The peer-reviewed journal Advances in Polar Science (APS) published Issue 35(3) in September 2024. This issue covers seven articles, the titles and highlights of which are presented below. All papers published on APS could be accessible and downloaded free of charge. See more details via APS website: aps.chinare.org.cn.

Picture: Cover of Issue 35(3)

(1) Recent advances in studies on changes in Arctic sea ice microstructure and implications to thermodynamic modeling

The study of Arctic sea ice has traditionally been focused on large-scale such as reductions of ice coverage, thickness, volumes and sea ice regime shift. Research has primarily concentrated on the impact of large-scale external factors such as atmospheric and oceanic circulations, and solar radiation. Additionally, Arctic sea ice also undergoes rapid micro-scale evolution such as gas bubbles formation, brine pockets migration and massive formation of surface scattering layer. Field studies like CHINARE (2008–2018) and MOSAiC (2019–2020) have confirmed these observations, yet the full understanding of those changes remain insufficient and superficial. In order to cope better with the rapidly changing Arctic Ocean, this study reviews the recent advances in the microstructure of Arctic sea ice in both field observations and laboratory experiments, and looks forward to the future objectives on the microscale processes of sea ice. The significant porosity and the cyclical annual and seasonal shifts likely modify the ice’s thermal, optical, and mechanical characteristics, impacting its energy dynamics and mass balance. Current thermodynamic models, both single-phase and dual-phase, fail to accurately capture these microstructural changes in sea ice, leading to uncertainties in the results. The discrepancy between model predictions and actual observations strongly motivates the parameterization on the evolution in ice microstructure and development of next-generation sea ice models, accounting for changes in ice crystals, brine pockets, and gas bubbles under the background of global warming. It helps to finally achieve a thorough comprehension of Arctic sea ice changes, encompassing both macro and micro perspectives, as well as external and internal factors.

Citation:  Lu P, Yu M, Wang L, et al. Recent advances in studies on changes in Arctic sea ice microstructure and implications to thermodynamic modeling. Adv Polar Sci, 2024, 35(3): 281-288, doi: 10.12429/j.advps.2024.0013

(2) Measurement of solid precipitation and blowing snow: current status and challenges

In this article, the relevant instruments and techniques for measuring solid precipitation and blowing snow are reviewed, with a focus on the in situ instrument measurements. Moreover, a literature review and specific observation activities for solid precipitation are provided, the working principles of several instruments are introduced, and the advantages and disadvantages, measurement performance, and specific application scenarios of the instruments are evaluated. Currently, there are numerous solid precipitation measurement instruments available, and the standardization and sustainability of these measurements also need to be considered. The purpose of the review is not to be exhaustive but to provide readers with information on the current status of the development of relevant technologies and the prospects for their application in the polar regions.

Citation:  Pan R, Liu X C, Shi J Y. Pan R, Liu X C, Shi J Y. Measurement of solid precipitation and blowing snow: current status and challenges. Adv Polar Sci, 2024, 35(3): 289-302, doi: 10.12429/j.advps.2024.0008. Adv Polar Sci, 2024, 35(3): 289-302, doi: 10.12429/j.advps.2024.0008

(3) Brightness temperature simulation of subarctic lake-ice evolution by HIGHTSI and SMRT model

Microwave brightness temperature (TB) can be used to retrieve lake ice thickness in the Arctic and subarctic regions. However, the accuracy of the retrieval is affected by the physical properties of lake ice. To improve the understanding of how lake ice affects TB, numerical modeling was applied. This study combined a physical thermodynamic ice model HIGHTSI with a microwave radiation transfer model SMRT to simulate the TB and lake ice evolution in 2002–2011 in Hulun Lake, China. The reanalyzed meteorological data were used as atmospheric forcing. The ice season was divided into the growth period, the slow growth period, and the ablation period. The simulations revealed that TB was highly sensitive to ice thickness during the ice season, especially vertical polarization measurement at 18.7 GHz. The quadratic polynomial fit for ice thickness to TB outperformed the linear fit, regardless of whether lake ice contained bubbles or not. A comparison of the simulated TB with space-borne TB showed that the simulated TB had the best accuracy during the slow growth period, with a minimum RMSE of 4.6 K. The results were influenced by the bubble radius and salinity. These findings enhance comprehension of the interaction between lake ice properties (including ice thickness, bubbles, and salinity) and TB during ice seasons, offering insights to sea ice in the Arctic and subarctic freshwater observations.

Citation:  Zhang Y X, Qiu Y B, Peng C T, et al. Brightness temperature simulation of subarctic lake-ice evolution by HIGHTSI and SMRT model. Adv Polar Sci, 2024, 35(3): 303-323 doi:10.12429/j.advps.2024.0011

(4) Glacial lakes under climate change: the imperative for comparative studies of microbial carbon metabolism in the Qinghai-Xizang Plateau and the Arctic

Glacial lakes, intimately linked to glacier termini, are crucial landscape features of the Qinghai-Xizang Plateau (Qinghai-Tibet Plateau) and the Arctic. Climate warming has accelerated glacier retreat and the rapid expansion of glacial lakes in both regions. Despite being typically considered harsh environments, these lakes serve as vital reservoirs for microbial biodiversity and carbon metabolism. In the face of climate change, glacial lake ecosystems over the Qinghai-Xizang Plateau and the Arctic are undergoing unprecedented transformations. This opinion editorial highlights the significance of conducting research and establishing long-term monitoring programs focused on microbial carbon metabolism in these glacial lakes.

Citation:  Liu K S, Liu Y Q. Glacial lakes under climate change: the imperative for comparative studies of microbial carbon metabolism in the Qinghai-Xizang Plateau and the Arctic. Adv Polar Sci, 2024, 35(3): 324-326, doi: 10.12429/j.advps.2024.0024

(5) Distributions of dissolved oxygen and apparent oxygen utilization in the Cosmonaut Sea and Amundsen Sea in austral summer 2022

Dissolved oxygen (DO) and apparent oxygen utilization (AOU) are essential parameters for evaluating the impact of climate change on marine ecosystems. In this study, we utilized data on DO and AOU collected from the Amundsen Sea (western Antarctic) and the Cosmonaut Sea (eastern Antarctic) during the 38th Chinese National Antarctic Research Expedition, along with chlorophyll a (Chl a) data, to analyze the impact of primary production and the spatial distribution and structural features of water masses in these regions. The findings show that the standard deviation range of parallel DO samples is between 0.1 and 3.9 μmol·L⁻¹, meeting the precision criteria of the survey method. AOU values lower than 0.0 μmol·L⁻¹ were commonly observed in the surface waters of both regions, with the highest incidence in the polynya of Amundsen Sea, indicating a strong influence of high primary production. The Cosmonaut Sea exhibited the highest AOU values (higher than 160.0 μmol·L⁻¹) in the 75–500 m layer, while AOU value in the Amundsen Sea did not exceed 160.0 μmol·L⁻¹, suggesting potential upwelling of Circumpolar Deep Water to 100 m in the Cosmonaut Sea with minimal changes in its properties, whereas significant changes were noted in the properties of upwelling modified Circumpolar Deep Water in the Amundsen Sea. AOU values lower than 125.0 μmol·L⁻¹ were detected in the near-bottom waters of the Cosmonaut Sea, indicating the presence of Antarctic Bottom Water.

Citation:  Ding Y F, Zhu C F, Zhang C, et al. Distributions of dissolved oxygen and apparent oxygen utilization in the Cosmonaut Sea and Amundsen Sea in austral summer 2022. Adv Polar Sci, 2024, 35(3): 327-369, doi: 10.12429/j.advps.2024.0018

(6) Distribution and abundance of krill in various areas of the Southern Ocean: dataset compilation based on samples collected in CHINARE during 2009–2019

This study investigates the composition, abundance, and basic biological parameters of krill in Prydz Bay, Antarctic Peninsula and Amundsen Sea by analyzing samples and environmental data from the Chinese National Antarctic Research Expeditions conducted between 2009/2010 and 2019/2020. The predominant krill species observed were Euphausia superba, Euphausia crystallorophias, and Thysanoessa macrura. T. macrura, although the most widespread, exhibited the lowest mean abundance (9.96 ind·(1000 m^–3)) and biomass (0.31 g·(1000 m^–3)), predominantly found in low-latitude regions of the Amundsen Sea while E. crystallorophias was most concentrated in polynyas of Prydz Bay. E. superba, with an average abundance of 34.05 ind·(1000 m^–3) and biomass of 11.80 g·(1000 m^–3), was mainly distributed in the Antarctic Peninsula and Prydz Bay. This study also identified regional variations in mean body length and frequency distributions of krill. The relationship between krill body length and wet weight followed a power-law pattern. Regional differences were observed in the relationship between krill abundance, biomass, and environmental factors with varying correlations. In the Amundsen Sea, no significant correlation was found between krill abundance and environmental factors. Notably, E. crystallorophias in Prydz Bay demonstrated a significant positive correlation with chlorophyll a concentration, while T. macrura abundance and biomass in the Antarctic Peninsula exhibited a significant negative correlation with ice-free days. The findings contribute valuable regional data on krill distribution, abundance, and biomass in the Southern Ocean, serving as foundational information for the conservation of the Southern Ocean ecosystem and Antarctic krill fishery management on a circumpolar scale.

Citation:  Fang X Y, Hu S G, Wang Y Q, et al. Distribution and abundance of krill in various areas of the Southern Ocean: dataset compilation based on samples collected in CHINARE during 2009–2019. Adv Polar Sci, 2024, 35(3): 370-384, doi: 10.12429/j.advps.2024.0007    

(7) Diversity and interactions of lichen mycobionts and photobionts in the Fildes Region, King George Island, maritime Antarctica

Lichens, as dual organisms comprising a major mycobiont and a major photobiont, exhibit remarkable survival capabilities in extreme conditions, such as those found in Antarctica. Despite their adaptability, the diversity and distribution of lichen photobionts in the ice-free areas of maritime Antarctica remain less understood compared to their mycobiont counterparts. In our study, we investigated the diversity of both lichen mycobionts and photobionts in 56 samples collected from the Fildes Region on King George Island, maritime Antarctica. Through sequencing of the nuclear ribosomal internal transcribed spacer regions and subsequent phylogenetic analysis, we examined the relationships and association patterns between mycobionts and photobionts. Our findings revealed 19 taxa of lichen mycobionts across 13 families and seven orders, along with nine photobiont species within the class Trebouxiophyceae. These photobionts encompassed six Trebouxia species, one Asterochloris species, one Chloroidium species, and one Stichococcus species. In particular, a new Trebouxia lineage (Trebouxia sp. OTU D08) and a new Chloroidium lineage were found. The analysis indicated that many mycobionts could be associated with multiple photobiont species, a pattern also observed among the photobionts. These results contribute significantly to our understanding of the complex diversity of lichen mycobionts and photobionts in the ice-free areas of maritime Antarctica.

Citation:  Zhu Y W, Yu L Y, Zhang T. Diversity and interactions of lichen mycobionts and photobionts in the Fildes Region, King George Island, maritime Antarctica. Adv Polar Sci, 2024, 35(3): 385-399, doi: 10.12429/j.advps.2024.0004