A Preliminary Study on the Relationship Between Arctic Oscillation and Daily SLP Variance in the Northern Hemisphere During Wintertime

In the present study, the authors investigated the relationship between the Arctic Oscillation (AO) and the high-frequency variability of daily sea level pressures in the Northern Hemisphere in winter (November through March), using NCEP/NCAR reanalysis datasets for the time period of 1948/49-2000/01. High-frequency signals are defined as those with timescales shorter than three weeks and measured in terms of variance, for each winter for each grid. The correlations between monthly mean AO index and high-frequency variance are conducted. A predominant feature is that several regional centers with high correlation show up in the middle to high latitudes. Significant areas include mid- to high-latitude Asia centered at Siberia, northern Europe and the middle-latitude North Atlantic east of northern Africa. Their strong correlations can also be confirmed by the singular value decomposition analysis of covariance between mean SLP and high-frequency variance. This indicates that the relationship of AO with daily Sea Level Pressure (SLP) is confined to some specific regions in association with the inherent atmospheric dynamics. In middle-latitude Asia, there is a significant (at the 95% level) trend of variance of-2.26% (10 yr)-1. Another region that displays a strong trend is the northwestern Pacific with a significant rate of change of 0.80% (10 yr)-1. If the winter of 1948/49, an apparent outlier, is excluded, a steady linear trend of +1.51% (10 yr)-1 shows up in northern Europe. The variance probability density functions (PDFs) are found to change in association with different AO phases. The changes corresponding to high and low AO phases, however, are asymmetric in these regions. Some regions such as northern Europe display much stronger changes in high AO years, whereas some other regions such as Siberia show a stronger connection to low AO conditions. These features are supported by ECMWF reanalysis data. However, the dynamical mechanisms involved in the AO-high frequency SLP variance connection have not been well understood, and this needs further study.

Pathways of Influence of the Northern Hemisphere Mid–high Latitudes on East Asian Climate: A Review

This paper reviews recent progress made by Chinese scientists on the pathways of influence of the Northern Hemisphere mid-high latitudes on East Asian climate within the framework of a“coupled oceanic-atmospheric(land-atmospheric or seaice-atmospheric)bridge”and“chain coupled bridge”.Four major categories of pathways are concentrated upon,as follows:Pathway A—from North Atlantic to East Asia;Pathway B—from the North Pacific to East Asia;Pathway C—from the Arctic to East Asia;and Pathway D—the synergistic effects of the mid-high latitudes and tropics.In addition,definitions of the terms“combined effect”,“synergistic effect”and“antagonistic effect”of two or more factors of influence or processes and their criteria are introduced,so as to objectively investigate those effects in future research.

Impact of interannual variations of spring sea ice in the Barents Sea on East Asian rainfall in June

This study reveals a significant relationship, on the interannual timescale, between a dipole mode, the second leading mode, of spring sea-ice anomalies in the Barents Sea and the following-summer rainfall in East Asia. Related to the dipole mode, with the heavier sea ice in the north and lighter sea ice in the southeast Barents Sea in spring, the East Asian summer subtropical rainy belt tends to move northward. The significant relationship is established through a wave train over northern Eurasia in the lower troposphere in June. The wave train enhances the northern East Asian low, which induces more rainfall to the north of the East Asian subtropical rainy belt and then attracts the subtropical rainy belt to move northward. This study suggests that the dipole mode of spring sea-ice anomalies in the Barents Sea may be a good precursor for the prediction of East Asian summer rainfall.

Historical Course Follows Climate Change: Patterns of the Northern Hemisphere — From Peoples’ Migration until the Industrial Revolution (3^rd-18^thCentury)

This paper relates to the statement that the so-called “Little Ice Age” (RCC 6: 1.350-1.800 A.D.) represents—besides the 8k-Event (8.200-8.000 yr cal. B.P.)—the fastest and strongest onset in Holocene History [1]. Its intention focuses on the correlation of interplaying natural processes (i.e. solar energy variation, aerosols, oceanic currents, volcanism as part of plate tectonics, heat flow) with social/political evidence through the time-span of Peoples’ Migration until Industrial Revolution (3rd-18th Century). The time-span comprises the cool/wet/respectively dry climate phase of the P.M. (260-550), a Climate Optimum (600-1.100 A.D.) owning a final Thermal Maximum (1.100-1.260 A.D.) and the “little Ice Age” (1.350-1.800 A.D.), the latter intercalated by the Spörer Minimum (1.460-1.550 A.D.) and the Maunder Minimum (1.650-1.720 A.D.). Thereby, an average temperature difference of 1.0°C - 2.0°C seems sufficient for incising climatic/cultural consequences [2]. It has become obvious that a Climate Optimum primarily provides constructive life conditions;however with a problematic final as the following “Effect-Chain” tells: balanced agricultural/cultural population growth → rich harvests → satisfying nourishment → health, encouragement → overpopulation under favorable materialistic conditions → increasing stress → lack of food, high prices → revolts → migration. In contrast, cool/wet/resp. dry conditions originate destructive/depressive conditions (see Peoples’ Migration) which initiate the following “Effect Chain”: bad agricultural conditions → poor/no harvesting → famine → disease, growing death rate → social, political revolts, wars → human cruelties with psychic/religious background (inquisition, witch-combustion → general chaos (30 yr-war) → death, migration (maritime endeavors, colonization). Furthermore, it should be stressed that volcanic aerosols play besides the solar influx variation—an important role on climate/cultural change [3]. However, the effects of oceanic currents’ heat flow of Mid-Oceanic Ridges and Hot Spots, as well as Earth-Magnetism and Sun/Earth Geometry are poorly understood in this context (Example: Iceland as hot spot situated on the Mid-Atlantic Ridge having been working since 40 Ma). The Chapter-introducing citations play a challenging role in regard to Science Criticism and touch the so-called 95% Confidence line (accepted realm of causal interrelation and according recommendation to Society [4]).

Ice Resistance Assessment for a Large Size Vessel Running in a Narrow Ice Channel Behind an Icebreaker

Large size vessels sailing in continuous level ice and broken ice of high concentration are mostly assisted by icebreakers.This is done in order to provide for fast transportation through the North Sea Route and safe operation in extreme ice conditions.Currently,new large size gas and oil carriers and container ships are being designed and built with beams much greater than the beams of existing icebreakers.At the same time,no mathematical description exists for the breaking mechanism of ice channel edges,when such vessels move under icebreaker escort.This paper suggests a simple method for assessment of the ice resistance in the case of a large ship running in an icebreaker channel;the method is based on modification of well-known semi-empirical methods for calculation of the ice resistance to ships in level and broken ice.The main feature of the proposed calculation scheme consists in that different methods are applied to estimate the ice resistance in broken ice and due to breaking of level ice edges.The combination of these methods gives a deliverable ice resistance of a large size vessel moving under icebreaker assistance in a newly made ice channel.In general,proposed method allows to define the speed of a carrier moving in an ice channel behind a modern linear icebreaker and could be applied at the ship design stage and during development of the marine transportation system.The paper also discusses the ways for further refinement of the assessment procedure suggested.

Distribution of the Permian Monodiexodina in Karakorum and Kunlun and its Geological Significance

The Permian fusulinoidean genus Monodiexodina is widely distributed in east Tethys. The genus might be an important indicator for the northern margin of Gondwana in northwestern China, but this is disputed. Monodiexodina-bearing areas can be restored as in either northern or southern middle latitudes with a symmetrical distribution between a high latitudinal, cool/cold water climatic realm and a paleotropical, warm water realm. Permian strata bearing Monodiexodina in Karakorum, Muztag Pear, and Buka Daban Pear of the east Kunlun Mountains can be correlated with each other. Faunal analyses and the stratigraphical position of Monodiexodina-bearing strata indicate that both Karakorum, east Kunlun, and the Pamirs were formed in a cool temperate sea area of the northern hemisphere in middle latitudes during the Permian, rather than at the Gondwana margin.

The state and fate of lake ice thickness in the Northern Hemisphere

Lake ice thickness(LIT)is important for regional hydroclimate systems,lake ecosystems,and human activities on the ice,and is thought to be highly susceptible to global warming.However,the spatiotemporal variability in LIT is largely unknown due to the difficulty in deriving in situ measurements and the lack of an effective remote sensing platform.Despite intensive development and applications of lake ice models driven by general circulation model output,evaluation of the global LIT is mostly based on assumed“ideal”lakes in each grid cell of the climate forcing data.A method for calculating the actual global LIT is therefore urgently needed.Here we use satellite altimetry to retrieve ice thickness for 16 large lakes in the Northern Hemisphere(Lake Baikal,Great Slave Lake,and others)with an accuracy of~0.2 m for almost three decades.We then develop a 1-D lake ice model driven primarily by remotely sensed data and cross-validated with the altimetric LIT to provide a robust means of estimating LIT for lakes larger than 50 km^(2)across the Northern Hemisphere.Mean LIT(annual maximum ice thickness)for 1313 simulated lakes and reservoirs covering~840,000 km^(2)for 2003–2018 is 0.63±0.02 m,corresponding to~485 Gt of water.LIT changes are projected for 2071–2099 under RCPs 2.6,6.0,and 8.5,showing that the mean LIT could decrease by~0.35 m under the worst concentration pathway and the associated lower ice road availability could have a significant impact on socio-economic activities.

A lake ice phenology dataset for the Northern Hemisphere based on passive microwave remote sensing

Lake ice phenology(LIP)is an essential indicator of climate change and helps with understanding of the regional characteristics of climate change impacts.Ground observation records and remote sensing retrieval products of lake ice phenology are abundant for Europe,North America,and the Tibetan Plateau,but there is a lack of data for inner Eurasia.In this work,enhanced-resolution passive microwave satellite data(PMW)were used to investigate the Northern Hemisphere Lake Ice Phenology(PMW LIP).The Freeze Onset(FO),Complete Ice Cover(CIC),Melt Onset(MO),and Complete Ice Free(CIF)dates were derived for 753 lakes,including 409 lakes for which ice phenology retrievals were available for the period 1978 to 2020 and 344 lakes for which these were available for 2002 to 2020.Verification of the PMW LIP using ground records gave correlation coefficients of 0.93 and 0.84 for CIC and CIF,respectively,and the corresponding values of the RMSE were 11.84 and 10.07 days.The lake ice phenology in this dataset was significantly correlated(P<0.001)with that obtained from Moderate Resolution Imaging Spectroradiometer(MODIS)data-the average correlation coefficient was 0.90 and the average RMSE was 7.87 days.The minimum RMSE was 4.39 days for CIF.The PMW is not affected by the weather or the amount of sunlight and thus provides more reliable data about the freezing and thawing process information than MODIS observations.The PMW LIP dataset pro-vides the basic freeze-thaw data that is required for research into lake ice and the impact of climate change in the cold regions of the Northern Hemisphere.The dataset is available at http://www.doi.org/10.11922/sciencedb.j00076.00081.

Navigability of the Northern Sea Route for Arc7 ice-class vessels during winter and spring sea-ice conditions

Sea ice hinders the navigability of the Arctic,especially in winter and spring.However,three Arc7 ice-class Liquefied Natural Gas carrying vessels safely transited the Northern Sea Route(NSR)without icebreaker assistance in January 2021.More and more Arc7 ice-class vessels are putting into the transit services in the NSR.Therefore,it is necessary to analyze sea-ice conditions and their impact on navigation during wintertime,and the future navigability of Arc7 ice-class vessels along the NSR during winter and spring.Based on sea ice datasets from satellite observations and a model using data assimilation,we explored the sea-ice conditions and their impact during the first three successful commercial voyages through the NSR in winter.In addition,we analyzed the sea ice variation and estimated navigability for Arc7 ice-class vessels in the NSR from January to June of the years 2021–2050 using future projections of the sea-ice cover by the Coupled Model Inter-comparison Project Phase 6(CMIP6)models under two emission scenarios(SSP2-4.5 and SSP5-8.5).The results reveal lower sea ice thickness and similar sea ice concentration during these three transits relative to the past 42 years(from 1979 to 2020).We found the thickness has a larger impact on the vessels’speeds than sea ice concentration.Very likely sea ice thickness played a larger role than the sea ice concentration for the successful transit of the NSR in winter 2021.Future projections suggest sea ice thickness will decrease further in most regions of the NSR from January to June under all scenarios enabling increased navigability of the NSR for Arc7 ice-class vessels.Such vessels could transit through the NSR from January to June under all scenarios by 2050,while some areas near the coast of East Siberian Sea remain inaccessible for Arc7 ice-class vessels in spring(April and May).These findings can support the strategic planning of shipping along the NSR in winter and spring.

Oxygen isotope stratigraphy and events in the northern South China Sea during the last 6 million years

Based on the stable isotopic analysis of more than 1000 samples of planktonic and benthic foraminifers from ODP Site 1148 in the northern South China Sea (SCS), the oxygen isotope stratigraphy has been applied to the last 3 million years for the first time in the SCS. Furthermore, the paleoceanographic changes in the northern SCS during the last 6 million years have been unraveled. The benthic foraminiferal δ180 record shows that before ~3.1 Ma the SCS was much more influenced by the warm intermediate water of the Pacific. The remarkable decrease in the deepwater temperature of the SCS during the period of 3.1-2.5 Ma demonstrates the formation of the Northern Hemisphere ice-sheet. However, the several sea surface temperature (SST) reductions during the early and middle Pliocene, reflected by the planktonic foraminiferal δ18O, might be related to the ice-sheet growth in the Antarctic region. Only those stepwise and irreversible SST reductions during the period of ~2.2-0.9 Ma could be related to the formation and growth of the Northern Hemisphere ice-sheet.

CLIMATIC ABRUPT CHANGE IN THE NORTHERN HEMISPHERE FOR 1920s AND 1950s

In recent years,a large number of papers on the climatic sudden change have been presented.From the viewpoint of climatic sudden change,two methods of studying climatic sudden change are applied in this paper.The Northern Hemi- sphere land temperature(NHLT)during 1851—1984,China temperature(CT)during 1873—1990 and the Northern Hemisphere sea-level pressure(NHSLP)at each grid point during 1899—1987 are analyzed by the moving T-test.The results show that there exist two climatic sudden changes in the 1920s and the 1950s during the past 100 years,and then features of circulation for the two sudden changes are discussed by the NHSLP data.

ANTARCTIC SEA ICE AND THE POLAR VORTEX INDEX:TEMPORAL AND SPATIAL CHARACTERISTICS AND THEIR RELATIONSHIP

The cluster analysis method has been used to divide the Antarctic sea ice variation field into 5 sectors.Then,for each of these sectors,the corresponding indexes of vortex area and vortex intensity on the 500 hPa level have been calcu- lated.These data were used to analyse the temporal and spatial characteristics of both Antarctic sea ice and the vortex index variations and their relationship.Our results show that substantial differences are presented in the climatic pattern and interannual variations of the sea ice data and vortex index in different sectors.The maximum sea ice extent varia- tions appear in sector 1 and sector 4.Oscillation periods of 2—2.5 and 5—7 years exist in the variations of sea ice extent and vortex index in most sectors.A positive trend is only found in sector 1 sea ice extent while the other sectors show negative trends.The average extent of the Antarctic sea ice as a whole has retreated at a rate of 1.6 latitudes per 100 years.The vortex areas for all sectors have decreased.Nevertheless,the vortex intensities in 3 sectors have increased.The relationship between sea ice and vortex characters in each sector is obvious,but a little complex.Sectors 1 and 5,which are located in the Southeast Pacific and South Atlantic,are the most sensitive areas in terms of sea ice/atmosphere interaction.

Impacts of 1.5℃ global warming on hydrological conditions of navigation along the Northern Sea Route and Northwest Passage

Arctic navigability is crucial to the global economy and landscape,while there is an omission in understanding how Arctic navigability changes as a function of 1.5℃ of the Paris Agreement.This study investigated the impact of 1.5℃ global warming above the preindustrial level on sea ice conditions and accessibility of the Northern Sea Route(NSR)and Northwest Passage(NWP)with the Polar Operational Limit Assessment Risk Indexing System and new risk demarcation criteria.The Arctic is colder on the Canadian side than on the European side under 1.5℃ warming.Sea ice is mostly less than three years old,and the younger,thinner and less concentrated ice is mainly in the seas along the NSR.Ships above Polar Class(PC)6 might be unimpeded along two passages all the year.Besides,the NSR and NWP have great potential for PC6 ships in October-December,while it is only the NSR for PC7 ships.Caution is still required when navigating the western East Siberian Sea,its surrounding straits,and the Parry Channel.These changes in hydrological conditions are important for global shipping,and this work is helpful for supporting coordinated international decision-making.

Joint Manifestations of PDO （Pacific Decadal Oscillation） and Negative AMO （Atlantic Multidecadal Oscillation） Phases in Winter Cyclonic Activity

The AMO （Atlantic Multidecadal Oscillation） and PDO （Pacific Decadal Oscillation） were considered as the main indicators of decadal-multidecadal variations of global climate system. Joint and separate AMO and PDO manifestations in the winter cyclonic activity on the global and regional scales for the Northern Hemisphere and Mediterranean and Black Sea were studied. Composite schemes of typical displacement of cyclonic active zones in Northern Hemisphere for two combinations of AMO and PDO phases are proposed.

20世纪70年代末前后北半球冬季对流层遥相关的时空演变研究

应用NOAA提供的1950～2008年月平均500hPa高度场再分析资料、海表温度、太平洋年代际振荡(PDO)指数和大西洋三极模(ATM)指数,研究了20世纪70年代末前后北半球冬季对流层遥相关的时空演变规律。相关分析、Mann-Kendall分析和凝聚小波分析的结果表明,20世纪70年代末以来,太平洋—北美(PNA)型、欧亚(EUP)型、西太平洋(WP)型和西大西洋(WA)型四种遥相关空间分布和时间演变产生较为显著的变化。空间分布的变化既体现在遥相关正、负异常中心的强度上,也体现在正、负异常的范围上;时间演变方面的变化则体现在PNA和WP遥相关指数具有上升趋势,EUP和WA遥相关指数具有一定下降趋势。20世纪70年代末以来,影响北半球冬季5种遥相关型的海温关键区均有所改变。其中,各大洋上影响EUP遥相关型的海温关键区面积显著缩小,影响WA遥相关型的太平洋海温关键区面积显著缩小,影响EA遥相关型海温关键区在北大西洋中南部改变明显;在16年以上时间尺度上,PDO变化是造成北半球冬季PNA、EUP、WP三种遥相关型变化的主要原因;ATM变化是造成北半球冬季WA和EA两种遥相关型变化的主要原因。

南沙海区晚上新世海水上层结构变化

对南沙海区水深 2 772m的ODP114 3站 10 0～ 15 0m井段共 10 1块沉积样品进行了浮游有孔虫分析 ,结果表明 ,从 3 2 7Ma到 2 5 5Ma该区表层海水温度逐步降低 ,温跃层逐步加深 ,推测是晚上新世北半球冰盖形成过程中 ,东亚季风相应加强的结果。与此同时 ,南沙与南海北部的温跃层深度差值不断加大 ,可能是西太平洋暖池最终形成或加强的表现。 3 2Ma前后 ,表层海水温度和海水温跃层深度都发生了急剧变化 。

北半球冬季极端低温事件变化及其与秋季海冰的联系

利用欧洲中期天气预报中心逐日的地面气温数据以及美国国家冰雪数据中心逐月的海冰密集度数据,并通过气候百分位法统计了逐月的极端低温事件日数,分析了1979-2016年冬季(12月至次年2月)北半球的极端低温事件与秋季(9-11月)北极海冰变化之间的关系,并挑选了典型年份探讨了秋季北极海冰对极端低温事件可能存在的影响机理。结果表明,北半球冬季极端低温事件与秋季关键海区(波弗特海、楚科奇海、巴伦支海和喀拉海)的海冰面积变化密切相关,其中亚洲北部区域冬季的极端低温事件与秋季关键海区的海冰面积有显著负相关关系,而青藏高原区域、非洲北部区域和北美东北部区域冬季的极端低温事件与秋季关键海区的海冰面积有显著正相关关系。通过对典型年份冬季北半球极端低温事件极度异常时的大气环流进行分析后发现,当秋季关键海区海冰异常偏少时,冬季西伯利亚高压偏强,其东部偏北风加强,使得欧亚大陆北部的气温偏低,极端低温事件偏多;冬季冰岛低压偏强,其南部的西南风加强,将低纬度温暖的空气带到了非洲北部区域,使其冬季气温偏高,极端低温事件偏少;高层异常反气旋主要位于格陵兰岛附近,其下沉气流不利于形成极端低温天气而导致北美东北部区域极端低温事件偏少。

北半球对流层厚度的时空变化特征

利用1948—2010年NCEP/NCAR逐月位势高度再分析资料、美国国家海洋局提供的1948—2010年逐月海温再分析资料,分别定义了1 000—500 hPa和500—200 hPa厚度,利用EOF、SVD等方法研究了北半球对流层厚度时空演变特征及其与大气环流和海面温度的关系。结果表明,冬季平均厚度EOF第一模态均具有北太平洋及附近高纬度亚洲大陆地区与北美大陆高纬地区反位相变化的特点,而夏季第一模态则是北半球范围内较一致的位相分布;冬、夏季平均厚度EOF第二模态均突出体现了欧亚大陆及附近地区与北半球其他地区反位相变化的特点;冬、夏季厚度场的变化形势与大气环流及海面温度具有密切联系。

北半球海冰与登陆广东台风的特征及关系分析

采用NOAA冰雪数据中心1979—2017年北半球海冰资料、中国气象局热带气旋资料中心1979—2018年台风资料,对登陆广东台风和北半球海冰的主要特征进行统计和分析,并对上一年和当年上半年北半球海冰范围与登陆广东台风的关系进行探讨。结果表明:每年均有台风登陆广东,常年平均3.5个。登陆台风中,STS级别最多,常年平均1.3个;TY、TD、TS、STY次之;SuperTY级别有2个。北半球海冰范围有明显的时间变化,1—5月为正距平,7—11月为负距平,其中6月正距平占54%,负距平占46%,1994年前为正距平,2001年转为负距平后一直维持;12月在2016年首次出现负距平,发生质变,其它为正距平。逐月分布呈单峰型,3月达到峰值,9月是谷值。年代际变化呈减少趋势。前期北半球海冰范围距平百分率与登陆广东的STY、STS和TD相关性高,可作为预测依据;其相关系数通过显著性水平0.05检验且排位前3位的分别是当年6、2月的北半球海冰范围距平与登陆广东的STY,上一年5月、当年2月与登陆广东的STS,当年5月与登陆广东的TD。

南极海冰涛动对北半球夏季大气环流的影响

南极海冰首要模态呈现偶极子型异常,正负异常中心分别位于别林斯高晋海/阿蒙森海和威德尔海。过去研究表明冬春季节南极海冰涛动异常对后期南极涛动(Antarctic Oscillation,AAO)型大气环流有显著影响,而AAO可以通过经向遥相关等机制影响北半球大气环流和东亚气候。本文中我们利用观测分析发现南极海冰涛动从5~7月(May-July,MJJ)到8~10月(August-October,ASO)有很好的持续性,并进一步分析其对北半球夏季大气环流的可能影响及其物理过程。结果表明,MJJ南极海冰涛动首先通过冰气相互作用在南半球激发持续性的AAO型大气环流异常,使得南半球中纬度和极地及热带之间的气压梯度加大,在MJJ至JAS,纬向平均纬向风呈现显著的正负相间的从南极到北极的经向遥相关型分布。对流层中层位势高度场上,在澳大利亚北部到海洋性大陆区域,出现显著的负异常,在东亚沿岸从低纬到高纬呈现南北走向的“-+-”太平洋—日本(Pacific-Japan,PJ)遥相关波列,其对应赤道中部太平洋及赤道印度洋存在显著的降水和海温负异常,西北太平洋至我国东部沿海地区存在显著降水正异常和温度负异常;低纬度北美洲到大西洋一带存在的负位势高度异常和北大西洋附近存在的正位势高度异常中心,构成一个类似于西大西洋型遥相关(Western Atlantic,WA)的结构,对应赤道南大西洋降水增加和南撒哈拉地区降水减少。从物理过程来看,南极海冰涛动首先通过局地效应影响Ferrel环流,进而通过经圈环流调整使得海洋性大陆区域和热带大西洋上方的Hadley环流上升支得到增强,海洋性大陆区域特别是菲律宾附近的热带对流活动偏强,激发类似于负位相的PJ波列,影响东亚北太平洋地区的大气环流,而热带大西洋对流增强和北传特征,则通过激发WA遥相关影响大西洋和欧洲地区的大气环流。以上两种通道将持续性MJJ至ASO南极海冰涛动强迫的大气环流信号从南半球中高纬度经热带地区传递到北半球中高纬地区,从而对热带和北半球夏季大气环流产生显著影响。