In the last decade, the atmospheric part of the climate system experienced a shift from pronounced zonal to stronger meridional flow configurations and regionally diverse changes and trends. The climate system shows c...In the last decade, the atmospheric part of the climate system experienced a shift from pronounced zonal to stronger meridional flow configurations and regionally diverse changes and trends. The climate system shows complex interactions and nonlinear behavior, manifested in global warming, rising ocean temperatures and the retreat of Arctic sea ice. Although atmospheric trends and changes are observed, underlying processes are not well understood. In this study we diagnose the interaction of large-scale atmospheric eddies and the mean flow with respect to diabatic heating and cooling processes that impact on the atmospheric advection of heat. For this purpose, three-dimensional Eliassen-Palm flux theory is used in combination with an analysis of the thermodynamic equation, diabatic heating and cooling and heat advection. The most recent decades of observed winter climate are evaluated in terms of climatology and trends over the Atlantic, Arctic and Eurasia. The change of the atmospheric circulation and related processes differ between early and late winter. In early winter, the interaction of macro-turbulent eddies with the mean flow is inhibited at the Atlantic jet stream entrance region and atmospheric heat is meridionally advected into the Arctic, both related to strong high pressure anomalies. In late winter, these anomalies are inverted and a negative phase of the Arctic Oscillation with a more wavy mean flow and a tendency towards stronger meridionalization is observed.展开更多
Surface albedo is defined as the ratio of incident and reflected solar irradiance and describes the ability of a surface to reflect, rather than absorb incident solar shortwave radiation. It is thus a crucial paramete...Surface albedo is defined as the ratio of incident and reflected solar irradiance and describes the ability of a surface to reflect, rather than absorb incident solar shortwave radiation. It is thus a crucial parameter in the climate system, particularly in the polar oceans. Sea ice albedo is a main driver for light transmission into the polar oceans and thus has a high impact on ocean warming, ice melting and marine primary production. During spring and summer, sea ice albedo can exhibit a significant spatial variability caused by meltwater accumulations on the ice. While complex and expensive solutions for albedo measurements are already available, we want to present a simple open-source design that allows for affordable mapping of spatially varying surface albedo on sea ice and beyond. Our solution is based on off-the-shelf components, such as an Arduino microcontroller integrating affordable light sensors, a GPS unit, data recording on memory card and data display into a simple field strengthened unit. We provide example data from two Arctic field deployments showing the capabilities and limitations of this system.展开更多
In recent decades, significant changes of Arctic sea ice have taken place. These changes are expected to influence the surface energy balance of the ice-covered Arctic Ocean. To quantify this energy balance and to inc...In recent decades, significant changes of Arctic sea ice have taken place. These changes are expected to influence the surface energy balance of the ice-covered Arctic Ocean. To quantify this energy balance and to increase our understanding of mechanisms leading to observed changes in the Arctic sea ice, the project ＂Advancing Modelling and Observing solar Radiation of Arctic sea ice--understanding changes and processes （AMORA）＂ was initiated and conducted from 2009 to 2013. AMORA was funded and organized under a frame of Norway-China bilateral collaboration program with partners from Finland, Germany, and the USA. The primary goal of the project was achieved by developing an autonomous spectral radiation buoy, deploying it on drifting sea ice close to the North Pole, and receiving a high-resolution time series of spectral radiation over and under sea ice from spring （before melt onset） to autumn （after freeze-up） 2012. Beyond this, in-situ sea ice data were collected during several field campaigns and simulations of snow and sea ice thermodynamics were performed. More autonomous measurements are available through deployments of sea ice mass balance buoys. These new observational data along with numerical model studies are helping us to better understand the key thermodynamic processes of Arctic sea ice and changes in polar climate. A strong scientific, but also cultural exchange between Norway, China, and the partners from the USA and Europe initiated new collaborations in Arctic reseach.展开更多
The Polar Regions play an important role in the global processes of our planet, from climate change to sea level rise, protection from UV （ultraviolet） radiation to uptake of carbon dioxide. In addition, their scien...The Polar Regions play an important role in the global processes of our planet, from climate change to sea level rise, protection from UV （ultraviolet） radiation to uptake of carbon dioxide. In addition, their scientific importance, extraordinary beauty and adventurous history provide perfect ingredients for both education and public outreach.Polar examples provide an excellent way to transmit basic concepts about a wide range of STEM （science, technology, engineering and mathematics） disciplines. The IPY （International Polar Year） brought educators and scientists together and provided the incentive for the formation of the PEI （Polar Educators International）, an organization encouraging the exchange of ideas between educators and researchers and enhancement of the profile of polar education on the international scene. Educators must be adequately informed about current scientific polar research and have the confidenceto teach it to students. Scientists have the knowledge and data to explain these complexities, but may lack the communication skills to make the subject accessible to non-technical audiences. The development of this new network between polar educators and scientists has the potential to break down walls that restrict international collaboration and understanding, provide educators with topical and reliable information and share best practices internationally in an effective way.展开更多
Overconsolidation ratio(OCR)is an important geotechnical parameter that plays a crucial role in the analysis and design of foundations and structures on clay deposits.In this study,five machine learning(ML)algorithms,...Overconsolidation ratio(OCR)is an important geotechnical parameter that plays a crucial role in the analysis and design of foundations and structures on clay deposits.In this study,five machine learning(ML)algorithms,including gradient boosting machine(GBM),random forest(RF),artificial neural network(ANN),support vector machine(SVM),and eXtreme gradient boosting(XGB)were developed to estimate the OCR of clays based on the piezocone penetration test data.The‘GridSearchCV’function from the Scikit-learn package was employed to perform hyper-parameter tuning and k-fold cross-validation,ensuring the best possible model performance.Vertical total stress(σ_(v0)),hydrostatic pore water pressure(u_(0)),corrected cone resistance(q_(t)),pore pressure elements at the cone tip(u_(1)),and above the cone base(u_(2)),along with the type of clay(intact or fissured)were selected as the main features of input data.Sensitivity analysis revealed that qt was the most influential parameter for RF,GBM,XGB,and SVM predictions,while all inputs affected the ANN model.It was found that the SVM model delivered the lowest accuracy in predicting OCR.In contrast,the XGB model showed the best performance,while the remaining models achieved reliable results,each with a coefficient of determination of 0.90 or higher.展开更多
We used in situ measurements and remote-sensing data sets to evaluate the mass budgets of the Lambert, Mellor and Fisher Glaciers and the basal melting and freezing rates beneath their flowbands on the Amery Ice Shelf...We used in situ measurements and remote-sensing data sets to evaluate the mass budgets of the Lambert, Mellor and Fisher Glaciers and the basal melting and freezing rates beneath their flowbands on the Amery Ice Shelf. Our findings show the Lambert and Mellor Glaciers upstream of the ANARE Lambert Glacier Basin (LGB) traverse may have positive imbalances of 3.9±2.1 Gt a-1 and 2.1±2.4 Gt a-1, respectively, while the Fisher Glacier is approximately in balance. The upstream region as a whole has a positive imbalance of 5.9±4.9 Gt a-1. The three same glaciers downstream of the ANARE LGB traverse line are in negative imbalance, where the whole downstream region has a negative imbalance of -8.5±5.8 Gt a-1. Overall the mass budgets of the Lambert, Mellor, and Fisher Glaciers are close to bal-ance, and the collective three-glacier system is also nearly in balance with a mass budget of -2.6±6.5 Gt a-1. The significant positive imbalances for the interior basin upstream of the ice-movement stations established in the early 1970s (GL line) reported previously are possibly due to an overestimate of the total accumulation and an underestimate of the ice flux through the GL line. The mean melting rate is -23.0±3.5 m ice a-1 near the southern grounding line, which decreases rapidly downstream, and transitions to refreezing at around 300 km from the southern extremity of the Amery Ice Shelf. Freezing rates along the flowbands are around 0.5±0.1 to 1.5±0.2 m ice a-1. The per-centage of ice lost from the interior by basal melting beneath the flowbands is about 80%±5%. The total basal melting and refreezing beneath the three flowbands is 50.3±7.5 Gt ice a-1 and 7.0±1.1 Gt ice a-1, respectively. We find a much larger total basal melting and net melting than the results for the whole Amery Ice Shelf derived from previous modeling and oceanographic measurements.展开更多
Rapid declines in Arctic sea ice have captured attention and pose significant challenges to a variety of stakeholders. There is a rising demand for Arctic sea ice prediction at daily to seasonal time scales, which is ...Rapid declines in Arctic sea ice have captured attention and pose significant challenges to a variety of stakeholders. There is a rising demand for Arctic sea ice prediction at daily to seasonal time scales, which is partly a sea ice initial condition problem. Thus, a multivariate data assimilation that integrates sea ice observations to generate realistic and skillful model initialization is needed to improve predictive skill of Arctic sea ice. Sea ice data assimilation is a relatively new research area. In this review paper, we focus on two challenges for implementing multivariate data assimilation systems for sea ice forecast. First, to address the challenge of limited spatiotemporal coverage and large uncertainties of observations, we discuss sea ice parameters derived from satellite remote sensing that(1) have been utilized for improved model initialization, including concentration, thickness and drift, and(2) are currently under development with the potential for enhancing the predictability of Arctic sea ice, including melt ponds and sea ice leads. Second, to strive to generate the ‘‘best" estimate of sea ice initial conditions by combining model simulations/forecasts and observations, we review capabilities and limitations of different data assimilation techniques that have been developed and used to assimilate observed sea ice parameters in dynamical models.展开更多
Plastic pollution is a planetary level threat which affects Earth’s environment and ecosystems.From the poles to deep ocean basins,the growth of plastic waste has already exceeded its limits.The projected increase of...Plastic pollution is a planetary level threat which affects Earth’s environment and ecosystems.From the poles to deep ocean basins,the growth of plastic waste has already exceeded its limits.The projected increase of plastic production and waste generation over the coming years makes the situation even more daunting.Even after stagnation in 2020 due to the COVID-19 pandemic,the global plastic production has also increased from 335 to 391 million metric tons(Mt)between 2016 and 2021(Fig.S1 online);yet currently post-consumer recycled and bio-based/attributed plastics only accounts~9%of the world’s plastic production[1].Statistically.展开更多
基金supported by the project “QUAntifying Rapid Climate Change in the Arctic: regional feedbackS and large-scale impacts” (QUARCCS) funded by the German Federal Ministry for Education and Research (BMBF) under grant agreement 03F0777Aby the Helmholtz Climate Initiative REKLIM
文摘In the last decade, the atmospheric part of the climate system experienced a shift from pronounced zonal to stronger meridional flow configurations and regionally diverse changes and trends. The climate system shows complex interactions and nonlinear behavior, manifested in global warming, rising ocean temperatures and the retreat of Arctic sea ice. Although atmospheric trends and changes are observed, underlying processes are not well understood. In this study we diagnose the interaction of large-scale atmospheric eddies and the mean flow with respect to diabatic heating and cooling processes that impact on the atmospheric advection of heat. For this purpose, three-dimensional Eliassen-Palm flux theory is used in combination with an analysis of the thermodynamic equation, diabatic heating and cooling and heat advection. The most recent decades of observed winter climate are evaluated in terms of climatology and trends over the Atlantic, Arctic and Eurasia. The change of the atmospheric circulation and related processes differ between early and late winter. In early winter, the interaction of macro-turbulent eddies with the mean flow is inhibited at the Atlantic jet stream entrance region and atmospheric heat is meridionally advected into the Arctic, both related to strong high pressure anomalies. In late winter, these anomalies are inverted and a negative phase of the Arctic Oscillation with a more wavy mean flow and a tendency towards stronger meridionalization is observed.
基金the Alfred-Wegener-Institut Helmholtz-Zentrum für Polar und Meeresforschungthe Helmholtz infrastructure initiative “Frontiers in Arctic marine Monitoring” (FRAM) for funding this projectfunded by a Sentinel North Postdoctoral Research Fellowship at Université Laval, Canada
文摘Surface albedo is defined as the ratio of incident and reflected solar irradiance and describes the ability of a surface to reflect, rather than absorb incident solar shortwave radiation. It is thus a crucial parameter in the climate system, particularly in the polar oceans. Sea ice albedo is a main driver for light transmission into the polar oceans and thus has a high impact on ocean warming, ice melting and marine primary production. During spring and summer, sea ice albedo can exhibit a significant spatial variability caused by meltwater accumulations on the ice. While complex and expensive solutions for albedo measurements are already available, we want to present a simple open-source design that allows for affordable mapping of spatially varying surface albedo on sea ice and beyond. Our solution is based on off-the-shelf components, such as an Arduino microcontroller integrating affordable light sensors, a GPS unit, data recording on memory card and data display into a simple field strengthened unit. We provide example data from two Arctic field deployments showing the capabilities and limitations of this system.
基金supported by the Research Council of Norway through AMORA (grant 193592)the Norwegian Polar Institute (NPI) and its Center for Ice, Climate and Ecosystems (ICE)support came from all partner institutes:Alfred-Wegener-Institut Helmholtz-Zentrum für Polarund Meeresforschung,Polar Research Institute of China,Dalian University of Technology(Grant no.NSFC41376186),Finnish Meteorological Institute, and the Cold Regions Research and Engineering Laboratory
文摘In recent decades, significant changes of Arctic sea ice have taken place. These changes are expected to influence the surface energy balance of the ice-covered Arctic Ocean. To quantify this energy balance and to increase our understanding of mechanisms leading to observed changes in the Arctic sea ice, the project ＂Advancing Modelling and Observing solar Radiation of Arctic sea ice--understanding changes and processes （AMORA）＂ was initiated and conducted from 2009 to 2013. AMORA was funded and organized under a frame of Norway-China bilateral collaboration program with partners from Finland, Germany, and the USA. The primary goal of the project was achieved by developing an autonomous spectral radiation buoy, deploying it on drifting sea ice close to the North Pole, and receiving a high-resolution time series of spectral radiation over and under sea ice from spring （before melt onset） to autumn （after freeze-up） 2012. Beyond this, in-situ sea ice data were collected during several field campaigns and simulations of snow and sea ice thermodynamics were performed. More autonomous measurements are available through deployments of sea ice mass balance buoys. These new observational data along with numerical model studies are helping us to better understand the key thermodynamic processes of Arctic sea ice and changes in polar climate. A strong scientific, but also cultural exchange between Norway, China, and the partners from the USA and Europe initiated new collaborations in Arctic reseach.
文摘The Polar Regions play an important role in the global processes of our planet, from climate change to sea level rise, protection from UV （ultraviolet） radiation to uptake of carbon dioxide. In addition, their scientific importance, extraordinary beauty and adventurous history provide perfect ingredients for both education and public outreach.Polar examples provide an excellent way to transmit basic concepts about a wide range of STEM （science, technology, engineering and mathematics） disciplines. The IPY （International Polar Year） brought educators and scientists together and provided the incentive for the formation of the PEI （Polar Educators International）, an organization encouraging the exchange of ideas between educators and researchers and enhancement of the profile of polar education on the international scene. Educators must be adequately informed about current scientific polar research and have the confidenceto teach it to students. Scientists have the knowledge and data to explain these complexities, but may lack the communication skills to make the subject accessible to non-technical audiences. The development of this new network between polar educators and scientists has the potential to break down walls that restrict international collaboration and understanding, provide educators with topical and reliable information and share best practices internationally in an effective way.
文摘Overconsolidation ratio(OCR)is an important geotechnical parameter that plays a crucial role in the analysis and design of foundations and structures on clay deposits.In this study,five machine learning(ML)algorithms,including gradient boosting machine(GBM),random forest(RF),artificial neural network(ANN),support vector machine(SVM),and eXtreme gradient boosting(XGB)were developed to estimate the OCR of clays based on the piezocone penetration test data.The‘GridSearchCV’function from the Scikit-learn package was employed to perform hyper-parameter tuning and k-fold cross-validation,ensuring the best possible model performance.Vertical total stress(σ_(v0)),hydrostatic pore water pressure(u_(0)),corrected cone resistance(q_(t)),pore pressure elements at the cone tip(u_(1)),and above the cone base(u_(2)),along with the type of clay(intact or fissured)were selected as the main features of input data.Sensitivity analysis revealed that qt was the most influential parameter for RF,GBM,XGB,and SVM predictions,while all inputs affected the ANN model.It was found that the SVM model delivered the lowest accuracy in predicting OCR.In contrast,the XGB model showed the best performance,while the remaining models achieved reliable results,each with a coefficient of determination of 0.90 or higher.
基金Sponsored by the NASA’s Polar Oceans and Ice Sheets Program, the National Natu-ral Science Foundation of China (Grant Nos. 40471028, 40231013 and 40476005)the Shu Guang Project supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation (Grant No. 05SG46)
文摘We used in situ measurements and remote-sensing data sets to evaluate the mass budgets of the Lambert, Mellor and Fisher Glaciers and the basal melting and freezing rates beneath their flowbands on the Amery Ice Shelf. Our findings show the Lambert and Mellor Glaciers upstream of the ANARE Lambert Glacier Basin (LGB) traverse may have positive imbalances of 3.9±2.1 Gt a-1 and 2.1±2.4 Gt a-1, respectively, while the Fisher Glacier is approximately in balance. The upstream region as a whole has a positive imbalance of 5.9±4.9 Gt a-1. The three same glaciers downstream of the ANARE LGB traverse line are in negative imbalance, where the whole downstream region has a negative imbalance of -8.5±5.8 Gt a-1. Overall the mass budgets of the Lambert, Mellor, and Fisher Glaciers are close to bal-ance, and the collective three-glacier system is also nearly in balance with a mass budget of -2.6±6.5 Gt a-1. The significant positive imbalances for the interior basin upstream of the ice-movement stations established in the early 1970s (GL line) reported previously are possibly due to an overestimate of the total accumulation and an underestimate of the ice flux through the GL line. The mean melting rate is -23.0±3.5 m ice a-1 near the southern grounding line, which decreases rapidly downstream, and transitions to refreezing at around 300 km from the southern extremity of the Amery Ice Shelf. Freezing rates along the flowbands are around 0.5±0.1 to 1.5±0.2 m ice a-1. The per-centage of ice lost from the interior by basal melting beneath the flowbands is about 80%±5%. The total basal melting and refreezing beneath the three flowbands is 50.3±7.5 Gt ice a-1 and 7.0±1.1 Gt ice a-1, respectively. We find a much larger total basal melting and net melting than the results for the whole Amery Ice Shelf derived from previous modeling and oceanographic measurements.
基金supported by the National Key R&D Program of China (2018YFA0605901)the NOAA Climate Program Office (NA15OAR4310163)+1 种基金the National Natural Science Foundation of China (41676185)and the Key Research Program of Frontier Sciences of Chinese Academy of Sciences (QYZDY-SSW-DQC021)
文摘Rapid declines in Arctic sea ice have captured attention and pose significant challenges to a variety of stakeholders. There is a rising demand for Arctic sea ice prediction at daily to seasonal time scales, which is partly a sea ice initial condition problem. Thus, a multivariate data assimilation that integrates sea ice observations to generate realistic and skillful model initialization is needed to improve predictive skill of Arctic sea ice. Sea ice data assimilation is a relatively new research area. In this review paper, we focus on two challenges for implementing multivariate data assimilation systems for sea ice forecast. First, to address the challenge of limited spatiotemporal coverage and large uncertainties of observations, we discuss sea ice parameters derived from satellite remote sensing that(1) have been utilized for improved model initialization, including concentration, thickness and drift, and(2) are currently under development with the potential for enhancing the predictability of Arctic sea ice, including melt ponds and sea ice leads. Second, to strive to generate the ‘‘best" estimate of sea ice initial conditions by combining model simulations/forecasts and observations, we review capabilities and limitations of different data assimilation techniques that have been developed and used to assimilate observed sea ice parameters in dynamical models.
基金supported by the National Natural Science Foundation of China(42322105 and 42071082)the National Key Research and Development Program of China(2020YFA0608503)+5 种基金the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0605)State Key Laboratory of Cryospheric Science(SKLCS-ZZ-2023)Gansu Provincial Science and Technology Program(22ZD6FA005)Longyuan and Outstanding YouthFund of Gansu Province(23JRRA612).supported by the European Union’s Horizon 2020 Research,Innovation Program under the Marie Sklodowska-Curie(101023635)Ocean Frontier Institute iPDF Canada First fund。
文摘Plastic pollution is a planetary level threat which affects Earth’s environment and ecosystems.From the poles to deep ocean basins,the growth of plastic waste has already exceeded its limits.The projected increase of plastic production and waste generation over the coming years makes the situation even more daunting.Even after stagnation in 2020 due to the COVID-19 pandemic,the global plastic production has also increased from 335 to 391 million metric tons(Mt)between 2016 and 2021(Fig.S1 online);yet currently post-consumer recycled and bio-based/attributed plastics only accounts~9%of the world’s plastic production[1].Statistically.
