This study assesses sea ice thickness(SIT)from the historical run of the Coupled Model Inter-comparison Project Phase 6(CMIP6).The SIT reanalysis from the Pan-Arctic Ice Ocean Modeling and Assimilation System(PIOMAS)p...This study assesses sea ice thickness(SIT)from the historical run of the Coupled Model Inter-comparison Project Phase 6(CMIP6).The SIT reanalysis from the Pan-Arctic Ice Ocean Modeling and Assimilation System(PIOMAS)product is chosen as the validation reference data.Results show that most models can adequately reproduce the climatological mean,seasonal cycle,and long-term trend of Arctic Ocean SIT during 1979-2014,but significant inter-model spread exists.Differences in simulated SIT patterns among the CMIP6 models may be related to model resolution and sea ice model components.By comparing the climatological mean and trend for SIT among all models,the Arctic SIT change in different seas during 1979-2014 is evaluated.Under the scenario of historical radiative forcing,the Arctic SIT will probably exponentially decay at-18%(10 yr)-1 and plausibly reach its minimum(equilibrium)of 0.47 m since the 2070s.展开更多
The Arctic sea-ice cover has decreased in extent,area,and thickness over the last six decades.Most global climate models project that the summer sea-ice extent(SIE)will decline to less than 1 million(mill.)km^(2) in t...The Arctic sea-ice cover has decreased in extent,area,and thickness over the last six decades.Most global climate models project that the summer sea-ice extent(SIE)will decline to less than 1 million(mill.)km^(2) in this century,ranging from 2030 to the end of the century,indicating large uncertainty.However,some models,using the same emission scenarios as required by the Paris Agreement to keep the global temperature below 2°C,indicate that the SIE could be about 2 mill.km^(2) in 2100 but with a large uncertainty of±1.5 mill.km^(2).Here,the authors take another approach by exploring the direct relationship between the SIE and atmospheric CO_(2) concentration for the summer-fall months.The authors correlate the SIE and In(CO_(2)/CO_(2)r)during the period 1979-2022,where CO_(2)r is the reference value in 1979.Using these transient regression equations with an R2 between 0.78 and 0.87,the authors calculate the value that the CO_(2) concentration needs to reach for zero SIE.The results are that,for July,the CO_(2) concentration needs to reach 691±16.5 ppm,for August 604±16.5 ppm,for September 563±17.5 ppm,and for October 620±21 ppm.These values of CO_(2)for an ice-free Arctic are much higher than the targets of the Paris Agreement,which are 450 ppm in 2060 and 425 ppm in 2100,under the IPCC SSP1-2.6 scenario.If these targets can be reached or even almost reached,the "no tipping point"hypothesis for the summer SIE may be valid.展开更多
China launched its Arctic research program and organized the first Chinese National Arctic Research Expedition (CHINARE-Arctic) in 1999. By 2016, six further expeditions had been conducted using the R/V Xuelong. The...China launched its Arctic research program and organized the first Chinese National Arctic Research Expedition (CHINARE-Arctic) in 1999. By 2016, six further expeditions had been conducted using the R/V Xuelong. The main region of the expeditions has focused on the Pacific sector of the Arctic Ocean for sea ice observations. The expeditions have used icebreaker, helicopter, boat, floe, and buoy platforms to perform these observations. Some new technologies have been developed, in particular, the underway auto-observing system for sea ice thickness using an electromagnetic instrument. The long-term measurement systems, e.g., the sea ice mass balance buoy, allow observations to extend from summer to winter. Some international cooperation projects have been involved in CHINARE-Arctic, especially the "Developing Arctic Modeling and Observing Capabilities for Long-Term Environmental Studies" project funded by the European Union during the International Polar Year. Arctic sea ice observations have been used to verify remote sensing products, identify changes in Arctic sea ice, optimize the parameterizations of sea ice physical processes, and assess the accessibility of ice-covered waters, especially around the Northeast Passage. Recommendations are provided as guidance to future CHINARE-Arctic projects. For example, a standardized operation system of sea ice observations should be contracted, and the observations of sea ice dynamics should be enhanced. The upcoming launch of a new Chinese icebreaker will allow increased ship time in support of future CHINARE Arctic oceanographic investigations.展开更多
Changes in the climate of the Arctic and of the Antarctic have been of great concern to the international scientific and social communities since the release in 2007 of the Intergovernmental Panel on Climate Change Fo...Changes in the climate of the Arctic and of the Antarctic have been of great concern to the international scientific and social communities since the release in 2007 of the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4). Since then, many new findings have been reported from observations and research carried out in the Arctic and Antarctic during the fourth International Polar Year (IPY). There is evidence that global warming is inducing rapid changes in the Arctic and Antarctic, in both a quantitative and qualitative sense, and that these regional changes could be used as indicators of global climate change. Declining Arctic sea ice could affect winter snowfall across much of the Northern Hemisphere by bringing harsher winters. Projections suggest that summertime Arctic sea ice will disappear by 2037. By the 2070s, the Antarctic ozone hole will recover to the level of the early 1980s, following the ban on the production of Freon earlier this century. With the loss of the shielding effect of the ozone hole, Antarctic surface temperatures will increase, ice sheets in East Antarctica will begin to melt, and the Antarctic sea ice will retreat. Therefore, sea level rise will become an increasingly serious issue this century. As sea surface temperature rises, the Southern Ocean will become less effective as a sink for atmospheric CO2 and the increase of surface CO2 will be faster than that in the atmosphere. Increased surface CO2 would lead to ocean acidification and affect ecological systems and food chains.展开更多
A regional sea ice-ocean coupled model for the Arctic Ocean was developed, based on the MlTgcm ocean circulation model and classical Hibler79 type two category thermodynamics-dynamics sea ice model.The sea ice dynamic...A regional sea ice-ocean coupled model for the Arctic Ocean was developed, based on the MlTgcm ocean circulation model and classical Hibler79 type two category thermodynamics-dynamics sea ice model.The sea ice dynamics and thermodynamics were considered based on Viscous-Plastic(VP) and Winton three-layer models,respectively.A detailed configuration of coupled model has been introduced.Special attention has been paid to the model grid setup,subgrid paramerization,ice-ocean coupling and open boundary treatment.The coupled model was then applied and two test run examples were presented.The first model run was a climatology simulation with 10 years(1992—2002) averaged NCAR/NCEP reanalysis data as atmospheric forcing.The second model run was a seasonal simulation for the period of 1992—2007.The atmospheric forcing was daily NCAR/NCEP reanalysis.The climatology simulation captured the general pattern of the sea ice thickness distribution of the Arctic,i.e.,the thickest sea ice is situated around the Canada Archipelago and the north coast of the Greenland. For the second model run,the modeled September Sea ice extent anomaly from 1992—2007 was highly correlated with the observations,with a linear correlation coefficient of 0.88.The minimum of the Arctic sea ice area in the September of 2007 was unprecedented.The modeled sea ice area and extent for this minimum was overestimated relative to the observations.However,it captured the general pattern of the sea ice retreat.展开更多
In the past 30 years,a large-scale change occurred in the Arctic climatic system,which had never been observed before 1980s.At the same time,the Arctic sea ice experienced a special evolution with more and more rapidl...In the past 30 years,a large-scale change occurred in the Arctic climatic system,which had never been observed before 1980s.At the same time,the Arctic sea ice experienced a special evolution with more and more rapidly dramatic declining.In this circumstance,the Arctic sea ice became a new focus of the Arctic research.The recent advancements about abrupt change of the Arctic sea ice are reviewed in this paper.The previous analyses have demonstrated the accelerated declining trend of Arctic sea ice extent in the past 30 years,based on in-situ and satellite-based observations of atmosphere,as well as the results of global and regional climate simulations.Especially in summer,the rate of decrease for the ice extents was above 10% per decade.In present paper,the evolution characteristics of the arctic sea ice and its possible cause are discussed in three aspects,i.e.the sea ice physical properties,the interaction process of sea ice,ocean and atmosphere and its response and feedback mechanism to global and arctic climate system.展开更多
Sea ice cover plays an important role in modulating local temperature through heat and moisture fuxes.The infuence of thin ice lead and polynya has been wellinvestigated,however,the effect of perennial ice(also called...Sea ice cover plays an important role in modulating local temperature through heat and moisture fuxes.The infuence of thin ice lead and polynya has been wellinvestigated,however,the effect of perennial ice(also called muliyear ice,MYI)has not.This study is motivated by it and investigated a hypothesis that changes in MYI concentration in winter triggers changes in short-term local 2-m air temperature.The hypothesis was tested using time series analysis of the two parameters and correlation between them.Data from the winters of 2004-2009 were used for the examination at three spatial scales.The hypothesis is found to be potentially accepted when MYI exists in a consolidated ice regime with negligible thin ice or open water in the surroundings,and the air temperature is low enough.Conditions for the acceptance of the hypothesis were quantitatively identified.The qualifications entail that the ice cell must experience daily change of MYI concentration meanwhile satisfy the criteria of total ice concentration(TIC),young ice concentration(YIC)and air temperature(Tar)in the surrounding area,which are TIC>88.3%,YIC<9.5%and T_(air)<-19.0℃.Inverse relationships between changes in MYI concentration and the corresponding changes in air temperature were developed retroactively using data that satisfied the acceptance conditions.The relationships varied with years,depending on ice conditions such as ice type distributions and snow cover.This study offers a first attempt to assess the effect of MYI on the same-day local surface air temperature using satelite observations,and provides evidence of this effect under quantitatively quanlifying conditions.展开更多
Sea ice,one of the most dominant barriers to Arctic shipping,has decreased dramatically over the past four decades.Arctic maritime transport is hereupon growing in recent years.To produce a long-term assessment of tra...Sea ice,one of the most dominant barriers to Arctic shipping,has decreased dramatically over the past four decades.Arctic maritime transport is hereupon growing in recent years.To produce a long-term assessment of trans-Arctic accessibility,we systematically revisit the daily Arctic navigability with a view to the combined effects of sea ice thickness and concentration throughout the period 1979−2020.The general trends of Navigable Windows(NW)in the Northeast Passage show that the number of navigable days is steadily growing and reached 89±16 days for Open Water(OW)ships and 163±19 days for Polar Class 6(PC6)ships in the 2010s,despite high interannual and interdecadal variability in the NWs.More consecutive NWs have emerged annually for both OW ships and PC6 ships since 2005 because of the faster sea ice retreat.Since the 1980s,the number of simulated Arctic routes has continuously increased,and optimal navigability exists in these years of record-low sea ice extent(e.g.,2012 and 2020).Summertime navigability in the East Siberian and Laptev Seas,on the other hand,varies dramatically due to changing sea ice conditions.This systematic assessment of Arctic navigability provides a reference for better projecting the future trans-Arctic shipping routes.展开更多
Arctic sea ice has significant seasonal variability. Prior to the 2000 s, it retreated about 15% in summer and fully recovered in winter. However, by the year 2007, Arctic sea ice extent experienced a catastrophic dec...Arctic sea ice has significant seasonal variability. Prior to the 2000 s, it retreated about 15% in summer and fully recovered in winter. However, by the year 2007, Arctic sea ice extent experienced a catastrophic decline to about 4.28×10^6 km^2, which was 50% lower than conditions in the 1950 s to the 1970 s(Serreze et al., 2008). That was a record low over the course of the modern satellite record, since 1979(note that the year 2012 became the new record low). This astonishing event drew wide-ranging attention in 2007-2009 during the 4 th International Polar Year. The dramatic decline of sea ice attracts many scientists’ interest and has become the focus of intense research since then. Currently, sea ice retreat is not only appearing around the marginal ice zone, but also in the pack ice inside the central Arctic(Zhao et al., 2018). In fact, premonitory signs had already been seen through other evidence. Before the disintegration of the Soviet Union, US naval submarines had been conducting an extensive survey under the sea ice and taking measurements of sea ice thickness. Their measurements revealed a gradual decrease of ice thickness to 1.8 m during winter by the end of the 20 th century, in contrast to the climatological mean of 3.1 m(Rothrock et al., 1999). However, this alarming result did not draw much attention since the Arctic was still severely cold at that time.展开更多
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
基金the National Natural Science Foundation of China(Grant Nos.41922044 and 41941009)the National Key R&D Program of China(Grant No.2019YFA0607004 and 2022YFE0106300)+1 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2020B1515020025 and 2019A1515110295)the Norges Forskningsråd(Grant No.328886).
文摘This study assesses sea ice thickness(SIT)from the historical run of the Coupled Model Inter-comparison Project Phase 6(CMIP6).The SIT reanalysis from the Pan-Arctic Ice Ocean Modeling and Assimilation System(PIOMAS)product is chosen as the validation reference data.Results show that most models can adequately reproduce the climatological mean,seasonal cycle,and long-term trend of Arctic Ocean SIT during 1979-2014,but significant inter-model spread exists.Differences in simulated SIT patterns among the CMIP6 models may be related to model resolution and sea ice model components.By comparing the climatological mean and trend for SIT among all models,the Arctic SIT change in different seas during 1979-2014 is evaluated.Under the scenario of historical radiative forcing,the Arctic SIT will probably exponentially decay at-18%(10 yr)-1 and plausibly reach its minimum(equilibrium)of 0.47 m since the 2070s.
基金funding support from the Nansen Scientific Society.
文摘The Arctic sea-ice cover has decreased in extent,area,and thickness over the last six decades.Most global climate models project that the summer sea-ice extent(SIE)will decline to less than 1 million(mill.)km^(2) in this century,ranging from 2030 to the end of the century,indicating large uncertainty.However,some models,using the same emission scenarios as required by the Paris Agreement to keep the global temperature below 2°C,indicate that the SIE could be about 2 mill.km^(2) in 2100 but with a large uncertainty of±1.5 mill.km^(2).Here,the authors take another approach by exploring the direct relationship between the SIE and atmospheric CO_(2) concentration for the summer-fall months.The authors correlate the SIE and In(CO_(2)/CO_(2)r)during the period 1979-2022,where CO_(2)r is the reference value in 1979.Using these transient regression equations with an R2 between 0.78 and 0.87,the authors calculate the value that the CO_(2) concentration needs to reach for zero SIE.The results are that,for July,the CO_(2) concentration needs to reach 691±16.5 ppm,for August 604±16.5 ppm,for September 563±17.5 ppm,and for October 620±21 ppm.These values of CO_(2)for an ice-free Arctic are much higher than the targets of the Paris Agreement,which are 450 ppm in 2060 and 425 ppm in 2100,under the IPCC SSP1-2.6 scenario.If these targets can be reached or even almost reached,the "no tipping point"hypothesis for the summer SIE may be valid.
基金supported financially by grants from the National Natural Science Foundation of China (Grant no. 41476170)National Key Research and Development Program of China (Grant no. 2016YFC1400300)Chinese Polar Environment Comprehensive Investigation and Assessment Program (Grant nos. CHINARE03-01/04-02/04-04)
文摘China launched its Arctic research program and organized the first Chinese National Arctic Research Expedition (CHINARE-Arctic) in 1999. By 2016, six further expeditions had been conducted using the R/V Xuelong. The main region of the expeditions has focused on the Pacific sector of the Arctic Ocean for sea ice observations. The expeditions have used icebreaker, helicopter, boat, floe, and buoy platforms to perform these observations. Some new technologies have been developed, in particular, the underway auto-observing system for sea ice thickness using an electromagnetic instrument. The long-term measurement systems, e.g., the sea ice mass balance buoy, allow observations to extend from summer to winter. Some international cooperation projects have been involved in CHINARE-Arctic, especially the "Developing Arctic Modeling and Observing Capabilities for Long-Term Environmental Studies" project funded by the European Union during the International Polar Year. Arctic sea ice observations have been used to verify remote sensing products, identify changes in Arctic sea ice, optimize the parameterizations of sea ice physical processes, and assess the accessibility of ice-covered waters, especially around the Northeast Passage. Recommendations are provided as guidance to future CHINARE-Arctic projects. For example, a standardized operation system of sea ice observations should be contracted, and the observations of sea ice dynamics should be enhanced. The upcoming launch of a new Chinese icebreaker will allow increased ship time in support of future CHINARE Arctic oceanographic investigations.
基金supported by the National Natural Science Foundation of China (Grant nos.40531007,41230529)the National High-tech Research & Development Program of China (Grant no.2008AA121703)+3 种基金the International Cooperation Project supported by Ministry of Science and Technology of China (Grant no.2009DFA22920)the International Cooperation Project supported by Chinese Arctic and Antarctic Administration (Grant nos.IC201013,IC201114,IC201201,and IC201308)the Chinese Polar Environmental Comprehensive Investigation and Assessment Programs (Grant nos.CHINARE2012-01-04-02,CHINARE2012-02-01,and CHINARE2012-03-04-02)the Ocean Public Welfare Scientific Research Project of China (Grant no.2004DIB5J178)
文摘Changes in the climate of the Arctic and of the Antarctic have been of great concern to the international scientific and social communities since the release in 2007 of the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4). Since then, many new findings have been reported from observations and research carried out in the Arctic and Antarctic during the fourth International Polar Year (IPY). There is evidence that global warming is inducing rapid changes in the Arctic and Antarctic, in both a quantitative and qualitative sense, and that these regional changes could be used as indicators of global climate change. Declining Arctic sea ice could affect winter snowfall across much of the Northern Hemisphere by bringing harsher winters. Projections suggest that summertime Arctic sea ice will disappear by 2037. By the 2070s, the Antarctic ozone hole will recover to the level of the early 1980s, following the ban on the production of Freon earlier this century. With the loss of the shielding effect of the ozone hole, Antarctic surface temperatures will increase, ice sheets in East Antarctica will begin to melt, and the Antarctic sea ice will retreat. Therefore, sea level rise will become an increasingly serious issue this century. As sea surface temperature rises, the Southern Ocean will become less effective as a sink for atmospheric CO2 and the increase of surface CO2 will be faster than that in the atmosphere. Increased surface CO2 would lead to ocean acidification and affect ecological systems and food chains.
基金supported by the National Science and Technology Support Program of China(Grants No.2006BAB18B03)the Polar Science Strategic Research Foundation of China(Grants No.20080223)
文摘A regional sea ice-ocean coupled model for the Arctic Ocean was developed, based on the MlTgcm ocean circulation model and classical Hibler79 type two category thermodynamics-dynamics sea ice model.The sea ice dynamics and thermodynamics were considered based on Viscous-Plastic(VP) and Winton three-layer models,respectively.A detailed configuration of coupled model has been introduced.Special attention has been paid to the model grid setup,subgrid paramerization,ice-ocean coupling and open boundary treatment.The coupled model was then applied and two test run examples were presented.The first model run was a climatology simulation with 10 years(1992—2002) averaged NCAR/NCEP reanalysis data as atmospheric forcing.The second model run was a seasonal simulation for the period of 1992—2007.The atmospheric forcing was daily NCAR/NCEP reanalysis.The climatology simulation captured the general pattern of the sea ice thickness distribution of the Arctic,i.e.,the thickest sea ice is situated around the Canada Archipelago and the north coast of the Greenland. For the second model run,the modeled September Sea ice extent anomaly from 1992—2007 was highly correlated with the observations,with a linear correlation coefficient of 0.88.The minimum of the Arctic sea ice area in the September of 2007 was unprecedented.The modeled sea ice area and extent for this minimum was overestimated relative to the observations.However,it captured the general pattern of the sea ice retreat.
基金support for this research is provided by National Key Natural ScienceFoundation(Grants No.40930848)National Science and Technology Supporting Item(Grants No.2006BAB18B03)+1 种基金National High Technology Research and Development Pro-gram 863(Grants No.2008AA121704)the National Natural Foundation of China(Grants No.40906099)
文摘In the past 30 years,a large-scale change occurred in the Arctic climatic system,which had never been observed before 1980s.At the same time,the Arctic sea ice experienced a special evolution with more and more rapidly dramatic declining.In this circumstance,the Arctic sea ice became a new focus of the Arctic research.The recent advancements about abrupt change of the Arctic sea ice are reviewed in this paper.The previous analyses have demonstrated the accelerated declining trend of Arctic sea ice extent in the past 30 years,based on in-situ and satellite-based observations of atmosphere,as well as the results of global and regional climate simulations.Especially in summer,the rate of decrease for the ice extents was above 10% per decade.In present paper,the evolution characteristics of the arctic sea ice and its possible cause are discussed in three aspects,i.e.the sea ice physical properties,the interaction process of sea ice,ocean and atmosphere and its response and feedback mechanism to global and arctic climate system.
基金supported by the National Key Research and Development Program of China(2019YFC1509104)National Natural Science Foundation of China(42106225,41976214).
文摘Sea ice cover plays an important role in modulating local temperature through heat and moisture fuxes.The infuence of thin ice lead and polynya has been wellinvestigated,however,the effect of perennial ice(also called muliyear ice,MYI)has not.This study is motivated by it and investigated a hypothesis that changes in MYI concentration in winter triggers changes in short-term local 2-m air temperature.The hypothesis was tested using time series analysis of the two parameters and correlation between them.Data from the winters of 2004-2009 were used for the examination at three spatial scales.The hypothesis is found to be potentially accepted when MYI exists in a consolidated ice regime with negligible thin ice or open water in the surroundings,and the air temperature is low enough.Conditions for the acceptance of the hypothesis were quantitatively identified.The qualifications entail that the ice cell must experience daily change of MYI concentration meanwhile satisfy the criteria of total ice concentration(TIC),young ice concentration(YIC)and air temperature(Tar)in the surrounding area,which are TIC>88.3%,YIC<9.5%and T_(air)<-19.0℃.Inverse relationships between changes in MYI concentration and the corresponding changes in air temperature were developed retroactively using data that satisfied the acceptance conditions.The relationships varied with years,depending on ice conditions such as ice type distributions and snow cover.This study offers a first attempt to assess the effect of MYI on the same-day local surface air temperature using satelite observations,and provides evidence of this effect under quantitatively quanlifying conditions.
基金the National Natural Science Foundation of China(No.41922044,41941009)the Guangdong Basic and Applied Basic Research Foundation(No.2020B1515020025)+1 种基金the fundamental research funds for the Norges Forskningsråd(No.328886)C Min acknowledges support from the China Scholarship Council(No.202006380131).
文摘Sea ice,one of the most dominant barriers to Arctic shipping,has decreased dramatically over the past four decades.Arctic maritime transport is hereupon growing in recent years.To produce a long-term assessment of trans-Arctic accessibility,we systematically revisit the daily Arctic navigability with a view to the combined effects of sea ice thickness and concentration throughout the period 1979−2020.The general trends of Navigable Windows(NW)in the Northeast Passage show that the number of navigable days is steadily growing and reached 89±16 days for Open Water(OW)ships and 163±19 days for Polar Class 6(PC6)ships in the 2010s,despite high interannual and interdecadal variability in the NWs.More consecutive NWs have emerged annually for both OW ships and PC6 ships since 2005 because of the faster sea ice retreat.Since the 1980s,the number of simulated Arctic routes has continuously increased,and optimal navigability exists in these years of record-low sea ice extent(e.g.,2012 and 2020).Summertime navigability in the East Siberian and Laptev Seas,on the other hand,varies dramatically due to changing sea ice conditions.This systematic assessment of Arctic navigability provides a reference for better projecting the future trans-Arctic shipping routes.
基金Funding was provided by Global Change Research Program of China (No. 2015CB953900)the Key Project of the National Natural Science Foundation of China (No. 41330960)
文摘Arctic sea ice has significant seasonal variability. Prior to the 2000 s, it retreated about 15% in summer and fully recovered in winter. However, by the year 2007, Arctic sea ice extent experienced a catastrophic decline to about 4.28×10^6 km^2, which was 50% lower than conditions in the 1950 s to the 1970 s(Serreze et al., 2008). That was a record low over the course of the modern satellite record, since 1979(note that the year 2012 became the new record low). This astonishing event drew wide-ranging attention in 2007-2009 during the 4 th International Polar Year. The dramatic decline of sea ice attracts many scientists’ interest and has become the focus of intense research since then. Currently, sea ice retreat is not only appearing around the marginal ice zone, but also in the pack ice inside the central Arctic(Zhao et al., 2018). In fact, premonitory signs had already been seen through other evidence. Before the disintegration of the Soviet Union, US naval submarines had been conducting an extensive survey under the sea ice and taking measurements of sea ice thickness. Their measurements revealed a gradual decrease of ice thickness to 1.8 m during winter by the end of the 20 th century, in contrast to the climatological mean of 3.1 m(Rothrock et al., 1999). However, this alarming result did not draw much attention since the Arctic was still severely cold at that time.
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.