北冰洋中心區(qū)海冰漂流與大氣過程

卞林根，王繼志，孫玉龍，等

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北冰洋中心區(qū)海冰漂流與大氣過程

卞林根，王繼志，孫玉龍，等

摘要：利用北冰洋中心區(qū)漂流自動氣象站（DAWS）2012 年9月—2013年2月的觀測數(shù)據(jù)，分析了北極點周圍海冰漂流軌跡和速度及相關(guān)大氣過程。結(jié)果顯示，北冰洋中心區(qū)海冰具有不穩(wěn)定漂流過程。2012年9月1日—2013年1月6日，DAWS所在海冰從西向西北方向漂流，2013年1 月6日以后穩(wěn)定地向東南方向漂流，平均移速為0.06 m/s，最大達到0.4 m/s。海冰漂流方向的突變和加速與穿極氣旋和急流的影響有關(guān)。凈輻射常出現(xiàn)短期突變過程，導(dǎo)致海冰從大氣吸收能量，減緩了海冰的輻射冷卻。爆發(fā)性增溫過程的最大幅度達到30℃，是由強穿極氣旋和伴隨的暖濕氣流向北極中心區(qū)輸送引起，這種現(xiàn)象在中低緯度十分罕見。增溫過程的作用是高空大氣向冰面輸送熱量，導(dǎo)致海冰破裂，海冰硬度的脆變，減緩海冰厚度的增長，這種過程可能是北極海冰面積和厚度減少重要過程。

關(guān)鍵詞：北冰洋；漂流自動氣象站；海冰運動；爆發(fā)性增溫；穿極氣旋

來源出版物：Monthly Weather Review, 2013, 141: 3786-3800

On the relationship between winter sea ice and summer atmospheric circulation over eurasia

Bingyi Wu; Renhe Zhang; Rosanne D’Arrigo; et al.

來源出版物：Journal of Climate, 2013, 26: 5523-5536

Fast atmospheric response to a sudden thinning of Arctic sea ice

Semmler, Tido; Jung, Thomas; Serrar, Soumia

來源出版物：Climate Dynamics, 2016, 46(3-4): 1015-1025

Investigation of the atmospheric mechanisms related to the autumn sea ice and winter circulation link in the Northern Hemisphere

King, Martin P; Hell, Momme; Keenlyside, Noel

lag relationships of the atmospheric anomalies related toNovember sea ice concentration are presented. Further analysis shows that the stratosphere-troposphere interaction may provide the memory in the system: positive (negative) sea ice concentration anomaly in November is associated with a strengthened (weakened) stratospheric polar vortex and these anomalies propagate downward leading to the positive (negative) NAO-like pattern in the late December to early January. This stratosphere mechanism may also play a role for Barents-Kara sea ice anomaly in December, but not for September and October. Consistently, Eliassen-Palm, eddy heat and momentum fluxes suggest that there is strong forcing of the zonal winds in November.

來源出版物：Climate Dynamics, 2016, 46(3-4): 1185-1195

The effect of downwelling longwave and shortwave radiation on arctic summer sea ice

Kapsch, Marie-Luise; Graversen, Rune Grand; Tjernstrom, Michael; et al.

來源出版物：Journal of Climate, 2016, 29(3): 1143-1159

Influence of sea ice on Arctic precipitation

Kopec, Ben G; Feng, Xiahong; Michel, Fred A; et al.

來源出版物：Proceedings of the National Academy of Sciences of the United States of America, 2016, 113(1): 46-51

Arctic sea ice and warm season North American extreme surface air temperatures

Budikova, Dagmar; Chechi, Leonardo

來源出版物：Climate Research, 2016, 67(1): 15-29

Evidence for a wavier jet stream in response to rapid Arctic warming

Francis, Jennifer A; Vavrus, Stephen J

來源出版物：Environmental Research Letters, 2015, 10(1): 014005

Arctic sea ice thickness loss determined using subsurface, aircraft, and satellite observations

Lindsay, R; Schweiger, A

來源出版物：Cryosphere, 2015, 9(1): 269-283

The role of ocean-atmosphere coupling in the zonal-mean atmospheric response to arctic sea ice loss

Deser, Clara; Tomas, Robert A; Sun, Lantao

來源出版物：Journal of Climate, 2015, 28(6): 2168-2186

Effects of arctic sea ice decline on weather and climate: A review

Vihma, Timo

來源出版物：Surveys in Geophysics, 2014, 35(5): 1175-1214

Robust Arctic sea-ice influence on the frequent Eurasian cold winters in past decades

Mori, Masato; Watanabe, Masahiro; Shiogama, Hideo; et al.

來源出版物：Nature Geoscience, 2014, 7(12): 869-873

Atmospheric impacts of Arctic sea-ice loss, 1979-2009: Separating forced change from atmospheric internal variability

Screen, James A; Deser, Clara; Simmonds, Ian; et al.

來源出版物：Climate Dynamics, 2014, 43(1-2): 333-344

September Arctic sea-ice minimum predicted by spring melt-pond fraction

Schroeder, David; Feltham, Daniel L; Flocco, Daniela; et al.

來源出版物：Nature Climate Change, 2014, 4(5): 353-357

On the 2012 record low Arctic sea ice cover: Combined impact of preconditioning
and an August storm

Parkinson, Claire L; Comiso, Josefino C

來源出版物：Geophysical Research Letters, 2013, 40(7): 1356-1361

The atmospheric response to three decades of observed arctic sea ice loss

Screen, James A; Simmonds, Ian; Deser, Clara; et al.

來源出版物：Journal of Climate, 2013, 26(4): 1230-1248

The impact of an intense summer cyclone on 2012 Arctic sea ice retreat

Zhang, Jinlun; Lindsay, Ron; Schweiger, Axel; et al.

來源出版物：Geophysical Research Letters, 2013, 40(4): 720-726

編輯：衛(wèi)夏雯

婦產(chǎn)科學(xué)

來源出版物：海洋學(xué)報（中文版）, 2014, 36(10): 48-55

來源出版物：Surv Geophys, 2014, 35: 1175-1214

Effects of arctic sea ice decline on weather and climate: A review

Timo Vihma

Abstract:The areal extent, concentration and thickness of sea ice in the Arctic Ocean and adjacent seas have strongly decreased during the recent decades, but cold, snow-rich winters have been common over mid-latitude land areas since 2005. A review is presented on studies addressing the local and remote effects of the sea ice decline on weather and climate. It is evident that the reduction in sea ice cover has increased the heat flux from the ocean to atmosphere in autumn and early winter. This has locally increased air temperature, moisture, and cloud cover and reduced the static stability in the lower troposphere. Several studies based on observations, atmospheric reanalyses, and model experiments suggest that the sea ice decline, together with increased snow cover in Eurasia, favours circulation patterns resembling the negative phase of the North Atlantic Oscillation and Arctic Oscillation. The suggested largescale pressure patterns include a high over Eurasia, which favours cold winters in Europe and northeastern Eurasia. A high over the western and a low over the eastern North America have also been suggested, favouring advection of Arctic air masses to North America. Mid-latitude winter weather is, however, affected by several other factors, which generate a large inter-annual variability and often mask the effects of sea ice decline. In addition, the small sample of years with a large sea ice loss makes it difficult to distinguish the effects directly attributable to sea ice conditions. Several studies suggest that, with advancing global warming, cold winters in mid-latitude continents will no longer be common during the second half of the twenty-first century. Recent studies have also suggested causal links between the sea ice decline and summer precipitation in Europe, the Mediterranean, and East Asia. Keywords: arctic; climate change; mid-latitude weather; sea ice; snow; winter weather Sea ice is the central component and most sensitive indicator of the Arctic climate system. Both the depletion and areal decline of the Arctic sea ice cover, observed since the 1970s, have accelerated since the millennium. While the relationship of global warming to sea ice reduction is evident and underpinned statistically, it is the connecting mechanisms that are explored in detail in this review. Sea ice erodes both from the top and the bottom. Atmospheric, oceanic and sea ice processes interact in nonlinear ways on various scales. Feedback mechanisms lead to an Arctic amplification of the global warming system: the amplification is both supported by the ice depletion and, at the same time, accelerates ice reduction. Knowledge of the mechanisms of sea ice decline grew during the 1990s and deepened when the acceleration became clear in the early 2000s. Record minimum summer sea ice extents in 2002, 2005, 2007 and 2012 provide additional information on the mechanisms. This article reviews recent progress in understanding the sea ice decline. Processes are revisited from atmospheric, oceanic and sea ice perspectives. There is strong evidence that decisive atmospheric changes are the major driver of sea ice change. Feedbacks due to reduced ice concentration, surface albedo, and ice thickness allow for additional local atmospheric and oceanic influences and self-supporting feedbacks. Large-scale ocean influences on Arctic Ocean hydrology and circulation are highly evident. Northward heat fluxes in the ocean are clearly impacting the ice margins, especially in the Atlantic sector of the Arctic. There is little indication of a direct and decisive influence of the warming ocean on the overall sea ice cover, due to an isolating layer of cold and fresh water underneath the sea ice. Formed by the freezing of sea water, sea ice defines the character of the marine Arctic. The principal purpose of this review is to synthesize the published efforts that document the potential impact of Arctic sea ice on remote climates. The emphasis is on atmospheric processes and the resulting modifications in surface conditions such as air temperature, precipitation patterns, and storm track behavior at interannual timescales across the middle and low latitudes of the Northern hemisphere during cool months. Addressed also are the theoretical, methodological, and logistical challenges facing the current observational and modeling studies that aim to improve our awareness of the role that Arctic sea ice plays in the definition of global climate. Moving towards an improved understanding of the role that polar sea ice plays in shaping the global climate is a subject of timely importance as the Arctic environment is currently undergoing rapid change with little slowing down forecasted for the future. Using the NCEP/NCAR and Japanese (JRA-25) re-analysis winter daily (Dec. 1 to Feb. 28) data for the period 1979 to 2012, this paper reveals the leading pattern of winter daily 850 hPa wind variability over northern Eurasia from a dynamic perspective. The results show that the leading pattern accounts for 18% of the total anomalous kinetic energy and consists of two sub-patterns: the dipole and the tripole wind patterns. The dipole wind pattern does not exhibit any apparent trend. The tripole wind pattern, however, has displayed significant trends since the late 1980s. The negative phase of the tripole wind pattern corresponds to an anomalous anticyclone over northern Eurasia during winter, as well as two anomalous cyclones respectively occurring over southern Europe and in the mid-high latitudes of East Asia. These anomalous cyclones in turn lead to enhanced winter precipitation in these two regions, as well as negative surface temperature anomalies over the mid-high latitudes of Asia. The intensity of the tripole wind pattern and the frequency of its extreme negative phase are significantly correlated with autumn Arctic sea ice anomalies. Simulation experiments further demonstrate that the winter atmospheric response to Arctic sea ice decrease is dynamically consistent with the observed trend in the tripole wind pattern over the past 24 winters, which is one of causes of the observed winterbook=38,ebook=38surface air temperature decline trend over Central and East Asia. The results of this study also imply that East Asia may experience more frequent and/or intense winter extreme weather events in association with the loss of Arctic sea ice. Using the NCEP/NCAR and JRA-25 re-analysis data, this paper investigates the association between winter sea ice concentration (SIC) in Baffin Bay southward to the eastern coast of Newfoundland, and the ensuing summer atmospheric circulation over the mid-high latitudes of Eurasia. It is found that winter SIC anomalies are significantly correlated with the ensuing summer 500 hPa height anomalies that dynamically correspond to the Eurasian pattern of 850 hPa wind variability and significantly influence summer rainfall variability over northern Eurasia. Spring atmospheric circulation anomalies south of Newfoundland, associated with persistent winter-spring SIC and a horseshoe-like pattern of sea surface temperature (SST) anomalies in the North Atlantic, act as a bridge linking winter SIC and the ensuing summer atmospheric circulation anomalies over northern Eurasia. Indeed, this study only reveals the association based on observations and simple simulation experiments with SIC forcing. The more precise mechanism for this linkage needs to be addressed in future work using numerical simulations with SIC and SST as the external forcings. Our results have the following implication: Winter SIC west of Greenland is a possible precursor for summer atmospheric circulation and rainfall anomalies over northern Eurasia. In order to understand the influence of a thinner Arctic sea ice on the wintertime atmosphere, idealized ensemble experiments with increased sea ice surface temperature have been carried out with the Integrated Forecast System of the European Centre for Medium-Range Weather Forecasts. The focus is on the fast atmospheric response to a sudden “thinning” of Arctic sea ice to disentangle the role of various different processes. We found that boundary layer turbulence is the most important process that distributes anomalous heat vertically. Anomalous longwave radiation plays an important role within the first few days before temperatures in the lower troposphere had time to adjust. The dynamic response tends to balance that due to boundary layer turbulence while cloud processes and convection play only a minor role. Overall the response of the atmospheric large-scale circulation is relatively small with up to 2 hPa in the mean sea level pressure during the first 15 days; the quasiequilibrium response reached in the second and third month of the integration is about twice as large. During the first few days the response tends to be baroclinic in the whole Arctic. Already after a few days an anti-cyclonic equivalent-barotropic response develops over north-western Siberia and north-eastern Europe. The structure resembles very much that of the atmospheric equilibrium response indicating that fast tropospheric processes such as fewer quasi-barotropic cyclones entering this continental area are key opposed to slower processes such as those involving, for example, stratosphere-troposphere interaction. The Arctic summer sea ice has diminished fast in recent decades. A strong year-to-year variability on top of this trend indicates that sea ice is sensitive to short-term climate fluctuations. Previous studies show that anomalous atmospheric conditions over the Arctic during spring and summer affect ice melt and the September sea ice extent (SIE). These conditions are characterized by clouds, humidity, and heat anomalies that all affect downwelling shortwave (SWD) and longwave (LWD) radiation to the surface. In general, positive LWD anomalies are associated with cloudy and humid conditions, whereas positive anomalies of SWD appear under clear-sky conditions. Here the effect of realistic anomalies of LWD and SWD on summer sea ice is investigated by performing experiments with the Community Earth System Model. The SWD and LWD anomalies are studied separately and in combination for different seasons. It is found that positive LWD anomalies in spring and early summer have significant impact on the September SIE, whereas winter anomalies show only little effect. Positive anomalies in spring and early summer initiate an earlier melt onset, hereby triggering several feedback mechanisms that amplify melt during the succeeding months. Realistic positive SWD anomalies appear only important if they occur after the melt has started and the albedo is significantly reduced relative to winter conditions. Simulations where both positive LWD and negative SWD anomalies are implemented simultaneously, mimicking cloudy conditions, reveal that clouds during spring have a significant impact on summer sea ice while summer clouds have almost no effect. Global climate is influenced by the Arctic hydrologic cycle, which is, in part, regulated by sea ice through its control on evaporation and precipitation. However, the quantitative link between precipitation and sea ice extent is poorly constrained. Here we present observational evidence for the response of precipitation to sea ice reduction and assess the sensitivity of the response. Changes in the proportion of moisture sourced from the Arctic with sea ice change in the Canadian Arctic and Greenland Sea regions over the past two decades are inferred from annually averaged deuterium excess (d-excess) measurements from six sites. Other influences on the Arctic hydrologic cycle, such as the strength of meridional transport, are assessed using the North Atlantic Oscillation index. We find that the independent, direct effect of sea ice on the increase of the percentage of Arctic sourced moisture (or Arctic moisture proportion, AMP) is 18.2± 4.6% and 10.8±3.6%/100000 km2sea ice lost for each region, respectively, corresponding to increases of 10.9± 2.8% and 2.7±1.1% 1 degrees C of warming in the vapor source regions. The moisture source changes likely result in increases of precipitation and changes in energy balance, creating significant uncertainty for climate predictions. A growing amount of evidence points to abook=40,ebook=40notable linkage between the changing Arctic cryosphere and weather in the middle latitudes of the Northern Hemisphere. Recent studies propose a series of mechanisms that make plausible the connection between Arctic amplification/sea ice decline and extreme weather. Using composite analyses, this study examines associations between the frequency of occurrence of boreal summer daily extreme surface air temperatures across North America and simultaneous mean Arctic sea ice concentration (SIC) conditions during the period 1979-2013. Four distinct regions show coherent relationships including large sections of the eastern USA, Canada and the Canadian Arctic, central North America, southeast USA, and the west coast from southern Canada to Alaska. Across the eastern USA and Canada, as well as in western North America, the connections are principally shaped by low ice conditions with an expected decline in the incidence of cool nights/days and an increase in the incidence of warm nights/days. The ice-temperature relationships observed in the other regions are mostly shaped by high ice conditions. Synoptic analyses indicate the associations to be reflected in mean summer surface air temperature (SAT) and surface anomaly flows, as well as in the 500 and 200 hPa geopotential height flow and mean zonal wind anomaly patterns. Areas with the greatest atmospheric flow modifications have been generally associated with regions that display most notable extreme temperature frequency modifications. Keywords: Arctic ice; summer extreme temperature; North America New metrics and evidence are presented that support a linkage between rapid Arctic warming, relative to Northern hemisphere mid-latitudes, and more frequent high-amplitude (wavy) jet-stream configurations that favor persistent weather patterns. We find robust relationships among seasonal and regional patterns of weaker poleward thickness gradients, weaker zonal upper-level winds, and a more meridional flow direction. These results suggest that as the Arctic continues to warm faster than elsewhere in response to rising greenhouse-gas concentrations, the frequency of extreme weather events caused by persistent jet-stream patterns will increase. Sea ice thickness is a fundamental climate state variable that provides an integrated measure of changes in the high-latitude energy balance. However, observations of mean ice thickness have been sparse in time and space, making the construction of observation-based time series difficult. Moreover, different groups use a variety of methods and processing procedures to measure ice thickness, and each observational source likely has different and poorly characterized measurement and sampling errors. Observational sources used in this study include upward-looking sonars mounted on submarines or moorings, electromagnetic sensors on helicopters or aircraft, and lidar or radar altimeters on airplanes or satellites. Here we use a curve-fitting approach to determine the large-scale spatial and temporal variability of the ice thickness as well as the mean differences between the observation systems, using over 3000 estimates of the ice thickness. The thickness estimates are measured over spatial scales of approximately 50 km or time scales of 1 month, and the primary time period analyzed is 2000-2012 when the modern mix of observations is available. Good agreement is found between five of the systems, within 0.15 m, while systematic differences of up to 0.5 m are found for three others compared to the five. The trend in annual mean ice thickness over the Arctic Basin is -0.58± 0.07 m decade-1over the period 2000-2012. Applying our method to the period 1975-2012 for the central Arctic Basin where we have sufficient data (the SCICEX box), we find that the annual mean ice thickness has decreased from 3.59 m in 1975 to 1.25 m in 2012, a 65% reduction. This is nearly double the 36% decline reported by an earlier study. These results provide additional direct observational evidence of substantial sea ice losses found in model analyses. The role of ocean-atmosphere coupling in thebook=41,ebook=41zonal-mean climate response to projected late twentyfirst-century Arctic sea ice loss is investigated using Community Climate System Model version 4 (CCSM4) at 1° spatial resolution. Parallel experiments with different ocean model configurations (full-depth, slab, and no interactive ocean) allow the roles of dynamical and thermodynamic ocean feedbacks to be isolated. In the absence of ocean coupling, the atmospheric response to Arctic sea ice loss is confined to north of 30°N, consisting of a weakening and equatorward shift of the westerlies accompanied by lower tropospheric warming and enhanced precipitation at high latitudes. With ocean feedbacks, the response expands to cover the whole globe and exhibits a high degree of equatorial symmetry: The entire troposphere warms, the global hydrological cycle strengthens, and the intertropical convergence zones shift equatorward. Ocean dynamics are fundamental to producing this equatorially symmetric pattern of response to Arctic sea ice loss. Finally, the absence of a poleward shift of the wintertime Northern Hemisphere westerlies in CCSM4’s response to greenhouse gas radiative forcing is shown to result from the competing effects of Arctic sea ice loss and greenhouse warming on the meridional temperature gradient in middle latitudes. The areal extent, concentration and thickness of sea ice in the Arctic Ocean and adjacent seas have strongly decreased during the recent decades, but cold, snow-rich winters have been common over mid-latitude land areas since 2005. A review is presented on studies addressing the local and remote effects of the sea ice decline on weather and climate. It is evident that the reduction in sea ice cover has increased the heat flux from the ocean to atmosphere in autumn and early winter. This has locally increased air temperature, moisture, and cloud cover and reduced the static stability in the lower troposphere. Several studies based on observations, atmospheric reanalyses, and model experiments suggest that the sea ice decline, together with increased snow cover in Eurasia, favours circulation patterns resembling the negative phase of the North Atlantic Oscillation and Arctic Oscillation. The suggested large-scale pressure patterns include a high over Eurasia, which favours cold winters in Europe and northeastern Eurasia. A high over the western and a low over the eastern North America have also been suggested, favouring advection of Arctic air masses to North America. Mid-latitude winter weather is, however, affected by several other factors, which generate a large inter-annual variability and often mask the effects of sea ice decline. In addition, the small sample of years with a large sea ice loss makes it difficult to distinguish the effects directly attributable to sea ice conditions. Several studies suggest that, with advancing global warming, cold winters in mid-latitude continents will no longer be common during the second half of the twenty-first century. Recent studies have also suggested causal links between the sea ice decline and summer precipitation in Europe, the Mediterranean, and East Asia Over the past decade, severe winters occurred frequently in mid-latitude Eurasia, despite increasing global and annual-mean surface air temperatures. Observations suggest that these cold Eurasian winters could have been instigated by Arctic sea-ice decline, through excitation of circulation anomalies similar to the Arctic Oscillation. In climate simulations, however, a robust atmospheric response to sea-ice decline has not been found, perhaps owing to energetic internal fluctuations in the atmospheric circulation. Here we use a 100-member ensemble of simulations with an atmospheric general circulation model driven by observation-based sea-ice concentration anomalies to show that as a result of sea-ice reduction in the Barents-Kara Sea, the probability of severe winters has more than doubled in central Eurasia. In our simulations, the atmospheric response to sea-ice decline is approximately independent of the Arctic Oscillation. Both reanalysis data and our simulations suggest that sea-ice decline leads to more frequent Eurasian blocking situations, which in turn favour cold-air advection to Eurasia and hence severe winters. Based on a further analysis ofbook=42,ebook=42simulations from 22 climate models we conclude that the sea-ice-driven cold winters are unlikely to dominate in a warming future climate, although uncertainty remains, due in part to an insufficient ensemble size. The ongoing loss of Arctic sea-ice cover has implications for the wider climate system. The detection and importance of the atmospheric impacts of sea-ice loss depends, in part, on the relative magnitudes of the sea-ice forced change compared to natural atmospheric internal variability (AIV). This study analyses large ensembles of two independent atmospheric general circulation models in order to separate the forced response to historical Arctic sea-ice loss (1979-2009) from AIV, and to quantify signal-to-noise ratios. We also present results from a simulation with the sea-ice forcing roughly doubled in magnitude. In proximity to regions of sea-ice loss, we identify statistically significant near-surface atmospheric warming and precipitation increases, in autumn and winter in both models. In winter, both models exhibit a significant lowering of sea level pressure and geopotential height over the Arctic. All of these responses are broadly similar, but strengthened and/or more geographically extensive, when the sea-ice forcing is doubled in magnitude. Signal-tonoise ratios differ considerably between variables and locations. The temperature and precipitation responses are significantly easier to detect (higher signal-to-noise ratio) than the sea level pressure or geopotential height responses. Equally, the local response (i.e., in the vicinity of sea-ice loss) is easier to detect than the mid-latitude or upper-level responses. Based on our estimates of signal-to-noise, we conjecture that the local near-surface temperature and precipitation responses to past Arctic sea-ice loss exceed AIV and are detectable in observed records, but that the potential atmospheric circulation, upper-level and remote responses may be partially or wholly masked by AIV. The area of Arctic September sea ice has diminished from about 7 million km2in the 1990s to less than 5 million km2in five of the past seven years, with a record minimum of 3.6 million km2in 2012. The strength of this decrease is greater than expected by the scientific community, the reasons for this are not fully understood, and its simulation is an on-going challenge for existing climate models. With growing Arctic marine activity there is an urgent demand for forecasting Arctic summer sea ice. Previous attempts at seasonal forecasts of ice extent were of limited skill. However, here we show that the Arctic sea-ice minimum can be accurately forecasted from melt-pond area in spring. We find a strong correlation between the spring pond fraction and September sea-ice extent. This is explained by a positive feedback mechanism: more ponds reduce the albedo; a lower albedo causes more melting; more melting increases pond fraction. Our results help explain the acceleration of Arctic sea-ice decrease during the past decade. The inclusion of our new melt-pond model promises to improve the skill of future forecast and climate models in Arctic regions and beyond A new record low Arctic sea ice extent for the satellite era, 3.4×106km2, was reached on 13 September 2012; and a new record low sea ice area, 3.0×106km2, was reached on the same date. Preconditioning through decades of overall ice reductions made the ice pack more vulnerable to a strong storm that entered the central Arctic in early August 2012. The storm caused the separation of an expanse of 0.4×106km2of ice that melted in total, while its removal left the main pack more exposed to wind and waves, facilitating the main pack’s further decay. Future summer storms could lead to a further acceleration of the decline in the Arctic sea ice cover and should be carefully monitored. Arctic sea ice is declining at an increasing rate with potentially important repercussions. To understand better the atmospheric changes that may have occurred in response to Arctic sea ice loss, this study presents results from atmospheric general circulation model (AGCM) experiments in which the only time-varying forcings prescribed were observed variations in Arctic sea ice and accompanying changes in Arctic sea surface temperatures from 1979 to 2009. Two independent AGCMs are utilized in order to assess the robustness of the response across different models. The results suggest that the atmospheric impacts of Arctic sea ice loss have been manifested most strongly within the maritime and coastal Arctic and in the lowermost atmosphere. Sea ice loss has driven increased energy transfer from the ocean to the atmosphere, enhanced warming and moistening of the lower troposphere, decreased the strength of the surface temperature inversion, and increased lower-tropospheric thickness; all of these changes are most pronounced in autumn and early winter (September-December). The early winter (November-December) atmospheric circulation response resembles the negative phase of the North Atlantic Oscillation (NAO); however, the NAO-type response is quite weak and is often masked by intrinsic (unforced) atmospheric variability. Some evidence of a late winter (March-April) polar stratospheric cooling response to sea ice loss is also found, which may have important implications for polar stratospheric ozone concentrations. The attribution and quantification of other aspects of the possible atmospheric response are hindered by model sensitivities and large intrinsic variability. The potential remote responses to Arctic sea ice change are currently hard to confirm and remain uncertain. This model study examines the impact of an intense early August cyclone on the 2012 record low Arctic sea ice extent. The cyclone passed when Arctic sea ice was thin and the simulated Arctic ice volume had already declined similar to 40% from the 2007-2011 mean. The thin sea ice pack and the presence of ocean heat in the near surface temperature maximum layer created conditions that made the ice particularly vulnerable to storms. During the storm, ice volume decreased about twice as fast as usual, owing largely to a quadrupling in bottom melt caused by increased upward ocean heat transport. This increased ocean heat flux was due to enhanced mixing in the oceanic boundary layer, driven by strong winds and rapid ice movement. A comparison with a sensitivity simulation driven by reduced wind speeds during the cyclone indicates that cyclone-enhanced bottom melt strongly reduces ice extent for about 2 weeks, with a declining effect afterward. The simulated Arctic sea ice extent minimum in 2012 is reduced by the cyclone but only by 0.15×106km2(4.4%). Thus, without the storm, 2012 would still have produced a record minimum.

Recent advances in understanding the Arctic climate system state and change from a sea ice perspective: A review

R. D?scher; T. Vihma; E. Maksimovich

來源出版物：Atmospheric Chemistry and Physics, 2014, 14: 13571–13600

Role of Arctic sea ice in global atmospheric circulation: A review

Dagmar Budikova

來源出版物：Global and Planetary Change, 2009, 68: 149–163

Winter weather patterns over northern eurasia and arctic sea ice loss

Bingyi Wu; D?rthe Handorf; Klaus Dethloff; et al.

Keywords:extreme weather event; tripole wind pattern; autumn sea ice decline; cold winter Arctic sea ice; Arctic boundary layer; atmospheric circulation; numerical modelling The relationship of Barents-Kara sea ice concentration in October and November with atmospheric circulation in the subsequent winter is examined using reanalysis and observational data. The analyses are performed on data with the 5-year running means removed to reduce the potential effects of slowly-varying external driving factors, such as global warming. We show that positive (negative) Barents-Kara sea ice concentration anomaly in autumn is associated with a positive (negative) North Atlantic Oscillation-like (NAO) pattern with lags of up to 3 months. The month-to-month variations in the climate impact of arctic sea ice; sea ice-atmosphere interaction; North Atlantic Oscillation; stratosphere downward propagation geographic location; entity; Arctic; sea ice; circulation; dynamics; clouds; physical meteorology and climatology; feedback; surface fluxes; models and modeling; climate models water cycle; precipitation; sea ice; climate change; deuterium excess jet stream; Arctic amplification; extreme weather arctic; climate change; mid-latitude weather; sea ice; snow; winter weather Arctic sea ice; atmospheric modelling; ensembles; detection and attribution; internal variability; signal-to-noise ratio