30 June 2024, Volume 35 Issue 2

    

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  Advances in Polar Science. 2024, 35(2): 142-142.

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Reviews
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  Pan-African metamorphism and magmatism in the Prydz Belt, East Antarctica: a geochronological perspective

  BAO Hong, WANG Wei-(RZ), LIU Xinshu, ZHAO Yue, GONG Tingnan, LIU Xiaochun, CUI Ying & TIAN Zuolin

  Advances in Polar Science. 2024, 35(2): 143-156. https://doi.org/10.12429/j.advps.2023.0023

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  The Prydz Belt in East Antarctica underwent extensive reworking during the late Neoprotertozoic–early Paleozoic Pan-African orogeny, which is characterized by granulite facies, clockwise P–T paths, and high dT/dP values. This study compiles the existing age and composition data of zircon and monazite from metamorphic rocks and links their key characteristics to the metamorphic evolution of the Prydz Belt. The frequency of zircon U–Pb ages starts to increase noticeably from ~555 Ma, peaking between 530 Ma and 520 Ma, followed by a dramatic decline after 520 Ma. High Th/U values (> 0.1) of zircon are observed from ~545 Ma, displaying a noticeable increasing trend in Th/U values before a rapid decline from ~520 Ma. The frequency of monazite ages progressively increases from ~540 Ma, reaching its peak at 515 Ma, and then rapidly decreases after 490 Ma. Combined with the crystallization behaviors of zircon and monazite, this study suggests that the systematic changes in Th/U values of zircon after 545 Ma indicate a transition in the thermal regime of the Prydz Belt towards the cooling stage. Abundant growth of zircon and monazite corresponds to the post-peak cooling process, while the crystallization peak of monazite lags behind that of zircon by ~5–15 Ma, which indicates a relatively low cooling rate. Though the granitic intrusions accompanied the entire metamorphic evolution, the majority of them are younger than 520 Ma. The results suggest that the Pan-African event likely peaked at ~555–545 Ma and gradually cooled to near-solidus conditions at ~520–510 Ma, with a relatively slow average cooling process.
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  Migration and role of zinc in biogeochemical cycles in the Antarctic Ice Sheet and the Southern Ocean

  Liu Jingwen, Li Chuanjin, DU Zhiheng, SHI Guitao, DING Minghu, SUN Bo & XIAO Cunde

  Advances in Polar Science. 2024, 35(2): 157-177. https://doi.org/10.12429/j.advps.2023.0032

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  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.
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  A progress review of black carbon deposition on Arctic snow and ice and its impact on climate change

  ZHANG Zilu, ZHOU Libo & ZHANG Meigen

  Advances in Polar Science. 2024, 35(2): 178-191. https://doi.org/10.12429/j.advps.2023.0024

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  The rapid warming of the Arctic, accompanied by glacier and sea ice melt, has significant consequences for the Earth’s climate, ecosystems, and economy. Black carbon (BC) deposition on snow and ice can trigger a significant reduction in snow albedo and accelerate melting of snow and ice in the Arctic. By reviewing the published literatures over the past decades, this work provides an overview of the progress in both the measurement and modeling of BC deposition and its impact on Arctic climate change. In summary, the maximum value of BC deposition appears in the western Russian Arctic (26 ng·g^–1), and the minimum value appears in Greenland (3 ng·g^–1). BC records in the Arctic ice core already peaked in 1920s and 1970s, and shows a regional difference between Greenland and Canadian Arctic. The different temporal variations of Arctic BC ice core records in different regions are closely related to the large variability of BC emissions and transportation processes across the Arctic region. Model simulations usually underestimate the concentration of BC in snow and ice by 2–3 times, and cannot accurately reflect the seasonal and regional changes in BC deposition. Wet deposition is the main removal mechanism of BC in the Arctic, and observations show different seasonal variations in BC wet deposition in Ny-Ålesund and Barrow. This discrepancy may result from varying contributions of anthropogenic and biomass burning (BB) emissions, given the strong influence by BC from BB emissions at Barrow. Arctic BC deposition significantly influences regional climate change in the Arctic, increasing fire activities in the Arctic have made BB source of Arctic BC more crucial. On average, BC in Arctic snow and ice causes an increase of +0.17 W·m^–2 in radiative forcing and 8 Gt·a^–1 in runoff in Greenland. As stressed in the latest Arctic Monitoring and Assessment Programme report, reliable source information and long-term and high-resolution observations on Arctic BC deposition will be crucial for a more comprehensive understanding and a better mitigation strategy of Arctic BC. In the future, it is necessary to collect more observations on BC deposition and the corresponding physical processes (e.g., snow/ice melting, surface energy balance) in the Arctic to provide reliable data for understanding and clarifying the mechanism of the climatic impacts of BC deposition on Arctic snow and ice.
Articles
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  Polymetamorphism of the ultrahigh-temperature granulites in the Rauer Group, East Antarctica: new evidence from zircon SHRIMP U-Pb ages

  TONG Laixi, LIU Zhao, LI Chao, LU Junsheng, YANG Wenqiang & WANG Yanbin

  Advances in Polar Science. 2024, 35(2): 192-206. https://doi.org/10.12429/j.advps.2024.0001

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  The Rauer Group is located on the eastern margin of the early Paleozoic Prydz Belt in East Antarctica, and the typical ultrahigh-temperature (UHT, >900 ℃) granulites outcrop on Mather Peninsula. However, the timing of UHT metamorphism and P–T path of the UHT granulites have long been debated, which is critical to understanding the tectonic nature and evolution history of the Prydz Belt. Thus, both a sapphirine-bearing UHT metapelitic granulite and a garnet-bearing UHT mafic granulite are selected for zircon SHRIMP U-Pb age dating. The results show that metamorphic zircon mantles yield weighted mean ²⁰⁶Pb/²³⁸U ages of 918±29 Ma and 901±29 Ma for the metapelitic and mafic granulites, respectively, while zircon rims and newly grown zircons yield weighted mean ²⁰⁶Pb/²³⁸U ages of 523±9 Ma and 532±11 Ma, respectively. These new zircon age data suggest that the UHT granulites may have experienced polymetamorphism, in which pre-peak prograde stage occurred in the early Neoproterozoic Grenvillian orogenesis (1000–900 Ma), whereas the UHT metamorphism occurred in the late Neoproterozoic to early Paleozoic Pan-African orogenesis (580–460 Ma). This implies that P–T path of the UHT granulites should consist of two separate high-grade metamorphic events including the Grenvillian and Pan-African events, which are supposed to be related to assembly of Rodinia and Gondwana supercontinents respectively, and hence the overprinting UHT metamorphic event may actually reflect an important intracontinental reworking.
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  Microscopic analysis on eukaryotic algae and cyanobacteria in nine seasonal lakes and ponds in Vestfjella, Dronning Maud Land, Antarctica

  Lauri ARVOLA, Matti LEPPÄRANTA& LI Zhijun

  Advances in Polar Science. 2024, 35(2): 206-218. https://doi.org/10.12429/j.advps.2023.0029

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  Antarctic continental lakes and ponds are among the most impoverished aquatic environments on earth but many of them support flourishing populations of cyanobacteria, eukaryotic algae, protozoans, and some multicellular animals. In this study, we present results of a microscopic analysis of cyanobacteria and eukaryotic algae from nine diverse types of Antarctic continental water bodies during one austral summer. The results supplement and enlarge our previous studies on the limnological characteristics of the epiglacial and supraglacial lakes and ponds in Dronning Maud Land, an area that has received little attention from limnologists. The taxon with highest frequency among the samples (n=79) was Mesotaenium cf. berggrenii, a eukaryotic Zygnematophyceae, which occurred in 82% of the samples with a maximum cell density of 68 cellsmL^–1 . The taxa with second and third highest frequency were the prokaryotes Gloeocapsopsis (60%) and Leptolyngbya (41%), followed by Chlamydomonas (34%) and Cyanothece (29%). The number of taxa varied between 7–21 among the lakes and ponds, being highest in a supraglacial lake, and lowest in an epiglacial lake. The results did not reveal any obvious correlation between the abundance of any taxa and the water chemistry, but water bodies with inorganic sediments had higher cell densities and biomasses than those without sediment. This suggests the importance of sediment in supporting biological diversity in these ultraoligotrophic lakes and ponds.
  
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  Antarctic red algae in dye-sensitized photoelectrochemical cells for water splitting 

  Florentina ARISPE & María Fernanda CERDÁ

  Advances in Polar Science. 2024, 35(2): 219-228. https://doi.org/10.12429/j.advps.2024.0005

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  Research and exploration of direct current power supply and distribution systems for Antarctic research stations

  WANG Lei

  Advances in Polar Science. 2024, 35(2): 228-237. https://doi.org/10.12429/j.advps.2023.0011

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  The power supply and distribution systems for Antarctic research stations have special characteristics. In light of a worldwide trend toward a gradual increase in the application of renewable energy, an analysis was performed to assess the feasibility of achieving a direct current power supply and distribution at Antarctic research stations by comparing the characteristics of direct current and alternating current electricity. Research was also performed on the status quo and future trends in direct current power supply and distribution systems in Antarctica research stations in combination with case studies.
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  Comparison of the precision of glacier flow rates derived from offset-tracking using Sentinel-2 and Landsat-8/9 imagery

  YANG Zhibin, CHEN Zhuoqi, LI Gang, MAO Yanting, FENG Xiaoman & CHENG Xiao

  Advances in Polar Science. 2024, 35(2): 238-251. https://doi.org/10.12429/j.advps.2023.0019

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  Offset-tracking is an essential method for deriving glacier flow rates using optical imagery. Sentinel-2 (S2) and Landsat-8/9 (L8/9) are popular optical satellites or constellations for polar studies, offering high spatial resolution with relatively short revisit time, wide swath width, and free accessibility. To evaluate and compare the precision of offset-tracking results yielded with these two kinds of data, in this study S2 and L8/9 imagery observed in Petermann Glacier in Greenland, Karakoram in High-Mountains Asia, and Amery Ice Shelf in the Antarctic are analyzed. Outliers and various systematic error sources in the offset-tracking results including orbital and strip errors were analyzed and eliminated at the pre-process stage. Precision at the off-glacier (bare rock) region was evaluated by presuming that no deformation occurred; then for both glacierized and the off-glacier regions, precision of velocity time series was evaluated based on error propagation theory. The least squares method based on connected components was used to solve flow rates time series based on multi-pair images offset-tracking. The results indicated that S2 achieved slightly higher precision than L8/9 in terms of both single-pair derived displacements and least square solved daily flow rates time series. Generally, the RMSE of daily velocity is 26% lower for S2 than L8/9. Moreover, S2 provided higher temporal resolution for monitoring glacier flow rates.
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  Methods for ice velocity mapping in West Antarctica using historical optical satellite images 

  ZHANG Yujie, AN Lu, TANG Leyue, LI Hongwei, HE Meixi & LI Rongxing

  Advances in Polar Science. 2024, 35(2): 253-263. https://doi.org/10.12429/j.advps.2024.0002

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  The Antarctic Ice Sheet harbors more than 90% of the Earth ice mass, with significant losses experienced through dynamic thinning, particularly in West Antarctica. The crucial aspect of investigating ice mass balance in historical periods preceding 1990 hinges on the utilization of ice velocities derived from optical satellite images. We employed declassified satellite images and Landsat images with normalized cross correlation based image matching, adopting an adaptive combination of skills and methods to overcome challenges encountered during the mapping of historical ice velocity in West Antarctica. A basin-wide synthesis velocity map encompassing the coastal regions of most large-scale glaciers and ice shelves in West Antarctica has already been successfully generated. Our results for historical ice velocities cover over 70% of the grounding line in most of the West Antarctic basins. Through adjustments, we uncovered overestimations in ice velocity measurements over an extended period, transforming our ice velocity map into a spatially deterministic, temporally average version. Among all velocity measurements, Thwaites Glacier exhibited a notable spatial variation in the fastest ice flowline and velocity distribution. Overestimation distributions on Thwaites Glacier displayed a clear consistency with the positions of subsequent front calving events, offering insights into the instabilities of ice shelves.
  
  
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  Promoting China-U.S. Arctic education cooperation: challenges, opportunities and recommendations

  HE Liu, SHAN Yanyan & LIU Feichao

  Advances in Polar Science. 2024, 35(2): 264-274. https://doi.org/10.12429/j.advps.2023.0017

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  Arctic education refers not only to the teaching, but also to research, communication, dissemination as well as popularization of knowledge related to the Arctic. This article reviews joint efforts between Chinese and American educators and researchers to promote cooperation and understanding in Arctic education and research, and examines the facing challenges of China-U.S. Arctic education cooperation which include current political or economic tensions between the two countries, the differing perspectives and priorities on Arctic policy, the disproportion in Arctic scientific research, different research methodologies and discourse system in social science. This article also argues that there are opportunities for the two countries to cooperate in Arctic education. Common goals and interests in the Arctic, Arctic-dedicated institutions with significant Arctic research capabilities and partnerships around the world provide foundations for Arctic education cooperation. The implementation of a new science-based Arctic treaty of the Arctic Council is an opportunity for China-U.S. Arctic education cooperation. As for future cooperation, it suggests that in addition to promoting the direct bilateral cooperation, cooperation within international cooperation platforms and mechanisms, especially within the Arctic Council also needs to be further promoted.
Letter & Trend
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  Some recent advances in remote sensing-based monitoring of changes in the Greenland Ice Sheet

  FENG Tiantian, JIA Jinyu, WANG Wei, YU Zeran, LIU Xingchen, LI Guojun, GU Yuanyuan & LI Rongxing

  Advances in Polar Science. 2024, 35(2): 275-280. https://doi.org/10.12429/j.advps.2023.0033

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  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.