In November 2020,the eastern Arctic experienced an extensive extreme warm anomaly(i.e.,the second strongest case since 1979),which was followed by extreme cold conditions over East Asia in early winter.The observed Ar...In November 2020,the eastern Arctic experienced an extensive extreme warm anomaly(i.e.,the second strongest case since 1979),which was followed by extreme cold conditions over East Asia in early winter.The observed Arctic warm anomaly in November 2020 was able to extend upwards to the upper troposphere,characterized as a deep Arctic warm anomaly.In autumn 2020,substantial Arctic sea-ice loss that exceeded the record held since1979,accompanied by increased upward turbulent heat flux,was able to strongly warm the Arctic.Furthermore,there was abundant northward moisture transport into the Arctic from the North Atlantic,which was the strongest in the past four decades.This extreme moisture intrusion was able to enhance the downward longwave radiation and strongly contribute to the warm conditions in the Arctic.Further analysis indicated that the remote moisture intrusion into the Arctic was promoted by the large-scale atmospheric circulation patterns,such as the wave train propagating from the midlatitude North Atlantic to the Arctic.This process may have been linked to the warmer sea surface temperature in the midlatitude North Atlantic.展开更多
Siberia experienced intense heat waves in 2020,and this unusual warming may have caused more wildfires and losses of permafrost than normal,both of which can be devastating to ecosystems.Based on observational data,th...Siberia experienced intense heat waves in 2020,and this unusual warming may have caused more wildfires and losses of permafrost than normal,both of which can be devastating to ecosystems.Based on observational data,this paper shows that there was an intense warming trend over Siberia(60°–75°N,70°–130°E)in June during 1979–2020.The linear trend of the June surface air temperature is 0.90℃/10 yr over Siberia,which is much larger than the area with the same latitudes(60°–75°N,0°–360°,trend of 0.46℃/10 yr).The warming over Siberia extends from the surface to about 300 h Pa.Increased geopotential height in the mid-to-upper troposphere plays an important role in shaping the Siberian warming,which favors more shortwave radiation reaching the surface and further heating the overlying atmosphere via upward turbulent heat flux and longwave radiation.The Siberian warming is closely related to Arctic sea-ice decline,especially the sea ice over northern Barents Sea and Kara Sea.Numerical experiments carried out using and atmospheric general circulation model(IAP-AGCM4.1)confirmed the contribution of the Arctic sea-ice decline to the Siberian warming and the related changes in circulations and surface fluxes.展开更多
While Arctic sea ice has been decreasing in recent decades that is largely due to anthropogenic forcing,the extent of Antarctic sea ice showed a positive trend during 1979–2015, followed by an abrupt decrease. The sh...While Arctic sea ice has been decreasing in recent decades that is largely due to anthropogenic forcing,the extent of Antarctic sea ice showed a positive trend during 1979–2015, followed by an abrupt decrease. The shortness of the satellite record limits our ability to quantify the possible contribution of anthropogenic forcing and internal variability to the observed Antarctic sea ice variability. In this study,ice core and fast ice records with annual resolution from six sites are used to reconstruct the annualresolved northernmost latitude of sea ice edge(NLSIE) for different sectors of the Southern Ocean, including the Weddell Sea(WS), Bellingshausen Sea(BS), Amundsen Sea(AS), Ross Sea(RS), and the Indian and western Pacific Ocean(Ind WPac). The linear trends of the NLSIE are analyzed for each sector for the past100–200 years and found to be à0.08°, à0.17°, +0.07°, +0.02°, and à0.03° per decade(!95% confidence level) for the WS, BS, AS, RS, and Ind WPac, respectively. For the entire Antarctic, our composite NLSIE shows a decreasing trend(à0.03° per decade, 99% confidence level) during the 20 th century, with a rapid decline in the mid-1950 s. It was not until the early 1980 s that the observed increasing trend occurred. A comparison with major climate indices shows that the long-term linear trends in all five sectors are largely dominated by the changes in the Southern Annular Mode(SAM). The multi-decadal variability in WS,BS, and AS is dominated by the Interdecadal Pacific Oscillation, whereas that in the Ind WPac and RS is dominated by the SAM.展开更多
基金supported by the Guangdong Major Project of Basic and Applied Basic Research [grant number 2020B0301030004]the National Natural Science Foundation of China [grant numbers 42025502 and 41875118]+1 种基金the Research Council of Norway project BASIC [grant number 325440]the State Scholarship Fund of the China Scholarship Council [grant number 202109045003]
文摘In November 2020,the eastern Arctic experienced an extensive extreme warm anomaly(i.e.,the second strongest case since 1979),which was followed by extreme cold conditions over East Asia in early winter.The observed Arctic warm anomaly in November 2020 was able to extend upwards to the upper troposphere,characterized as a deep Arctic warm anomaly.In autumn 2020,substantial Arctic sea-ice loss that exceeded the record held since1979,accompanied by increased upward turbulent heat flux,was able to strongly warm the Arctic.Furthermore,there was abundant northward moisture transport into the Arctic from the North Atlantic,which was the strongest in the past four decades.This extreme moisture intrusion was able to enhance the downward longwave radiation and strongly contribute to the warm conditions in the Arctic.Further analysis indicated that the remote moisture intrusion into the Arctic was promoted by the large-scale atmospheric circulation patterns,such as the wave train propagating from the midlatitude North Atlantic to the Arctic.This process may have been linked to the warmer sea surface temperature in the midlatitude North Atlantic.
基金supported by the National Key R&D Pro-gram of China[grant number 2017YFE0111800]the National Natural Science Foundation of China[grant numbers 41790472 and 41822502]。
文摘Siberia experienced intense heat waves in 2020,and this unusual warming may have caused more wildfires and losses of permafrost than normal,both of which can be devastating to ecosystems.Based on observational data,this paper shows that there was an intense warming trend over Siberia(60°–75°N,70°–130°E)in June during 1979–2020.The linear trend of the June surface air temperature is 0.90℃/10 yr over Siberia,which is much larger than the area with the same latitudes(60°–75°N,0°–360°,trend of 0.46℃/10 yr).The warming over Siberia extends from the surface to about 300 h Pa.Increased geopotential height in the mid-to-upper troposphere plays an important role in shaping the Siberian warming,which favors more shortwave radiation reaching the surface and further heating the overlying atmosphere via upward turbulent heat flux and longwave radiation.The Siberian warming is closely related to Arctic sea-ice decline,especially the sea ice over northern Barents Sea and Kara Sea.Numerical experiments carried out using and atmospheric general circulation model(IAP-AGCM4.1)confirmed the contribution of the Arctic sea-ice decline to the Siberian warming and the related changes in circulations and surface fluxes.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA19070103)the National Key Research & Development Program of China (2018YFA0605901)+1 种基金the State Key Laboratory of Cryospheric Science (SKLCS-ZZ-2021)the National Natural Science Foundation of China (42071086, 41425003, 41941009)。
文摘While Arctic sea ice has been decreasing in recent decades that is largely due to anthropogenic forcing,the extent of Antarctic sea ice showed a positive trend during 1979–2015, followed by an abrupt decrease. The shortness of the satellite record limits our ability to quantify the possible contribution of anthropogenic forcing and internal variability to the observed Antarctic sea ice variability. In this study,ice core and fast ice records with annual resolution from six sites are used to reconstruct the annualresolved northernmost latitude of sea ice edge(NLSIE) for different sectors of the Southern Ocean, including the Weddell Sea(WS), Bellingshausen Sea(BS), Amundsen Sea(AS), Ross Sea(RS), and the Indian and western Pacific Ocean(Ind WPac). The linear trends of the NLSIE are analyzed for each sector for the past100–200 years and found to be à0.08°, à0.17°, +0.07°, +0.02°, and à0.03° per decade(!95% confidence level) for the WS, BS, AS, RS, and Ind WPac, respectively. For the entire Antarctic, our composite NLSIE shows a decreasing trend(à0.03° per decade, 99% confidence level) during the 20 th century, with a rapid decline in the mid-1950 s. It was not until the early 1980 s that the observed increasing trend occurred. A comparison with major climate indices shows that the long-term linear trends in all five sectors are largely dominated by the changes in the Southern Annular Mode(SAM). The multi-decadal variability in WS,BS, and AS is dominated by the Interdecadal Pacific Oscillation, whereas that in the Ind WPac and RS is dominated by the SAM.
