Polar Science最新文献

Antarctic krill (Euphausia superba), a typical aggregation species, is the keystone species in the Antarctic ecosystem and supports an important fishery in the Southern Ocean. The unique topographic conditions of this region provide an important habitat for krill, and it has therefore become a critical krill fishing ground. To investigate the factors affecting krill hotspot patterns in the central basin of the Bransfield Strait in autumn 2021, an area with a high level of krill biomass and a persistent fishing ground, we used Getis-Ord G_i* approach to perform a hotspot analysis of the spatial and temporal variability of krill distribution. From this analysis we examined the relationship between krill distribution in hotspot and coldspot areas and environment variables such as geospatial features and eddy kinetic energy. We found that environmental variables generally showed opposing trends for krill distribution at hot- and coldspot areas. Moreover, geospatial features, including the distance to 200m and 1000m isobaths and depth, may be the dominant factor determining krill habitat characteristics, and moderate levels of eddy kinetic energy were conducive to krill aggregation.

Changes in climate and environment can impact the sustainability of populations and biodiversity. Understanding population genetic diversity in the past and present can help us better predict species' responses to future environmental change. Antarctica has experienced drastic environmental change which threatens its biodiversity. In this study, we characterized the phylogeography and population genetic structure of Belgica antarctica, a wingless midge that is endemic to the western Antarctic Peninsula. This insect has adaptive features to withstand extremes in temperature, salinity, humidity, anoxia and pH. Belgica antarctica is widespread on widely dispersed islands of ice-free habitat, but questions remain regarding its genetic history, diversity and gene flow. We created nuclear-based, single nucleotide polymorphism (SNP) markers and genotyped 229 individuals from 11 populations to examine historical and current population genetic patterns. Our results support recent divergence among populations on different islands within the last 1 Mya. Furthermore, despite a lack of wings, B. antarctica exhibited frequent migration among islands, perhaps via ocean currents or phoresy with Antarctic vertebrates (e.g. seabirds). The close link between the evolutionary history of B. antarctica and the region's environment and ecology emphasize the importance of understanding its population dynamics to predict its persistence under environmental change.

The Greenland ice sheet melting status is critical for global sea level rise and climate change. Based on the CryoSat-2 altimetry data from 2011 to 2021, the 5 km × 5 km DEMs of the Greenland ice sheet were derived by adopting the kriging interpolation method. Then the changes in elevation and volume of the ice sheet were calculated by using the intersection method. The changes in the ice sheet were analysed, and the results show that: (1) The accuracy of the Greenland DEMs obtained based on satellite altimetry data is region-dependent, with better accuracy in inland areas and higher elevation errors in marginal areas. (2) The inland area elevation remains unchanged basically or even shows an increasing trend, and there is an apparent melting trend in the marginal area, especially on the west coast. The contribution of the ice sheet melting mainly comes from elevations below 2000 m. (3) The main body of the Greenland ice sheet is melting with an elevation change rate of −13.27 ± 0.86 cm·a⁻¹ and a volume change rate of −202.47 ± 14.8 km³·a⁻¹. The rate of the Greenland ice sheet thinning has slowed down compared with the changes from 2003 to 2009.

Microplastics pollution in the oceans has become a new environmental threat in recent years. Microplastics have been found even in remote polar sea areas, including in water, sediment, sea ice, marine snow, and marine organisms in polar sea areas. Here, we reviewed 54 scientific studies on the distribution characteristics and pollution status of microplastics in polar oceans. We identified the potential sources and fates of microplastics in polar oceans. Microplastics in polar regions are mainly originated from the ocean current drift input, riverine input, fishing and shipping activities, microplastics emission in polar human settlements, and atmospheric migration. Microplastics have a potential to pose a threat on the polar marine organisms, and affect the stability of polar marine ecosystems. There is an urgent need further study to establish standardized methods and analysis processes and strengthen source control for microplastic pollution in polar oceans.

This paper reports how the World Data System International Technology Office (WDS-ITO) has contributed resources in the Polar Research Data Management community. The office has focused on federated search and data enhancement practices that bridge the gap between data holdings in the Arctic and Antarctic polar research communities and has built a shared catalog characterized by harmonized “dialects'' of metadata standards. The portal, referred to as the Polar Federated Search (PFS) site, is part of a larger set of WDS-ITO polar support activities and allows researchers to find data that has been published in multiple repositories serving both Arctic and Antarctic data (World Data System – International Technology Office, 2022). The portal provides federated search capability through a single interface. The PFS indexes repository landing pages that have been enriched with the addition of semantic markup marrying the best practices from the web publishing world with domain specific metadata. This technique leads to broader discovery, notably by Google Dataset Search, and better reuse of data repository holdings. Increasingly, the base ontology that has been adopted for use in these markup activities is Schema.org (SDO) a simple ontology developed in the commercial sector. This article outlines the steps and progressions made throughout the first year of PFS development, its highlights, and describes how these infrastructures move far beyond metadata discovery to include data integration, analysis, visualization and advanced, reproducible workflows.

Two funnel-and-gate permeable reactive barriers (PRBs) with settling ponds comprised of a composite liner (geomembrane and geosynthetic clay liners (GCL)) were installed at Resolution Island (BAF-5), Nunavut to contain residual polychlorinated biphenyls (PCBs) moving with the sediment and annual snowmelt. The long-term performance of the geosynthetics used in the PRB funnels is studied for physical integrity and diffusive barrier properties after nine years of operation. Exhumed geomembrane specimens are compared with virgin material by index testing: diffusive resistance to benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds, as well as puncture, burst, and tensile strength. Exhumed GCLs are evaluated concerning hydraulic conductivity, the mass of bentonite per unit area, and swell index. The migration of PCBs through the composite liner system by diffusion is modelled and the diffusive and sorptive properties of the geomembrane (D_g = 1.7 × 10⁻¹⁴ m²/s, S_gf = 160,000) and GCL (D_e = 3.1 × 10⁻¹⁰ m²/s, bentonite plus fibers layer K_d = 15 mL/g, cover geotextile K_d = 12,000 mL/g, and carrier geotextile K_d = 16,000 mL/g) were calculated. Modelling results estimate that the composite liner was successfully containing PCBs. This was confirmed by downgradient monitoring. The challenges of the location and terrain, PRB design, construction, and maintenance are discussed along with recommendations for designing PRBs in other remote and cold region environments.

Surface bio-optical constituents (Chl-a, light-absorption coefficient of phytoplankton (a_ph (443)), detritus (a_d(443)), coloured dissolved organic matter (a_CDOM(443))), and hydrographic variables were studied across the fronts along 57.5°E during 2011, 2013 and 2015 in the Indian sector of Southern Ocean to understand their interannual variability and phytoplankton pigment package effect. Latitudinal increases of Chl-a, a_ph(443), and a_CDOM(443) were observed in 2011 and 2013. Mean Chl-a was higher in 2013 than in 2015 and 2011. The Chl-a specific absorption (a*_ph(443)) latitudinally decreased implying ‘pigment package effect’ with increasing latitude. Interannually increase of a_ph blue (443)/red (675) ratio suggested higher non-photosynthetic absorption during 2013 and 2015 than in 2011. The relative contributions of bio-optical constituents to total absorption (a_t) showed interannual decrease in a_ph(443) and increase in a_CDOM(443) and a_d(443) inferring phytoplankton growth and decay phases. The robust a_ph(443)-Chl-a relationship during 2011 was used to derive a_ph(443) for other years, which holds good for in situ and satellite-derived counterparts. a_CDOM(443) positively correlated with Chl-a and negatively with CDOM-spectral slope (S_300-500), suggesting autochthonous sources. Satellite-retrieved Chl-a, a_ph(443) showed significant correlation (p < 0.001) with in situ data. This study provides baseline bio-optical data for understanding phytoplankton size-class, and improvement of bio-optical algorithms in this relatively inaccessible polar region.

Liquid clouds scatter the downward shortwave radiation more than ice clouds, which modulates the surface heat budget. Therefore, a better representation of the cloud phase in climate models, validated by observations, is needed to improve future projections. A ceilometer is a land-based observation system for clouds. This study focused on a new lidar ceilometer with a depolarization function (Vaisala CL61) for distinguishing cloud phases. The data were compared with cloud particle sensor (CPS) sondes at Kitami City in Japan in March 2022. Multiple layers characterized one case with smaller liquid water content at the lower boundary layer, while the other case was a deep liquid cloud layer case with more liquid water content at the cloud bottom. The linear depolarization ratios were well matched in both observing systems. The CL61 detected the signal below the first layer with the amount of liquid water content at 0.4 g m⁻³ (or bottom of the layer with 0.4 g m⁻³).

The 2020 summer season had more frequent than usual occurrences of noctilucent clouds (NLCs) in the Northern Hemisphere at middle latitudes (45–50°N), with the lowest latitude at which NLCs were seen being 34.1°N. In order to investigate a reason for this extraordinary NLC season, we have analyzed long-term Aura/MLS satellite data for all available summer periods from 2005 to 2021. Both Aura/MLS summer temperature and water vapor in the mesopause region, between about 79 and 89 km altitude, have been considered. There has been a decrease in the summer mesopause temperature between 2016 and 2020. At the same time, water vapor mixing ratio has significantly increased (by about 12–17%) in the zonal mean H₂O value in the 2020 summer compared to 2017. There exists a positive linear trend in the H₂O amount by about 5% between 2005 and 2021 at middle latitudes 45–50°N at 0.0046 hPa. A combination of lower mesopause temperature and water vapor mixing ratio maximum at middle latitudes is the main reason for frequent and widespread occurrences of NLCs seen around the globe at middle latitudes in the summer of 2020. The 24th solar cycle minimum can explain neither the H₂O maximum nor NLC maximum in 2020.

Autonomous sondes are used to study the Antarctic subglacial environment, yet they risk of being frozen in ice due to heating failure. To recover an accidently frozen sonde this paper describes a concept for a hot-water rescue ice drilling system. A special hot-water drill tool was designed to drill downward along the cable/sonde and melt surrounding ice. Theoretical estimation indicated the power system needed to provide hot water at a flow rate of 25 L/min and a pressure of more than 4.2 MPa to release the sonde at ice depth of 500 m. Laboratory testing and field testing near the Chinese Zhongshan Station in Antarctica demonstrated rationality of the concept. Potential risks were estimated and corresponding solutions presented. The hot-water rescue ice drilling system mentioned in the paper provides a safety guarantee for subglacial lake successful exploration, furthermore supports more ideas for future ice sheet exploration.