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1.
使用维多利亚大学的地球系统模式进行模拟,选取1800-2500年间较高的CO2浓度情景（RCP8.5）,分析由于CO2增加引起的气候变化对海洋碳循环的影响。当气候敏感度为3.0 K时,相对于无气候变化,到2100年,由于大气CO2增加造成的气候变化导致海表面温度升高2.7 K,北大西洋深水流量减少4.5 Sv,海洋对人为碳的年吸收减少0.8 Pg C;比较人为溶解无机碳在海洋中的垂直累积分布,发现气候变化对海洋吸收大气CO2的影响在北大西洋区域最明显。1800-2500年,相对于不考虑气候变化的情景,模式模拟的气候变化导致整个海洋对人为碳的累积吸收总量减少23.1%,其中北大西洋减少32.0%。此外,比较不同气候敏感度（0～4.5 K,间隔为0.5 K）的模拟结果发现,气候敏感度越高,气候变化对海洋吸收CO2能力的抑制作用越明显。 相似文献
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3.
潮汐混合对大西洋经圈翻转环流(AMOC)模拟影响的数值模拟研究 总被引：1，自引：1，他引：0
海洋中的潮汐混合对大西洋经圈翻转环流AMOC(Atlantic Meridional Overturning Circulation)模拟的影响是海洋环流模式研究的热点问题之一。本文采用IAP/LASG发展的气候系统海洋模式LICOM(LASG/IAP Climate system Ocean Model)及与海冰耦合模式进行了有无潮汐混合方案的试验,重点探讨了潮汐混合对AMOC强度模拟的影响。结果显示,引入潮汐混合后模拟的AMOC强度极大值比对照试验增加约1倍,更接近RAPID(Rapid Climate Change Programme)观测。而且,潮汐混合试验中模拟的AMOC上层环流深度(3200 m)比对照试验加深1000 m左右,同样更接近RAPID观测。海洋底部的垂直混合增强,使海洋层结变得更加不稳定,加强了北大西洋高纬地区,特别是拉布拉多海等地区的深对流,这是AMOC加强的直接原因。同时,潮汐混合试验中上层海洋环流也加强,增加了中低纬副热带高盐海水向高纬输送,使表层增密,海洋层结更加不稳定,也可以进一步增强AMOC。 相似文献
4.
地球工程是指通过人工方法在大规模尺度上干预气候系统,使地球气候降温的一种手段。CO2移除是地球工程的主要途径之一。文中概述了CO2移除地球工程的科学背景、各种CO2移除方法的利弊、大尺度应用CO2移除方法可能产生的气候效应和风险,以及CO2移除方案在未来气候情景研究中的现状。在第六次国际耦合模式比较计划（CMIP6）框架下开展的CO2移除模式比较计划（CDRMIP),为深入研究CO2移除地球工程减缓气候变化的效能和气候系统对其的响应提供了统一试验方案和平台。CDRMIP的开展,对地球工程和气候变化研究具有重要的促进作用。 相似文献
5.
Uncertainty in projections of the South Asian summer monsoon under global warming by CMIP6 models: Role of tropospheric meridional thermal contrast 
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下载免费PDF全文 本文基于第六次国际耦合模式比较计划共18个模式的工业革命前实验和CO2浓度突然四倍实验,发现在CO2四倍强迫下,南亚夏季风环流呈显著减弱趋势,但减弱强度存在较大模式间差异.利用Webster-Yang指数和经向哈得莱环流指数的下降趋势表征SASM减弱强度,发现该下降趋势与欧亚大陆-印度洋之间对流层上层经向温度梯度的变化值(EUTT-IUTT)高度相关.进一步利用气候反馈-响应分析方法进行分析,发现EUTT-IUTT变化的模式间差异主要来自于大气动力过程,其次是云的短波辐射效应的贡献.地表潜热通量和云的长波辐射效应缩小了EUTT-IUTT变化的模式间差异. 相似文献
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曹龙 《气候变化研究进展》2021,17(6):664-670
IPCC AR6报告中控温1.5℃和2℃的低排放情景需要在21世纪中叶以后实现净负CO2排放,这需要在很大程度上依赖CO2移除措施。AR6对CO2移除的主要评估结论如下：CO2移除有潜力从大气中去除CO2（高信度);如果CO2移除量超过CO2排放量,将实现净负CO2排放,降低大气CO2浓度,减缓海洋酸化（高信度);通过CO2移除方法从大气中去除的CO2会部分被海洋和陆地释放的CO2抵消（非常高信度);如果净负CO2排放可以实现并且持续,CO2引起的全球升温趋势将会逐渐扭转,但是气候系统的其他变化（例如海平面升高）仍会在未来的几十年到千年尺度上持续（高信度);不同CO2移除方法会对生物化学循环和气候产生广泛的影响,这些影响会加强或减弱CO2移除的降温潜力,并且影响水资源、食物生产和生物多样性（高信度）。 相似文献
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卫星短波红外CO2遥感获得大气低层CO2浓度信息,已成为目前国际热点研究领域。结合气候变化及碳源、汇观测需求,利用高精度大气辐射传输模式研究了高光谱分辨率、高精度CO2探测目标的可实现性。针对高光谱CO2探测器光栅分光、阵列探测器特点,分析了光谱分辨率、光谱采样率等关键技术指标对CO2探测的可能影响;基于辐射敏感度因子分析了不同探测精度要求下的信噪比需求。结果表明:高光谱CO2探测器首先应具有足够高的光谱分辨率,以便从太阳反射连续谱段中分辨出CO2吸收线;为保证CO2光谱的准确性,光谱仪所用探测器面元应该保证光谱采样率大于2;尽管探测边界层内CO2浓度1%变化所要求的信噪比难以达到,但探测整层大气CO2浓度1%的变化所需要的信噪比是可以实现的。 相似文献
8.
本文是用简单海一气耦合模型模拟温盐环流在全球增暖事件中作用的研究工作的第二部分。在研究海－气耦合系统的增暖过程之前，我们先利用单独的大西洋温盐环流模式模拟和分析了海表热异常向深海的传输过程。结果表明温盐环流在海洋对热异常的响应过程中是被削弱的；对各种物理过程在热异常向深海传输过程中的作用的分析表明，对流在热异常由海表向深海的输送过程中起着关键的作用。在这基础上，我们利用本文第一部分中复制的二维海洋温盐环流模式和一个零维的能量平衡大气模式，在大气和海洋表层始终处于热平衡状态的假定下建立了一个高度简化的海气耦合系统，用数值试验方法研究了该系统对于和大气ＣＯ２浓度突然加倍相当的辐射强迫的迁延响应，着重分析了温盐环流在全球增暖过程中的作用。结果表明：１）两大洋的平衡响应结果有显著差别：太平洋是温盐环流的上翻区，热量主要通过扩散过程由海表向深海渗透，因而海表升温较快，深海加热较慢，而且增温幅度几乎是南北均一的；在北大西洋深水形成区。由于对流与垂直平流共同作用，海表吸收的热量迅速下传，使得大西洋平均海表增温速度要比太平洋慢。而其深海增温则要快得多，并且增温幅度在南北方向是不均匀的。（２）北大西洋在增暖过程中由于其温度垂 相似文献
9.
使用HadCM3L气候模式,针对突然增加的4倍CO2浓度和增加4%的太阳辐射强迫进行一系列理想化模拟试验,分析并比较了CO2强迫和太阳辐射强迫对气候系统的影响机制和异同。模拟结果表明,突然增加的4倍CO2浓度和增加4%的太阳辐射造成的长期全球表面平均温度变化基本相同,但二者造成降水的变化差异很大。气候系统对CO2和太阳辐射的响应可以分为快响应和慢响应两个部分,而降水的差异主要体现在大约1个月时间尺度内的快响应阶段,在这一时间段,陆地区域CO2的气孔效应减少了植被的蒸腾作用,导致降水受到抑制;海洋区域CO2的辐射效应会首先导致大气长波吸收增强,而海洋的比热较大,所以海表温度变化落后于低层大气,低层大气的垂直稳定度增加,海表向上蒸发受到抑制。此外,比较不同时间尺度上CO2对气候系统的影响,可以发现在1个月的短时间尺度上,对陆地而言,CO2的气孔效应对气候系统的影响占主导地位,但在数年以上更长的时间尺度上,CO2的辐射效应是导致地气系统温度升高的主要原因。 相似文献
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地球系统模式结果表明大气CO2浓度的快速增加是气候变化重要的原因之一。卫星资料分析结果表明，大气CO2浓度并非均一的，而是有明显的区域差异，以人类活动为主的碳排放会影响这一区域差异。这种空间差异如何影响区域地表气温对CO2的敏感度，需要进一步深入系统的研究，利用地球系统模式BNU-ESM(Earth System Model of Beijing Normal University)进行数值模拟，并与观测数据进行比较，结果表明：在试验模拟结果2°C阈值内，非均匀CO2浓度试验的CO2浓度增加阈值范围小于均匀CO2浓度试验结果，偏少约为4.3 ppm(106)。在区域尺度上，中国地表气温对CO2敏感度普遍低于美国、欧洲以及北半球平均水平，这表明CO2浓度空间差异对地表气温的敏感度的影响存在明显区域差异，很可能是CO2浓度辐射效应与气候系统反馈过程的共同作用结果，这需要进一... 相似文献
11.
Atmosphere?Cocean general circulation models (AOGCMs) predict a weakening of the Atlantic meridional overturning circulation (AMOC) in response to anthropogenic forcing of climate, but there is a large model uncertainty in the magnitude of the predicted change. The weakening of the AMOC is generally understood to be the result of increased buoyancy input to the north Atlantic in a warmer climate, leading to reduced convection and deep water formation. Consistent with this idea, model analyses have shown empirical relationships between the AMOC and the meridional density gradient, but this link is not direct because the large-scale ocean circulation is essentially geostrophic, making currents and pressure gradients orthogonal. Analysis of the budget of kinetic energy (KE) instead of momentum has the advantage of excluding the dominant geostrophic balance. Diagnosis of the KE balance of the HadCM3 AOGCM and its low-resolution version FAMOUS shows that KE is supplied to the ocean by the wind and dissipated by viscous forces in the global mean of the steady-state control climate, and the circulation does work against the pressure-gradient force, mainly in the Southern Ocean. In the Atlantic Ocean, however, the pressure-gradient force does work on the circulation, especially in the high-latitude regions of deep water formation. During CO2-forced climate change, we demonstrate a very good temporal correlation between the AMOC strength and the rate of KE generation by the pressure-gradient force in 50?C70°N of the Atlantic Ocean in each of nine contemporary AOGCMs, supporting a buoyancy-driven interpretation of AMOC changes. To account for this, we describe a conceptual model, which offers an explanation of why AOGCMs with stronger overturning in the control climate tend to have a larger weakening under CO2 increase. 相似文献
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Jiangbo JIN Xiao DONG Juanxiong HE Yi YU Hailong LIU Minghua ZHANG Qingcun ZENG He ZHANG Xin GAO Guangqing ZHOU Yaqi WANG 《大气科学进展》2022,39(1):55-66
State-of-the-art coupled general circulation models(CGCMs)are used to predict ocean heat uptake(OHU)and sealevel change under global warming.However,the projections of different models vary,resulting in high uncertainty.Much of the inter-model spread is driven by responses to surface heat perturbations.This study mainly focuses on the response of the ocean to a surface heat flux perturbation F,as prescribed by the Flux-Anomaly-Forced Model Intercomparison Project(FAFMIP).The results of ocean model were compared with those of a CGCM with the same ocean component.On the global scale,the changes in global mean temperature,ocean heat content(OHC),and steric sea level(SSL)simulated in the OGCM are generally consistent with CGCM simulations.Differences in changes in ocean temperature,OHC,and SSL between the two models primarily occur in the Arctic and Atlantic Oceans(AA)and the Southern Ocean(SO)basins.In addition to the differences in surface heat flux anomalies between the two models,differences in heat exchange between basins also play an important role in the inconsistencies in ocean climate changes in the AA and SO basins.These discrepancies are largely due to both the larger initial value and the greater weakening change of the Atlantic meridional overturning circulation(AMOC)in CGCM.The greater weakening of the AMOC in the CGCM is associated with the atmosphere–ocean feedback and the lack of a restoring salinity boundary condition.Furthermore,differences in surface salinity boundary conditions between the two models contribute to discrepancies in SSL changes. 相似文献
13.
Simulated Spatiotemporal Response of Ocean Heat Transport to Freshwater Enhancement in North Atlantic and Associated Mechanisms 下载免费PDF全文
下载免费PDF全文 The Atlantic Meridional Overturning Circulation(AMOC)transports a large amount of heat to northern high latitudes,playing an important role in the global climate change.Investigation of the freshwater perturbation in North Atlantic(NA)has become one of the hot topics in the recent years.In this study,the mechanism and pathway of meridional ocean heat transport(OHT)under the enhanced freshwater input to the northern high latitudes in the Atlantic are investigated by an ocean-sea ice-atmosphere coupled model.The results show that the anomalous OHT in the freshwater experiment(FW)is dominated by the meridional circulation kinetic and ocean thermal processes.In the FW,OHT drops down during the period of weakened AMOC while the upper tropical ocean turns warmer due to the retained NA warm currents.Conversely,OHT recovers as the AMOC recovers,and the mechanism can be generalized as:1)increased ocean heat content in the tropical Southern Ocean during the early integration provides the thermal condition for the recovery of OHT in NA;2)the OHT from the Southern Ocean enters the NA through the equator alongthe deep Ekman layer;3)in NA,the recovery of OHT appears mainly along the isopycnic layers of 24.70-25.77 below the mixing layer.It is then transported into the mixing layer from the "outcropping points"innorthern high latitudes,and finally released to the atmosphere by the ocean-atmosphere heat exchange. 相似文献
14.
We investigate the sensitivity of the transient climate change to a tidal mixing scheme. The scheme parameterizes diapycnal diffusivity depending on the location of energy dissipation over rough topography, whereas the standard configuration uses horizontally constant diffusivity. We perform ensemble climate change experiments with two setups of MPIOM/ECHAM5, one setup with the tidal mixing scheme and the second setup with the standard configuration. Analysis of the responses of the transient climate change to CO2 increase reveals that the implementation of tidal mixing leads to a significant reduction of the transient surface warming by 9 %. The weaker surface warming in the tidal run is localized particularly over the Weddell Sea, likely caused by a stronger ocean heat uptake in the Southern Ocean. The analysis of the ocean heat budget reveals that the ocean heat uptake in both experiments is caused by changes in convection and advection. In the upper ocean, heat uptake is caused by reduced convection and enhancement of the Deacon Cell, which appears also in isopycnal coordinates. In the deeper ocean, heat uptake is caused by reduction of convective cooling associated with the circulation polewards of 65°S. Tidal mixing leads to stronger heat uptake in the Southern Ocean by causing stronger changes in advection, namely a stronger increase in the Deacon Cell and a stronger reduction in advective cooling by the circulation polewards of 65°S. Counter-intuitively, the relation between tidal mixing and greater heat storage in the deep ocean is an indirect one, through the influence of tidal mixing on the circulation. 相似文献
15.
S. J. Kim 《Climate Dynamics》2004,22(6-7):639-651
The role of reduced atmospheric CO2 concentration and ice sheet topography plus its associated land albedo on the LGM climate is investigated using a coupled atmosphere-ocean-sea ice climate system model. The surface cooling induced by the reduced CO2 concentration is larger than that by the ice sheet topography plus other factors by about 30% for the surface air temperature and by about 100% for the sea surface temperature. A large inter-hemispheric asymmetry in surface cooling with a larger cooling in the Northern Hemisphere is found for both cases. This asymmetric inter-hemispheric temperature response is consistent in the ice sheet topography case with earlier studies using an atmospheric model coupled with a mixed-layer ocean representation, but contrasts with these results in the reduced CO2 case. The incorporation of ocean dynamics presumably leads to a larger snow and sea ice feedback as a result of the reduction in northward ocean heat transport, mainly as a consequence of the decrease in the North Atlantic overturning circulation by the substantial freshening of the North Atlantic convection regions. A reversed case is found in the Southern Ocean. Overall, the reduction in atmospheric CO2 concentration accounts for about 60% of the total LGM climate change. 相似文献
16.
Seawater property changes in the North Atlantic Ocean affect the Atlantic meridional overturning circulation (AMOC), which transports warm water northward from the upper ocean and contributes to the temperate climate of Europe, as well as influences climate globally. Previous observational studies have focused on salinity and freshwater variability in the sinking region of the North Atlantic, since it is believed that a freshening North Atlantic basin can slow down or halt the flow of the AMOC. Here we use available data to show the importance of how density patterns over the upper ocean of the North Atlantic affect the strength of the AMOC. For the long-term trend, the upper ocean of the subpolar North Atlantic is becoming cooler and fresher, whereas the subtropical North Atlantic is becoming warmer and saltier. On a multidecadal timescale, the upper ocean of the North Atlantic has generally been warmer and saltier since 1995. The heat and salt content in the subpolar North Atlantic lags that in the subtropical North Atlantic by about 8–9 years, suggesting a lower latitude origin for the temperature and salinity anomalies. Because of the opposite effects of temperature and salinity on density for both long-term trend and multidecadal timescales, these variations do not result in a density reduction in the subpolar North Atlantic for slowing down the AMOC. Indeed, the variations in the meridional density gradient between the subpolar and subtropical North Atlantic Ocean suggest that the AMOC has become stronger over the past five decades. These observed results are supported by and consistent with some oceanic reanalysis products. 相似文献
17.
Vertical heat transports in the ocean and their effect on time-dependent climate change 总被引：2，自引：0，他引：2
J. M. Gregory 《Climate Dynamics》2000,16(7):501-515
In response to increasing atmospheric concentrations of greenhouse gases, the rate of time-dependent climate change is determined
jointly by the strength of climate feedbacks and the efficiency of processes which remove heat from the surface into the deep
ocean. This work examines the vertical heat transport processes in the ocean of the HADCM2 atmosphere–ocean general circulation
model (AOGCM) in experiments with CO2 held constant (control) and increasing at 1 per year (anomaly). The control experiment shows that global average heat exchanges
between the upper and lower ocean are dominated by the Southern Ocean, where heat is pumped downwards by the wind-driven circulation
and diffuses upwards along sloping isopycnals. This is the reverse of the low-latitude balance used in upwelling–diffusion
ocean models, the global average upward diffusive transport being against the temperature gradient. In the anomaly experiment,
weakened convection at high latitudes leads to reduced diffusive and convective heat loss from the deep ocean, and hence to
net heat uptake, since the advective heat input is less affected. Reduction of deep water production at high latitudes results
in reduced upwelling of cold water at low latitudes, giving a further contribution to net heat uptake. On the global average,
high-latitude processes thus have a controlling influence. The important role of diffusion highlights the need to ensure that
the schemes employed in AOGCMs give an accurate representation of the relevant sub-grid-scale processes.
Received: 8 July 1999 / Accepted: 17 November 1999 相似文献
18.
成里京 《气候变化研究进展》2020,16(2):172-181
工业革命以来,大气中温室气体不断增加,驱动了全球变暖。IPCC第五次评估报告(AR5)指出,人类排放的温室气体导致的地球系统能量增加中90%以上都被海洋吸收,使得海洋增暖,海洋热含量增加。IPCC最新发布的《气候变化中的海洋和冰冻圈特别报告》(SROCC)发现：自1970年以来,几乎确定海洋上层2000 m在持续增暖。1993—2017年间的增暖速率至少为1969—1993年的2倍,体现出显著的变暖增强趋势。此外,在20世纪90年代以后,2000 m以下的深海也已观测到了变暖信号,尤其是在南大洋(30°S以南)。在1970—2017年间,南大洋上层2000 m储存了全球海洋约35%~43%的热量,在2005—2017年期间增加到45%~62%。基于耦合气候模型预估,几乎可确定海洋将在21世纪持续增暖,2018—2100年间海洋热含量上升幅度可能是1970—2017年间的5~7倍(RCP8.5情景)或2~4倍(RCP2.6情景)。变暖导致的热膨胀效应贡献了1993年以来全球海平面上升的约43%。 相似文献
19.
The heat budget of the upper Arctic Ocean is examined in an ensemble of coupled climate models under idealised increasing CO2 scenarios. All of the experiments show a strong amplification of surface air temperatures but a smaller increase in sea surface temperature than the rest of the world as heat is lost to the atmosphere as the sea-ice cover is reduced. We carry out a heat budget analysis of the Arctic Ocean in an ensemble of model runs to understand the changes that occur as the Arctic becomes ice free in summer. We find that as sea-ice retreats heat is lost from the ocean surface to the atmosphere contributing to the amplification of Arctic surface temperatures. Furthermore, heat is mixed upwards into the mixed layer as a result of increased upper ocean mixing and there is increased advection of heat into the Arctic as the ice edge retreats. Heat lost from the upper Arctic Ocean to the atmosphere is therefore replenished by mixing of warmer water from below and by increased advection of warm water from lower latitudes. The ocean is therefore able to contribute more to Arctic amplification. 相似文献
20.
Multi-centennial variability controlled by Southern Ocean convection in the Kiel Climate Model 总被引：1，自引：0，他引：1
A quasi-oscillatory multi-centennial mode of open ocean deep convection in the Atlantic sector of the Southern Ocean in the Kiel Climate Model is described. The quasi-periodic occurrence of the deep convection causes variations in regional and global surface air temperature, Southern Hemisphere sea ice coverage, Southern Ocean and North Atlantic sea surface height, the Antarctic Circumpolar Current and the Atlantic Meridional Overturning Circulation (AMOC). The deep convection is stimulated by a strong built-up of heat at mid-depth. When the heat reservoir is virtually depleted a coincidental strong freshening event at the sea surface shuts down the convection. The heat originates from relatively warm deep water formed in the North Atlantic. The several decades lasting recharge process of the heat reservoir depends on the AMOC and the Weddell Gyre and sets a minimum delay for the deep convection to recur. While the strength of the AMOC increases, the Weddell Gyre weakens during the non-convective regime. Convection onset and shutdown also depend on the stochastic occurrence of favorable sea surface conditions, which contributes to the multi-centennial period of the phenomenon. The shutdown triggers a century-long deviation in AMOC strength caused by significant reductions in bottom water formation and surface salinity in the Southern Ocean’s Atlantic sector. Additional numerical experimentation reveals that sea ice has an important effect on the frequency of occurrence and intensity of the deep convection. Further, we find intriguing similarities to the Weddell Polynya observed during the 1970s. 相似文献