30 June 2023, Volume 34 Issue 2

    

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  Advances in Polar Science. 2023, 34(2): 67.

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Reviews
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  Arctic summertime anticyclonic circulation mode and its influence on substantial sea ice depletion: a review

  BI Haibo, LIANG Xi, LEI Ruibo, HU Mengqi, WEI Shuo

  Advances in Polar Science. 2023, 34(2): 67-79. https://doi.org/10.12429/j.advps.2022.0053

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  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.
Articles
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  Modified Circumpolar Deep Water inflow to the Dotson- Getz Trough in the summers of 2020 and 2022

  XIE Chunhu, SHI Jiuxin, SUN Yongming, JIANG Jindong, Guy D. WILLIAMS, SHUAI Hongtao, LIN Lijin, XIAO Changhao, CAO Yong, WANG Kun

  Advances in Polar Science. 2023, 34(2): 80-90. https://doi.org/10.12429/j.advps.2023.0102

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  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.
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  Mesozooplankton distribution and diversity from the Bering Sea shelf to the Chukchi Sea

  XU Zhiqiang, WANG Chaofeng, CHAO Yuan, WAN Aiyong & ZHANG Guangtao

  Advances in Polar Science. 2023, 34(2): 91-104. https://doi.org/10.12429/j.advps.2022.0054

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  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.
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  Nitrogen transformation processes in soil along a High Arctic tundra transect 

  GUO Mengjie, WANG Qing, ZHANG Wanying, JIAO Yi, SUN Bowen, HOU Lijun, ZHU Renbin

  Advances in Polar Science. 2023, 34(2): 105-124. https://doi.org/10.12429/j.advps.2022.0057

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  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 ) 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  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.
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  Investigating the impact of atmospheric parameters on sea ice variability in and around Svalbard

  Dency V PANICKER, Bhasha VACHHARAJANI& Rohit SRIVASTAVA

  Advances in Polar Science. 2023, 34(2): 125-143. https://doi.org/10.12429/j.advps.2022.0050

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  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.
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  Evolution and impacts of the United States’ Arctic strategy and China’s responses

  LIAO Junjie, PAN Min

  Advances in Polar Science. 2023, 34(2): 144-152. https://doi.org/10.12429/j.advps.2023.0107

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  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.
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  Call for Papers: Special Issue “Past and Present Climatic Change in Antarctica”

  Advances in Polar Science. 2023, 34(2): 153-153.

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  The main purpose of this issue is to provide new information and reviews on climate changes in Antarctica. We welcome the submission of manuscripts on the following but not limited topics: 
  (1) Geological, paleontological, and biological contributions that reveal paleoclimates and paleoecosystems.
  (2) Responses of populations and ecosystems to climate and environmental change.
  (3) Recent techniques and networks for environmental observations.
  
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  Eleven “Opinion Editorials” were published since its introduction

  Advances in Polar Science. 2023, 34(2): 154-154.

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