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.

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.

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.

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.

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.

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.

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.

Reconciled estimation of Antarctic ice sheet mass balance and contribution to global sea level change from 1996 to 2021

The Antarctic Ice Sheet(AIS)has been losing ice mass and contributing to global sea level rise(GSLR).Given its mass that is enough to cause~58 m of GSLR,accurate estimation of mass balance trend is critical for AIS mass loss monitoring and sea level rise forecasting.Here,we present an improved approach to reconciled solutions of mass balance in AIS and its regions from multiple contributing solutions using the input-out,altimetric,and gravimetric methods.In comparison to previous methods,such as IMBIE 2018,this approach utilizes an adaptive data aggregation window to handle the heterogeneity of the contributing solutions,including the number of solutions,temporal distributions,uncertainties,and estimation techniques.We improved the regression-based method by using a two-step procedure that establishes ensembled solutions within each method(input-output,altimetry,or gravimetry)and then estimates the method-independent reconciled solutions.For the first time,16contributing solutions from 8 Chinese institutions are used to estimate the reconciled mass balance of AIS and its regions from1996 to 2021.Our results show that AIS has lost a total ice mass of~3213±253 Gt during the period,an equivalent of~8.9±0.7 mm of GSLR.There is a sustained mass loss acceleration since 2006,from 88.1±3.6 Gt yr^(-1)during 1996–2005 to 130.7±8.4 Gt yr^(-1)during 2006–2013 and further to 157.0±9.0 Gt yr^(-1)during 2014–2021.The mass loss signal in the West Antarctica and Antarctic Peninsula is dominant and clearly presented in the reconciled estimation and contributing solutions,regardless of estimation methods used and fluctuation of surface mass balance.Uncertainty and challenges remain in mass balance estimation in East Antarctica.This reconciled estimation approach can be extended and applied for improved mass balance estimation in the Greenland Ice Sheet and mountain glacier regions.

Mass balance of the Antarctic Ice Sheet from 2013 to 2018 estimated using the input-output method with updated remote sensing products

The Antarctic Ice Sheet(AIS)has been losing ice mass and contributing to the rise in the global sea-level(GSL)for the last 4 decades,as quantified by using satellite observations.We developed a framework for implementing the state-of-the-art input-output(IO)method that has the advantage of explicit estimation of the mass balance of individual glaciers,basins and the continent.We estimated the mass balance of the AIS from 2013 to 2018 using improved observations and updated datasets recently made available,including annual ice flow velocity maps from the Inter-mission Time Series of Land Ice Velocity and Elevation(ITS_LIVE)dataset,the Bed Machine and the Princess Elizabeth Land(PEL)Earth System Science Data(ESSD)datasets,and the surface mass balance from the RACMO 2.3 system.For example,using the improved ice thickness data,the proposed method for ice discharge estimation enables a 10%reduction of uncertainty in ice discharge.During the period of 2013–2018,an ice discharge acceleration of 6.9±6.5 Gt yr^(–2)in West Antarctica(WA)was detected,which contributed significantly to the estimated mass loss of~1069 Gt(–178.2±108.9 Gt yr^(–1))in the AIS.On the other hand,Queen Maud Land,East Antarctica(EA),showed clearly a mass gain rate of 56.0±10.0 Gt yr^(–1)due to the regional increase in surface mass balance.Our results extended the estimation period by 3 years in comparison to the published study using the same annual velocity maps from the ITS_LIVE dataset.Furthermore,our results,along with those from other studies using the IO method,reassures the acceleration of recent mass loss in WA and Wilkes Land in EA,which are caused by glacier thinning and ice shelf basal melting.Compared with the long-term mass balance record since 1979,our results suggest that the mass loss in AIS accelerated in the last decade.The developed framework can be modified for mass balance estimation of the AIS or for other ice sheets by using velocity maps from other satellite data or from different periods.

Trend of mass change in the Antarctic ice sheet recovered from the GRACE temporal gravity field

It is important to quantify mass variations in the Antarctic ice sheet hybrid filtering scheme employing a combination of the decorrelated to study the global sea-level rise and climate change. A filter P3M6 and 300 km Fan filter was used, and the sur- face mass variations over the Antarctic are recovered from GRACE CSR RL04 monthly gravity field models from August 2002 to June 2010. After deduction of leakage errors using the GLDAS hydrological model and postglacial rebound effects using the glacial isostatic adjustment model IJ05, the variations in the ice sheet mass are obtained. The results reveal that the rate of melting of the Antarctic ice sheet is 80.0 Gt/a and increasing and contributes 0.22 mm/a to the global sea-level rise; the mass loss rate is 78.3 Gt/a in the West Antarctic and 1.6 Gt/a in the East Antarctic. The average mass loss rate increases from 39.3 Gt/a for the period 2002-2005 to 104.2 Gt/a for the period 2006-2010, and its corresponding contribution to the global sea-level rise increases from 0.11 to 0.29 mm/a, which indicates accelerated ice mass loss over the Antarctic since 2006. Moreover, the mass accumulation rates for Enderby Land and Wilkes Land along the coast of East Antarctica decrease for the period 2006-2008 but increase evidently after 2009.

Analyzing Antarctic ice sheet snowmelt with dynamic Big Earth Data

Big Earth Data—big data associated with Earth sciences—can potentially revolutionize research on climate change,sustainable development,and other issues of global concern.For example,analyzing massive amounts of satellite imagery of polar environments,which are sensitive to the effects of climate change,provides insights into global climate trends.This study proposes a method to use Big Earth Data to explore changes in snowmelt over the Antarctic ice sheet from 1979 to 2016.The method uses Zernike moments to observe melt area in Antarctica and uses the Mann-Kendall test to detect temporal changes and abnormal information about the continent’s melt area.The melting trend in the time-series data matched the changes in temperature and seasonal transitions.The results do not demonstrate significant change in the area of surface melt;however,abrupt changes in melt conditions linked to temperature changes over the Antarctic ice sheet were observed within the time series.The experiment results demonstrate that the proposed method is robust,adaptive,and capable of extracting the core features of melting snow.

Impact of the formation and ablation of Antarctic ice sheet on the global geoid and sea level

It is convenient to investigate the gravimetry using a harmonic spheric function for the description of the distribution and thickness of the Antarctic ice sheet. The gravitational theory and the Stokes' harmonic spheric function formula were used to determine the impact of the Antarctic ice cap on the global geoid. The Antarctic ice cap is formed from the condensation of seawater vapour whose mass is equal to a layer of seawater 59 m thick of covering the earth's surface, i.e. 2.7×10 19 kg. This will cause the global averaged geoid to decrease for around 23 m. The authors' computations show that the Antractic ice cap has a great impact on the global geoid, which increases (+) in some regions, but decreases (-) in other reigions. The geoid is +115 m, -37 m and +8 m at the South Pole, the 25°S parallel and the North Pole, respectively. If the Antarctic ice cap melts completely, on the rigid Earth's surface the seawater and geoid will return to its original position (and height) due to the balancing force of the fluid. Since the crust is almost in a state of isostasy, assuming that the crust is an elastic solid and the mantle is an incompressible fluid, the load of seawater will deflect the crust and drive the mantle material to flow. The material above the isostatic surface compensates mutually. If the densities of the mantle and seawater are 3270 kg/m 3 and 1030 kg/m 3, respectively, then the variation in the elevation of the continent is only 2.8 m with respect to the sea level after the Antarctic ice cap melts;it is not larger than that estimated by some people.It is worth noting that the above results were derived from an ideal Earth model. In the real Earth, the mantle and crust are visco elastic.

Distribution of ice thickness and subglacial topography of the "Chinese Wall" around Kunlun Station,East Antarctica

As fundamental parameters of the Antarctic Ice Sheet,ice thickness and subglacial topography are critical factors for studying the basal conditions and mass balance in Antarctica.During CHINARE 24（the 24 th Chinese National Antarctic Research Expedition,2007/08）,the research team used a deep ice-penetrating radar system to measure the ice thickness and subglacial topography of the ＂Chinese Wall＂ around Kunlun Station,East Antarctica.Preliminary results show that the ice thickness varies mostly from 1600 m to 2800 m along the ＂Chinese Wall＂,with the thickest ice being 3444 m,and the thinnest ice 1255 m.The average bedrock elevation is 1722 m,while the minimum is just 604 m.Compared with the northern side of the ice divide,the ice thickness is a little greater and the subglacial topography lower on the southern side,which is also characterized by four deep valleys.We found no basal freeze-on ice in the Gamburtsev Subglacial Mountains area,subglacial lakes,or water bodies along the ＂Chinese Wall＂.Ice thickness and subglacial topography data extracted from the Bedmap 2 database along the ＂Chinese Wall＂ are consistent with our results,but their resolution and accuracy are very limited in areas where the bedrock fluctuates intensely.The distribution of ice thickness and subglacial topography detected by ice-penetrating radar clarifies the features of the ice sheet in this ＂inaccessible＂ region.These results will help to advance the study of ice sheet dynamics and the determination of future locations of the GSM＇s geological and deep ice core drilling sites in the Dome A region.

The difference of atmospheric chemical loadings shown by electrical conductivity of snow and ice between Antarctica, Arctic and Qinghai-Tibetan Plateau

The relationship of ECM with ice acidity and impurities concentrations are much different between the Qinghai Tibetan Plateau and the polar regions. On the Qinghai Tibetan Plateau, ECM is dependent on the mineral ions (i.e., Ca 2+ , Mg 2+ , SO 2- 4, etc.) mainly derived from crustal sources, thus displays a positive linear correlation between ECM and these ions. While in polar ice sheets, however, ECM of snow and ice is mainly dependent on the acidic roots such as Cl -, SO 2- 4 and NO - 3 that mostly come from ocean. Therefore, there is good relationship between ECM and concentration of H +. However, the relationship between ECM and major ions has complicated geographical differentiation in the whole Arctic. For instance, there no longer exits the same simple relationship in the central Arctic as that in the Greenland Ice Sheet, probably due to the disturbance of Arctic haze. In general, ECM of snow and ice is a potential indicator of atmospheirc envirmment of cold regions.

GPS-derived horizontal ice flow velocities along the traverse route from Zhongshan Station to Dome-A, East Antarctica

The traverse route from Zhongshan Station to Dome A is one of the most important expedition routes of ITASE Project. China carried out 3 inland traverses during the 1996/1997, 1997/1998, 1998/1999 austral summer field seasons. The field team reached inland 300 km, 500 km and 1100 km away from Zhongshan Station respectively. Some ice motion stakes were set up, occupied and reoccupied along the route by GPS technology. It showed that the ice along the traverse route flowed with an 8 25 ma -1 velocity to the northwest, the direction of the bottom of Lambert Glacier Basin. They coincide with the results along the eastern section from LGB59 70 of the LGB route deduced by Australia in both values and directions. Furthermore, the directions of the horizontal flow are perpendicular to the surface topography contour. The much larger velocity at the point of LT980 with an approximate value of 100 ma -1 was probed. It was caused by a 15 km wide trough on the bed beneath this point.

Last deglacial relative sea level variations in Antarctica derived from glacial isostatic adjustment modelling

We present relative sea level （RSL） curves in Antarctica derived from glacial isostatic adjustment （GIA）predictions based on the melting scenarios of the Antarctic ice sheet since the Last Glacial Maximum （LGM）given in previous works.Simultaneously,Holocene-age RSL observations obtained at the raised beaches along the coast of Antarctica are shown to be in agreement with the GIA predictions.The differences from previously published ice-loading models regarding the spatial distribution and total mass change of the melted ice are significant.These models were also derived from GIA modelling; the variations can be attributed to the lack of geological and geographical evidence regarding the history of crustal movement due to ice sheet evolution.Next,we summarise the previously published ice load models and demonstrate the RSL curves based on combinations of different ice and earth models.The RSL curves calculated by GIA models indicate that the model dependence of both the ice and earth models is significantly large at several sites where RSL observations were obtained.In particular,GIA predictions based on the thin lithospheric thickness show the spatial distributions that are dependent on the melted ice thickness at each sites.These characteristics result from the short-wavelength deformation of the Earth.However,our predictions strongly suggest that it is possible to find the average ice model despite the use of the different models of lithospheric thickness.By sea level and crustal movement observations,we can deduce the geometry of the post-LGM ice sheets in detail and remove the GIA contribution from the crustal deformation and gravity change observed by space geodetic techniques,such as GPS and GRACE,for the estimation of the Antarctic ice mass change associated with recent global warming.

Dome Argus: Ideal site for deep ice drilling

Located on the centre of ice drainage range, the highest Dome Argus （Dome A） of East Antarctic Ice Sheet （EAIS）, could be represented as an ideal site for deep ice cores drilling containing oldest paleo-climate records. To select a suitable drilling site for deep ice core, it needs gather all information pertaining to the local meteorology, ice sheet landforms, ice thickness, subgla- cial topography of bed rocks, ice velocity, internal structures of ice sheet, etc. Based on the International Partnerships in Ice Core Sciences （IPICS）, we present recent achievement of glaciological research and its perspective at Dome A in this paper. We system- atically discussed the merits and possible ventures of potential drilling sites around Dome A. Among all the candidates, we find that the Chinese Antarctic Kunlun Station is the best site for and assess further the possibility to obtain a replicate core for carrying out the first deep ice core drilling campaign. We emphasize studying dynamics and evolution of climate change.

Glaciological observations at Dome Argus, East Antarctica

Dome Argus （Dome A） in East Antarctica is a potentially likely site to meet one of the major objectives of the International Partnerships in Ice Core Sciences （IPICS） on the oldest ice core, and thus has aroused wide public and scientific interest. Since 2004/2005, many glaciological investigations have been conducted in this region. These have included GPS and ground-penetrating radar surveys, snow pit and ice core drilling, stake network measurements, and meteorological observations. In this article, the main results of these glaciological investigations in the Dome A region are summarized. We present details of the surface mass balance on different timescales and its spatial variability, geochemical characteristics of the surface snow, and paleo-environment reconstruction of ice cores. Finally, perspectives on the prospects for future studies are suggested.

250 years of accumulation, oxygen isotope and chemical records in a firn core from Princess Elizabeth Land, East Antarctica

A 51.85-m tim core collected from site DT001 （accumulation rate 127 kgm^-2a^-1, mean annual temperature -33.1 ℃） on Princess Elizabeth Land, East Antarctica, during the 1996-97 Chinese First Antarctic Inland Expedition has been analyzed for chemical composition and oxygen isotope ratio. A comparison between the seasonal variations of major ions was carried out in order to reduce the dating uncertainty, using the volcanic markers as time constrains. A deposition period of 251 years was determined. The calculated accumulation rates display an increasing trend before 1820, while after 1820, the trend of the accumulation is not obvious. Overall, temperature change in the region shows a slight increasing trend over the past 250 years. But, notably, a temperature decline of -2 ℃ is observed from 1860 to the present. This feature, at odds with the warming trend over the past century recorded in both hemispheres, likely reflects a regional characteristic related to the lack of a high latitude/low latitude link in the Southern Hemisphere circulation patterns. The results of the glaciochemical records of the firn core show that the mean concentrations of Cl^-, Na^＋ and Mg^2＋ are similar to those reported from other sites in East Antarctica. However, the mean concentration of Ca^2＋ is much higher than that reported from other regions, suggesting the influence of the strong local terrestrial sources in Princess Elizabeth Land. There is no evidence of a positive correlation between NO3^- concentrations and solar activity （11-year solar cycle and solar cycle length）, although solar proton events may account for some of the NO3^- peak values in the record.

Internal layering structure and subglacial conditions along a traverse line from Zhongshan Station to Dome A,East Antarctica,revealed by ground-based radar sounding

During the 21st Chinese National Antarctic Research Expedition(CHINARE 21,2004/05),a radar dataset was collected using a ground-based radar system,along a traverse line from Zhongshan Station to DT401(130 km from the Kunlun station).The internal layering structure and subglacial conditions were revealed along the radar profi le.Continuous internal layers,disturbed layers,and echo-free zones(EFZs)along the profi le were identifi ed and classifi ed,and the spatial distribution was presented.Based on recent surface ice velocity data,we found that the internal layers at a depth of 200-300 m in the upper ice sheet are continuous,smooth,and nearly parallel to the ice surface topography.In addition,the thick band of continuous layers changes little with increasing latitude.At depths below 300 m,the geometric structure of the internal layers and the vertical width of the EFZ band are infl uenced by the surface ice velocity and bed topography.The relatively high disturbance,layer discontinuity,and larger EFZ band width directly correspond to a higher surface ice velocity and a sharper bed topography.In particular,we found that at a depth of 650-950 km,the Lambert Glacier Rift in the Gamburtsev Mountains has a higher ice fl ow;moreover,the revealed internal layers are disturbed or broken,and the maximal vertical width of the EFZ band most likely exceeds 2000 m.