·編者按·

北極海冰與全球氣候變化

·編者按·

根據(jù)NASA與NSIDC（美國國家冰雪數(shù)據(jù)中心）的研究數(shù)據(jù)顯示，今年冬季北極海冰覆蓋面積，為有衛(wèi)星記錄以來的最小值（圖1）。2016年3月24日，冬季北極海冰達(dá)到年度最大值，覆蓋面積為1452萬km2，但這卻是自1979年有衛(wèi)星記錄以來的最小值，這個(gè)數(shù)值比1981年至2010年冬季北極最大海冰覆蓋面積的平均值縮減了111.6萬km2。之前北極海冰有記錄以來的最小覆蓋面積，發(fā)生在2015年2月15日，冬季北極海冰達(dá)到年度最大值，覆蓋面積為1454萬km2，也就是說2016年冬季海冰的覆蓋面積比2015年少了2萬km2?？傮w上來說，冬季北極海冰的覆蓋面積每10年大約下降2.8%，遠(yuǎn)小于夏季北極海冰的縮小面積，但都反映了北極長期變暖的趨勢(shì)。

圖1　北極海冰覆蓋情況（美國國家雪冰中心統(tǒng)計(jì)）

北極海冰（arctic sea ice）是指北極地區(qū)直接由海水凍結(jié)而成的咸水冰，亦包括進(jìn)入海洋中的大陸冰川、冰山和冰島等。長期以來，北冰洋由密集的海冰所覆蓋，夏季北冰洋海冰面積僅占冬季面積的10%左右。自20世紀(jì)70年代以來，全球氣溫持續(xù)升高，而北極的增暖趨勢(shì)是全球平均的2倍以上。據(jù)科學(xué)家預(yù)測(cè)，在不久的將來，將會(huì)出現(xiàn)夏季無冰的北冰洋。北極海冰消融以及北極增暖不僅影響北極地區(qū)的生態(tài)環(huán)境，而且通過復(fù)雜的反饋過程對(duì)北半球天氣氣候產(chǎn)生影響。

已有的研究表明，在冬季，北極可以影響我國的天氣和氣候。我國北方冬季普遍增暖和極端嚴(yán)寒天氣都與北極的作用密不可分。北極變化改變了大氣環(huán)流，對(duì)沙塵和霧霾的輸送強(qiáng)度產(chǎn)生重要影響。春季和秋季是冷暖氣團(tuán)彼此交鋒和消長時(shí)期，通常與鋒區(qū)的活動(dòng)和北方的干旱過程相聯(lián)系。北極的可能影響還有很多方面，如對(duì)海上風(fēng)暴、夏季酷熱、秋季降雪的影響等，其中大部分尚未充分研究。

北極對(duì)我國氣候的影響會(huì)導(dǎo)致一系列重大的社會(huì)經(jīng)濟(jì)影響。比如對(duì)主要產(chǎn)糧區(qū)氣候的影響，直接威脅到我國的糧食安全。又如氣候?yàn)?zāi)害的發(fā)生，對(duì)全國產(chǎn)生多種可能的災(zāi)害。對(duì)北極變化的深入研究是推動(dòng)北極變化對(duì)我國氣候影響研究的主要渠道，攻克一系列尚未解決的科學(xué)問題，為解決北極影響我國的過程和機(jī)理、提高氣候預(yù)測(cè)精度和水平奠定堅(jiān)實(shí)的基礎(chǔ)，支持國家有關(guān)部門提出切實(shí)的措施和必要的對(duì)策，應(yīng)對(duì)北極變化對(duì)我國氣候的強(qiáng)烈影響。

本專題得到秦大河院士（中國氣象局）、趙進(jìn)平教授（中國海洋大學(xué)）、沈永平研究員（《冰川凍土》編輯部）、武炳義副研究員（中國科學(xué)院大氣物理研究所）的大力支持。

·熱點(diǎn)數(shù)據(jù)排行·

截至2016年3月4日，中國知網(wǎng)（CNKI）和Web of Science（WOS）的數(shù)據(jù)報(bào)告顯示，以“北極海冰（Arctic sea ice）”為詞條可以檢索到的期刊文獻(xiàn)分別為201條與7688條，本專題將相關(guān)數(shù)據(jù)按照：研究機(jī)構(gòu)發(fā)文數(shù)、作者發(fā)文數(shù)、期刊發(fā)文數(shù)、被引用頻次進(jìn)行排行，結(jié)果如下。

研究機(jī)構(gòu)發(fā)文數(shù)量排名（CNKI）

研究機(jī)構(gòu)發(fā)文數(shù)量排名（WOS）

作者發(fā)文數(shù)量排名（CNKI）

作者發(fā)文數(shù)量排名（WOS）

期刊發(fā)文數(shù)量排名（CNKI）

期刊發(fā)文數(shù)量排名（WOS）

根據(jù)中國知網(wǎng)（CNKI）數(shù)據(jù)報(bào)告，以“北極海冰（Arctic sea ice）”為詞條可以檢索到的高被引論文排行結(jié)果如下。

國內(nèi)數(shù)據(jù)庫高被引論文排行

（數(shù)據(jù)來源：中國知網(wǎng)，檢索時(shí)間：2016-03-04）

根據(jù)Web of Science統(tǒng)計(jì)數(shù)據(jù)，以“北極海冰（Arctic sea ice）”為詞條可以檢索到的高被引論文排行結(jié)果如下。

國外數(shù)據(jù)庫高被引論文排行

·經(jīng)典文獻(xiàn)推薦·

基于Web of Science檢索結(jié)果，利用Histcite軟件選取LCS（Local Citation Score，本地引用次數(shù)）TOP 50文獻(xiàn)作為節(jié)點(diǎn)進(jìn)行分析，得到本領(lǐng)域推薦的經(jīng)典文獻(xiàn)如下。

本領(lǐng)域經(jīng)典文獻(xiàn)

來源出版物：Journal of Geophysical Research Atmospheres, 1989, 94(C10): 14485-14498

Recent decrease of sea level pressure in the central Arctic

Walsh, JE; Chapman, WL; Shy, TL

Abstract: Arctic sea level pressure data from the period of the Arctic Ocean Buoy Program show a significant decrease in the annual mean. In every calendar month, the annual mean is lower in the second half of the 1979-1994 period than in the first. The changes of the annual means are larger in the central Arctic than anywhere else in the Northern Hemisphere. The decreases are largest and statistically significant in the autumn and winter. The annual anomalies became negative relative to the 16-yr mean in the 1980s and have been negative in every year since 1988. Correspondingly, the mean anticyclone in the Arctic pressure field has weakened and the vorticity of the gradient wind held over the central Arctic Ocean has became more positive than at any time in the past several decades. The pressure decrease, which has been compensated by pressure increases over the subpolar oceans, implies that the wind forcing of sea ice contains an enhanced cyclonic component relative to earlier decades.

來源出版物：Journal of Climate, 1996, 9(2): 480-486

Thinning of the Arctic sea-ice cover

Rothrock, DA; Yu, Y; Maykut, GA; et al.

Abstract: Comparison of sea-ice draft data acquired on submarine cruises between 1993 and 1997 with similar data acquired between 1958 and 1976 indicates that the mean ice draft at the end of the melt season has decreasedby about 1.3 m in most of the deep water portion of the Arctic Ocean, from 3.1 m in 1958-1976 to 1.8 m in the 1990s. The decrease is greater in the central and eastern Arctic than in the Beaufort and Chukchi seas. Preliminary evidence is that the ice cover has continued to become thinner in some regions during the 1990s.

來源出版物：Geophysical Research Letters, 1999, 26(23): 3469-3472

Arctic sea ice extents, areas, and trends, 1978-1996

Parkinson, CL; Cavalieri, DJ; Gloersen, P; et al.

Abstract: Satellite passive-microwave data for November 1978 through December 1996 reveal marked seasonal, regional, and interannual variabilities, with an overall decreasing trend of ?34300±3700 km2/yr(?2.8%/decade) in Arctic sea ice extents over the 18.2-year period. Decreases occur in all seasons and on a yearly average basis, although they are largest in spring and smallest in autumn. Regionally, the Kara and Barents Seas have the largest decreases, at ?15200±1900 km2/yr(?10.5%/decade), followed by the Seas of Okhotsk and Japan, the Arctic Ocean, Greenland Sea, Hudson Bay, and Canadian Archipelago. The yearly average trends for the total, the Kara and Barents Seas, and the Seas of Okhotsk and Japan all have high statistical significance, with the null hypothesis of a 0 slope being rejected at a 99% confidence level. Regions showing increasing yearly average ice extents are Baffin Bay/Labrador Sea, the Gulf of St. Lawrence, and the Bering Sea, with only the increases in the Gulf of St. Lawrence being statistically significant at the 99% level. Hemispheric results for sea ice areas exhibit the same ?2.8%/decade decrease as for ice extents and hence a lower absolute decrease(?29500±3800 km2/yr), with the ice-free area within the ice pack correspondingly decreasing at ?4800±1600 km2/yr. Confidence levels for the trends in ice areas and ice-free water areas exceed 99% and 95%, respectively. Nonetheless, interannual variability is high, and, for instance, the Arctic Ocean ice extents have a positive trend 1990–1996, in spite of their negative trend for the time period as a whole.

來源出版物：Journal of Geophysical Research Oceans, 1999, 104(C9): 20837-20856

The Arctic’s rapidly shrinking sea ice cover: A research synthesis

Stroeve, Julienne C; Serreze, Mark C; Holland, Marika M; et al.

Abstract: The sequence of extreme September sea ice extent minima over the past decade suggests acceleration in the response of the Arctic sea ice cover to external forcing, hastening the ongoing transition towards a seasonally open Arctic Ocean. This reflects several mutually supporting processes. Because of the extensive open water in recent Septembers, ice cover in the following spring is increasingly dominated by thin, first-year ice(ice formed during the previous autumn and winter) that is vulnerable to melting out in summer. Thinner ice in spring in turn fosters a stronger summer ice-albedo feedback through earlier formation of open water areas. A thin ice cover is also more vulnerable to strong summer retreat under anomalous atmospheric forcing. Finally, general warming of the Arctic has reduced the likelihood of cold years that could bring about temporary recovery of the ice cover. Events leading to the September ice extent minima of recent years exemplify these processes.

來源出版物：Climatic Change, 2012, 110(3-4): 1005-1027

·推薦綜述·

北極海冰減退引起的北極放大機(jī)理與全球氣候效應(yīng)

趙進(jìn)平，史久新，王召民，李志軍，黃菲

北極是地球的寒極，是北半球氣候系統(tǒng)穩(wěn)定的重要基礎(chǔ)之一。長期以來，北冰洋由密集的海冰覆蓋，夏季北冰洋海冰融化面積僅占冬季的10%左右。自從20世紀(jì)70年代以來，全球氣溫持續(xù)升高，全球變暖已經(jīng)成為不爭(zhēng)的事實(shí)。全球變暖對(duì)北極產(chǎn)生了持續(xù)的影響，導(dǎo)致北極逐漸變暖。21世紀(jì)以來，北極增暖的趨勢(shì)是全球平均水平的2倍，被稱為“北極放大”現(xiàn)象。

北極放大的原因之一是其下墊面主要是海洋。夏季海冰厚度和覆蓋面積的減小直接導(dǎo)致海洋吸收太陽輻射能的增加，一方面加劇海冰的融化，一方面越來越多的開闊海面對(duì)大氣產(chǎn)生異常加熱，形成正反饋效應(yīng)。在各種可能的反饋中，最為明確的正反饋是海冰—?dú)鉁胤答仯幢┓凑章史答仯?。這種加快的正反饋過程不僅會(huì)影響極區(qū)的氣候變化，而且還會(huì)加劇北極對(duì)高緯氣候的放大效應(yīng)。由于更加溫暖的寒極改變了地球熱機(jī)的行為，對(duì)全球氣候產(chǎn)生非常顯著的影響。海冰和海洋的變化過程將會(huì)導(dǎo)致北極氣候變化到達(dá)臨界點(diǎn)（tipping point），產(chǎn)生強(qiáng)烈的全球效應(yīng)。

本文根據(jù)國內(nèi)外最新研究成果，歸納關(guān)于北極海冰減退引起的北極放大機(jī)理與全球氣候效應(yīng)有關(guān)的主要科學(xué)問題，從更廣闊的視野看待北極的變化，指出需要重點(diǎn)開展的研究工作，促進(jìn)多學(xué)科的交叉，推動(dòng)北極科學(xué)的發(fā)展。

1北極海冰快速變化的關(guān)鍵物理因素

北極海冰的變化與全球變暖幾乎是同時(shí)發(fā)生的。20世紀(jì)70年代起，北極海冰覆蓋范圍呈不斷減小的變化趨勢(shì)，海冰厚度和海冰密集度也持續(xù)降低，北冰洋多年冰減少。海冰變化的早期主要是海冰厚度的變化，海冰覆蓋率的變化并不顯著，沒有引起足夠的注意。21世紀(jì)以來，海冰覆蓋范圍出現(xiàn)顯著變化。2007年發(fā)生了北極海冰覆蓋面積突然減少31%的事件，引起了北極科學(xué)界的高度關(guān)注。2012年，北極海冰又一次發(fā)生了驟減，海冰覆蓋范圍降到歷史新低，是迄今觀測(cè)到的最小海冰覆蓋率。

最新的研究表明，2007年和2012年夏季北極海冰覆蓋面積大幅度減少在過去1450年以來都是獨(dú)一無二的。CMIPS模擬結(jié)果顯示，在RCP8.5情景下，模式結(jié)果無一例外地表現(xiàn)出在未來20～40年會(huì)出現(xiàn)夏季無冰的北冰洋。海冰的減少被認(rèn)為是北極放大現(xiàn)象的關(guān)鍵因素。海冰的減少不僅與氣溫升高有關(guān)，還受以下各種因素的影響：

1）隨著北極氣溫的升高，海冰內(nèi)部結(jié)構(gòu)發(fā)生了微妙的變化。海冰吸收外界熱量，冰晶體之間的鹵水通道擴(kuò)張，冰內(nèi)部的固態(tài)、液態(tài)、氣態(tài)成分比例不斷發(fā)生變化。冰的結(jié)構(gòu)體現(xiàn)為與以往不同的復(fù)合材料，冰的光學(xué)、熱學(xué)、力學(xué)、電學(xué)、磁學(xué)等性質(zhì)發(fā)生相應(yīng)的變化。其中光學(xué)、熱學(xué)性質(zhì)的變化決定了海冰在生消過程中的熱質(zhì)平衡；力學(xué)性質(zhì)變化決定了海冰在外界動(dòng)力下的破碎過程，這些變化直接決定海冰快速變化過程因。

2）冰面融池是積雪融化的產(chǎn)物，迄今觀測(cè)到夏季北極最大的融池覆蓋率達(dá)到56%以上，對(duì)海冰的融化有不可忽視的影響。由于融池表面反照率低，融池水吸收的太陽短波輻射多，通過沖洗效應(yīng)影響海冰的融化因，導(dǎo)致氣—冰—海熱力學(xué)結(jié)構(gòu)發(fā)生變化，直接加快海冰的融化過程。近年來，通透的融池比例增大，海冰的大尺度應(yīng)變特征也發(fā)生了變化，進(jìn)而影響海冰的動(dòng)力破碎過程。

3）積雪變化是海冰變化最重要的因素之一。如果春季積雪快速融化，會(huì)使海冰直接暴露在日光下，導(dǎo)致夏季海冰大量消融。如果春季積雪保留到夏季，會(huì)大幅削減到達(dá)海冰的太陽輻射，使大量海冰保存到下一年。由于積雪的觀測(cè)手段很少，人們對(duì)積雪的了解很不充分。衛(wèi)星遙感反演積雪信息主要是光學(xué)遙感和微波遙感兩大類。光學(xué)遙感只能用于研究積雪的覆蓋范圍，而被動(dòng)微波遙感可以反演0.5 m以下厚度的積雪。Markus等利用SSM/I微波輻射計(jì)數(shù)據(jù)反演積雪深度，與船測(cè)月平均積雪深度相比，相關(guān)系數(shù)為0.81，平均偏差為3.5 cm。美國國家冰雪數(shù)據(jù)中心（National Snow and Ice Data Center, NSIDC）發(fā)布了基于Aqua/AMSR-E數(shù)據(jù)反演的積雪深度產(chǎn)品。在北極，積雪深度反演的誤差很大，尤其是對(duì)其準(zhǔn)確性缺乏檢驗(yàn)的手段。人們期待更準(zhǔn)確的數(shù)據(jù)問世，以增加對(duì)積雪熱力學(xué)作用的深入研究。

4）海冰的運(yùn)動(dòng)也是改變海冰特性的重要因素之一。北極海冰平均漂流場(chǎng)體現(xiàn)為穿極流和波弗特渦流2個(gè)主要特征。近年來隨著海冰減少，北極海冰漂流速度增加，2004—2009年的冰速增大46%/10 a。北極中央?yún)^(qū)域冰速的變化被認(rèn)為主要是由風(fēng)場(chǎng)增強(qiáng)造成的，而北冰洋邊緣海海冰加速則是由海冰變薄引起的。Wang等的研究表明，海冰漂流場(chǎng)變化的不僅是冰速，而且體現(xiàn)為漂流類型的變化。根據(jù)1978—2006年的漂流數(shù)據(jù)分析，海冰漂流可以分為4種主要流型：標(biāo)準(zhǔn)流型（38%），反氣旋流型（15%）、氣旋式流型（16%）以及反對(duì)稱流型（15%）。這些流型表明，海冰的漂流有不同的輻聚輻散特征，對(duì)海冰的變化有多種影響。人們密切關(guān)注的是，當(dāng)海冰進(jìn)一步減退、密集度減小、冰厚變薄之后，海冰的漂流會(huì)有什么變化。

5）影響海冰漂流場(chǎng)變化的主要因素是大氣環(huán)流的變化。海冰一方面受風(fēng)應(yīng)力的驅(qū)動(dòng)而發(fā)生運(yùn)動(dòng)，另一方面又受到冰場(chǎng)內(nèi)部的相互制約，二者并不完全一致，但有很高的相關(guān)性。北極濤動(dòng)（The Aretie Oscillation, AO）指數(shù)是北極大氣環(huán)流的重要指數(shù)。研究表明，當(dāng)AO為正位相時(shí)，波弗特流渦較小，穿極流更靠近西北冰洋；而當(dāng)AO為負(fù)位相時(shí)，波弗特流渦范圍很大，穿極流向東北冰洋偏移。

綜上所述，除了氣溫升高之外，海冰結(jié)構(gòu)、冰面融池、冰面積雪和海冰運(yùn)動(dòng)構(gòu)成了海冰融化的主要影響因素，其中大部分因素的作用還不清楚，有些參數(shù)的觀測(cè)很困難，需要開發(fā)特殊的觀測(cè)手段獲取數(shù)據(jù)。在北極氣溫顯著升高背景下，海冰內(nèi)部結(jié)構(gòu)發(fā)生了很大的變化，需要明確認(rèn)識(shí)海冰結(jié)構(gòu)的變化，并將其熱力學(xué)特性的改變定量表達(dá)出來。北極的融池覆蓋率升高會(huì)導(dǎo)致海冰迅速破碎，需要揭示融池本身的熱力學(xué)特征及其對(duì)海冰的熱力學(xué)和動(dòng)力學(xué)過程的影響。北極的積雪在春季全部融化，是容易被忽視的因素，但事實(shí)上積雪的作用直接影響到夏季海冰的去留，需要深入揭示積雪與海冰變化的聯(lián)系。此外，海冰厚度的變化、海冰的側(cè)向融化和海冰漂移過程都是影響海冰變化的關(guān)鍵因素，相關(guān)的物理過程需要深入研究。

2北極海冰變化導(dǎo)致的主要海洋過程

事實(shí)上，北極的海洋變化是影響海冰變化的最重要因素之一。北極海冰范圍和密集度減小使得冰間水道增加，穿過冰間水道進(jìn)入海洋的太陽輻射能增加，導(dǎo)致海洋獲得了更多的熱量，是“北極放大”過程的主要能量來源。過去30年的海冰減退極大地改變了北冰洋上混合層的熱收支。數(shù)值模擬的結(jié)果表明，北冰洋上層海洋在21世紀(jì)增暖能量的80%來自于海表面的熱通量。北冰洋的海表面溫度（Sea Surface Temperature, SST）從1995年左右開始出現(xiàn)升溫，2000年之后更為突出，2007年夏季的SST距平高達(dá)5℃。在幾乎全部被海冰覆蓋的北極中央?yún)^(qū)，夏季海洋的上50 m層也有顯著增溫，混合層的溫度能夠高于冰點(diǎn)0.4℃。北極季節(jié)性無冰區(qū)面積年際差異很大，導(dǎo)致?！?dú)忾g熱通量發(fā)生較大的季節(jié)性和年際波動(dòng)，對(duì)整個(gè)北冰洋熱含量長期變化的貢獻(xiàn)率接近1/3。北冰洋上層海洋增暖最重要的現(xiàn)象是次表層暖水的出現(xiàn)，后來國外將其稱為近表層溫度極大值(Near Surface Temperature Maximum)。次表層暖水發(fā)生在20～40 m深度范圍內(nèi)，溫度在-0.5℃以上，是儲(chǔ)存太陽輻射的一種特殊形式。1993—2009年，次表層暖水的溫度上升了1.5℃。次表層暖水的熱量釋放會(huì)導(dǎo)致北極海冰提前融化和延后凍結(jié)，意味著季節(jié)性海冰區(qū)的范圍正在擴(kuò)大，對(duì)海洋熱儲(chǔ)存帶來非常大的影響。計(jì)算表明，北冰洋夏季上層海洋變暖足以使冬季的海冰生長減少0.75 m，使秋季的結(jié)冰推遲2周至2個(gè)月。

雖然海洋在不斷地增暖，但海洋實(shí)際增加的熱含量并不多。海洋吸收的熱量絕大多數(shù)通過湍流運(yùn)動(dòng)向上傳輸，這些熱量被稱為冰下海洋熱通量。冰下海洋熱通量有著顯著的季節(jié)變化，冬季較小，在8月可以達(dá)到40～60 W/m2。在冰間水道中，海洋熱通量會(huì)通過長波輻射、感熱和潛熱通量直接進(jìn)入大氣，成為影響大氣熱過程的主要因素，在北極放大過程中被稱為“海洋強(qiáng)迫”。在海冰之下，海洋熱通量中只有很少部分進(jìn)入海冰，并通過海冰進(jìn)入大氣。以往認(rèn)為穿過海冰的熱通量為2 W/m2。后來的觀測(cè)表明，這一數(shù)值被低估了近1倍。夏季到達(dá)冰下的海洋熱通量遠(yuǎn)大于穿過海冰散熱的熱通量，導(dǎo)致大量熱量在冰下積聚，直接造成海冰的底部融化，是海冰厚度減薄的主要因素。

海洋熱通量的絕大部分能量來自太陽短波輻射，還有一部分來自海洋的熱平流。海洋環(huán)流在2個(gè)方面導(dǎo)致海水熱量的輸運(yùn)與再分配：一是將低緯度的暖水（太平洋水和大西洋水）輸運(yùn)到北冰洋；二是把北冰洋內(nèi)部加熱的水體重新分布，主要體現(xiàn)在表層環(huán)流對(duì)海洋熱量的再分配。表層環(huán)流隨風(fēng)場(chǎng)變化，其細(xì)節(jié)結(jié)構(gòu)還需要深入研究。通過白令海峽進(jìn)入的太平洋入流，在夏季直接影響楚科奇海海冰融化，在冬季則成為保留在北極海冰之下的一個(gè)次表層海洋熱源，對(duì)北冰洋太平洋扇區(qū)的海冰減退有重要貢獻(xiàn)。實(shí)際上，太平洋水水層厚度只有幾十米，入流流量只有1 Sv左右，攜帶的熱量在融冰中很快耗盡，無法對(duì)北冰洋深處的海冰融化產(chǎn)生顯著影響。真正影響大范圍海冰的是開闊水域受到局地加熱的水體，這些水體不斷進(jìn)入冰區(qū)加劇海冰融化。相比之下，來自弗萊姆海峽的大西洋入流水層厚度數(shù)百米，流量5 Sv以上，不僅深刻影響北冰洋中大西洋扇區(qū)的海冰，維系了大面積的冰間湖，而且通過對(duì)流潛沉到200 m以下，形成北極中層水，通過環(huán)極邊界流輸送到北冰洋各個(gè)海盆。北冰洋海盆區(qū)北極中層水的熱量被鹽躍層抑制不能上傳，但在北冰洋邊緣海域存在上升流，將暖水帶到近表層海域，導(dǎo)致加拿大海盆外圍的海冰大范圍融化。

大西洋亞極地海區(qū)的強(qiáng)對(duì)流是全球熱鹽環(huán)流的主要?jiǎng)恿?，而北冰洋淡水含量變化是影響該海區(qū)對(duì)流和層化過程的重要因素。Proshutinsky等首次開展了針對(duì)北冰洋淡水含量的研究，此前并未引起關(guān)注的北冰洋淡水含量變化成為近年來的研究熱點(diǎn)。北冰洋中心海區(qū)在20世紀(jì)呈現(xiàn)出咸化趨勢(shì)，淡水以（239±270）km3/10 a的速度減少。但在20世紀(jì)末以來，淡水含量呈顯著增加態(tài)勢(shì)。到2010年，加拿大海盆淡水含量接近45800 km3，約占北冰洋淡水總量的60%，是北冰洋淡水的主要分布區(qū)域。研究發(fā)現(xiàn)，除2006年以外，2003—2008年夏季加拿大海盆淡水含量每年增加1 m以上厚度。夏季太平洋水的鹽度范圍已從1993年的變化為2008年的28～32。淡水含量的變化引起海面動(dòng)力地形的改變，進(jìn)而引起了環(huán)流的調(diào)整，改變著波弗特流渦的流型和密度結(jié)構(gòu)。加拿大海盆中的淡水通過弗拉姆海峽和加拿大北極群島進(jìn)入北大西洋，引起了表面鹽度降低和層化加強(qiáng)，成為影響北歐海和北大西洋對(duì)流過程以及全球海洋經(jīng)向翻轉(zhuǎn)環(huán)流的重要因素。

北冰洋常年存在的主鹽躍層被稱為永久性鹽躍層。在北冰洋的中央?yún)^(qū)，特別是阿蒙森海盆和馬可羅夫海盆，鹽躍層的上部表現(xiàn)為溫度保持在冰點(diǎn)附近，而鹽度隨深度顯著增加的特殊溫鹽結(jié)構(gòu)特征，被稱為冷鹽躍層。冷鹽躍層的形成和變化一直是北冰洋研究的熱點(diǎn)。在2000年前后，馬可羅夫海盆的冷鹽躍層經(jīng)歷了從消退到恢復(fù)的特殊變化，引起了廣泛的關(guān)注。在加拿大海盆，由于太平洋水的匯入，鹽躍層結(jié)構(gòu)不同于冷鹽躍層，而是表現(xiàn)為雙躍層結(jié)構(gòu)。近年的觀測(cè)資料顯示，在北冰洋次表層海水中還存在一個(gè)季節(jié)性鹽躍層。夏季，隨著海冰的消融，在20 m附近會(huì)出現(xiàn)一個(gè)低溫低鹽的鹽躍層；秋季過后，該鹽躍層會(huì)慢慢消失。這個(gè)次表層鹽躍層是次表層暖水發(fā)生的必要條件。由于北冰洋存在多重的鹽度躍層，每個(gè)鹽躍層都會(huì)對(duì)垂直方向的熱量傳輸起到抑制作用，下層的熱量上不來，上層的熱量下不去。因此，北冰洋有氣候效應(yīng)的水體實(shí)際上只有幾十米厚。

北極的變化以海冰變化為主要特征，海洋的作用不那么直觀。然而，海洋才是北極變化獲取能量的關(guān)鍵因素，是太陽能的轉(zhuǎn)換器和儲(chǔ)存器。北極海洋的變化還有很多問題沒有搞清楚，如北極上層海洋的溫鹽結(jié)構(gòu)如何影響對(duì)太陽輻射的吸收？海洋內(nèi)部能量如何在上層海洋中均勻化？海洋的能量如何在融冰和向大氣傳熱之間進(jìn)行分配？海洋儲(chǔ)存的熱量如何調(diào)控秋季的對(duì)流，延緩海冰的凍結(jié)？這些海洋過程對(duì)北極海冰變化是至關(guān)重要的，需要深入研究北極海冰減退引起的上層海洋熱儲(chǔ)存增加，北冰洋夏季熱量儲(chǔ)存的延遲釋放及其對(duì)海冰的影響，北冰洋上層環(huán)流引起的熱量平流輸送與分配，北極上升流引起的中層水熱量垂向輸送，極地淡水含量的變化對(duì)海洋層化及動(dòng)力高度變化的影響，北冰洋鹽躍層結(jié)構(gòu)變化及其對(duì)熱量儲(chǔ)存和轉(zhuǎn)換的影響。

3北極正在發(fā)生的氣候和天氣變化

在過去30余年，北極的氣溫呈現(xiàn)持續(xù)增暖的趨勢(shì)，21世紀(jì)以來北極的增暖幅度約為全球平均值的2倍，被稱為“北極放大”現(xiàn)象。北極增暖的關(guān)鍵問題是熱量從何而來。由于近年來太陽活動(dòng)沒有明顯異常，北極增暖不是由地球之外的因素引起的，只能來源于地球系統(tǒng)內(nèi)部。人們最早想到了可能是低緯度更多的熱量進(jìn)入了北極地區(qū)。然而，多年的觀測(cè)結(jié)果表明，來自低緯度的熱量確有變化，但對(duì)北極增暖的貢獻(xiàn)不明顯。因而，北極增暖的熱量主要來自北極自身額外獲得的能量。在太陽輻射強(qiáng)度基本保持不變的前提下，北極能量的增加與氣候系統(tǒng)中的正反饋過程相聯(lián)系。人們研究了各種可能的反饋過程，主要是冰雪反照率反饋（snow/ice-albedo feed-back）、水汽反饋（water vapor feedback）和云輻射反饋（cloud radiation feedback）3種。研究表明，水汽的作用并不構(gòu)成正反饋，因?yàn)楸娴乃偸翘幱陲柡蜖顟B(tài)。云是直接影響太陽輻射的因素，其反饋?zhàn)饔米盍钊岁P(guān)注。云的反饋是很多反饋的組合，包括云分布、云中水含量、液滴大小、云溫度、降雨、相變等多種過程引起的反饋網(wǎng)。1982—1999年衛(wèi)星遙感得到的云數(shù)據(jù)表明，北極春季和夏季云量增大，而冬季云量減小。但是總體來看，云的變化并不是引起海冰減少的主要因素。研究表明，北極增暖的反饋主要是冰雪反照率反饋，即海冰減少導(dǎo)致海洋吸收熱量的增加，這些熱量釋放給大氣，引起氣溫增加。后來將這種反饋更為準(zhǔn)確地稱為海冰—?dú)鉁胤答仯╥ce temperature feedback）。

北極氣溫升高同時(shí)引起大氣環(huán)流的復(fù)雜變化，通過對(duì)海面氣壓場(chǎng)（Sea Level Pressure, SLP）時(shí)間序列數(shù)據(jù)進(jìn)行EOF分析，可以得到AO的空間分布和時(shí)間系數(shù)，后者稱為北極濤動(dòng)指數(shù)（Aretie Oscillation Index, AOI）。由于北極變暖，北極濤動(dòng)的強(qiáng)度也顯著下降，AOI在最近10年呈現(xiàn)弱的負(fù)位相。Zhao等網(wǎng)研究了北極濤動(dòng)的空間變化，確定了北極濤動(dòng)的空間變化指數(shù)。結(jié)果表明，1950年以來的北極濤動(dòng)空間變化大體可分為3個(gè)階段：1950—1970年是正位相階段，代表全球變暖以前的情形；1970—1998年是負(fù)位相階段，大體代表全球變暖但北極沒有明顯變暖的情形。1998年至今是正負(fù)位相不明顯的階段，代表北極變暖的階段，表明北極濤動(dòng)的影響范圍變小。這段時(shí)間AO與北極海冰的變化趨勢(shì)并不一致，二者之間的關(guān)系表現(xiàn)出明顯的“退藕（decou-pled）”現(xiàn)象。

北極上空大氣環(huán)流異常的優(yōu)勢(shì)模態(tài)除AO外，還存在偶極子型（Dipole Anomaly, DA）的東西半球振蕩。最近的研究結(jié)果表明，2007年北極海冰急劇減少后AO的響應(yīng)越來越弱，且更偏向于出現(xiàn)負(fù)位相，海冰與大氣的藕合關(guān)系更多地體現(xiàn)在與DA的藕合相關(guān)上。Liu等的研究表明，最近幾年北極海冰快速減少引起的大氣環(huán)流異常響應(yīng)并不是傳統(tǒng)的AO模態(tài)，也不是穩(wěn)定的DA模態(tài)，而是一種更為復(fù)雜的大氣環(huán)流異常型，導(dǎo)致了近年來北半球極端降雪和嚴(yán)寒頻發(fā)，但其復(fù)雜的影響途徑仍需進(jìn)一步的深入研究。近幾十年，AO/NAO向負(fù)位相的轉(zhuǎn)變表征了對(duì)流層西風(fēng)帶的減弱，這種大氣環(huán)流的變化可以引起北半球大陸的變冷。大氣環(huán)流主要模態(tài)的空間形態(tài)變化也會(huì)引起陸地變冷。研究表明，北極放大效應(yīng)可加強(qiáng)大氣環(huán)流的這些變化。

在北極增暖背景下，不僅大氣環(huán)流發(fā)生異常，中尺度的氣旋活動(dòng)風(fēng)暴軸向北移動(dòng)，中緯度地區(qū)進(jìn)入北極地區(qū)的氣旋頻率和強(qiáng)度增強(qiáng)，北極地區(qū)生成的氣旋活動(dòng)頻率和強(qiáng)度也有增強(qiáng)的趨勢(shì)。北極氣旋活動(dòng)的增強(qiáng)導(dǎo)致海冰迅速減少，引發(fā)更強(qiáng)烈的風(fēng)暴潮畫。

對(duì)大氣而言，海洋的作用無比重要，是大氣變化的主要能量來源，北極氣候的變化機(jī)制被稱為海洋強(qiáng)迫。在海洋強(qiáng)迫下，需要解決的科學(xué)問題很多，最重要的關(guān)鍵問題有：北極海冰快速減退條件下的氣—冰—海藕合過程，海洋強(qiáng)迫對(duì)北極放大正反饋機(jī)制的貢獻(xiàn)，北極天氣尺度系統(tǒng)變化及其在北極放大過程中的作用，北極云霧對(duì)北極放大的負(fù)反饋?zhàn)饔?。通過相關(guān)的研究，才能深入認(rèn)識(shí)北極?！?dú)庀到y(tǒng)正在發(fā)生的變化。

4北極變化對(duì)北半球和中國氣候的影響

北極氣候的變化導(dǎo)致了北極能量新的平衡，北極作為寒極的性質(zhì)發(fā)生了重大變化，受到影響的不僅是北極地區(qū)，而且對(duì)中緯度地區(qū)產(chǎn)生巨大影響，主要體現(xiàn)在風(fēng)暴路徑以及行星波及其能量傳播。

已有研究表明，北半球大氣環(huán)流對(duì)北極海冰異常的響應(yīng)存在直接和間接2種。直接響應(yīng)主要是北極局地的響應(yīng)，引起春季積雪的減少并導(dǎo)致海冰減退。北極海冰對(duì)中國氣候的影響可以通過大氣環(huán)流異常的間接響應(yīng)來實(shí)現(xiàn)。

經(jīng)過多年的資料收集和思索，Overland等提出了北極變化與全球變化相互影響的機(jī)理，認(rèn)為全球變暖啟動(dòng)了北極海冰的減少，進(jìn)而發(fā)生海洋吸收熱量增加和加熱大氣的正反饋過程，反過來影響全球變暖過程。具體而言，中高緯度大氣羅斯貝波理論可以解釋北極對(duì)中緯度影響的機(jī)制。隨著北極變暖海冰融化，北極放大效應(yīng)最主要的一個(gè)表現(xiàn)是北極寒極的變暖，熱帶與極區(qū)溫差減小，導(dǎo)致羅斯貝波加深（振幅增大）和帶狀風(fēng)減弱，進(jìn)而引起羅斯貝波傳播速度減慢，使得中緯度天氣系統(tǒng)持續(xù)時(shí)間更長，造成中緯度極端天氣事件增多，干旱、熱浪、嚴(yán)寒等更為嚴(yán)重。羅斯貝波加深的最常見表現(xiàn)就是大氣阻塞高壓或西風(fēng)槽的發(fā)展和加強(qiáng)。關(guān)于羅斯貝波的加深機(jī)理，以往的研究中主要有大氣內(nèi)部動(dòng)力過程和非絕熱加熱等外部強(qiáng)迫2種觀點(diǎn)，其中大氣內(nèi)部動(dòng)力過程主要包括波流相互作用、共振理論、多平衡態(tài)理論、非線性孤立波理論、偶極子理論、天氣尺度渦旋的激發(fā)以及天氣尺度波與行星尺度波的非線性相互作用理論等幾種理論，但這些理論基本上都是基于準(zhǔn)地轉(zhuǎn)近似理論框架，對(duì)于極區(qū)的強(qiáng)非線性效應(yīng)的貢獻(xiàn)考慮不足。由于極區(qū)地球自轉(zhuǎn)效應(yīng)增強(qiáng)，極區(qū)的渦旋特征類似于臺(tái)風(fēng)外圍渦旋羅斯貝波的效應(yīng)。因此，建立合適的極區(qū)非線性動(dòng)力學(xué)模型來研究羅斯貝波加深的機(jī)理是一項(xiàng)不可或缺的工作。

我國學(xué)者指出AO/NAO能通過影響西伯利亞高壓進(jìn)而影響東亞冬季風(fēng)，表明北極海冰快速消融后北半球中高緯度大氣環(huán)流的異常響應(yīng)已由原來的緯向型（0波結(jié)構(gòu)的AO）向較高頻的經(jīng)向型（DA為1波定常波結(jié)構(gòu)）過渡，大氣優(yōu)勢(shì)模態(tài)對(duì)北極放大的響應(yīng)表現(xiàn)出更復(fù)雜的異常環(huán)流型，大氣對(duì)極區(qū)這種異常加熱的響應(yīng)可能會(huì)產(chǎn)生高緯度定常波的響應(yīng)，可以向南形成幾支穩(wěn)定的氣流通道引導(dǎo)冷空氣南下，進(jìn)而影響中緯度地區(qū)的氣候變化。

通過大氣再分析資料分析、海表溫度資料分析以及大氣環(huán)流數(shù)值模擬發(fā)現(xiàn)，北極秋季海冰減少可以引起高緯高壓系統(tǒng)的發(fā)展，甚至有利于阻塞高壓的發(fā)展與維持，這一機(jī)制可能是中國2008年1～2月出現(xiàn)嚴(yán)重的持續(xù)性凍雨的主要原因。在北極放大的背景下，歐亞大陸反氣旋活動(dòng)強(qiáng)度出現(xiàn)了明顯的增強(qiáng)趨勢(shì)，反氣旋強(qiáng)度變化與歐亞中緯度地區(qū)的極端溫度事件日數(shù)存在顯著相關(guān)，其中與東亞

特別是我國東部地區(qū)關(guān)系尤為明顯。我國大部分地區(qū)位于中緯度氣候帶，氣候系統(tǒng)深受北極過程的影響。遙遠(yuǎn)的北極海冰的異常變化如何影響中國的氣候變化，目前仍然是一個(gè)需要深入研究的問題。我們認(rèn)為，北極影響我國氣候的因素事實(shí)上是環(huán)球羅斯貝波的變異問題，不僅與北極問題有關(guān)，也與熱帶過程有關(guān)；不僅與中國過程有關(guān)，也與歐洲和北美的問題有關(guān)。北極變化對(duì)我國氣候和天氣的影響機(jī)理還很不清楚，需要深入研究大氣對(duì)極區(qū)異常加熱外強(qiáng)迫的定常波響應(yīng)特征、極區(qū)渦旋羅斯貝波的動(dòng)力特征及其在中高緯度羅斯貝波加深過程中的作用、高緯度羅斯貝波加深的非線性機(jī)理、北極放大過程對(duì)北極濤動(dòng)長期變化的影響等。通過對(duì)這些過程的認(rèn)識(shí)，搞清北極變化對(duì)我國氣候變化和相關(guān)災(zāi)害性天氣事件的影響方式。

5討論

當(dāng)北極快速變化展現(xiàn)在人們面前的時(shí)候，科學(xué)界受到極大的震撼，所有的科學(xué)家都沒有預(yù)測(cè)出北極的快速變化，所有的模式都沒有能模擬出海冰的快速減退。人們發(fā)現(xiàn)，對(duì)北極海冰、海洋和大氣過程的理解還沒有真正深入到海冰變化的物理實(shí)質(zhì)。最近5年的時(shí)間里，一些科學(xué)家反思了北極研究的現(xiàn)狀和問題，認(rèn)為還是應(yīng)該從大的科學(xué)問題著眼，從具體的物理過程入手，重新認(rèn)識(shí)變化了的北極?？茖W(xué)界將北極海冰變化的原因歸結(jié)于全球氣候變化和在北極發(fā)生的各種正反饋，認(rèn)為是這些正反饋導(dǎo)致海洋吸收了更多的熱量，加強(qiáng)了氣—冰—海之間的相互作用，引起海冰的進(jìn)一步減退。已有的研究表明，這種研究思路是正確的。然而認(rèn)識(shí)這些正反饋卻并不容易，因?yàn)楸睒O發(fā)生的主要正反饋都涉及到海洋和海冰變化的物理過程，而這些過程的大部分并沒有搞清楚，甚至知之甚少。因此，近年來關(guān)于北極變化正反饋的研究進(jìn)展并不大。在深入研究北極發(fā)生的物理過程，尤其要研究北極變暖之后各種變性的物理過程和新產(chǎn)生的物理過程，探索北極變化的物理實(shí)質(zhì)。研究基礎(chǔ)的物理過程，只靠同化數(shù)據(jù)和再分析數(shù)據(jù)是不夠的，需要有針對(duì)性地開展大規(guī)模現(xiàn)場(chǎng)觀測(cè)，獲得北極變化過程的實(shí)測(cè)數(shù)據(jù)，才能真正反映和認(rèn)識(shí)這些物理過程。

與此同時(shí)，北極變化對(duì)我國氣候的影響也逐步顯現(xiàn)。已有的研究表明，在冬季，北極的變化通過大氣環(huán)流影響我國北方的氣候。我國北方冬季普遍增暖和極端嚴(yán)寒天氣都與北極的作用密不可分。北極變化改變了大氣環(huán)流，對(duì)沙塵和霧霾的輸送方向產(chǎn)生重要影響。春季和秋季是冷暖氣團(tuán)消長時(shí)期，通常與鋒區(qū)的活動(dòng)和北方的干旱過程相聯(lián)系。初步研究表明，我國2008年和2011年南方的大規(guī)模凍雨與北極海冰的變化密切相關(guān)，而且同時(shí)發(fā)生的北方干旱導(dǎo)致華北主要產(chǎn)糧區(qū)冬小麥大幅度減產(chǎn)。北極的可能影響還有很多，如對(duì)海上風(fēng)暴、夏季酷熱、秋季降雪的影響等，其中大部分尚未充分研究。

北極對(duì)我國氣候的影響會(huì)產(chǎn)生重大的社會(huì)影響。首先是對(duì)主要產(chǎn)糧區(qū)氣候的影響，直接威脅到我國的糧食安全。其次是氣候?yàn)?zāi)害的發(fā)生，對(duì)全國產(chǎn)生多種可能的災(zāi)害。對(duì)北極變化的深入研究是推動(dòng)北極變化對(duì)我國氣候影響研究的主要渠道，攻克一系列尚未解決的科學(xué)問題，為解決北極影響我國的過程和機(jī)理、提高氣候預(yù)測(cè)精度和水平奠定堅(jiān)實(shí)的基礎(chǔ)，支持國家有關(guān)部門提出切實(shí)的措施和必要的對(duì)策，應(yīng)對(duì)北極變化對(duì)我國氣候的強(qiáng)烈影響。

【作者單位：中國海洋大學(xué)；南京信息工程大學(xué)；大連理工大學(xué)】

（摘自《地球科學(xué)進(jìn)展》2015年第9期）

·高被引論文摘要·

被引頻次：110

IPCC第一工作組第五次評(píng)估報(bào)告對(duì)全球氣候變化認(rèn)知的最新科學(xué)要點(diǎn)

沈永平，王國亞

2013年9月27日，在瑞典首都斯德哥爾摩，聯(lián)合國政府間氣候變化專門委員會(huì)第一工作組第五次評(píng)估報(bào)告《Climate Change 2013: The Physical Science Basis》決策者摘要（Summary for Policymakers, SPM）發(fā)布，隨后于9月30日公布了報(bào)告全文。報(bào)告指出，全球氣候系統(tǒng)變暖的事實(shí)是毋庸置疑的，自1950年以來，氣候系統(tǒng)觀測(cè)到的許多變化是過去幾十年甚至近千年以來史無前例的。全球幾乎所有地區(qū)都經(jīng)歷了升溫過程，變暖體現(xiàn)在地球表面氣溫和海洋溫度的上升、海平面的上升、格陵蘭和南極冰蓋消融和冰川退縮、極端氣候事件頻率的增加等方面。全球地表持續(xù)升溫，1880—2012年全球平均溫度己升高0.85℃[0.65～1.06℃]；過去30 a，每10 a地表溫度的增暖幅度高于1850年以來的任何時(shí)期。在北半球，1983—2012年可能是最近1400 a來氣溫最高的30 a。特別是1971—2010年間海洋變暖所吸收熱量占地球氣候系統(tǒng)熱能儲(chǔ)量的90%以上，海洋上層（0～700 m）己經(jīng)變暖。與此同時(shí)，1979—2012年北極海冰面積每10 a以3.5%～4.1%的速度減少；自20世紀(jì)80年代初以來，大多數(shù)地區(qū)多年凍土層的溫度己升高。全球氣候變化是由自然影響因素和人為影響因素共同作用形成的，但對(duì)于1950年以來觀測(cè)到的變化，人為因素極有可能是顯著和主要的影響因素。目前，大氣中溫室氣體濃度持續(xù)顯著上升，CO2、CH4和N2O等溫室氣體的濃度己上升到過去800 ka來的最高水平，人類使用化石燃料和土地利用變化是溫室氣體濃度上升的主要原因。在人為影響因素中，向大氣排放CO2的長期積累是主要因素，但非CO2溫室氣體的貢獻(xiàn)也十分顯著?？刂迫蛏郎氐哪繕?biāo)與控制溫室氣體排放的目標(biāo)有關(guān)，但由此推斷的長期排放目標(biāo)和排放空間數(shù)值在科學(xué)上存在著很大的不確定性。

IPCC WGI AR5；氣候變化；未來變化；溫室氣體；關(guān)鍵結(jié)論

來源出版物：冰川凍土, 2013, 35(5): 1068-1076

被引頻次：91

IPCC第五次評(píng)估報(bào)告第一工作組報(bào)告的亮點(diǎn)結(jié)論

秦大河，Thomas Stocker

摘要：IPCC第五次評(píng)估報(bào)告（AR5）第一工作組（WGI）報(bào)告的亮點(diǎn)結(jié)論，是過去7年全世界氣候變化科學(xué)研究成果凝練出來的精華。20世紀(jì)50年代以來全球氣候變暖的一半以上是人類活動(dòng)造成的。1971年以來人為排放溫室氣體產(chǎn)生熱量的93%進(jìn)入了海洋，海洋還吸收了大約30%人為排放的CO2，導(dǎo)致海表水pH值下降了0.1，等等。采用全球耦合模式比較計(jì)劃第五階段（CMIP5）的模式，預(yù)估未來全球氣候變暖仍將持續(xù)，21世紀(jì)末全球平均地表溫度在1986—2005年的基礎(chǔ)上將升高0.3～4.8℃。限制氣候變化需要大幅度持續(xù)減少溫室氣體排放。如果將1861—1880年以來的人為CO2累積排放控制在1000 Gt C，那么人類有超過66%的可能性把未來升溫幅度控制在2℃以內(nèi)（相對(duì)于1861—1880年）。

關(guān)鍵詞：氣候變化；溫室氣體；IPCC AR5；WGI

來源出版物：氣候變化研究進(jìn)展, 2014, 10(1): 1-6

被引頻次：39

北極海冰對(duì)大氣環(huán)流與氣候影響的觀測(cè)分析和試驗(yàn)研究

黃士松，楊修群，謝倩

摘要：文主要根據(jù)1953—1977年資料，從觀測(cè)分析和數(shù)值試驗(yàn)兩方面研究了北極海冰覆蓋面積異常對(duì)全球的大氣環(huán)流和氣候、特別是對(duì)中國氣候的影響，發(fā)現(xiàn)北極海冰的影響可與中東赤道太平洋海溫異常的影響相比擬，甚或可以超過，指出在氣候和長期天氣預(yù)報(bào)研究工作中，極冰變異及其影響需要很好重視。

關(guān)鍵詞：北極海冰；大氣環(huán)流；數(shù)值試驗(yàn)

來源出版物：海洋學(xué)報(bào), 1992, 14(6): 32-46

被引頻次：34

秋—冬季節(jié)北極海冰對(duì)冬季西伯利亞高壓的影響

武炳義，蘇京志，張人禾

摘要：冬季西伯利亞高壓強(qiáng)度與前期秋到冬季北冰洋東部、歐亞大陸北部邊緣海區(qū)海冰密集度呈現(xiàn)顯著的負(fù)相關(guān)關(guān)系。研究結(jié)果顯示，秋冬季北冰洋海冰密集度與同期海表溫度異?？蓪?dǎo)致冬季西伯利亞高壓與歐亞大陸中高緯度及東亞的地表氣溫異常。數(shù)值試驗(yàn)結(jié)果進(jìn)一步證實(shí)該結(jié)論，并且所有的數(shù)值試驗(yàn)結(jié)果一致表明，較低的海冰密集度能導(dǎo)致歐亞大陸中高緯度地表溫度負(fù)異常。本文提出了一種機(jī)制來解釋秋冬季北極海冰密集度和冬季西伯利亞高壓的聯(lián)系。9月份海冰密集度為預(yù)測(cè)冬季西伯利亞高壓提供了一個(gè)潛在的前期信號(hào)，而若由單純的熱帶海溫異常則不能預(yù)測(cè)冬季西伯利亞高壓強(qiáng)度。在近20 a來（1990—2009年）冬季西伯利亞高壓呈現(xiàn)增強(qiáng)的趨勢(shì)，并伴隨著亞洲大陸中高緯度地表溫度的降溫趨勢(shì)，從而導(dǎo)致近年來東亞嚴(yán)冬頻發(fā)。最后，討論了冬季西伯利亞高壓和地表氣溫短期趨勢(shì)的成因。

關(guān)鍵詞：北極海冰；西伯利亞高壓；東亞氣候；嚴(yán)冬頻發(fā)

來源出版物：科學(xué)通報(bào), 2011, 56(27): 2335-2343

被引頻次：34

近30 a北極海冰異常變化趨勢(shì)

張璐，張占海，李群，等

摘要：在過去30 a間，北極氣候發(fā)生了前所未有的異常變化，北極海冰變化更是經(jīng)歷了令人矚目的、從平緩到突變的縮減過程，因此，北冰洋及其海冰的研究得到廣泛的重視。綜述當(dāng)前國內(nèi)外有關(guān)北極海冰快速變化的研究工作，對(duì)這些大氣的現(xiàn)場(chǎng)觀測(cè)和衛(wèi)星遙感資料的分析，以及一些全球和區(qū)域氣候模擬的結(jié)果，基本上一致地指出了近30 a來北極海冰的快速衰減趨勢(shì)，尤其是夏季北極海冰正以每10 a超過10%的變化幅度快速減少。從海冰的基本物理特征、與大氣海洋相互作用的物理過程、及其對(duì)全球和北極氣候變化的響應(yīng)和反饋機(jī)制，研究形成這種快速變化的因子——海表面氣溫增暖，太平洋與大西洋入流的熱鹽性質(zhì)變化，以及大氣環(huán)流模態(tài)的影響等。

關(guān)鍵詞：北極；海冰范圍；突變；氣候

來源出版物：極地研究, 2009, 21(4): 344-352

被引頻次：34

北極海冰變化的時(shí)間和空間型

汪代維，楊修群

摘要：利用44 a（1951—1994年）北極海冰密度逐月資料，分析提出了一種與北極冰自然季節(jié)變化相吻合的分季法，并根據(jù)這種分季法，使用EOF分解，揭示了北極各季海冰面積異常的特征空間型及其對(duì)應(yīng)的時(shí)間變化尺度。結(jié)果表明：1）北極冰面積異常變化的關(guān)鍵區(qū)，冬季（2—4月）主要位于北大西洋一側(cè)的格陵蘭海、巴倫支海和戴維斯海峽以及北太平洋一側(cè)的鄂霍次克海和白令海，夏季（8—10月）則主要限于從喀拉海、東西伯利亞海、楚科奇海到波佛特海的緯向帶狀區(qū)域內(nèi)，格陵蘭海和巴倫支海是北極海冰面積異常變化的最重要區(qū)域；2）春（5—7月）、秋（11月—次年1月）季各主要海區(qū)海冰面積異常基本呈同相變化，夏季東西伯利亞海、楚科奇海、波佛特海一帶海冰面積異常和喀拉海呈反相變化，而冬季巴倫支海、格陵蘭海海冰面積異常和戴維斯海峽、拉布拉多海、白令海、鄂霍次克海的海冰變化呈反相變化；3）北極冰總面積過去44 a來確實(shí)經(jīng)歷了一種趨勢(shì)性的減少，并且疊加在這種趨勢(shì)變化之上的是年代尺度變化，其中春季（5—7月）海冰面積異常變化對(duì)年平均北極冰總面積異常變化作出了主要貢獻(xiàn)；4）位于北太平洋一側(cè)極冰面積異常型基本具有半年的持續(xù)性，而位于北大西洋一側(cè)極冰面積異常型具有半年至一年的持續(xù)性。

關(guān)鍵詞：北極海冰；長期趨勢(shì)；年代尺度變化；持續(xù)性

來源出版物：氣象學(xué)報(bào), 2002, 60(2): 129-138

被引頻次：30

北極海冰的厚度和面積變化對(duì)大氣環(huán)流影響的數(shù)值模擬

武炳義，黃榮輝，高登義

摘要：文中利用中國科學(xué)院大氣物理研究所設(shè)計(jì)的兩層大氣環(huán)流模式，模擬研究了北極海冰厚度和面積變化對(duì)大氣環(huán)流的影響，尤其是對(duì)東亞區(qū)域氣候變化的影響。模式中海冰厚度處理趨于合理分布嗎，導(dǎo)致東亞冬、夏季風(fēng)偏強(qiáng)，使冬季西伯利亞高壓和冰島低壓的模擬結(jié)果更趨合理；另一方面，海冰厚度變化可以激發(fā)出跨越歐亞大陸的行星波傳播，在低緯度地區(qū)，該行星波由西太平洋向東太平洋地區(qū)傳播；海冰厚度變化對(duì)低緯度地區(qū)的對(duì)流活動(dòng)也有影響。冬季北極巴倫支海海冰變化對(duì)后期大氣環(huán)流也有顯著的影響。數(shù)值模擬結(jié)果表明：冬季巴倫支海海冰偏多（少）時(shí)，春季（4—6月）北太平洋中部海平面氣壓升高（降低），阿留申低壓減弱（加深），有利于春季白令海海冰偏少（多）；而夏季，亞洲大陸熱低壓加深（減弱），500 hPa西太平洋副熱帶高壓位置偏北（南）、強(qiáng)度偏強(qiáng)（弱），東亞夏季風(fēng)易偏強(qiáng)（弱）。

關(guān)鍵詞：北極海冰；厚度；東亞季風(fēng)；巴倫支海；數(shù)值模擬

來源出版物：氣象學(xué)報(bào), 2001, 59(4): 414-428

被引頻次：27

寧夏春季沙塵暴與北極海冰之間的遙相關(guān)關(guān)系

楊建玲，何金海，趙光平

摘要：根據(jù)寧夏沙塵暴發(fā)生次數(shù)資料、北極海冰密集度資料和NCEP/NCAR再分析500、850 hPa高度場(chǎng)、風(fēng)場(chǎng)資料，得出了寧夏春季沙塵暴發(fā)生次數(shù)的變化規(guī)律及其與北極海冰面積之間的年代際和年際相關(guān)關(guān)系，發(fā)現(xiàn)寧夏春季沙塵暴發(fā)生次數(shù)與歐亞大陸北部的喀拉海、巴倫支海和格陵蘭海冰面積之間存在較顯著的年代際、年際相關(guān)關(guān)系。通過合成和相關(guān)分析知，寧夏春季沙塵暴偏多、偏少狀況有明顯不同的環(huán)流背景場(chǎng)，秋季格陵蘭海冰異常變化通過影響其后一段時(shí)間的大氣環(huán)流背景場(chǎng)，從而對(duì)寧夏沙塵暴產(chǎn)生影響。初步得出當(dāng)格陵蘭海秋季海冰面積增（減?。?，次年春季蒙古至西伯利亞一帶500、850 hPa高壓場(chǎng)降低（升高），風(fēng)場(chǎng)有明顯的氣旋性（反氣旋性）特點(diǎn)，在寧夏至新疆一帶西風(fēng)明顯偏強(qiáng)（偏弱），說明冷空氣活動(dòng)次數(shù)偏多（少），對(duì)應(yīng)寧夏春季沙塵暴發(fā)生次數(shù)偏多（少）。通過海冰將全球氣候變暖和寧夏（我國北方）沙塵暴總減少趨勢(shì)聯(lián)系起來，初次提出在環(huán)境總體惡化情況下，我國沙塵暴發(fā)生次數(shù)總體趨于減少，很可能是全球氣候變暖所致。

關(guān)鍵詞：北極海冰；寧夏；沙塵暴；遙相關(guān)

來源出版物：南京氣象學(xué)院學(xué)報(bào), 2003, 26(3): 296-307

被引頻次：27

南、北極海冰的長期變化趨勢(shì)及其與大氣環(huán)流的聯(lián)系

趙玉春，孫照渤，王葉紅

摘要：采用南、北極海冰面積指數(shù)1°×1°經(jīng)緯度格點(diǎn)資料及海平面氣壓資料，運(yùn)用多種統(tǒng)計(jì)方法，研究了南、北極海冰的長期變化趨勢(shì)、突變特征及其與大氣環(huán)流的聯(lián)系，發(fā)現(xiàn)近年來南極冬、春、秋季海冰逐漸減少，夏季海冰逐漸增加；北極春、夏、秋季海冰均不同程度地減少，冬季海冰變化趨勢(shì)不明顯；南、北極各季海冰的年際變化均存在一定的突發(fā)性，大氣環(huán)流在海冰突變年前后有顯著的差異。

關(guān)鍵詞：海冰；突變；大氣環(huán)流

來源出版物：南京氣象學(xué)院學(xué)報(bào), 2001, 24(1): 119-126

被引頻次：27

與北大西洋接壤的北極海冰和年際氣候變化

武炳義，黃榮輝，高登義

摘要：冬季與北大西洋接壤的北極海冰面積變化與北大西洋區(qū)域氣候變化有著非常密切的聯(lián)系。當(dāng)冬季北大西洋濤動(dòng)指數(shù)處于異常偏高（低）時(shí)期，冰島低渦加深（減弱）位置偏北（南），北大西洋副熱帶高壓也偏強(qiáng)（弱），并且位置也偏北（南），導(dǎo)致中緯度緯向西風(fēng)偏強(qiáng)（弱），受其影響中緯度北大西洋海溫升高（降低），因而增強(qiáng)（減弱）暖洋流向高緯度區(qū)域輸送，流入巴倫支海的北大西洋海水增多（減少），致使巴倫支海南部混合層水溫偏高（偏低）；同時(shí)，大氣溫度場(chǎng)分布也表明，歐洲北部及其相鄰的北極區(qū)域增暖（變冷）以及巴芬灣、戴維斯海峽附近區(qū)域氣溫降低（升高），致使喀拉海、巴倫支海海冰減少（增多）以及巴芬灣、戴維斯海峽海冰增加（減少）。

關(guān)鍵詞：冬季；北大西洋濤動(dòng)；海冰面積

來源出版物：科學(xué)通報(bào), 2000, 45(18): 1993-1998

被引頻次：3034

Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century

Rayner, NA; Parker, DE; Horton, EB; et al.

Abstract: We present the Met Office Hadley Centre’s sea ice and sea surface temperature(SST) data set, HadISST1, and the nighttime marine air temperature(NMAT) data set, HadMAT1. HadISST1 replaces the global sea ice and sea surface temperature(GISST) data sets and is a unique combination of monthly globally complete fields of SST and sea ice concentration on a 1degrees latitude-longitude grid from 1871. The companion HadMAT1 runs monthly from 1856 on a 5 degrees latitude-longitude grid and incorporates new corrections for the effect on NMAT of increasing deck(and hence measurement) heights. HadISST1 and HadMAT1 temperatures are reconstructed using a two-stage reducedspace optimal interpolation procedure, followed by superposition of quality-improved gridded observations onto the reconstructions to restore local detail. The sea ice fields are made more homogeneous by compensating satellite microwave-based sea ice concentrations for theimpact of surface melt effects on retrievals in the Arctic and for algorithm deficiencies in the Antarctic and by making the historical in situ concentrations consistent with the satellite data. SSTs near sea ice are estimated using statistical relationships between SST and sea ice concentration. HadISST1 compares well with other published analyses, capturing trends in global, hemispheric, and regional SST well, containing SST fields with more uniform variance through time and better month-to-month persistence than those in GISST. HadMAT1 is more consistent with SST and with collocated land surface air temperatures than previous NMAT data sets.

來源出版物：Journal of Geophysical Research-Atmospheres, 2003, 108(D14): 1063-1082

被引頻次：772

The role of sea ice and other fresh water in the Arctic circulation

Aagaard K; Carmack EC

Abstract: Salinity stratification is critical to the vertical circulation of the high-latitude ocean. We here examine the control of the vertical circulation in the northern seas, and the potential for altering it, by considering the budgets and storage of fresh water in the Arctic Ocean and in the convective regions to the south. We find that the presentday Greenland and Iceland seas, and probably also the Labrador Sea, are rather delicately poised with respect to their ability to sustain convection. Small variations in the fresh water supplied to the convective gyres from the Arctic Ocean via the East Greenland Current can alter or stop the convection in what may be a modern analog to the halocline catastrophes proposed for the distant past. The North Atlantic salinity anomaly of the 1960s and 1970s is a recent example; it must have had its origin in an increased fresh water discharge from the Arctic Ocean. Similarly, the freshening and cooling of the deep North Atlantic in recent years is a likely manifestation of the increased transfer of fresh water from the Arctic Ocean into the convective gyres. Finally, we note that because of the temperature dependence of compressibility, a slight salinity stratification in the convective gyres is required to efficiently ventilate the deep ocean.

來源出版物：Journal of Geophysical Research Atmospheres, 1989, 94(C10): 14485-14498

被引頻次：611

Accelerated decline in the Arctic Sea ice cover

Comiso, Josefino C; Parkinson, Claire L; Gersten, Robert; et al.

Abstract: Satellite data reveal unusually low Arctic sea ice coverage during the summer of 2007, caused in part by anomalously high temperatures and southerly winds. The extent and area of the ice cover reached minima on 14 September 2007 at 4.1×106km2and 3.6×106km2, respectively. These are 24% and 27% lower than the previous record lows, both reached on 21 September 2005, and 37% and 38% less than the climatological averages. Acceleration in the decline is evident as the extent and area trends of the entire ice cover(seasonal and perennial ice) have shifted from about -2.2% and -3.0% per decade in 1979 1996 to about -10.1% and -10.7% per decade in the last 10 years. The latter trends are now comparable to the high negative trends of -10.2% and -11.4% per decade for the perennial ice extent and area, 1979-2007.

來源出版物：Geophysical Research Letters, 2008, 35(1): L01703

被引頻次：568

Thinning of the Arctic sea-ice cover

Rothrock, DA; Yu, Y; Maykut, GA; et al.

Abstract: Comparison of sea-ice draft data acquired on submarine cruises between 1993 and 1997 with similar data acquired between 1958 and 1976 indicates that the mean ice draft at the end of the melt season has decreased by about 1.3 m in most of the deep water portion of the Arctic Ocean, from 3.1 m in 1958-1976 to 1.8 m in the 1990s. The decrease is greater in the central and eastern Arctic than in the Beaufort and Chukchi seas. Preliminary evidence is that the ice cover has continued to become thinner in some regions during the 1990s.

來源出版物：Geophysical Research Letters, 1999, 26(23): 3469-3472

被引頻次：542

Arctic sea ice decline: Faster than forecast

Stroeve, Julienne; Holland, Marika M; Meier, Walt; et al.

Abstract: From 1953 to 2006, Arctic sea ice extent at the end of the melt season in September has declined sharply. All models participating in the Intergovernmental Panel on Climate Change Fourth Assessment Report(IPCC AR4) show declining Arctic ice cover over this period. However, depending on the time window for analysis, none or veryfew individual model simulations show trends comparable to observations. If the multi-model ensemble mean time series provides a true representation of forced change by greenhouse gas(GHG) loading, 33%-38% of the observed September trend from 1953-2006 is externally forced, growing to 47%-57% from 1979-2006. Given evidence that as a group, the models underestimate the GHG response, the externally forced component may be larger. While both observed and modeled Antarctic winter trends are small, comparisons for summer are confounded by generally poor model performance.

來源出版物：Geophysical Research Letters, 2007, 34(9): L09501

被引頻次：382

Arctic sea ice extents, areas, and trends, 1978-1996

Parkinson, CL; Cavalieri, DJ; Gloersen, P; et al.

Abstract: Satellite passive-microwave data for November 1978 through December 1996 reveal marked seasonal, regional, and interannual variabilities, with an overall decreasing trend of ?34300±3700 km2/yr(?2.8%/decade) in Arctic sea ice extents over the 18.2-year period. Decreases occur in all seasons and on a yearly average basis, although they are largest in spring and smallest in autumn. Regionally, the Kara and Barents Seas have the largest decreases, at ?15200±1900 km2/yr(?10.5%/decade), followed by the Seas of Okhotsk and Japan, the Arctic Ocean, Greenland Sea, Hudson Bay, and Canadian Archipelago. The yearly average trends for the total, the Kara and Barents Seas, and the Seas of Okhotsk and Japan all have high statistical significance, with the null hypothesis of a 0 slope being rejected at a 99% confidence level. Regions showing increasing yearly average ice extents are Baffin Bay/Labrador Sea, the Gulf of St. Lawrence, and the Bering Sea, with only the increases in the Gulf of St. Lawrence being statistically significant at the 99% level. Hemispheric results for sea ice areas exhibit the same ?2.8%/decade decrease as for ice extents and hence a lower absolute decrease(?29500±3800 km2/yr), with the ice-free area within the ice pack correspondingly decreasing at ?4800±1600 km2/yr. Confidence levels for the trends in ice areas and ice-free water areas exceed 99% and 95%, respectively. Nonetheless, interannual variability is high, and, for instance, the Arctic Ocean ice extents have a positive trend 1990–1996, in spite of their negative trend for the time period as a whole.

來源出版物：Journal of Geophysical Research Oceans, 1999, 104(C9): 20837-20856

被引頻次：374

Response of sea ice to the Arctic oscillation

Rigor, IG; Wallace, JM; Colony, RL

Abstract: Data collected by the International Arctic Buoy Programme from 1979 to 1998 are analyzed to obtain statistics of sea level pressure(SLP) and sea ice motion(SIM). The annual and seasonal mean fields agree with those obtained in previous studies of Arctic climatology. The data show a 3-hPa decrease in decadal mean SLP over the central Arctic Ocean between 1979-1988 and 1989-1998. This decrease in SLP drives a cyclonic trend in SIM, which resembles the structure of the Arctic Oscillation(AO). Regression maps of SIM during the wintertime(January-March) AO index show 1) an increase in ice advection away from the coast of the East Siberian and Laptev Seas, which should have the effect of producing more new thin ice in the coastal flaw leads; 2) a decrease in ice advection from the western Arctic into the eastern Arctic; and 3) a slight increase in ice advection out of the Arctic through Fram Strait. Taken together, these changes suggest that at least part of the thinning of sea ice recently observed over the Arctic Ocean can be attributed to the trend in the AO toward the high-index polarity. Rigor et al. showed that year-to-year variations in the wintertime AO imprint a distinctive signature on surface air temperature(SAT) anomalies over the Arctic, which is reflected in the spatial pattern of temperature change from the 1980s to the 1990s. Here it is shown that the memory of the wintertime AO persists through most of the subsequent year: spring and autumn SAT and summertime sea ice concentration are all strongly correlated with the AO index for the previous winter. It is hypothesized that these delayed responses reflect the dynamical influence of the AO on the thickness of the wintertime sea ice, whose persistent “footprint” is reflected in the heat fluxes during the subsequent spring, in the extent of open water during the subsequent summer, and the heat liberated in the freezing of the open water during the subsequent autumn.

來源出版物：Journal of Climate, 2002, 15(18): 2648-2663

被引頻次：350

Two circulation regimes of the wind driven Arctic Ocean

Proshutinsky, AY; Johnson, MA

Abstract: The major goal of this paper is to demonstratethe existence in the Arctic Ocean of two regimes of wind-forced circulation. We simulated the vertically averaged currents, sea level heights, and ice drift in the Arctic Ocean from 1946 to 1993 using a two-dimensional, wind-forced, barotropic model that includes frictional coupling between the ocean and ice. The model has a spatial resolution of 55.5 km and is driven by winds, river runoff, and an imposed but realistic sea level slept: Between the Pacific and the Atlantic Oceans. There is a good agreement between velocities from observed buoy motions and velocities of modeled ice drift even though the model lacks Ocean baroclinicity and ice thermodynamics. The results indicate that wind-driven motion in the central Arctic alternates between anticyclonic and cyclonic circulation, with each regime persisting for 5-7 years, based upon our analysis of the modeled sea level and ice motion. Anticyclonic wind-driven motion in the central Arctic appeared during 1946-1952, 1958-1963, 1972-1979, and 1984-1988, and cyclonic motion appeared during 1953-1957, 1964-1971, 1980-1983, and 1989-1993. Shifts from one regime to another are forced by changes in the location and intensity of the Icelandic low and the Siberian high. The two regimes may help explain the significant, basin-scale changes ih the Arctic’s temperature and salinity structure observed recently; the Great Salinity Anomaly; and the variability of ice conditions iii the Arctic Ocean.

來源出版物：Journal of Geophysical Research-Oceans, 1997, 102(C6): 12493-12514

被引頻次：325

The central role of diminishing sea ice in recent Arctic temperature amplification

Screen, James A; Simmonds, Ian

Abstract: The rise in Arctic near-surface air temperatures has been almost twice as large as the global average in recent decades-a feature known as ‘Arctic amplification’. Increased concentrations of atmospheric greenhouse gases have driven Arctic and global average warming; however, the underlying causes of Arctic amplification remain uncertain. The roles of reductions in snow and sea ice cover and changes in atmospheric and oceanic circulation, cloud cover and water vapour are still matters of debate. A better understanding of the processes responsible for the recent amplified warming is essential for assessing the likelihood, and impacts, of future rapid Arctic warming and sea ice loss. Here we show that the Arctic warming is strongest at the surface during most of the year and is primarily consistent with reductions in sea ice cover. Changes in cloud cover, in contrast, have not contributed strongly to recent warming. Increases in atmospheric water vapour content, partly in response to reduced sea ice cover, may have enhanced warming in the lower part of the atmosphere during summer and early autumn. We conclude that diminishing sea ice has had a leading role in recent Arctic temperature amplification. The findings reinforce suggestions that strong positive ice-temperature feedbacks have emerged in the Arctic, increasing the chances of further rapid warming and sea ice loss, and will probably affect polar ecosystems, ice-sheet mass balance and human activities in the Arctic.

來源出版物：Nature, 2010, 464(7293): 1334-1337

被引頻次：325

Future abrupt reductions in the summer Arctic sea ice

Holland, Marika M; Bitz, Cecilia M; Tremblay, Bruno

Abstract: We examine the trajectory of Arctic summer sea ice in seven projections from the Community Climate System Model and find that abrupt reductions are a common feature of these 21st century simulations. These events have decreasing September ice extent trends that are typically 4 times larger than comparable observed trends. One event exhibits a decrease from 6 million km2to 2 million km2in a decade, reaching near ice-free September conditions by 2040. In the simulations, ice retreat accelerates as thinning increases the open water formation efficiency for a given melt rate and the ice-albedo feedback increases shortwave absorption. The retreat is abrupt when ocean heat transport to the Arctic is rapidly increasing. Analysis from multiple climate models and three forcing scenarios indicates that abrupt reductions occur in simulations from over 50% of the models and suggests that reductions in future greenhouse gas emissions moderate the likelihood of these events.

來源出版物：Geophysical Research Letters, 2006, 33(23): L23503

·推薦論文摘要·

北極海域漁業(yè)資源開發(fā)現(xiàn)狀及對(duì)策

焦敏，陳新軍，高郭平

摘要：隨著全球變暖，北極海冰覆蓋面積逐年減少。在全球海洋漁業(yè)資源衰退的大背景下，北極漁業(yè)資源的開發(fā)和合理利用備受世界各國關(guān)注，越來越多的國際組織和科學(xué)家開始對(duì)北極漁業(yè)進(jìn)行探索研究。由于北極地區(qū)環(huán)境惡劣，海洋魚類的種類和資源量相比其他地區(qū)較少，但隨著北極海冰的融化，北極漁業(yè)資源開發(fā)和利用成為可能，北極潛在的未充分開發(fā)利用的漁業(yè)資源正吸引著有關(guān)國家的高度關(guān)注。為此，本文通過收集國內(nèi)外相關(guān)文獻(xiàn)，對(duì)北極漁業(yè)種類、資源狀況及其開發(fā)現(xiàn)狀進(jìn)行了分析，同時(shí)提出了中國參與北極漁業(yè)資源開發(fā)和利用的對(duì)策與建議。

關(guān)鍵詞：北極海域；漁業(yè)資源；捕撈量；發(fā)展對(duì)策

來源出版物：極地研究, 2015, 27(2): 219-227

北極海冰減退引起的北極放大機(jī)理與全球氣候效應(yīng)

趙進(jìn)平，史久新，王召民

摘要：自20世紀(jì)70年代以來，全球氣溫持續(xù)增高，對(duì)北極產(chǎn)生了深刻的影響。21世紀(jì)以來，北極的氣溫變化是全球平均水平的2倍，被稱為“北極放大”現(xiàn)象。北極海冰覆蓋范圍呈不斷減小的趨勢(shì)，2012年北極海冰已經(jīng)不足原來的40%，如此大幅度的減退是過去1450 a以來獨(dú)有的現(xiàn)象?？茖W(xué)家預(yù)測(cè)，不久的將來，將會(huì)出現(xiàn)夏季無冰的北冰洋。全球變暖背景下北極內(nèi)部發(fā)生的正反饋過程是北極放大現(xiàn)象的關(guān)鍵，不僅使極區(qū)的氣候發(fā)生顯著變化，而且對(duì)全球氣候產(chǎn)生非常顯著的影響，導(dǎo)致很多極端天氣氣候現(xiàn)象的發(fā)生。北極科學(xué)的重要使命之一是揭示這些正反饋過程背后的機(jī)理。北極放大有關(guān)的重大科學(xué)問題主要與氣—冰—海相互作用有關(guān)，海冰是北極放大中最活躍的因素，要明確海冰結(jié)構(gòu)的變化，充分考慮融池、側(cè)向融化、積雪和海冰漂移等因素，將海冰熱力學(xué)特性的改變定量表達(dá)出來。海洋是北極變化獲取能量的關(guān)鍵因素，是太陽能的轉(zhuǎn)換器和儲(chǔ)存器，要認(rèn)識(shí)海洋熱通量背后的能量分配問題，即能量儲(chǔ)存與釋放的聯(lián)系機(jī)理，認(rèn)識(shí)淡水和躍層結(jié)構(gòu)變化對(duì)海氣耦合的影響。全面認(rèn)識(shí)北極氣候系統(tǒng)的變化是研究北極放大的最終目的，要揭示氣—冰—海相互作用過程、北極海洋與大氣之間反饋的機(jī)理、北極變化過程中的氣旋和阻塞過程、北極云霧對(duì)北極變化的影響。在對(duì)北極海冰、海洋和氣候深入研究的基礎(chǔ)上，重點(diǎn)研究極地渦旋羅斯貝波的核心作用，以及羅斯貝波變異的物理過程，深入研究北極變化對(duì)我國氣候影響的主要渠道、關(guān)鍵過程和理。關(guān)鍵詞：北極放大；海洋強(qiáng)迫；海冰；氣候變化；氣—冰—海相互作用

來源出版物：地球科學(xué)進(jìn)展, 2015, 30(9): 985-995

聯(lián)系郵箱：趙進(jìn)平，jpzhao@ouc.edu.cn

秋季北極海冰與歐亞冬季氣溫在年代際和年際尺度上的不同聯(lián)系

何金海，武豐民，祁莉

摘要：北極海冰的急劇消融在近年來歐亞大陸頻發(fā)的低溫事件中扮演著關(guān)鍵角色。秋季北極海冰的偏少對(duì)應(yīng)著冬季歐亞大陸的低溫天氣，然而二者的聯(lián)系在年代際和年際兩種時(shí)間尺度上存在顯著區(qū)別。本文運(yùn)用1979—2012年哈德萊中心第一套海冰覆蓋率（HadISST1）、歐洲中心（ERA_Interim）的2 m溫度、風(fēng)場(chǎng)、海平面氣壓場(chǎng)、高度場(chǎng)等資料，分別研究了年代際和年際時(shí)間尺度上前期秋季北極海冰與歐亞冬季氣溫的聯(lián)系。結(jié)果表明，歐亞和北極地區(qū)（0°～160°E，15°N～90°N）的冬季氣溫具有顯著的年代際和年際變化。在年代際尺度上，溫度異常分布在21世紀(jì)初由北極冷—大陸暖轉(zhuǎn)為北極暖—大陸冷。這一年代際轉(zhuǎn)折與前期秋季整個(gè)北極地區(qū)的海冰年代際減少聯(lián)系密切。秋季北極全區(qū)海冰年代際偏少對(duì)應(yīng)冬季歐亞大陸中高緯地區(qū)的高壓異常，有利于北大西洋的暖濕氣流北上和北極的冷空氣南侵，造成北極暖—大陸冷的溫度分布；在年際時(shí)間尺度上，溫度異常分布主要由第一模態(tài)的年際變化部分和第二模態(tài)組成，且第一模態(tài)包含的年際變率信號(hào)也存在顯著的年代際變化。年際尺度上全區(qū)北極海冰對(duì)歐亞冬季氣溫的影響遠(yuǎn)不及位于北冰洋西南邊緣的巴倫支海、喀拉海和拉普捷夫海西部（30°E～120°E，75°N～85°N）的關(guān)鍵區(qū)海冰影響顯著。關(guān)鍵區(qū)內(nèi)海冰的偏少會(huì)引發(fā)冬季的北大西洋濤動(dòng)負(fù)位相，導(dǎo)致北大西洋吹往歐亞大陸的暖濕氣流減弱和歐亞大陸中高緯地區(qū)的氣溫偏低。

關(guān)鍵詞：秋季北極海冰；冬季歐亞低溫；年代際；年際

來源出版物：地球物理學(xué)報(bào), 2015, 58(4): 1089-1102

聯(lián)系郵箱：武豐民，wfm_nuist@163.com

北極海冰的年代際轉(zhuǎn)型與中國凍雨年代際變化的關(guān)系

牛璐，黃菲，周曉

摘要：基于1961—2013年HadISST海冰密集度資料，定義了北極海冰的季節(jié)性融冰指數(shù)，結(jié)果顯示近幾十年來北極季節(jié)性融冰范圍呈顯著的上升趨勢(shì)，并分別在20世紀(jì)70年代末和90年代中期存在顯著的年代際轉(zhuǎn)型，相應(yīng)地，中國凍雨發(fā)生頻數(shù)總體上呈現(xiàn)出顯著的減少趨勢(shì)，但也存在顯著的年代際轉(zhuǎn)型。在20世紀(jì)70年代末之前，北極季節(jié)性融冰范圍較小但顯著增長，中國凍雨頻數(shù)年際變化振幅較大，且主要受巴倫支海、喀拉海海冰的影響；20世紀(jì)70年代末至90年代中期北極季節(jié)性融冰范圍維持振蕩特征，沒有顯著的線性趨勢(shì)，中國凍雨頻數(shù)變化振幅減小，與北極海冰相關(guān)較弱，主要相關(guān)因子為北大西洋及北太平洋海表溫度變化；而90年代中期以后，北極海冰融化加快，特別是2007年以后，季節(jié)性融冰范圍大大增加，而中國凍雨頻數(shù)處于低發(fā)時(shí)段，其變化與太平洋扇區(qū)海冰及堪察加半島附近海溫呈顯著負(fù)相關(guān)，季節(jié)性融冰的顯著區(qū)域也從東西伯利亞海逆時(shí)針旋轉(zhuǎn)向波弗特海-加拿大群島北部擴(kuò)張，同時(shí)向北極中央?yún)^(qū)擴(kuò)張。不同年代影響凍雨的海溫或海冰關(guān)鍵海區(qū)不同，產(chǎn)生特定的大氣環(huán)流異常響應(yīng)，進(jìn)而影響到我國凍雨。

關(guān)鍵詞：凍雨；季節(jié)性融冰；年代際轉(zhuǎn)型；大氣環(huán)流異常；海溫

來源出版物：海洋學(xué)報(bào), 2015, 37(11): 105-117

聯(lián)系郵箱：黃菲，huangf@mail.ouc.edu.cn

中部型El Nino與北極海冰變化的聯(lián)系

左濤，陳錦年，王凡

摘要：采用統(tǒng)計(jì)方法，分析了熱帶太平洋SSTA與北極海冰之間的聯(lián)系。結(jié)果表明：北極海冰從20世紀(jì)80年代初由正距平轉(zhuǎn)換為負(fù)距平，以-1.5%速率/10 a快速消融。盡管冬季海冰也出現(xiàn)減少趨勢(shì)，但最大海冰減少出現(xiàn)在夏秋季，9月為1年中海冰減少最快的月份。相關(guān)分析發(fā)現(xiàn)，北極海冰的快速減少與熱帶太平洋海溫變化存在密切聯(lián)系，赤道中西部SSTA與北極海冰的關(guān)系更明顯。Nino 4區(qū)域SSTA變化與北極海冰存在時(shí)滯3 a左右的最佳相關(guān)，6—10月SSTA對(duì)北極海冰影響最顯著。通過分析，初步認(rèn)為Nino4區(qū)域SSTA主要通過影響北半球中緯度氣壓場(chǎng)和經(jīng)向環(huán)流場(chǎng)，進(jìn)而影響AO變化，最終對(duì)北極海冰產(chǎn)生影響。

關(guān)鍵詞：北極海冰密集度；快速消融；中部型El Nino；AO

來源出版物：海洋湖沼通報(bào), 2015(3): 1-13

北半球夏季中高緯度大氣阻塞對(duì)北極海冰變化的影響

肖貽青，黃斌，刁一娜

摘要：利用NCEP/NCAR再分析逐日500 hPa高度場(chǎng)資料，對(duì)北半球夏季中高緯度大氣阻塞特征進(jìn)行統(tǒng)計(jì)分析，發(fā)現(xiàn)大氣阻塞活動(dòng)頻率高的地區(qū)主要集中在白令海峽區(qū)域、鄂霍次克海區(qū)域、歐亞大陸區(qū)域及格陵蘭區(qū)域。而通過NSIDC提供的衛(wèi)星觀測(cè)資料發(fā)現(xiàn)近30年夏季海冰容易減少的區(qū)域正好對(duì)應(yīng)阻塞活動(dòng)北部的高緯度地區(qū)。分別通過對(duì)以上4個(gè)區(qū)域有阻塞發(fā)生相對(duì)沒有阻塞發(fā)生時(shí)的500 hPa位勢(shì)高度場(chǎng)、地面溫度場(chǎng)、850 hPa經(jīng)向瞬變熱通量輸送和平流輸送等異常變化場(chǎng)進(jìn)行對(duì)比分析，結(jié)果發(fā)現(xiàn)夏季中高緯度阻塞頻率的增加對(duì)海冰的減少有顯著影響，主要體現(xiàn)在阻塞的發(fā)生發(fā)展可通過增加高緯度地面溫度、對(duì)極地的熱量輸送和暖平流輸送來加快海冰的融化。這種阻塞引起的熱力作用在鄂霍次克海和歐亞大陸區(qū)域效果更為顯著。

關(guān)鍵詞：北極海冰；北極增暖；阻塞

來源出版物：極地研究, 2015, 27(4): 364-378

聯(lián)系郵箱：肖貽青，xxyyqq1222@163.com

累積海冰密集度及其在認(rèn)識(shí)北極海冰快速變化的作用

王維波，趙進(jìn)平

摘要：為定量分析北冰洋海冰密集度年際差異，提出并采用累積海冰密集度（ASIC）概念。利用SSMR/SSMI的分辨率為25 km的海冰密集度數(shù)據(jù)，分別研究了1979—2011年北極海冰在融冰期（4—9月）和結(jié)冰期（10月至翌年3月）的變化過程以及2個(gè)冰期內(nèi)ASIC的區(qū)域差異。研究發(fā)現(xiàn)，在1979—1989年、1989—1999年和1999—2009年期間，融冰期海冰發(fā)生明顯變化的范圍都遠(yuǎn)遠(yuǎn)大于結(jié)冰期海冰發(fā)生明顯變化的范圍。1998—2010年，融冰期內(nèi)發(fā)生加速融化的海區(qū)并沒有都出現(xiàn)結(jié)冰期冰量減小的現(xiàn)象。在此期間融冰期ASIC減小，結(jié)冰期ASIC也減小的海域僅集中在楚克奇海、新地島北部海域以及格陵蘭島東西海岸。融冰期ASIC減小，而結(jié)冰期ASIC無明顯變化的海域包括波弗特海、東西伯利亞海、拉普捷夫海和喀拉海。這些區(qū)域與局地陸地徑流侵入的海域重合。研究發(fā)現(xiàn)，在這些區(qū)域，融冰期ASIC減少是陸地徑流增大加速海冰融化引起的。在結(jié)冰期，陸地徑流加速海水結(jié)冰的作用消除融冰期海水吸收大量太陽輻射能后發(fā)生推遲結(jié)冰的現(xiàn)象，使得ASIC無明顯變化。融冰期ASIC減小，而結(jié)冰期ASIC增大的區(qū)域只有白令海。研究結(jié)果證明累積海冰密集度能夠去除海冰高頻變化而只表現(xiàn)低頻變化，能夠描述海冰的年際變化特征。同時(shí)由于海冰變化與海洋中其他物理參數(shù)存在顯著關(guān)系，變T的ASIC可以更加方便地描述次表層葉綠素最大值層深度的變化。

關(guān)鍵詞：海冰變化；陸地徑流；北冰洋

來源出版物：地球科學(xué)進(jìn)展, 2014, 29(6): 713-722

聯(lián)系郵箱：王維波，wbwang@live.com

北極海冰消融及其對(duì)歐亞冬季低溫影響的研究進(jìn)展

武豐民，何金海，祁莉

摘要：21世紀(jì)以來北極氣候系統(tǒng)正在發(fā)生著劇烈變化。北極海冰史無前例的急劇消融是其中最重要的指示和衡量標(biāo)志。北極海冰的急劇消融與北極氣溫升高緊密聯(lián)系，在近年來歐亞大陸頻發(fā)的冬季低溫事件中也扮演著關(guān)鍵角色。首先介紹了北極海冰的季節(jié)特征及近年來的消融現(xiàn)狀，并從動(dòng)力學(xué)和熱力學(xué)2個(gè)方面總結(jié)了海冰急劇消融的可能原因。闡述了北極增溫的季節(jié)特點(diǎn)及其與北極海冰消融的關(guān)系。分析了北極海冰消融與歐亞大陸冷冬頻發(fā)的聯(lián)系及其可能機(jī)理?；趯?duì)以上研究進(jìn)展的總結(jié)，提出了該研究領(lǐng)域尚需解決的幾個(gè)問題，為相關(guān)研究提供參考。

關(guān)鍵詞：北極增幅；大氣環(huán)流異常；歐亞冷冬

來源出版物：地球科學(xué)進(jìn)展, 2014, 29(8): 913-921

聯(lián)系郵箱：何金海，hejhnew@nuist.edu.cn

秋季北極海冰對(duì)中國冬季氣溫的影響

謝永坤，劉玉芝，黃建平

摘要：利用海冰資料、中國地面氣候資料、環(huán)流特征量資料及NCEP/NCAR再分析資料，研究了秋季北極海冰變化對(duì)中國冬季平均氣溫、日氣溫變率以及異常低溫天氣的影響。分析結(jié)果表明，秋季北極海冰異常偏多年中國冬季常為暖冬；異常偏少年中國冬季常為冷冬，且異常低溫天氣出現(xiàn)頻率更高，常發(fā)生低溫災(zāi)害事件。秋季北極海冰通過影響后期的北半球極渦、東亞冬季風(fēng)和西伯利亞高壓進(jìn)而影響中國冬季的平均氣溫，且通過影響冬季異常強(qiáng)西伯利亞高壓的出現(xiàn)頻次，影響中國冬季異常低溫天氣的發(fā)生頻次。合成分析結(jié)果表明，秋季北極海冰異常偏少年的冬季，中國以北亞歐大陸高緯度的偏北風(fēng)較強(qiáng)，且中國及其以北的中高緯度地區(qū)空氣異常偏冷，導(dǎo)致極地和高緯度的冷空氣易向南爆發(fā),造成中國冬季氣溫偏低，異常低溫天氣頻發(fā)。

關(guān)鍵詞：北極海冰；冬季氣溫；日氣溫變率；異常低溫天氣

來源出版物：氣象學(xué)報(bào), 2014, 72(4): 703-710

中國近50年寒潮冷空氣的時(shí)空特征及其與北極海冰的關(guān)系

朱晨玉，黃菲，石運(yùn)昊，等

摘要：利用中國具有較長時(shí)間序列的527個(gè)站點(diǎn)1961—2010年的日平均溫度觀測(cè)資料，美國國家環(huán)境預(yù)報(bào)中心和國家大氣研究中心（NCEP/NCAR）再分析資料以及伊利萊諾斯大學(xué)的海冰密集度資料，分析了我國近50年來寒潮的時(shí)空變化及與其相聯(lián)系的海冰和大氣環(huán)流異常的關(guān)系。結(jié)果表明，中國寒潮冷空氣活動(dòng)頻數(shù)存在兩個(gè)主要模態(tài)，第一模態(tài)表現(xiàn)在中國北方冷空氣活動(dòng)頻數(shù)呈年代際減少趨勢(shì)，1980年之前寒潮冷空氣頻數(shù)偏多，1990年后寒潮冷空氣頻數(shù)偏少；第二模態(tài)表現(xiàn)為我國南方冷空氣頻數(shù)的年際振蕩特征。第一模態(tài)寒潮冷空氣頻數(shù)的減少主要與全球變暖有關(guān)，北極海冰的減少使得1980年代后期北極濤動(dòng)加強(qiáng)，并激發(fā)出歐亞遙相關(guān)波列進(jìn)而影響我國的寒潮冷空氣活動(dòng)。第二模態(tài)則與近些年來夏季北極海冰的快速融化以及北極大氣出現(xiàn)偶極子型環(huán)流異常有關(guān)，通過激發(fā)跨極型和類歐亞遙相關(guān)波列影響到后冬的中國南方寒潮冷空氣活動(dòng)增多。

關(guān)鍵詞：寒潮；海冰；全球變暖；AO；EU；遙相關(guān)型；偶極子異常

來源出版物：中國海洋大學(xué)學(xué)報(bào)（自然科學(xué)版）, 2014, 44(12): 12-20

聯(lián)系郵箱：黃菲，Huangf@ouc.edu.cn

北半球冰蓋融化與北半球低溫暴雪的相關(guān)性

楊冬紅，楊學(xué)祥

摘要：2006—2013年北半球頻遭低溫暴雪襲擊。引力模型的計(jì)算結(jié)果表明：北極冰蓋大量融化導(dǎo)致北極地區(qū)海平面和大氣等位面的大幅度下降，壓力變化迫使北極地區(qū)冷水和冷空氣流向北半球中低緯度地區(qū)。太平洋海溫下降導(dǎo)致全球變暖停止。極地冰蓋融化后全球海平面都將上升，這是一個(gè)錯(cuò)誤的觀點(diǎn)。最新模型研究表明，如果格林蘭冰蓋融化可導(dǎo)致其附近海平面將下降100 m，北蘇格蘭的海平面將下降3 m，冰島周圍海平面將下降10 m，南美部分地區(qū)海平面將上升10 m。冰蓋融化導(dǎo)致地表巨量物質(zhì)轉(zhuǎn)移，改變了地球內(nèi)外重力場(chǎng)，地球內(nèi)核南移100 m，北極和南極海平面分別下降和上升7 cm。在海平面附近，大氣等位面的變化幅度與海平面變化幅度非常接近。近期北極海冰和冰蓋的融化只是最新模型的一個(gè)縮影。北極大量冷水和冷空氣在下降等位面的壓力下流過北半球中低緯度地區(qū)，導(dǎo)致北半球頻遭低溫暴雪襲擊。在“全球變暖間斷”現(xiàn)象持續(xù)了長達(dá)16 a之后，科學(xué)家正全力探究“全球變暖間斷”現(xiàn)象背后的深層次原因.最新研究指出，1997—1998年赤道太平洋進(jìn)入一個(gè)持續(xù)很久的低溫狀態(tài)，抑制了全球變暖的速度。海水溫度的波動(dòng)被稱作拉馬德雷現(xiàn)象（PDO），這種現(xiàn)象是解開“間斷”謎團(tuán)的關(guān)鍵。

關(guān)鍵詞：冰蓋；海平面；潮汐；地震；低溫

來源出版物：地球物理學(xué)進(jìn)展, 2014, 29(2): 610-615

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(dòng)氣象站（DAWS）2012 年9月—2013年2月的觀測(cè)數(shù)據(jù)，分析了北極點(diǎn)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(dá)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(dá)到30℃，是由強(qiáng)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(dòng)氣象站；海冰運(yùn)動(dòng)；爆發(fā)性增溫；穿極氣旋

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

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

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

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

Abstract: 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.

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

Abstract: 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.

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.

Abstract: 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 wintersurface 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.

Keywords: extreme weather event; tripole wind pattern; autumn sea ice decline; cold winter

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.

Abstract: 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.

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

Abstract: 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.

Keywords: Arctic sea ice; Arctic boundary layer; atmospheric circulation; numerical modelling

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

Keywords: 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 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.

Keywords: climate impact of arctic sea ice; sea ice-atmosphere interaction; North Atlantic Oscillation; stratosphere downward propagation

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.

Abstract: 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.

Keywords: geographic location; entity; Arctic; sea ice; circulation; dynamics; clouds; physical meteorology and climatology; feedback; surface fluxes; models and modeling; climate models

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.

Abstract: 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.

Keywords: water cycle; precipitation; sea ice; climate change; deuterium excess

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

Abstract: A growing amount of evidence points to anotable 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

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

Abstract: 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.

Keywords: jet stream; Arctic amplification; extreme weather

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

Abstract: 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.

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

Abstract: The role of ocean-atmosphere coupling in thezonal-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.

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

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 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

Keywords: arctic; climate change; mid-latitude weather; sea ice; snow; winter weather

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.

Abstract: 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 ofsimulations 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.

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.

Abstract: 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.

Keywords: Arctic sea ice; atmospheric modelling; ensembles; detection and attribution; internal variability; signal-to-noise ratio

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.

Abstract: 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

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

Abstract: 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.

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.

Abstract: 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.

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.

Abstract: 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.

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

編輯：衛(wèi)夏雯

The role of sea ice and other fresh water in the Arctic circulation

Aagaard K; Carmack EC

Salinity stratification is critical to the vertical circulation of the high-latitude ocean. We here examine the control of the vertical circulation in the northern seas, and the potential for altering it, by considering the budgets and storage of fresh water in the Arctic Ocean and in the convective regions to the south. We find that the present-day Greenland and Iceland seas, and probably also the Labrador Sea, are rather delicately poised with respect to their ability to sustain convection. Small variations in the fresh water supplied to the convective gyres from the Arctic Ocean via the East Greenland Current can alter or stop the convection in what may be a modern analog to the halocline catastrophes proposed for the distant past. The North Atlantic salinity anomaly of the 1960s and 1970s is a recent example; it must have had its origin in an increased fresh water discharge from the Arctic Ocean. Similarly, the freshening and cooling of the deep North Atlantic in recent years is a likely manifestation of the increased transfer of fresh water from the Arctic Ocean into the convective gyres. Finally, we note that because of the temperature dependence of compressibility, a slight salinity stratification in the convective gyres is required to efficiently ventilate the deep ocean.

sea surface temperature; sea ice; night marine air temperature; climate data reconstruction; bias correction; climate change