1928 research outputs found
Sort by
Chemicals of Emerging Arctic Concern - Summary for Policy Makers
Get PDFThis policy summary refers to the most recent AMAP assessment which looks at a wide rang of chemicals newly and recently detected in Arctic ecosystems. These chemicals of emerging concern contribute to an even broader understanding of how Arctic pollution is changing, which is the primary focus of this summary document and the basis for the recommendations of the AMAP Working Group
Mechanisms associated with winter intraseasonal extreme sea ice extent in the Weddell Sea
Get PDFPrevious studies have shown evidence of atmospheric extratropical wave trains modulating sea ice area in the Weddell and Amundsen/Bellingshausen seas on intraseasonal time-scales (20–100 d). Here we investigate mechanisms relating intraseasonal extreme sea ice extent and Ekman layer dynamics with emphasis on the Weddell Sea. This study extends from 1989 to 2013 and focuses on the winter season. Wind stress τ is calculated with winds from the Climate Forecast System reanalysis (CFSR) to evaluate momentum transfer between the atmosphere and the Ekman layer. Lag-composites of the anomalies of Ekman transport and the Ekman pumping indicate that divergence of mass in the Ekman layer and upwelling lead the occurrence of extreme sea ice contraction on intraseasonal time-scales in the Weddell Sea. Opposite conditions (i.e., convergence of the mass and downwelling) lead extreme sea ice expansion on intraseasonal time-scales. This study suggests that the Ekman pumping resulting from the anomalous wind stress on intraseasonal time-scales can transport these warmer waters to the surface contributing to sea ice melting. Additionally, high resolution sea ice fraction and ocean currents obtained from satellite and in situ data are used to investigate in detail mechanisms associated with persistent extreme sea ice expansion and contraction on intraseasonal time-scales. These case studies reveal that atmospheric circumpolar waves on intraseasonal time-scales can induce contrasting anomalies of about ±20% in sea ice concentration at the Weddell and western Antarctica Peninsula margins within less than 30 d. This study shows that extreme anomalies in sea ice may lag between 5–25 d (1–5 pentads) the ocean-atmospheric forcing on intraseasonal
time-scales
Country Report 2017: Reports from the Adhering Bodies of the International Permafrost Association
Get PDFA network for long-term monitoring of vegetation in the area of Fildes Peninsula, King George Island
Get PDFClimate warming has become evident in the maritime Antarctic over the past decades, and has already influenced the growing season and the population size of two native vascular plants in Antarctica, Deschampsia antarctica and Colobanthus quitensis. Both vascular plant species are therefore regarded as good bioindicators of regional warming in west Antarctica. To carry out long-term monitoring of vegetation (mainly using D. antarctica) and build a comprehensive research platform for multi-disciplinary study (including botany, microbiology, ecology, and environmental science) for Chinese scientists, 13 permanent plots were established in January and February of 2013–2015 in the area of Fildes Peninsula (King George Island). Here we present the benchmark data of the first observations from these plots, including site characteristics, and the population and associates of D. antarctica in each plot. The basic data are important to understand the vegetation change, distribution range, and expansion of D. antarctica in Antarctica under future climate change scenarios
Comparison of two pretreatment methods for mercury stable isotope analysis in Antarctic moss
Get PDFMercury (Hg) stable isotope analysis can provide new insight for understanding the biogeochemistry and sources of Hg in the polar regions. To completely extract the low contents of Hg in polar samples and to avoid isotopic fractionation during the sample preparation stage, an effective and reliable pretreatment method is needed. In this work, two different pretreatment methods were compared for measuring Hg stable isotopes in Antarctic moss samples. One method was acid digestion (HNO3︰ H2O2=5︰3, v/v) and the second was a combustion-trapping treatment with a trapping solution (HNO3:HCl=2:1, v/v). There were no significant differences in the analytical results obtained with the two methods. The overall mean values and uncertainties of total Hg (THg) and the isotopic compositions of Hg in the referenced materials were all in good agreement with the certified and reported values, indicating that both methods were accurate and applicable. Acid digestion is highly efficient, while the combustion-trapping method can be used to treat samples with low Hg content. The proposed methods were successfully used to determine the Hg isotopic compositions in moss samples collected from the Antarctic
Advances in Chinese Arctic and subarctic research in marine biology and ecology with emphasis on the Pacific Arctic sector
Get PDFThe Arctic is one of the most sensitive regions that respond through feedback to global climate changes. Climatic, hydrological and ecological changes in the Arctic are clear evidence of global warming. In 2012 and 2014, the 5th and 6th Chinese National Arctic Research Expeditions undertook studies in the Bering Sea, the Arctic Ocean (including the Chukchi Sea), and the Norwegian Sea. These studies provided us with a better understanding of the marine biology and ecology in the Arctic and subarctic regions, particularly in the Pacific Arctic sector. Rapid changes observed in the Arctic environment include the shrinking of cold-water masses in the Bering Sea in the summer, and elevated water temperatures promoting phytoplankton blooms, leading to an increase in phytoplankton transferred to higher trophic levels. As a result, the transfer efficiency of organic matter toward the bottom weakened, leading to a reduction in benthic biomass. This is consistent with expectations that the overall carbon and energy flux will ultimately switch from the dominant mode of sea ice–algae–benthos to one of phytoplankton–zooplankton. Influenced by Pacific water inflow, fluvial runoff and melting sea ice, the Chukchi Sea exhibited different responses to various environmental changes. Interactions between water masses led to other interannual ecological shifts. With the increase in sea ice melt and sunlight in the central region of the Arctic Ocean, the relative abundance of heterotrophic bacteria is expected to increase, and play a vital role in the Arctic microbial loop
Sea ice classification in the Weddell Sea based on scatterometer data
Get PDFSea ice type is an important factor for accurately calculating sea ice parameters such as sea ice concentration, sea ice area and sea ice thickness using satellite remote sensing data. In this study, sea ice in the Weddell Sea was classified from scatterometer data by the histogram threshold method and the Spreen model method, and evaluated and validated with the Antarctic Sea Ice Processes and Climate (ASPeCt) sea ice type ship-based observations. The results show that the two methods can both distinguish multi-year (MY) ice and first-year (FY) ice during the ice growth season, and that the histogram threshold method has a relatively larger MY ice classification extent than the Spreen model. The classification accuracy of the histogram threshold method is 77.8%, while the Spreen model method accuracy is 80.3% compared with the ship-based observations, thus indicating that the Spreen model method is better for discriminating MY ice from FY ice from scatterometer data. These results provide a basis and reference for further retrieval of long-time sea ice type information for the whole Antarctica
Spatial variability in sea-ice algal biomass: an under-ice remote sensing perspective
Get PDFSea-ice algae are a paramount feature of polar marine ecosystems and ice algal standing stocks are characterized by a high spatio-temporal variability. Traditional sampling techniques, e.g., ice coring, are labor intensive, spatially limited and invasive, thereby limiting our understanding of ice algal biomass variability patterns. This has consequences for quantifying ice-associated algal biomass distribution, primary production, and detecting responses to changing environmental conditions. Close-range under-ice optical remote sensing techniques have emerged as a capable alternative providing non-invasive estimates of ice algal biomass and its spatial variability. In this review we first summarize observational studies, using both classical and new methods that aim to capture biomass variability at multiple spatial scales and identify the environmental drivers. We introduce the complex multi-disciplinary nature of under-ice spectral radiation profiling techniques and discuss relevant concepts of sea-ice radiative transfer and bio-optics. In addition, we tabulate and discuss advances and limitations of different statistical approaches used to correlate biomass and under-ice light spectral composition. We also explore theoretical and technical aspects of using Unmanned Underwater Vehicles (UUV), and Hyperspectral Imaging (HI) technology in an under-ice remote sensing context. The review concludes with an outlook and way forward to combine platforms and optical sensors to quantify ice algal spatial variability and establish relationships with its environmental drivers
GTN-P - Strategy and Implementation Plan 2016-2020
Get PDFPermafrost is recognized as Essential Climate Variable (ECV) within the Global Climate Observing System of UN and ICSU organisations. The Global Terrestrial Network for Permafrost (GTN-P) is the primary international programme concerned with long-term monitoring of permafrost. The core mission of the GTN-P is sustained comprehensive long-term monitoring network, in order to provide consistent, representative and high quality standardized long-term data series of selected permafrost parameters at key sites and to assess their state and changes over time. The Strategy and Implementation Plan 2016-2020 outlines recent progress and future challenges facing the network. It describes the governance and management structure of GTN-P, linkages to regional and global observing systems, management process and reporting strategies. It presents measurement methods and protocols used in field data collection and state of the art data management system, which was recently designed and implemented to process, analyse, and visualize permafrost data. It concludes with the outlook of the future developments of the network in order to sustain and succeed its core mission of providing long-term observations and maintain the availability of data collected
Determination of grounding line on the Amery Ice Shelf using Sentinel-1 radar interferometry data
Get PDFDelineation of the grounding line (GL) is necessary for calculating the mass balance of Antarctica, but GL measurements for most of the continent remain at a relatively coarse level. We used Sentinel-1 constellation data to map the GL of the Amery Ice Shelf (AIS) using double-differential synthetic aperture radar interferometry. The ice thickness anomaly deduced from hydrostatic equilibrium and existing Antarctic GL products is compared with our result. With this new and very accurate GL, we detected new ice rises in the north of the AIS. Our new measurement shows no major change of the AIS GL, particularly in the southernmost part