The Arctic plays a fundamental role in the climate system and has shown significant climate change in recent decades,including the Arctic warming and decline of Arctic sea-ice extent and thickness. In contrast to the ...The Arctic plays a fundamental role in the climate system and has shown significant climate change in recent decades,including the Arctic warming and decline of Arctic sea-ice extent and thickness. In contrast to the Arctic warming and reduction of Arctic sea ice, Europe, East Asia and North America have experienced anomalously cold conditions, with record snowfall during recent years. In this paper, we review current understanding of the sea-ice impacts on the Eurasian climate.Paleo, observational and modelling studies are covered to summarize several major themes, including: the variability of Arctic sea ice and its controls; the likely causes and apparent impacts of the Arctic sea-ice decline during the satellite era,as well as past and projected future impacts and trends; the links and feedback mechanisms between the Arctic sea ice and the Arctic Oscillation/North Atlantic Oscillation, the recent Eurasian cooling, winter atmospheric circulation, summer precipitation in East Asia, spring snowfall over Eurasia, East Asian winter monsoon, and midlatitude extreme weather; and the remote climate response(e.g., atmospheric circulation, air temperature) to changes in Arctic sea ice. We conclude with a brief summary and suggestions for future research.展开更多
In contrast to previous studies that have tended to focus on the influence of the total Arctic sea-ice cover on the East Asian summer tripole rainfall pattern, the present study identifies the Barents Sea as the key r...In contrast to previous studies that have tended to focus on the influence of the total Arctic sea-ice cover on the East Asian summer tripole rainfall pattern, the present study identifies the Barents Sea as the key region where the June sea-ice variability exerts the most significant impacts on the East Asian August tripole rainfall pattern, and explores the teleconnection mechanisms involved. The results reveal that a reduction in June sea ice excites anomalous upward air motion due to strong near-surface thermal forcing, which further triggers a meridional overturning wave-like pattern extending to midlatitudes.Anomalous downward motion therefore forms over the Caspian Sea, which in turn induces zonally oriented overturning circulation along the subtropical jet stream, exhibiting the east–west Rossby wave train known as the Silk Road pattern. It is suggested that the Bonin high, a subtropical anticyclone predominant near South Korea, shows a significant anomaly due to the eastward extension of the Silk Road pattern to East Asia. As a possible descending branch of the Hadley cell, the Bonin high anomaly ultimately triggers a meridional overturning, establishing the Pacific–Japan pattern. This in turn induces an anomalous anticyclone and cyclone pair over East Asia, and a tripole vertical convection anomaly meridionally oriented over East Asia. Consequently, a tripole rainfall anomaly pattern is observed over East Asia. Results from numerical experiments using version 5 of the Community Atmosphere Model support the interpretation of this chain of events.展开更多
This study focuses on the climatic impacts of the Atlantic Multidecadal Oscillation (AMO) as a mode of internal vari- ability. Given the difficulties involved in excluding the effects of external forcing from intern...This study focuses on the climatic impacts of the Atlantic Multidecadal Oscillation (AMO) as a mode of internal vari- ability. Given the difficulties involved in excluding the effects of external forcing from internal variation, i.e., owing to the short record length of instrumental observations and historical simulations, we assess and compare the AMO and its related climatic impacts both in observations and in the "Pre-industrial" experiments of models participating in CMIP5. First, we evaluate the skill of the 25 CMIP5 models' "Historical" simulations in simulating the observational AMO, and find there is generally a considerable range of skill among them in this regard. Six of the models with higher skill relative to the other models are selected to investigate the AMO-related climate impacts, and it is found that their "Pre-industrial" simulations capture the essential features of the AMO. A positive AMO favors warmer surface temperature around the North Atlantic, and the Atlantic ITCZ shifts northward leading to more rainfall in the Sahel and less rainfall in Brazil. Furthermore, the results confirm the existence of a teleconnection between the AMO and East Asian surface temperature, as well as the late withdrawal of the Indian summer monsoon, during positive AMO phases. These connections could be mainly caused by internal climate variability. Opposite patterns are true for the negative phase of the AMO.展开更多
A simple air-sea coupled model, the atmospheric general circulation model (AGCM) of the National Centers for Environmental Prediction coupled to a mixed-layer slab ocean model, is employed to investigate the impact ...A simple air-sea coupled model, the atmospheric general circulation model (AGCM) of the National Centers for Environmental Prediction coupled to a mixed-layer slab ocean model, is employed to investigate the impact of air-sea coupling on the signals of the Atlantic Multidecadal Oscillation (AMO). A regional coupling strategy is applied, in which coupling is switched off in the extratropical North Atlantic Ocean but switched on in the open oceans elsewhere. The coupled model is forced with warm-phase AMO SST anomalies, and the modeled responses are compared with those from parallel uncoupled AGCM experiments with the same SST forcing. The results suggest that the regionally coupled responses not only resemble the AGCM simulation, but also have a stronger intensity. In comparison, the coupled responses bear greater similarity to the observational composite anomaly. Thus, air-sea coupling enhances the responses of the East Asian winter climate to the AMO. To determine the mechanism responsible for the coupling amplification, an additional set of AGCM experiments, forced with the AMO-induced tropical SST anomalies, is conducted. The SST anomalies are extracted from the simulated AMO-induced SST response in the regionally coupled model. The results suggest that the SST anomalies contribute to the coupling amplification. Thus, tropical air-sea coupling feedback tends to enhance the responses of the East Asian winter climate to the AMO.展开更多
A 600-year pre-industrial simulation with Bergen Climate Model(BCM)Version 2 is used to investigate the linkage between winter Arctic Oscillation(AO)and the Southeast Asian summer monsoon(SEASM)on the inter-decadal ti...A 600-year pre-industrial simulation with Bergen Climate Model(BCM)Version 2 is used to investigate the linkage between winter Arctic Oscillation(AO)and the Southeast Asian summer monsoon(SEASM)on the inter-decadal timescale.The results indicate an in-phase relationship between the AO and SEASM with periods of approximately 16–32 and 60–80 years.During the positive phase of winter AO,an anomalous surface anti-cyclonic atmosphere circulation appears over North Pacific in winter.The corresponding anomalies in ocean circulation and surface heat flux,particularly the latent and sensible heat flux,resemble a negative Pacific Decadal Oscillation(PDO)-like sea surface temperature(SST)pattern.The AO-associated PDO-like winter SST can persist into summer and can therefore lead to inter-decadal variability of summer monsoon rainfall in East and Southeast Asia.展开更多
A simple approach that considers both internal decadal variability and the effect of anthropogenic forcing is developed to predict the decadal components of global sea surface temperatures (SSTs) for the three decades...A simple approach that considers both internal decadal variability and the effect of anthropogenic forcing is developed to predict the decadal components of global sea surface temperatures (SSTs) for the three decades 2011-2040. The internal decadal component is derived by harmonic wave expansion analyses based on the quasiperiodic evolution of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO), as obtained from observational SST datasets. Furthermore, the external decadal component induced by anthropogenic forcing is assessed with a second-order fit based on the ensemble of projected SSTs in the experiments with multiple coupled climate models associated with the third Coupled Model Intercomparison Project (CMIP3) under the Intergovernmental Panels on Climate Change (IPCC) Special Reports on Emissions Scenario (SRES) A1B. A validation for the years from 2002 to 2010 based on a comparison of the predicted and the observed SST and their spatial correlation, as well as the root mean square error (RMSE), suggests that the approach is reasonable overall. In addition, the predicted results over the 50°S-50°N global band, the Indian Ocean, the western Pacific Ocean, the tropical eastern Pacific Ocean, and the North and the South Atlantic Ocean are presented.展开更多
In this paper, the dynamic effect of oceanic upwelling on the intensity of El Nio-Southern Oscillation (ENSO) is studied using a simple coupled model (Zebiak-Cane Model). The term balance analysis in the temperature...In this paper, the dynamic effect of oceanic upwelling on the intensity of El Nio-Southern Oscillation (ENSO) is studied using a simple coupled model (Zebiak-Cane Model). The term balance analysis in the temperature variability equation shows that the anomalous upwelling of the mean vertical temperature gradient and the mean advection of the anomalous meridional temperature gradient are the two of most important factors that determine the intensity of ENSO events, in which the "vertical oceanic heat flux" in the eastern equatorial Pacific (EEP) is the primary influencing factor. The lag correlation between "vertical heat flux (VHF)" and ENSO intensity shows that the highest correlation occurs when the former leads the latter by one to two weeks. The VHF is positively correlated with the background thermocline strength in the EEP, and an increase of both could result in strong ENSO variability. Comparison of the forced and coupled experiments suggests that the coupled process can affect both the intensity and frequency of ENSO.展开更多
To quantify the relative contributions of Arctic sea ice and unforced atmospheric internal variability to the “warm Arctic, cold East Asia”(WACE) teleconnection, this study analyses three sets of large-ensemble simu...To quantify the relative contributions of Arctic sea ice and unforced atmospheric internal variability to the “warm Arctic, cold East Asia”(WACE) teleconnection, this study analyses three sets of large-ensemble simulations carried out by the Norwegian Earth System Model with a coupled atmosphere–land surface model, forced by seasonal sea ice conditions from preindustrial, present-day, and future periods. Each ensemble member within the same set uses the same forcing but with small perturbations to the atmospheric initial state. Hence, the difference between the present-day(or future) ensemble mean and the preindustrial ensemble mean provides the ice-loss-induced response, while the difference of the individual members within the present-day(or future) set is the effect of atmospheric internal variability. Results indicate that both present-day and future sea ice loss can force a negative phase of the Arctic Oscillation with a WACE pattern in winter. The magnitude of ice-induced Arctic warming is over four(ten) times larger than the ice-induced East Asian cooling in the present-day(future) experiment;the latter having a magnitude that is about 30% of the observed cooling. Sea ice loss contributes about 60%(80%) to the Arctic winter warming in the present-day(future) experiment. Atmospheric internal variability can also induce a WACE pattern with comparable magnitudes between the Arctic and East Asia. Ice-lossinduced East Asian cooling can easily be masked by atmospheric internal variability effects because random atmospheric internal variability may induce a larger magnitude warming. The observed WACE pattern occurs as a result of both Arctic sea ice loss and atmospheric internal variability, with the former dominating Arctic warming and the latter dominating East Asian cooling.展开更多
基金the National Natural Science Foundation of China[Grants No.41991283]the Research Council of Norway Funded Project BASIC[Grant No.325440]Chinese-Norwegian Collaboration Projects Within Climate funded by the Research Council of Norway(COMBINED)[Grant No.328935].
基金supported by the Research Council of Norway through the Blue Arc project (207650/ E10)the European Union 7th Framework Programme (FP7 20072013) through the NACLIM project (308299)+1 种基金the National Natural Sciences Foundation of China through projects 41375083 and 41210007the Nord Forsk-funded project GREENICE (61841): Impacts of Sea-Ice and Snow-Cover Changes on Climate, Green Growth, and Society
文摘The Arctic plays a fundamental role in the climate system and has shown significant climate change in recent decades,including the Arctic warming and decline of Arctic sea-ice extent and thickness. In contrast to the Arctic warming and reduction of Arctic sea ice, Europe, East Asia and North America have experienced anomalously cold conditions, with record snowfall during recent years. In this paper, we review current understanding of the sea-ice impacts on the Eurasian climate.Paleo, observational and modelling studies are covered to summarize several major themes, including: the variability of Arctic sea ice and its controls; the likely causes and apparent impacts of the Arctic sea-ice decline during the satellite era,as well as past and projected future impacts and trends; the links and feedback mechanisms between the Arctic sea ice and the Arctic Oscillation/North Atlantic Oscillation, the recent Eurasian cooling, winter atmospheric circulation, summer precipitation in East Asia, spring snowfall over Eurasia, East Asian winter monsoon, and midlatitude extreme weather; and the remote climate response(e.g., atmospheric circulation, air temperature) to changes in Arctic sea ice. We conclude with a brief summary and suggestions for future research.
基金supported by the National Key R&D Program of China(Grant No.2016YFA0600703)the National Natural Science Foundation of China(Grant Nos.41605059,41505073 and 41375083)+1 种基金the Young Talent Support Program of the China Association for Science and Technology(Grant No.2016QNRC001)the Research Council of Norway SNOWGLACE(244166/E10)project
文摘In contrast to previous studies that have tended to focus on the influence of the total Arctic sea-ice cover on the East Asian summer tripole rainfall pattern, the present study identifies the Barents Sea as the key region where the June sea-ice variability exerts the most significant impacts on the East Asian August tripole rainfall pattern, and explores the teleconnection mechanisms involved. The results reveal that a reduction in June sea ice excites anomalous upward air motion due to strong near-surface thermal forcing, which further triggers a meridional overturning wave-like pattern extending to midlatitudes.Anomalous downward motion therefore forms over the Caspian Sea, which in turn induces zonally oriented overturning circulation along the subtropical jet stream, exhibiting the east–west Rossby wave train known as the Silk Road pattern. It is suggested that the Bonin high, a subtropical anticyclone predominant near South Korea, shows a significant anomaly due to the eastward extension of the Silk Road pattern to East Asia. As a possible descending branch of the Hadley cell, the Bonin high anomaly ultimately triggers a meridional overturning, establishing the Pacific–Japan pattern. This in turn induces an anomalous anticyclone and cyclone pair over East Asia, and a tripole vertical convection anomaly meridionally oriented over East Asia. Consequently, a tripole rainfall anomaly pattern is observed over East Asia. Results from numerical experiments using version 5 of the Community Atmosphere Model support the interpretation of this chain of events.
基金jointly supported by the National Natural Science Foundation of China(Grant No.41421004)the National Key Basic Research Development Program of China(Grant No.2016YFA0601802 and 2015CB453202)the National Natural Science Foundation of China(Grant Nos.41375085)
文摘This study focuses on the climatic impacts of the Atlantic Multidecadal Oscillation (AMO) as a mode of internal vari- ability. Given the difficulties involved in excluding the effects of external forcing from internal variation, i.e., owing to the short record length of instrumental observations and historical simulations, we assess and compare the AMO and its related climatic impacts both in observations and in the "Pre-industrial" experiments of models participating in CMIP5. First, we evaluate the skill of the 25 CMIP5 models' "Historical" simulations in simulating the observational AMO, and find there is generally a considerable range of skill among them in this regard. Six of the models with higher skill relative to the other models are selected to investigate the AMO-related climate impacts, and it is found that their "Pre-industrial" simulations capture the essential features of the AMO. A positive AMO favors warmer surface temperature around the North Atlantic, and the Atlantic ITCZ shifts northward leading to more rainfall in the Sahel and less rainfall in Brazil. Furthermore, the results confirm the existence of a teleconnection between the AMO and East Asian surface temperature, as well as the late withdrawal of the Indian summer monsoon, during positive AMO phases. These connections could be mainly caused by internal climate variability. Opposite patterns are true for the negative phase of the AMO.
基金supported by the strategic project of the Chinese Academy of Sciences(Grant No.XDA11010406)the National Natural Science Foundation of China (Grant Nos.41375085 and 41421004)
文摘A simple air-sea coupled model, the atmospheric general circulation model (AGCM) of the National Centers for Environmental Prediction coupled to a mixed-layer slab ocean model, is employed to investigate the impact of air-sea coupling on the signals of the Atlantic Multidecadal Oscillation (AMO). A regional coupling strategy is applied, in which coupling is switched off in the extratropical North Atlantic Ocean but switched on in the open oceans elsewhere. The coupled model is forced with warm-phase AMO SST anomalies, and the modeled responses are compared with those from parallel uncoupled AGCM experiments with the same SST forcing. The results suggest that the regionally coupled responses not only resemble the AGCM simulation, but also have a stronger intensity. In comparison, the coupled responses bear greater similarity to the observational composite anomaly. Thus, air-sea coupling enhances the responses of the East Asian winter climate to the AMO. To determine the mechanism responsible for the coupling amplification, an additional set of AGCM experiments, forced with the AMO-induced tropical SST anomalies, is conducted. The SST anomalies are extracted from the simulated AMO-induced SST response in the regionally coupled model. The results suggest that the SST anomalies contribute to the coupling amplification. Thus, tropical air-sea coupling feedback tends to enhance the responses of the East Asian winter climate to the AMO.
基金supported by the National Basic Research Program of China(Grant No.2012CB955401)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA05110203)the Center for Climate Dynamics(Project:Integrated Model-data Approach for Understanding Multidecadal Natural Climate Variability)
文摘A 600-year pre-industrial simulation with Bergen Climate Model(BCM)Version 2 is used to investigate the linkage between winter Arctic Oscillation(AO)and the Southeast Asian summer monsoon(SEASM)on the inter-decadal timescale.The results indicate an in-phase relationship between the AO and SEASM with periods of approximately 16–32 and 60–80 years.During the positive phase of winter AO,an anomalous surface anti-cyclonic atmosphere circulation appears over North Pacific in winter.The corresponding anomalies in ocean circulation and surface heat flux,particularly the latent and sensible heat flux,resemble a negative Pacific Decadal Oscillation(PDO)-like sea surface temperature(SST)pattern.The AO-associated PDO-like winter SST can persist into summer and can therefore lead to inter-decadal variability of summer monsoon rainfall in East and Southeast Asia.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDA05090406 and XDA05110203)the special projects of the China Meteorological Administration(Grant No.GYHY201006022)contribution to the DecCen and Blue Arc projects funded by the Research Council of Norway and to the Centre for Climate Dynamics at the Bjerknes Centre
文摘A simple approach that considers both internal decadal variability and the effect of anthropogenic forcing is developed to predict the decadal components of global sea surface temperatures (SSTs) for the three decades 2011-2040. The internal decadal component is derived by harmonic wave expansion analyses based on the quasiperiodic evolution of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO), as obtained from observational SST datasets. Furthermore, the external decadal component induced by anthropogenic forcing is assessed with a second-order fit based on the ensemble of projected SSTs in the experiments with multiple coupled climate models associated with the third Coupled Model Intercomparison Project (CMIP3) under the Intergovernmental Panels on Climate Change (IPCC) Special Reports on Emissions Scenario (SRES) A1B. A validation for the years from 2002 to 2010 based on a comparison of the predicted and the observed SST and their spatial correlation, as well as the root mean square error (RMSE), suggests that the approach is reasonable overall. In addition, the predicted results over the 50°S-50°N global band, the Indian Ocean, the western Pacific Ocean, the tropical eastern Pacific Ocean, and the North and the South Atlantic Ocean are presented.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40976007 and 41176002)the Special Fund for Meteorological Scientific Research in the Public Interest of China Meteorological Administration (Grant No. GYHY201006022)the Norwegian Research Council through the East Asian DecCen Project (Grant No. 193690/S30)
文摘In this paper, the dynamic effect of oceanic upwelling on the intensity of El Nio-Southern Oscillation (ENSO) is studied using a simple coupled model (Zebiak-Cane Model). The term balance analysis in the temperature variability equation shows that the anomalous upwelling of the mean vertical temperature gradient and the mean advection of the anomalous meridional temperature gradient are the two of most important factors that determine the intensity of ENSO events, in which the "vertical oceanic heat flux" in the eastern equatorial Pacific (EEP) is the primary influencing factor. The lag correlation between "vertical heat flux (VHF)" and ENSO intensity shows that the highest correlation occurs when the former leads the latter by one to two weeks. The VHF is positively correlated with the background thermocline strength in the EEP, and an increase of both could result in strong ENSO variability. Comparison of the forced and coupled experiments suggests that the coupled process can affect both the intensity and frequency of ENSO.
基金supported by the National Key Research and Development Program of China[grant number 2016YFA0601802]the National Natural Science Foundation of China[grant number41375085],[grant number 421004]the Strategic Project of the Chinese Academy of Sciences[grant number XDA11010401]
基金supported by the Chinese-Norwegian Collaboration Projects within Climate Systems jointly funded by the National Key Research and Development Program of China (Grant No.2022YFE0106800)the Research Council of Norway funded project MAPARC (Grant No.328943)+2 种基金the support from the Research Council of Norway funded project BASIC (Grant No.325440)the Horizon 2020 project APPLICATE (Grant No.727862)High-performance computing and storage resources were performed on resources provided by Sigma2 - the National Infrastructure for High-Performance Computing and Data Storage in Norway (through projects NS8121K,NN8121K,NN2345K,NS2345K,NS9560K,NS9252K,and NS9034K)。
文摘To quantify the relative contributions of Arctic sea ice and unforced atmospheric internal variability to the “warm Arctic, cold East Asia”(WACE) teleconnection, this study analyses three sets of large-ensemble simulations carried out by the Norwegian Earth System Model with a coupled atmosphere–land surface model, forced by seasonal sea ice conditions from preindustrial, present-day, and future periods. Each ensemble member within the same set uses the same forcing but with small perturbations to the atmospheric initial state. Hence, the difference between the present-day(or future) ensemble mean and the preindustrial ensemble mean provides the ice-loss-induced response, while the difference of the individual members within the present-day(or future) set is the effect of atmospheric internal variability. Results indicate that both present-day and future sea ice loss can force a negative phase of the Arctic Oscillation with a WACE pattern in winter. The magnitude of ice-induced Arctic warming is over four(ten) times larger than the ice-induced East Asian cooling in the present-day(future) experiment;the latter having a magnitude that is about 30% of the observed cooling. Sea ice loss contributes about 60%(80%) to the Arctic winter warming in the present-day(future) experiment. Atmospheric internal variability can also induce a WACE pattern with comparable magnitudes between the Arctic and East Asia. Ice-lossinduced East Asian cooling can easily be masked by atmospheric internal variability effects because random atmospheric internal variability may induce a larger magnitude warming. The observed WACE pattern occurs as a result of both Arctic sea ice loss and atmospheric internal variability, with the former dominating Arctic warming and the latter dominating East Asian cooling.