalysis data against ice-core measurements suggests that further improvements to reanalysis models are needed.

Chinese radioglaciological studies on the Antarctic ice sheet: progress and prospects

Chinese radioglaciological studies on the Antarctic ice sheet(AIS) began in 2004/05 when the 21 st Chinese National Antarctic Research Expedition(CHINARE 21) team arrived at Dome A for the first time and radio echo sounding(RES) was conducted along the inland traverse and in the Dome A region. Subsequently, more field surveys were conducted along the traverse and in the Dome A region using different radar systems targeting different scientific purposes, such as revealing the landscape of the Gamburtsev Subglacial Mountains by detailed grid RES, or locating a deep ice core drilling site by mapping and studying internal structures, bedrock topography and subglacial conditions in the Dome A region. Furthermore, the evolution of the AIS was inferred from the typical mountain glaciation topography beneath Dome A, and the age of the deep ice core at Kunlun Station was estimated through numerical modeling. Recently, the Snow Eagle 601 airplane was acquired and an airborne geophysical system was constructed to survey the AIS in Princess Elizabeth Land during CHINARE 32(2015/16) and CHINARE 33(2016/17) in order to fill the large data gap there. In this paper, we review both the recent progress of Chinese radioglaciological science in Antarctica and future proposed work.

Ice sheet controls on fine-grained deposition at the southern Mendeleev Ridge since the penultimate interglacial

Clay minerals deposited at the southern Mendeleev Ridge in the Arctic Ocean have a unique provenance,which can be used to reconstruct changes in the local sedimentary environment.We show that sediments in core ARC7-E23 record high-frequency changes in clay minerals since the penultimate interglacial.The clay minerals,grain size,and ice-rafted debris indicate the extent of the East Siberia Ice Sheet(ESIS).During the glacial periods of Marine Isotope Stage 2(MIS2)and MIS4,the southern Mendeleev Ridge was likely covered by an ESIS-extended ice shelf,blocking almost all sediment input from the Canadian Arctic and Laptev Sea,but allowing transport of fine-grained sediments from the East Siberian and Chukchi Sea shelves.After ESIS retreat,the Beaufort Gyre and Transpolar Drift became the primary transport mechanism for the distally sourced sediments.Climate conditions in MIS3 enhanced both the oceanic circulation and sediment transport.

Seasonal variations of the near surfacelayer parameters over the Antarctic ice sheet in Princess Elizabeth Land,East Antarctica

Analysis of sensible heat flux （ Qh ）, latent heat flux （ Qe ）, Richardson number （Ri） ,bulk transport coefficient （Cd） and katabatic windsare presented by using the meteorological data in the near surface layer from an automatic weather station （AWS） in Princess Elizabeth Land, East Antarctica ice sheet and the data of corresponding period at Zhongshan station in 2002. It shows that annual mean air temperature at LGB69 is -25.6℃, which is 16.4℃ lower than that at Zhongshan, where the elevation is lower and located on the coast. The temperature lapse rate is about 1.0℃/110 m for the initial from coast to inland. The turbulence heat flux at LGB69 displays obvious seasonal variations with the average sensible heat flux -17.9 W/m^2 and latent heat flux -0.9 W/m^2. The intensity （Qh ＋ Qe ） of coolling source is - 18.8 W/m^2 meaning the snow surface layer obtains heat from atmosphere. The near surface atmosphere is near-neutral stratified with bulk transport coefficients （Cd） around 2.8 ×10^-3 ,and it is near constant when the wind speed higher than 8 m/s. The speed and the frequency of easterly Katabatic winds at LGB69 were higher than that at Zhongshan Station.

Evolution of the North Atlantic Current and Barents Ice Sheet as revealed by grain size populations in the northern Norwegian Sea during the last 60 ka

The grain size distribution of bulk sediment samples was decomposed in a core to reconstruct paleoceanographic evolution over the past 60 ka in the northern Norwegian Sea.The results show that sediments consisted of 3–4 grain populations derived from the North Atlantic Current(NAC)and Barents Ice Sheet(BIS).The grain size data suggest three palaeoceanographic evolution stages:(1)an environment affected by BIS and NAC and changed with the interstadial/stadial transition in phase with the Greenland ice-core record at 60–31 ka BP,during which discharge of icebergs and the content of the coarsest population containing ice-rafted debris(IRD)in the sediments increased significantly during stadial,while the fine silt population containing volcanic glasses increased with the enhancement of NAC during the interstadial;(2)an extreme environment controlled by BIS at31–13 ka BP.BIS reached to its maximum at about 31 ka BP and the turbid plumes that formed at the leading edge of BIS contributed to a significant increase in the clayey population in sediments.Icebergs drained into the northern Norwegian Sea with periodical calving of the BIS at 31–19 ka BP.Subsequently,the ablation of the BIS discharged massive floods with clayey sediments and icebergs into the Norwegian Sea at 19–13 ka BP,resulting in a constant increase in clay and IRD in sediments;and(3)a marine environment similar to the present one under the strong influence of NAC following the complete melting of the BIS after 13 ka BP,NAC is the dominant transport agent and no IRD occurred in sediments.The fine silt populations containing volcanic glasses transported by NAC significantly increased.

Mass change of the Antarctic ice sheet inferred from ICESat and CryoSat-2

This study examined the mass change of the Antarctic ice sheet(AIS) based on ICESat and CryoSat-2 observations. We estimated the AIS exhibited mass losses of-101±15 Gt·aduring the ICESat period(Sept–Nov 2003 to Sept–Oct 2009) and-186±55 Gt·aduring the CryoSat-2 period(Jan 2011 to Dec 2015). Mass losses occurred mainly in the sectors of the Amundsen and Bellingshausen seas. Benefitting from the 30-d subcycle of CryoSat-2, we obtained monthly estimates of mass evolution. Considerable annual variations were observed in the mass evolution sequences and the climatological monthly mass evolution. Seasonal mass evolutions in the sectors of the Bellingshausen and Amundsen seas were found most representative of the annual variation. The geographical distribution characteristics of interannual AIS mass evolution were revealed by the annual average mass evolution sequences. During Jan 2011 to Dec 2015, the ice sheets in the sectors of the Bellingshausen and Amundsen seas, and the Totten Glacier, experienced increasingly rapid areal mass loss. An area of mass gain with a moderate rate of increase was found between Dronning Maud Land and Enderby Land. Rapid mass accumulation has occurred in a limited area of the Kamb Ice Stream.

Greenland Ice Sheet Elevation Change in Winter and Influence of Atmospheric Teleconnections in the Northern Hemisphere

The relationship between the variability of the surface elevation of the Greenland Ice Sheet (GIS) in winter and sea level pressure is identified through analysis of data from satellite-borne radar altimeters, together with meteorological data fields during 1993 2005. We found that both the North Pacific Oscillation (NPO) and the North Atlantic Oscillation (NAO), the two major teleconnection patterns of the atmospheric surface pressure fields in the Northern Hemisphere, significantly influence the GIS winter elevation change. Further, it is suggested that the NPO may affect the GIS accumulation by influencing the NAO, particularly by changing the intensity and location of the Icelandic Low.

Preliminary research on the transmission path of nssSO_4^(2-) and NO_3^- in Antarctic ice sheet

The main sources of nssSO 2- 4 and NO - 3 were summarized in this paper. By analyzing the spatial distribution features of major ions in Antarctic ice sheet and studying on the different time of the same volcanic event recorded by different ice cores from different regions in Antarctica, this paper intends to study the transmission path of nssSO 2- 4 and NO - 3. Results show that nssSO 2- 4 and NO - 3 are transmitted to the ice sheet through long distance and high altitude. The procedure of the transmission is that nssSO 2- 4 and NO - 3 are transmitted to the level between the top of troposphere and the bottom of stratosphere, then subsided to the ice sheet surface and spread to other regions.

An Improved Method for Modeling Spatial Distribution of δD in Surface Snow over Antarctic Ice Sheet

Using the recent compilation of the isotopic composition data of surface snow of Antarctic ice sheet, we proposed an improved interpolation method of δD, which utilizes geographical factors （i.e., latitude and altitude） as the primary predictors and incorporates inverse distance weighting （IDW） technique. The method was applied to a high-resolution digital elevation model （DEM） to produce a grid map of multi-year mean δD values with lkm spatial resolution for Antarctica. The mean absolute deviation between observed and estimated data in the map is about 5.4‰, and the standard deviation is 9‰. The resulting δD pattern resembles well known characteristics such as the depletion of the heavy isotopes with increasing latitude and distance from coast line, but also reveals the complex topographic effects.

Greenland Ice Sheet surface melt:A review

Surface melt has great impacts on the Greenland Ice Sheet （GrlS） mass balance and thereby has become the focus of significant GrlS research in recent years. The production, transport, and release processes of surface meltwater are the keys to understanding the poten- tial impacts of the GrlS surface melt. These hydrological processes can elucidate the following scientific questions： How much melt- water is produced atop the GrlS？ What are the characteristics of the meltwater-formed supraglacial hydrological system？ How does the meltwater influence the GrlS motion？ The GrlS supraglacial hydrology has a number of key roles and yet continues to be poorly understood or documented. This paper summarizes the current understanding of the GrlS surface melt, emphasizing the three essential supraglacial hydrological processes： （1） meltwater production： surface melt modeling is an important approach to acquire surface melt information, and areas, depths, and volumes of supraglacial lakes extracted from remotely sensed imagery can also provide surface melt information; （2） meltwater transport： the spatial distributions of supraglacial lakes, supraglacial sarams, moulins, and crevasses demonstrate the characteristics of the supraglacial hydrological system, revealing the meltwater transport process; and （3） meltwater release： the release of meltwater into the englacial and the subglacial ice sheet has important but undetermined impacts on the GrlS motion. The correlation between surface runoff and the GrlS motion speed is employed to understand these influences.

GLIMMER Antarctic Ice Sheet Model,an experimental research of moving boundary condition

A 3-D coupled ice sheet model, GLIMMER model is introduced, and an idealized ice sheet experiment under the EISMINT-1 criterion of moving boundary condition is presented. The results of the experiment reveal that for a steady-state ice sheet profile the characteristic curves describe the process of evolution which are accordant with theoretical estimates. By solving the coupled thermodynamics equations of ice sheet, one may find the characteristic curves which derived from the conservation of the mass, energy and momentum to the ice flow profile. At the same time, an agreement, approximate to the GLIMMER case and the confirmed theoretical results, is found. Present study is explorihg work to introduce and discuss the handicaps of EISMINT criterion and GLIMMER, and prospect a few directions of the GLIMMER model.

EVOLUTION OF THE ANTARCTIC ICE SHEET SINCE LATE PLEISTOCENE

Available data show that the of fossil plants testified that the Antarctica was a rather warm or even hot and humid region covered with forest from Devonian to Cretaceous [periods. Furthermore, even Antarctic coasts stilll kept in a warm and humid condition until early Tertiary of 37 Ma ago. It therefore can be considered that the Antarctica was not situated at its present position, but in tropic or temperate zone before the Tertiary.Antarctic ice sheet has begun to appear in the Pligocene of 26Ma ago. It was very much earlier than the glaciations in everywhere of the world. For the reasons a most important event was the separating of Antarctic Peninsula from South America in 35 Ma ago. Drake Passage therefore occurred and Antarctic circulation appeared, and then Antarctic continent became an isolated cold land.Glacial changes have happened on the Antarctic ice sheet from late Tertiary to Quaternary periods. However, it has been confirmed that the Antarctic ice sheet has a great extension during the latest Pleistocene glaciation of 25000-l0000a B. P. About 18000a ago, the Antarctic ice sheet was 450-1000 m thicker and much larger than that at present. By that time the ice sheet grounded on the conticental shelves. Sea level might be 100-150 m or more lower than present sea level. Sca ice covered areas in winter and in summer were 10 and 2 times respectively than that today.It was much warmer in middle Holocene (7500-5000 a B. P.) than today in Antarctic region. By that time, a large amount of ice was melt away, which, on one hand.[caused a rapid rising of sea level, transgression immediately occurred; on the other hand, as continental load decreased due to the melting of ice sheet, the isostatic uplifting consequently followed and the marine terraces formed along Antarctic coasts in middle Holocene, Now the glacio-isostatic uplift is still going on. For a total uplift of 10-25 m since 6000 a B. P. the mean rate of 1.5-4mm/a is estimated in different places of Antarctic coasts.Antarctic ice sheet (including ice shelves) has been retreating recently, Meanwhile, the inland snow accumulation has been increasing in the past decades of years, both of them are corresponding to the rising of annual mean temperature since 1910 A. D.

The extraction of elevation information of ice-sheet surface on south area of the Larsemann Hills in East Antarctica

Based on the setting up of the function relation between the radiant brightness of ice surface and the elevation control point in Antarctica, the experiments for the extraction of elevation information by using thermal infrared image of Landsat TM band 6, and the ice surface topographical maps in area nearby Larsemann Hills have been performed.