夏季外来气旋对北极太平洋扇区海冰的影响
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摘要
近40年来,北极太平洋扇区8～10月海冰面积显著减少,其减少速率几乎是大西洋扇区的3倍,且该扇区海冰面积年际变率显著,标准差达6×105km2.基于ECMWF提供的再分析气象数据和NSIDC提供的海冰密集度、海冰运动及气旋资料,分析了外来气旋活动对北极太平洋扇区海冰面积年际变化的影响.研究表明:每年7～9月的外来气旋异常偏多(偏少)时,北极太平洋扇区海冰面积明显减少(增多),二者负相关最显著的区域位于楚科奇海、波弗特海、东西伯利亚海及中央海区.深入分析其作用机制发现:外来气旋活动加强时,受其对地表能量平衡和温度平流等综合影响,北极扇区大部分地区气温都明显上升,从而促进了该扇区海冰消融.同时气旋活动带来的大风会驱动海冰运动,使得边缘海区易形成更多开阔水域,海水显著增暖,加剧边缘海海冰融化.除此之外,气旋大风还会造成东西伯利亚海海冰向东和向南更暖的区域输送,也利于海冰的消融.总体来看,北极太平洋扇区海冰消融主要与气旋的热力作用有关,其动力作用主要影响边缘海域.
Over the last four decades, the area of Arctic sea ice has decreased substantially during the end of melting season(August to October), along with significant regional differences. The decreasing rate averaged over sea ice area in the Arctic Pacific sector(APS) is about-0.45×10~6 km~2 decade~(-1) during 1979-2016, which is almost three times of that in the Atlantic sector. Besides,great year-to-year fluctuations are observed in the summertime sea ice area of APS with the standard deviation up to 6×10~5 km~2.The conspicuous interannual variability, however, has received relatively little attention, with its mechanisms not clear yet. In fact, the summertime Arctic sea ice melting is impacted by a number of factors, including surface winds, low-level Arctic clouds, moisture and heat transports into the Arctic, which are all closely connected with extratropical cyclone activities in the Arctic. The extratropical cyclones originated mainly from mid-latitude are often accompanied by stronger winds and heavier precipitation than those generated from Arctic cyclones. In addition, the total extratropical cyclone activity shows a close relationship with the total moisture and heat transports into the Arctic. It is hence hypothesized that more extratropical cyclones entering the Arctic would intensify surface winds and bring about a burst of high moisture content, inducing the more significant sea ice melting in summer. Subsequently, using monthly datasets of sea ice concentration, sea ice motion, and cyclone characteristics for the period of 1979-2016 from National Snow and Ice Data Center(NSIDC), the influence of extratropical cyclones entering the APS on the local sea ice area is investigated in the annual time scale. The cyclone characteristics dataset have been obtained based on the updated Serreze(1997) algorithm to daily Sea Level Pressure(SLP)data with six-hour intervals, which have been widely used to monitor extratropical cyclones in previous studies. Statistical analysis demonstrates that it plays a crucial role of the extratropical cyclones entering the APS in July, August and September(JAS), which are mostly from the Eurasia. The summertime sea ice area in APS reduces(increases) significantly with the increasing(decreasing) extratropical cyclones in JAS. The negative correlation is especially significant in the Chukchi Sea, the Beaufort Sea, the East Siberian Sea and the Central Arctic Ocean. Based on the monthly ERA-interim reanalysis data from 1978 to 2016, including 2 m temperature, sea surface temperature, water vapor, surface level pressure, provided by European Centre for Medium-Range Weather Forecast(ECWMF), it is also revealed that the activity of extratropical cyclones can impact sea ice both thermodynamically and dynamically. Intensified extratropical cyclones would affect processes of surface energy balance and heat advection, leading to the increasing air temperature above the APS and contributing to the ice melting. Meanwhile,surface winds associated with the cyclone are likely to affect the sea ice motion and expand the area of open water, which result in ocean warming and ice melting, especially in the marginal ice zone. Moreover, in the East Siberian Sea, cyclonic winds tend to transport the ice eastwards and southwards to warmer areas, which also aggravate the further melting. In general, the melting of summertime sea ice in the APS is greatly affected by thermodynamic processes of extratropical cyclones, while dynamic processes have limited impact, particularly in the marginal ice zone. It should be noted that, as the Arctic continues to warm up,mounting evidences suggest that the Arctic sea ice has become continuously thinner, which means less energy is required to achieve a reduction in areal coverage. Therefore, abundant reasons indicate that the cyclone activity will play an increasingly important role in the Arctic sea ice variability and it will remain a heated topic of debate for the coming future.
Over the last four decades, the area of Arctic sea ice has decreased substantially during the end of melting season(August to October), along with significant regional differences. The decreasing rate averaged over sea ice area in the Arctic Pacific sector(APS) is about-0.45×10~6 km~2 decade~(-1) during 1979-2016, which is almost three times of that in the Atlantic sector. Besides,great year-to-year fluctuations are observed in the summertime sea ice area of APS with the standard deviation up to 6×10~5 km~2.The conspicuous interannual variability, however, has received relatively little attention, with its mechanisms not clear yet. In fact, the summertime Arctic sea ice melting is impacted by a number of factors, including surface winds, low-level Arctic clouds, moisture and heat transports into the Arctic, which are all closely connected with extratropical cyclone activities in the Arctic. The extratropical cyclones originated mainly from mid-latitude are often accompanied by stronger winds and heavier precipitation than those generated from Arctic cyclones. In addition, the total extratropical cyclone activity shows a close relationship with the total moisture and heat transports into the Arctic. It is hence hypothesized that more extratropical cyclones entering the Arctic would intensify surface winds and bring about a burst of high moisture content, inducing the more significant sea ice melting in summer. Subsequently, using monthly datasets of sea ice concentration, sea ice motion, and cyclone characteristics for the period of 1979-2016 from National Snow and Ice Data Center(NSIDC), the influence of extratropical cyclones entering the APS on the local sea ice area is investigated in the annual time scale. The cyclone characteristics dataset have been obtained based on the updated Serreze(1997) algorithm to daily Sea Level Pressure(SLP)data with six-hour intervals, which have been widely used to monitor extratropical cyclones in previous studies. Statistical analysis demonstrates that it plays a crucial role of the extratropical cyclones entering the APS in July, August and September(JAS), which are mostly from the Eurasia. The summertime sea ice area in APS reduces(increases) significantly with the increasing(decreasing) extratropical cyclones in JAS. The negative correlation is especially significant in the Chukchi Sea, the Beaufort Sea, the East Siberian Sea and the Central Arctic Ocean. Based on the monthly ERA-interim reanalysis data from 1978 to 2016, including 2 m temperature, sea surface temperature, water vapor, surface level pressure, provided by European Centre for Medium-Range Weather Forecast(ECWMF), it is also revealed that the activity of extratropical cyclones can impact sea ice both thermodynamically and dynamically. Intensified extratropical cyclones would affect processes of surface energy balance and heat advection, leading to the increasing air temperature above the APS and contributing to the ice melting. Meanwhile,surface winds associated with the cyclone are likely to affect the sea ice motion and expand the area of open water, which result in ocean warming and ice melting, especially in the marginal ice zone. Moreover, in the East Siberian Sea, cyclonic winds tend to transport the ice eastwards and southwards to warmer areas, which also aggravate the further melting. In general, the melting of summertime sea ice in the APS is greatly affected by thermodynamic processes of extratropical cyclones, while dynamic processes have limited impact, particularly in the marginal ice zone. It should be noted that, as the Arctic continues to warm up,mounting evidences suggest that the Arctic sea ice has become continuously thinner, which means less energy is required to achieve a reduction in areal coverage. Therefore, abundant reasons indicate that the cyclone activity will play an increasingly important role in the Arctic sea ice variability and it will remain a heated topic of debate for the coming future.
引文
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2 Ogi M,Rigor I G.Trends in Arctic sea ice and the role of atmospheric circulation.Atmos Sci Lett,2013,14:97-101
3 Zhang J,Lindsay R,Steele M,et al.What drove the dramatic retreat of arctic sea ice during summer 2007?Geophys Res Lett,2008,35:L11505
4 Zhang J,Lindsay R,Schweiger A,et al.The impact of an intense summer cyclone on 2012 Arctic sea ice retreat.Geophys Res Lett,2013,40:720-726
5 Maslanik J A,Fowler C,Stroeve J,et al.A younger,thinner Arctic ice cover:Increased potential for rapid,extensive sea-ice loss.Geophys Res Lett,2007,34:L24501
6 Haine T W N,Martin T.The Arctic-Subarctic sea ice system is entering a seasonal regime:Implications for future Arctic amplification.Sci Rep,2017,7:4618
7 D?scher R,Vihma T,Maksimovich E.Recent advances in understanding the Arctic climate system state and change from a sea ice perspective:Areview.Atmos Chem Phys,2014,14:13571-13600
8 Walsh J E,Chapman W L,Shy T L.Recent decrease of sea level pressure in the central Arctic.J Clim,1996,9:480-486
9 Thompson D W J,Wallace J M.The Arctic oscillation signature in the wintertime geopotential height and temperature fields.Geophys Res Lett,1998,25:1297-1300
10 Wu B,Overland J E,D’Arrigo R.Anomalous Arctic surface wind patterns and their impacts on September sea ice minima and trend.Tellus A-Dyn Meteor Oceanogr,2012,64:18590
11 Rigor I G,Wallace J M,Colony R L.Response of sea ice to the Arctic Oscillation.J Clim,2002,15:2648-2663
12 Parkinson C L,Comiso J C.On the 2012 record low Arctic sea ice cover:Combined impact of preconditioning and an August storm.Geophys Res Lett,2013,40:1356-1361
13 Screen J A,Simmonds I,Keay K.Dramatic interannual changes of perennial Arctic sea ice linked to abnormal summer storm activity.J Geophys Res,2011,116:D15105
14 Simmonds I,Keay K.Extraordinary September Arctic sea ice reductions and their relationships with storm behavior over 1979-2008.Geophys Res Lett,1979,36:L19715
15 Ogi M,Wallace J M.The role of summer surface wind anomalies in the summer Arctic sea ice extent in 2010 and 2011.Geophys Res Lett,2012,39:L09704
16 Kay J E,L’Ecuyer T,Gettelman A,et al.The contribution of cloud and radiation anomalies to the 2007 Arctic sea ice extent minimum.Geophys Res Lett,2008,35:L08503
17 Woods C,Caballero R.The role of moist intrusions in winter Arctic warming and sea ice decline.J Clim,2016,29:4473-4485
18 Villamil-Otero G A,Zhang J,He J,et al.Role of extratropical cyclones in the recently observed increase in poleward moisture transport into the Arctic Ocean.Adv Atmos Sci,2018,35:85-94
19 Sorteberg A,Walsh J E.Seasonal cyclone variability at 70°N and its impact on moisture transport into the Arctic.Tellus A,2008,60:570-586
20 Sui C J,Zhang Z H,Wu H D,et al.Interannual and interdecadal variability of Arctic sea ice extent from 1979-2012(in Chinese).Chin J Polar Res,2015,27:174-182[隋翠娟,张占海,吴辉碇,等.1979~2012年北极海冰范围年际和年代际变化分析.极地研究,2015,27:174-182]
21 Lee H J,Kwon M O,Yeh S W,et al.Impact of poleward moisture transport from the North Pacific on the acceleration of sea ice loss in the Arctic since 2002.J Clim,2017,30:6757-6769
22 Serreze M C,Barrett A P.The summer cyclone maximum over the central Arctic Ocean.J Clim,2008,21:1048-1065
23 Zhang X,Walsh J E,Zhang J,et al.Climatology and interannual variability of Arctic cyclone activity:1948-2002.J Clim,1948,17:2300-2317
24 Crawford A D,Serreze M C.Does the summer Arctic frontal zone influence Arctic Ocean cyclone activity?J Clim,2016,29:4977-4993
25 Qin T,Wei L X,Sun H L.Statistic and variability of cyclones in Arctic in 1979-2012(in Chinese).Mar Forecast,2015,32:39-45[秦听,魏立新,孙虎林.进入极区温带气旋的时空变化特征分析.海洋预报,2015,32:39-45]
26 Wu J,Gao G P,Xu F X,et al.Main features of cyclones migrating into the Arctic via 70°N(in Chinese).Chin J Polar Res,2018,30:391-405[吴静,高郭平,徐飞翔,等.向极跨越70°N气旋的主要特征分析.极地研究,2018,30:391-405]
27 Neu U,Akperov M G,Bellenbaum N,et al.IMILAST:A community effort to intercompare extratropical cyclone detection and tracking algorithms.Bull Amer Meteor Soc,2013,94:529-547
28 Serreze M C,Carse F,Barry R G,et al.Icelandic low cyclone activity:Climatological features,linkages with the NAO,and relationships with recent changes in the Northern Hemisphere circulation.J Clim,1997,10:453-464
29 Koyama T,Stroeve J,Cassano J,et al.Sea ice loss and Arctic cyclone activity from 1979 to 2014.J Clim,2017,30:4735-4754
30 Serreze M.Northern Hemisphere Cyclone Locations and Characteristics from NCEP/NCAR Reanalysis Data,Version 1.Boulder,Colorado USA.NSIDC:National Snow and Ice Data Center,2009,https://doi.org/10.5067/XEPCLZKPAJBK
31 Wang D W,Yang X Q.Temporal and spatial patterns of Arctic sea ice variations(in Chinese).Acta Meteor Sin,2002,60:129-138[汪代维,杨修群.北极海冰变化的时间和空间型.气象学报,2002,60:129-138]
32 Kriegsmann A,Brümmer B.Cyclone impact on sea ice in the central Arctic Ocean:A statistical study.Cryosphere,2014,8:303-317
2 Ogi M,Rigor I G.Trends in Arctic sea ice and the role of atmospheric circulation.Atmos Sci Lett,2013,14:97-101
3 Zhang J,Lindsay R,Steele M,et al.What drove the dramatic retreat of arctic sea ice during summer 2007?Geophys Res Lett,2008,35:L11505
4 Zhang J,Lindsay R,Schweiger A,et al.The impact of an intense summer cyclone on 2012 Arctic sea ice retreat.Geophys Res Lett,2013,40:720-726
5 Maslanik J A,Fowler C,Stroeve J,et al.A younger,thinner Arctic ice cover:Increased potential for rapid,extensive sea-ice loss.Geophys Res Lett,2007,34:L24501
6 Haine T W N,Martin T.The Arctic-Subarctic sea ice system is entering a seasonal regime:Implications for future Arctic amplification.Sci Rep,2017,7:4618
7 D?scher R,Vihma T,Maksimovich E.Recent advances in understanding the Arctic climate system state and change from a sea ice perspective:Areview.Atmos Chem Phys,2014,14:13571-13600
8 Walsh J E,Chapman W L,Shy T L.Recent decrease of sea level pressure in the central Arctic.J Clim,1996,9:480-486
9 Thompson D W J,Wallace J M.The Arctic oscillation signature in the wintertime geopotential height and temperature fields.Geophys Res Lett,1998,25:1297-1300
10 Wu B,Overland J E,D’Arrigo R.Anomalous Arctic surface wind patterns and their impacts on September sea ice minima and trend.Tellus A-Dyn Meteor Oceanogr,2012,64:18590
11 Rigor I G,Wallace J M,Colony R L.Response of sea ice to the Arctic Oscillation.J Clim,2002,15:2648-2663
12 Parkinson C L,Comiso J C.On the 2012 record low Arctic sea ice cover:Combined impact of preconditioning and an August storm.Geophys Res Lett,2013,40:1356-1361
13 Screen J A,Simmonds I,Keay K.Dramatic interannual changes of perennial Arctic sea ice linked to abnormal summer storm activity.J Geophys Res,2011,116:D15105
14 Simmonds I,Keay K.Extraordinary September Arctic sea ice reductions and their relationships with storm behavior over 1979-2008.Geophys Res Lett,1979,36:L19715
15 Ogi M,Wallace J M.The role of summer surface wind anomalies in the summer Arctic sea ice extent in 2010 and 2011.Geophys Res Lett,2012,39:L09704
16 Kay J E,L’Ecuyer T,Gettelman A,et al.The contribution of cloud and radiation anomalies to the 2007 Arctic sea ice extent minimum.Geophys Res Lett,2008,35:L08503
17 Woods C,Caballero R.The role of moist intrusions in winter Arctic warming and sea ice decline.J Clim,2016,29:4473-4485
18 Villamil-Otero G A,Zhang J,He J,et al.Role of extratropical cyclones in the recently observed increase in poleward moisture transport into the Arctic Ocean.Adv Atmos Sci,2018,35:85-94
19 Sorteberg A,Walsh J E.Seasonal cyclone variability at 70°N and its impact on moisture transport into the Arctic.Tellus A,2008,60:570-586
20 Sui C J,Zhang Z H,Wu H D,et al.Interannual and interdecadal variability of Arctic sea ice extent from 1979-2012(in Chinese).Chin J Polar Res,2015,27:174-182[隋翠娟,张占海,吴辉碇,等.1979~2012年北极海冰范围年际和年代际变化分析.极地研究,2015,27:174-182]
21 Lee H J,Kwon M O,Yeh S W,et al.Impact of poleward moisture transport from the North Pacific on the acceleration of sea ice loss in the Arctic since 2002.J Clim,2017,30:6757-6769
22 Serreze M C,Barrett A P.The summer cyclone maximum over the central Arctic Ocean.J Clim,2008,21:1048-1065
23 Zhang X,Walsh J E,Zhang J,et al.Climatology and interannual variability of Arctic cyclone activity:1948-2002.J Clim,1948,17:2300-2317
24 Crawford A D,Serreze M C.Does the summer Arctic frontal zone influence Arctic Ocean cyclone activity?J Clim,2016,29:4977-4993
25 Qin T,Wei L X,Sun H L.Statistic and variability of cyclones in Arctic in 1979-2012(in Chinese).Mar Forecast,2015,32:39-45[秦听,魏立新,孙虎林.进入极区温带气旋的时空变化特征分析.海洋预报,2015,32:39-45]
26 Wu J,Gao G P,Xu F X,et al.Main features of cyclones migrating into the Arctic via 70°N(in Chinese).Chin J Polar Res,2018,30:391-405[吴静,高郭平,徐飞翔,等.向极跨越70°N气旋的主要特征分析.极地研究,2018,30:391-405]
27 Neu U,Akperov M G,Bellenbaum N,et al.IMILAST:A community effort to intercompare extratropical cyclone detection and tracking algorithms.Bull Amer Meteor Soc,2013,94:529-547
28 Serreze M C,Carse F,Barry R G,et al.Icelandic low cyclone activity:Climatological features,linkages with the NAO,and relationships with recent changes in the Northern Hemisphere circulation.J Clim,1997,10:453-464
29 Koyama T,Stroeve J,Cassano J,et al.Sea ice loss and Arctic cyclone activity from 1979 to 2014.J Clim,2017,30:4735-4754
30 Serreze M.Northern Hemisphere Cyclone Locations and Characteristics from NCEP/NCAR Reanalysis Data,Version 1.Boulder,Colorado USA.NSIDC:National Snow and Ice Data Center,2009,https://doi.org/10.5067/XEPCLZKPAJBK
31 Wang D W,Yang X Q.Temporal and spatial patterns of Arctic sea ice variations(in Chinese).Acta Meteor Sin,2002,60:129-138[汪代维,杨修群.北极海冰变化的时间和空间型.气象学报,2002,60:129-138]
32 Kriegsmann A,Brümmer B.Cyclone impact on sea ice in the central Arctic Ocean:A statistical study.Cryosphere,2014,8:303-317
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