首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
王坤  毕海波  黄珏 《海洋科学》2022,46(4):44-54
北极海冰作为一个巨大的淡水资源库, 每年向全球输送大量淡水资源, 从北极输出的海冰在向南输送的过程中融化, 对海洋水循环与水环境产生影响, 进而影响全球气候变化, 弗雷姆海峡作为北极海冰输出的主要通道, 对其研究显得尤为重要。为了解弗雷姆海峡海冰长期输出量, 利用美国冰雪数据中心（NSIDC）发布的海冰密集度、海冰厚度与海冰漂移速度数据, 计算得到 1979 年至 2019 年弗雷姆海峡海冰输出面积通量与 2010 至 2019 年弗雷姆海峡海冰输出体积通量, 并在此基础上分析弗雷姆海峡近 40 a 海冰输出量的变化状况以及弗雷姆海峡海冰输出的年际变化、季节变化, 并分析了影响弗雷姆海峡海冰输出量的可能原因。结果表明: 近 40 a 弗雷姆海峡年均海冰输出面积通量为 7.83×105 km2,近 10 a 弗雷姆海峡海冰年均输出体积通量为 1.34×106 km3, 从长期来看, 弗雷姆海峡海冰输出面积通量呈略微增加趋势, 弗雷姆海峡海冰输出体积通量在 2010—20...  相似文献   

2.
地球系统模式FIO-ESM对北极海冰的模拟和预估   总被引：5，自引：3，他引：2  
评估了地球系统模式FIO-ESM(First Institute of Oceanography-Earth System Model)基于CMIP5(Coupled Model Intercomparison Project Phase 5)的历史实验对北极海冰的模拟能力,分析了该模式基于CMIP5未来情景实验在不同典型浓度路径(RCPs,Representative Concentration Pathways)下对北极海冰的预估情况。通过与卫星观测的海冰覆盖范围资料相比,该模式能够很好地模拟出多年平均海冰覆盖范围的季节变化特征,模拟的气候态月平均海冰覆盖范围均在卫星观测值±15%范围以内。FIO-ESM能够较好地模拟1979-2005年期间北极海冰的衰减趋势,模拟衰减速度为每年减少2.24×104 km2,但仍小于观测衰减速度(每年减少4.72×104 km2)。特别值得注意的是:不同于其他模式所预估的海冰一直衰减,FIO-ESM对21世纪北极海冰预估在不同情景下呈现不同的变化趋势,在RCP2.6和RCP4.5情景下,北极海冰总体呈增加趋势,在RCP6情景下,北极海冰基本维持不变,而在RCP8.5情景下,北极海冰呈现继续衰减趋势。  相似文献   

3.
The Fram Strait(FS) is the primary region of sea ice export from the Arctic Ocean and thus plays an important role in regulating the amount of sea ice and fresh water entering the North Atlantic seas. A 5 a(2011–2015) sea ice thickness record retrieved from Cryo Sat-2 observations is used to derive a sea ice volume flux via the FS. Over this period, a mean winter accumulative volume flux(WAVF) based on sea ice drift data derived from passivemicrowave measurements, which are provided by the National Snow and Ice Data Center(NSIDC) and the Institut Francais de Recherche pour d'Exploitation de la Mer(IFREMER), amounts to 1 029 km~3(NSIDC) and1 463 km~3(IFREMER), respectively. For this period, a mean monthly volume flux(area flux) difference between the estimates derived from the NSIDC and IFREMER drift data is –62 km~3 per month(–18×10~6 km~2 per month).Analysis reveals that this negative bias is mainly attributable to faster IFREMER drift speeds in comparison with slower NSIDC drift data. NSIDC-based sea ice volume flux estimates are compared with the results from the University of Bremen(UB), and the two products agree relatively well with a mean monthly bias of(5.7±45.9) km~3 per month for the period from January 2011 to August 2013. IFREMER-based volume flux is also in good agreement with previous results of the 1990 s. Compared with P1(1990/1991–1993/1994) and P2(2003/2004–2007/2008), the WAVF estimates indicate a decline of more than 600 km~3 in P3(2011/2012–2014/2015). Over the three periods, the variability and the decline in the sea ice volume flux are mainly attributable to sea ice motion changes, and second to sea ice thickness changes, and the least to sea ice concentration variations.  相似文献   

4.
By combing satellite-derived ice motion and concentration with ice thickness fields from a popular model PIOMAS we obtain the estimates of ice volume flux passing the Fram Strait over the 1979–2012 period. Since current satellite and field observations for sea ice thickness are limited in time and space, the use of PIOMAS is expected to fill the gap by providing temporally continued ice thickness fields. Calculated monthly volume flux exhibits a prominent annual cycle with the peak record in March(roughly 145 km3/month) and the trough in August(10 km~3/month). Annual ice volume flux(1 132 km~3) is primarily attributable to winter(October through May) outflow(approximately 92%). Uncertainty in annual ice volume export is estimated to be 55 km~3(or 5.7%). Our results also verified the extremely large volume flux appearing between late 1980 s and mid-1990 s. Nevertheless, no clear trend was found in our volume flux results. Ice motion is the primary factor in the determination of behavior of volume flux. Ice thickness presented a general decline trend may partly enhance or weaken the volume flux trend. Ice concentration exerted the least influences on modulating trends and variability in volume flux. Moreover, the linkage between winter ice volume flux and three established Arctic atmospheric schemes were examined. Compared to NAO, the DA and EOF3 mechanism explains a larger part of variations of ice volume flux across the strait.  相似文献   

5.
Arctic sea ice can incorporate sediment and associated chemical species during its formation in shallow shelf environments and can also intercept atmospherically transported material during transit. Release of this material in ice ablation areas (e.g. the Fram Strait) enhances fluxes of both sediments and associated species in such areas. We have used a suite of natural (7Be, 210Pb) and anthropogenic (137Cs, 239Pu, 240Pu) radionuclides in sea ice, sea-ice sediments (SIS), sediment trap material and bottom sediments from the Fram Strait to estimate transit times of sea ice from source to ablation areas, calculate radionuclide fluxes to the Fram Strait and investigate the role of sea-ice entrained sediments in sedimentation processes. Sea ice intercepts and transports the atmospherically supplied radionuclides 7Be and 210Pb, which are carried in the ice and are scavenged by any entrained SIS. All of the 7Be and most of the excess 210Pb measured in SIS collected in the Fram Strait are added to the ice during transit through the Arctic Ocean, and we use these radionuclides as chronometers to calculate ice transit times for individual ice floes. Transit times estimated from the 210Pb inventories in two ice cores are 1–3 years. Values estimated from the 7Be/210Pbexcess activity ratio of SIS are about 3–5 years. Finally, equilibrium values of the activity ratio of 210Pb to its granddaughter 210Po in the ice cores indicate transit times of at least 2 years. These transit times are consistent with back-trajectory analyses of the ice floes. The latter, as well as the clay-mineral assemblage of the SIS (low smectite and high illite content), suggest that the sampled sea-ice floes originated from the eastern Siberian Arctic shelf seas such as the eastern Laptev Sea and the East Siberian Sea. This result is in agreement with the relatively low activities of 239,240Pu and 137Cs and the 240Pu/239Pu atom ratios (∼0.18, equivalent to that in global fallout) in SIS, indicating that prior global atmospheric fallout, rather than nuclear fuel reprocessing facilities, forms the main source of these anthropogenic radionuclides reaching the western Fram Strait at the time of sampling (1999). Transport of radionuclides by sea ice through the Arctic Ocean, either associated with entrained SIS or dissolved in the ice, accounts for a significant flux in ablation areas such as the Fram Strait, up to several times larger than the current atmospheric flux in the area. Calculated fluxes derived from sea-ice melting compare well to fluxes obtained from sediment traps deployed in the Fram Strait and are consistent with inventories in bottom sediments. 240Pu/239Pu atomic ratios lower than 0.18 in bottom sediments from the Fram Strait provide evidence that plutonium from a source other than atmospheric fallout has reached the area. Most likely sources of this Pu include tropospheric fallout from atomic weapons testing of the former Soviet Union prior to 1963 and Pu released from nuclear reprocessing facilities, intercepted and transported by sea ice to the ablation areas. Future work is envisaged to more thoroughly understand the actual mechanisms by which radionuclides are incorporated in sea ice, focusing on the quantification of the efficiency of scavenging by SIS and the effect of melting and refreezing processes over the course of several years during transit.  相似文献   

6.
Sea ice and the snow pack on top of it were investigated using Chinese National Arctic Research Expedition(CHINARE) buoy data.Two polar hydrometeorological drifters,known as Zeno? ice stations,were deployed during CHINARE 2003.A new type of high-resolution Snow and Ice Mass Balance Arrays,known as SIMBA buoys,were deployed during CHINARE 2014.Data from those buoys were applied to investigate the thickness of sea ice and snow in the CHINARE domain.A simple approach was applied to estimate the average snow thickness on the basis of Zeno~ temperature data.Snow and ice thicknesses were also derived from vertical temperature profile data based on the SIMBA buoys.A one-dimensional snow and ice thermodynamic model(HIGHTSI) was applied to calculate the snow and ice thickness along the buoy drift trajectories.The model forcing was based on forecasts and analyses of the European Centre for Medium-Range Weather Forecasts(ECMWF).The Zeno~ buoys drifted in a confined area during 2003–2004.The snow thickness modelled applying HIGHTSI was consistent with results based on Zeno~ buoy data.The SIMBA buoys drifted from 81.1°N,157.4°W to 73.5°N,134.9°W in 15 months during2014–2015.The total ice thickness increased from an initial August 2014 value of 1.97 m to a maximum value of2.45 m before the onset of snow melt in May 2015;the last observation was approximately 1 m in late November2015.The ice thickness based on HIGHTSI agreed with SIMBA measurements,in particular when the seasonal variation of oceanic heat flux was taken into account,but the modelled snow thickness differed from the observed one.Sea ice thickness derived from SIMBA data was reasonably good in cold conditions,but challenges remain in both snow and ice thickness in summer.  相似文献   

7.
北极海冰变化影响着全球物质平衡、能量交换和气候变化。本文基于CryoSat-2测高数据和OSI SAF海冰密集度及海冰类型产品,分析了2010-2017年北极海冰面积、厚度和体积的季节和年际变化特征,结合NCEP再分析资料探讨了融冰期北极气温异常和夏季风异常对海冰变化的影响。结果表明,结冰期海冰面积的增加量波动较大,海冰厚度的增加量呈明显下降趋势。融冰期海冰厚度的减小量波动较大,2013年以后融冰期海冰面积的减小量逐年增加。海冰体积的变化趋势和面积变化更相似,融冰期的减小速率大于结冰期的增加速率。融冰期北极海表面大气温度异常与海冰融化量正相关。夏季风影响海冰的辐合和辐散,在弗拉姆海峡海冰的输运过程中起关键作用,促进了北冰洋表层水向大洋深层的传输。  相似文献   

8.
随着北极地区气候变暖的加剧,北极海冰正在急剧消融,海冰的减少增加了北极地区航道的适航性。本文利用遥感数据反演得到的海冰运动产品对北极海冰输出区域以及东北航道以北区域的海冰运动特征进行了量化。结果显示,从北极中央海域向弗拉姆海峡以及格陵兰海流出海冰的南向位移量呈现出显著增长趋势,海冰的平均南向位移量在2007-2014年间达到1511 km,是2007年之前（617 km）的两倍以上,反映了北极穿极流（TDS）强度在不断增强。通过长时间序列分析发现,春季东北航道以北区域的海冰北向漂移速度在喀拉海呈现+0.04 厘米/秒/年的显著增长趋势（P<0.05）。海冰北向漂移对于东北航道的开通具有显著的影响,在拉普捷夫海与喀拉海,海冰北向运动速度与航道适航期的决定系数分别达到0.33（P<0.001）和0.15（P<0.05）。东西伯利亚海、拉普捷夫海以及喀拉海存在冰间湖区域的春季海冰面积变化与航道的适航期密切相关,海冰的北向漂移对拉普捷夫海和喀拉海的海冰面积减少也有显著影响,这说明北向漂移促进了海冰的离岸输送,造成海冰面积减少的同时形成冰间水道或冰间湖促使航道开通。为探究大气环流指数对海冰运动以及东北航道适航期的影响,本文利用大气再分析数据计算了中央北极指数（CAI）和北极大气偶极子异常（DA）指数。相关性分析表明,CAI比DA更能解释东北航道的适航期,而且CAI能够解释北极海冰输出区域海冰南向位移量变化的45%。最近10年,夏季正相位的CAI进一步加强,通过加强海冰离岸输运和冰间湖活动加剧了东北航道区域海冰变薄及其强度变弱,从而促进了东北航道的开通。  相似文献   

9.
Calculations were performed using a model of the combined circulation of the Atlantic Ocean (from 20° S), the Arctic Ocean, and the Bering Sea with a resolution of 0.25° by latitude and longitude for 1958–2006. The results are compared with observational data and results obtained by other models. Model estimates were obtained for the evolution of the Atlantic water inflow into the Arctic basin through the Fram Strait and the Barents Sea. Increased transports of Atlantic water inflow into the Arctic basin were found for the first half of the 1990s and 2004–2006. The relation between Atlantic water transports into the Arctic basin and variations in the North Atlantic oscillation is shown. A positive trend of Atlantic water inflow into the Arctic basin through the Fram Strait (0.061 Sv per year) was revealed. The evolution of the freshwater-layer thickness in the Beaufort Circulation (BC) is considered. There are three periods of its increased values combined with the increased anticyclonic vorticity of BC currents: the 1960s, the 1980s, and from 1999 until now. The model estimate for a statistical mean timescale of the cycle of freshwater concentration and sink from the BC is 16 years, which is close to currently existing estimates. The evolution of anticyclonic vorticity of currents leads the variations in the freshwater-layer thickness of the BC by 1.75 years. Since the mid-1970s, there have been long positive trends of both the freshwater-layer thickness and anticyclonic vorticity of currents in the BC. In the same time period, there has been a satellite-registered negative trend in the ice area in the Arctic, which was reproduced by the model.  相似文献   

10.
The Fram Strait is very important with regard to heat and mass exchange in the Arctic Ocean, and the large quantities of heat carried north by the West Spitsbergen Current (WSC) influence the climate in the Arctic region as a whole. A large volume of water and ice is transported through Fram Strait, with net water transport of 1.7–3.2 Sv southward in the East Greenland Current and a volume ice flux in the range of 0.06–0.11 Sv. The mean annual ice flux is about 866,000 km2 yr−1. The Kongsfjorden–Krossfjorden fjord system on the coast of Spitsbergen, or at the eastern extreme of Fram Strait, is mainly affected by the northbound transport of water in the WSC. Mixing processes on the shelf result in Transformed Atlantic Water in the fjords, and the advection of Atlantic water also carries boreal fauna into the fjords. The phytoplankton production is about 80 g C m−2 yr−1 in Fram Strait, and has been estimated both below and above this for Kongsfjorden. The zooplankton fauna is diverse, but dominated in terms of biomass by calanoid copepods, particularly Calanus glacialis and C. finmarchicus. Other important copepods include C. hyperboreus, Metridia longa and the smaller, more numerous Pseudocalanus (P. minutus and P. acuspes), Microcalanus (M. pusillus and M. pygmaeus) and Oithona similis. The most important species of other taxa appear to be the amphipods Themisto libellula and T. abyssorum, the euphausiids Thysanoessa inermis and T. longicaudata and the chaetognaths Sagitta elegans and Eukrohnia hamata. A comparison between the open ocean of Fram Strait and the restricted fjord system of Kongsfjorden–Krossfjorden can be made within limitations. The same species tend to dominate, but the Fram Strait zooplankton fauna differs by the presence of meso- and bathypelagic copepods. The seasonal and inter-annual variation in zooplankton is described for Kongsfjorden based on the record during July 1996–2002. The ice macrofauna is much less diverse, consisting of a handful of amphipod species and the polar cod. The ice-associated biomass transport of ice-amphipods was calculated, based on the ice area transport, at about 3.55 × 106 ton wet weight per year or about 4.2 × 105 t C yr−1. This represents a large energy input to the Greenland Sea, but also a drain on the core population residing in the multi-year pack ice (MYI) in the Arctic Ocean. A continuous habitat loss of MYI due to climate warming will likely reduce dramatically the sympagic food source. The pelagic and sympagic food web structures were revealed by stable isotopes. The carbon sources of particulate organic matter (POM), being Ice-POM and Pelagic-POM, revealed different isotopic signals in the organisms of the food web, and also provided information about the sympagic–pelagic and pelagic–benthic couplings. The marine food web and energy pathways were further determined by fatty acid trophic markers, which to a large extent supported the stable isotope picture of the marine food web, although some discrepancies were noted, particularly with regard to predator–prey relationships of ctenophores and pteropods.  相似文献   

11.
The Arctic Mediterranean is important for climate studies because of its unique thermodynamic characteristics and its potential role in freshwater export, which would influences air-sea and ice-sea interactions and may change the North Atlantic thermohaline circulation. It is difficult to obtain consistent and complete estimates of heat and freshwater budgets due to sparse observation. In this paper, we use a coupled Arctic ocean/sea-ice model with NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data, long-term gauged river runoff data, precipitation data and estimates of volume transports to examine heat and freshwater budgets and pathways in dynamically and thermodynamically consistence. The model implements Neptune effect, flux-corrected-transport algorithm and more sophisticated treatments of heat and freshwater fluxes. Uncertainties and deficiencies in the modeling were also evaluated. Results indicate that the Arctic Ocean is provided heat mainly from the Fram Strait branch of Atlantic water at about 46 TW, which is within the range in literature. The Barents Sea branch carries about 43 TW of net heat entering the Barents Sea, but only 2 TW of net heat enters the Arctic Ocean. The Atlantic water is significantly modified in the Barents Sea. About 39 TW of heat is lost, which is consistent with the range of estimates by Simonsen and Haugan (1996). The model suggests 79,422 km3 of freshwater storage mainly distributing the Canada Basin, the Beaufort Sea and the Eurasian coast, which is in a good agreement with estimate by Aagaard and Carmack (1989). Freshwater origins from river runoff, precipitation and the Bering Strait throughflow. Liquid freshwater mainly exports via the Canadian Archipelago and Fram Strait at the rates of 3100 km3/yr and 1400 km3/yr. Sea-ice is dominantly transported through Fram Strait with 1923 km3/yr. Model discrepancies exist and climate drift is clear, which require comprehensive physical treatments of mixing processes and dense water processes in the model.  相似文献   

12.
To determine the exchanges between the Nordic Seas and the Arctic Ocean through Fram Strait is one of the most important aspects, and one of the major challenges, in describing the circulation in the Arctic Mediterranean Sea. Especially the northward transport of Arctic Intermediate Water (AIW) from the Nordic Seas into the Arctic Ocean is little known. In the two-ship study of the circulation in the Nordic Seas, Arctic Ocean - 2002, the Swedish icebreaker Oden operated in the ice-covered areas in and north of Fram Strait and in the western margins of Greenland and Iceland seas, while RV Knorr of Woods Hole worked in the ice free part of the Nordic Seas. Here two hydrographic sections obtained by Oden, augmented by tracer and velocity measurements with Lowered Acoustic Doppler Current Profiler (LADCP), are examined. The first section, reaching from the Svalbard shelf across the Yermak Plateau, covers the region north of Svalbard where inflow to the Arctic Ocean takes place. The second, western, section spans the outflow area extending from west of the Yermak Plateau onto the Greenland shelf. Geostrophic and LADCP derived velocities are both used to estimate the exchanges of water masses between the Nordic Seas and the Arctic Ocean. The geostrophic computations indicate a total flow of 3.6 Sv entering the Arctic on the eastern section. The southward flow on the western section is found to be 5.1 Sv. The total inflow to the Arctic Ocean obtained using the LADCP derived velocities is much larger, 13.6 Sv, and the southward transport on the western section is 13.7 Sv, equal to the northward transport north of Svalbard. Sulphur hexafluoride (SF6) originating from a tracer release experiment in the Greenland Sea in 1996 has become a marker for the circulation of AIW. From the geostrophic velocities we obtain 0.5 Sv and from the LADCP derived velocities 2.8 Sv of AIW flowing into the Arctic. The annual transport of SF6 into the Arctic Ocean derived from geostrophy is 5 kg/year, which is of the same magnitude as the observed total annual transport into the North Atlantic, while the LADCP measurements (19 kg/year) imply that it is substantially larger. Little SF6 was found on the western section, confirming the dominance of the Arctic Ocean water masses and indicating that the major recirculation in Fram Strait takes place farther to the south.  相似文献   

13.
2016年8月7－14日中国第七次北极科学考察期间,在83°N附近设立的长期浮冰站开展了辐射和湍流通量观测研究。结果表明,观测期间反照率变化范围为0.64~0.92,平均反照率为0.78;基于现场观测数据评估了PW79、HIRHAM、ARCSYM和CCSM3 4种不同复杂度的反照率参数化方案在天气尺度的表现,最为复杂的CCSM3结果优于其他参数化方案,但不能体现降雪条件下的反照率快速增长。浮冰区冰雪面平均净辐射为18.10 W/m2,平均感热通量为1.73 W/m2,平均潜热通量为5.55 W/m2,海冰表面消融率为（0.30±0.22） cm/d,表明此时北冰洋浮冰正处于快速消融期。冰面的平均动量通量为0.098（kg·m/s）/（m2·s）,动量通量与风速有很好的对应关系,相关系数达0.80。  相似文献   

14.
李淑瑶  崔红艳 《海岸工程》2022,41(2):162-172
基于北极海冰密集度、海冰范围、大气环流和海温数据,研究了1982—2001年与2002—2021年两阶段各20 a间北极秋季海冰的时空变化特征及其原因。结果表明,近20 a（2002—2021年）北极海冰密集度的下降中心由过去（1982—2001年）的楚科奇海及白令海峡一带,转移至亚欧大陆海岸的巴伦支海附近,且海冰范围每10 a减少量由0.44×106 km2增长至0.72×106 km2,减少速度加快约64%。秋季北极海冰范围与海水表面温度（Sea Surface Temperature,SST）、表面气温（Surface Air Temperature,SAT）及比湿（Specific Humidity）均呈显著负相关。2002—2021年的相关系数较1982—2001年有所提高,且与温度相关系数最高的月份提前了一个月。通过对海水表面温度、表面气温、比湿、气压场和风场的经验正交分解（Empirical Orthogonal Function,EOF）可知,1982—2001年间,北极地区的温度及比湿的上升中心集中在楚科奇海及白令海峡一带;2002—2021年间,上升中心则转移至巴伦支海一带。气压场和风场在前后两阶段也出现了中心转移的分布变化。北极地区大气与海洋环流各因素的协同变化影响着北极海冰的消融。  相似文献   

15.
基于CryoSat-2卫星测高数据的北极海冰体积估算方法   总被引：1，自引：1，他引：0  
近30年来,北极海冰正发生着剧烈的变化。海冰体积是量化海冰变化的重要指标之一。本文以2015年CryoSat-2卫星测高数据和OSI SAF海冰类型产品为基础。提取了浮冰出水高度、积雪深度、海冰密集度、海冰类型等属性信息,通过数据内插、投影变换、栅格转换、空间重采样等工作将海冰属性信息统一为25 km×25 km分辨率的栅格数据集。根据流体静力学平衡原理,逐个估算栅格像元对应的海冰厚度值,将其与对应的海冰面积相乘,估算了北极海冰密集度大于75%海域的海冰体积,并分析了海冰厚度和体积的月变化和季节变化特征。用NASA IceBridge海冰厚度产品对反演的海冰厚度进行验证。结果表明二者相关系数为0.72,有较高的一致性。北极海冰平均厚度春季最大,夏季最小,分别约为2.99 m和1.77 m,最厚的海冰集中在格陵兰沿岸北部和埃尔斯米尔半岛以北海域。多年冰平均厚度大于一年冰。冬季海冰体积最大,约为23.30×103 km3,经过夏季的融化,减少了近70%。一年冰体积季节波动较大,而多年冰体积相对稳定,季节变化不明显。  相似文献   

16.
A numerical simulation with a coupled sea-ice model of the Arctic and North Atlantic oceans is used to study the influence that the interannual variations in the Siberian river discharge have on the distribution and propagation of freshwater in this region. In numerical experiments we compared simulations with the use of observational data on the discharge of the most significant Siberian rivers (Ob, Yenisei, and Lena) against the results of climatic seasonally average variations of their discharges. This comparison showed that the interannual variations may have significant consequences despite their smallness when compared with oceanic-scale water transport. These consequences include (1) the intensification of either cyclonic or anticyclonic components of motion of the subsurface Arctic Ocean waters and, as a result, the redistribution of freshwater fluxes from Arctic regions between the Fram Strait and the straits of the Canadian Archipelago. A change in the store of fresh Arctic Ocean waters due to interannual variations in the Ob, Yenisei, and Lena discharges is approximately ±400 km3, whereas the volume of water redirected in this regard, which forms a link between some straits, reaches 15 thousand km3. On the other hand, (2) insignificant changes in the propagation direction of freshwaters are multiply enhanced in the process of their motion in the North Atlantic as part of the subpolar gyre because of their smaller or larger involvement in the processes of vertical mixing. As a result of this, anomalies of freshwater develop considerably far from the river mouths, like in the region of the Azores islands, and are 5–6 times larger than the maximum values of the accumulated variability volumes of the river discharge.  相似文献   

17.
北极各海域海冰覆盖范围的变化特征   总被引：2，自引：1，他引：1  
Sea ice in the Arctic has been reducing rapidly in the past half century due to global warming.This study analyzes the variations of sea ice extent in the entire Arctic Ocean and its sub regions.The results indicate that sea ice extent reduction during 1979–2013 is most significant in summer,following by that in autumn,winter and spring.In years with rich sea ice,sea ice extent anomaly with seasonal cycle removed changes with a period of 4–6 years.The year of 2003–2006 is the ice-rich period with diverse regional difference in this century.In years with poor sea ice,sea ice margin retreats further north in the Arctic.Sea ice in the Fram Strait changes in an opposite way to that in the entire Arctic.Sea ice coverage index in melting-freezing period is an critical indicator for sea ice changes,which shows an coincident change in the Arctic and sub regions.Since 2002,Region C2 in north of the Pacific sector contributes most to sea ice changes in the central Aarctic,followed by C1 and C3.Sea ice changes in different regions show three relationships.The correlation coefficient between sea ice coverage index of the Chukchi Sea and that of the East Siberian Sea is high,suggesting good consistency of ice variation.In the Atlantic sector,sea ice changes are coincided with each other between the Kara Sea and the Barents Sea as a result of warm inflow into the Kara Sea from the Barents Sea.Sea ice changes in the central Arctic are affected by surrounding seas.  相似文献   

18.
Arctic sea-ice motion and its relation to pressure field   总被引：5，自引：0，他引：5  
Daily Arctic sea-ice motion maps during the winter seasons (December–March) from December 1988 to March 2003 derived from NSCAT, QuikSCAT, SSM/I, and AMSRE data by a wavelet analysis method have been merged with those derived from buoy data. These merged sea-ice motion data have been used to study the circulation regimes and winter-to-winter variability of Arctic sea-ice motion. The relation between sea-ice motion and the pressure field in the Arctic Ocean was also studied by applying Principal Component Analysis (PCA) to the monthly merged sea-ice motion data and the monthly pressure field data from IABP. The mean Arctic sea-ice motion map of the 15 winter seasons has two distinct features: the Beaufort Gyre and a cyclonic circulation system in the Eurasian Basin, which moves ice from the Laptev Sea to Fram Strait. The strengths and sizes of the two features change from one winter season to another. Seasons with a strong or normal Beaufort Gyre alternate with seasons with a weak or no Beaufort Gyre every one to three seasons. The principal components of the first two modes of PCA of the monthly sea-ice motion are closely correlated with their counterparts of the monthly pressure field in the Arctic Ocean. The mode-one components of these two anomalies alternate between anticyclonic and cyclonic circulation systems. The correlation between Arctic Oscillation indexes and the principal components of the first mode of PCA of the monthly Arctic sea-ice motion is low but statistically significant.  相似文献   

19.
A coupled ice-ocean model is configured for the pan-Arctic and northern North Atlantic Ocean with a 27.5 km resolution. The model is driven by the daily atmospheric climatology averaged from the 40-year NCEP reanalysis (1958–1997). The ocean model is the Princeton Ocean Model (POM), while the sea ice model is based on a full thermodynamical and dynamical model with plastic-viscous rheology. A sea ice model with multiple categories of thickness is utilized. A systematic model-data comparison was conducted. This model reasonably reproduces seasonal cycles of both the sea ice and the ocean. Climatological sea ice areas derived from historical data are used to validate the ice model performance. The simulated sea ice cover reaches a maximum of 14 × 106 km2 in winter and a minimum of 6.7 × 106 km2 in summer. This is close to the 95-year climatology with a maximum of 13.3 × 106 km2 in winter and a minimum of 7 × 106 km2 in summer. The simulated general circulation in the Arctic Ocean, the GIN (Greenland, Iceland, and Norwegian) seas, and northern North Atlantic Ocean are qualitatively consistent with historical mapping. It is found that the low winter salinity or freshwater in the Canada Basin tends to converge due to the strong anticyclonic atmospheric circulation that drives the anticyclonic ocean surface current, while low summer salinity or freshwater tends to spread inside the Arctic and exports out of the Arctic due to the relaxing wind field. It is also found that the warm, saline Atlantic Water has little seasonal variation, based on both simulation and observations. Seasonal cycles of temperature and salinity at several representative locations reveals regional features that characterize different water mass properties.  相似文献   

20.
1982-2016年北极开阔水域变化   总被引：1，自引：0，他引：1  
李海丽  柯长青 《海洋学报》2017,39(12):109-121
近30年来,北极海冰覆盖范围大幅缩减,开阔水域也相应地发生显著变化。本文利用美国雪冰中心的海冰密集度产品以及美国海洋和大气科学管理局的海水表面温度数据产品,分析了1982-2016年北极开阔水域面积以及开阔水域季节长度的年际变化,并进一步探讨了海水表面温度对开阔水域时空变化的影响。结果表明北极开阔水域面积平均每年增加55.89×103 km2,海冰消退时间以平均0.77 d/a的速度在提前,海冰出现时间以平均0.82 d/a的速度在延迟,导致开阔水域季节长度以平均1.59 d/a的速度在增加。2016年达到了有遥感观测资料以来开阔水域面积和开阔水域季节长度的最大值,分别为13.52×106 km2和182 d。9个海区的开阔水域变化特征有一定的差异,对开阔水域变化贡献最大的有北冰洋核心区、喀拉海和巴伦支海。海水表面温度对开阔水域的变化有着重要影响,且影响的程度与纬度相关,即高纬度地区的海水表面温度对开阔水域的影响高于低纬度地区。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号