The co-variation of surface wind speed and sea surface temperature (SST) over the Gulf Stream frontal region is investigated using high-resolution satellite measurements and atmospheric reanalysis data. Results show t...The co-variation of surface wind speed and sea surface temperature (SST) over the Gulf Stream frontal region is investigated using high-resolution satellite measurements and atmospheric reanalysis data. Results show that the pattern of positive SST-surface wind speed correlations is anchored by strong SST gradient and marine atmospheric boundary layer (MABL) height front, with active warm and cold-ocean eddies around. The MABL has an obvious transitional structure along the strong SST front, with greater (lesser) heights over the north (south) side. The significant positive SST-surface wind-speed perturbation correlations are mostly found over both strong warm and cold eddies. The surface wind speed increases (decreases) about 0.32 (0.41) m/s and the MABL elevates (drops) approximate 55 (54) m per 1℃ of SST perturbation induced by warm (cold) eddies. The response of the surface wind speed to SST perturbations over the mesoscale eddies is mainly attributed to the momentum vertical mixing in the MABL, which is confirmed by the linear relationships between the downwind (crosswind) SST gradient and wind divergence (curl).展开更多
A preliminary attempt is made to address Stommel’s suggestion that the established offshore shear in the Gulf Stream’s surface velocity is large (up to 0.5 f, where f is the Coriolis parameter) and that this needs t...A preliminary attempt is made to address Stommel’s suggestion that the established offshore shear in the Gulf Stream’s surface velocity is large (up to 0.5 f, where f is the Coriolis parameter) and that this needs to be understood better. Using Bernoulli’s law in conjunction with the geostrophic relation leads to the prediction that the shear should equal f. If a certain sea level variation across the Stream is proposed within the warm Stream water, it is qualitatively possible to reduce the shear value below f, but more work in the future will confirm or refute this idea.展开更多
Based on high-resolution,Array for Real-time Geostrophic Oceanography(Argo)profiles and Sea Level Anomaly(SLA)data,this study statistically analyzes and compares turbulent diapycnal mixing profiles inside and outside ...Based on high-resolution,Array for Real-time Geostrophic Oceanography(Argo)profiles and Sea Level Anomaly(SLA)data,this study statistically analyzes and compares turbulent diapycnal mixing profiles inside and outside mesoscale eddies in the Gulf Stream region.The result indicates that average diapycnal diffusivity at 300–540 m depths in anticyclonic eddies reaches4.0×10-5 m2 s-1.This is significantly higher than the 1.6×10-5 m2 s-1 outside eddies and 0.8×10-5 m2 s-1 in cyclonic eddies.Probabilities of diapycnal diffusivity greater than 10-4 m2 s-1 within anticyclonic and cyclonic eddies and outside eddies are29%,5%and 12%,respectively.However,magnitudes of average diapycnal diffusivity at 540–900 m depths in these three cases are of the same order,10-5 m2 s-1.Twenty-four of a total 38 anticyclonic eddies had enhanced mixing in the ocean interior,and 22 were observed during or shortly after strong winds.The coincidence between enhanced mixing and strong wind stress indicates that more wind-induced,near-inertial wave energy propagates downward in anticyclonic eddies.The deeper part of 12 profiles(below 540 m)in anticyclonic eddies had vertical overturns with Thorpe scale exceeding 5 m,among which three profiles had overturns reaching 20 m.Enhanced mixing may have occurred in deep layers of some profiles,although it was not evident in average conditions.展开更多
利用公共大气模式(community atmosphere model version 5,CAM5)的数值试验结果,探究了湾流(gulf stream,GS)及其延伸体区海洋锋(简称为GS区海洋锋)对其上空的温带气旋内上升气流的影响机制。在模式控制试验中,对出现在GS区的气旋性扰...利用公共大气模式(community atmosphere model version 5,CAM5)的数值试验结果,探究了湾流(gulf stream,GS)及其延伸体区海洋锋(简称为GS区海洋锋)对其上空的温带气旋内上升气流的影响机制。在模式控制试验中,对出现在GS区的气旋性扰动异常作了合成分析。结果表明,当气旋性扰动异常位于海洋锋上空时,扰动发展迅速,且海洋锋以南和扰动异常中心以北(50°N附近、海洋锋以北)出现了两支强上升流。通过能量收支分析发现,当气旋性扰动异常中心到达海洋锋上空时,其中心及北侧的涡动有效位能(eddy available potential energy,EAPE)和涡动动能(eddy kinetic energy,EKE)显著加强,这与海洋锋提供的热量和水汽密切相关。而海洋锋强度的对比试验结果表明,在气旋性扰动异常中心到达海洋锋上空前后,海洋锋对扰动异常区域内的EAPE和EKE方程各项的影响不同。在气旋性扰动异常前部到达海洋锋上空时,海洋锋主要通过影响向高纬的涡动热量和水汽输送增强了锋面以北的斜压产生项(EAPE方程中的源项),这为气旋性扰动异常中心北侧(锋面北侧)的EKE发展提供了能量来源。而在扰动异常中心到达海洋锋上空时,中心以北的上升运动和降水大幅加强,这主要增强了此处的非绝热加热项(EAPE方程中的另一个源项),并继续促进了气旋性扰动异常的发展。展开更多
This is the first report of the Barents Sea Ice Edge (BIE) project. The BIE position has varied between latitude 76<span style="white-space:nowrap;">°</span>N and above 82<span style=&...This is the first report of the Barents Sea Ice Edge (BIE) project. The BIE position has varied between latitude 76<span style="white-space:nowrap;">°</span>N and above 82<span style="white-space:nowrap;">°</span>N during the last 440 years. During the period 10,000 to 6000 years ago, Arctic climate was significantly warmer than today. We review various oceanic and atmospheric factors that may have an effect on the BIE position. The Gulf Stream beat with respect to alternations in flow intensity and N-S distribution plays a central role for the changes in climate and BIE position during the last millennium. This occurred in combination with external forcing from total solar irradiation, Earth’s shielding strength, Earth’s geomagnetic field intensity, Earth’s rotation, jet stream changes;all factors of which are ultimately driven by the planetary beat on the Sun, the Earth and the Earth-Moon system. During the last 20 years, we see signs of changes and shifts that may signal the end of the late 20<sup>th</sup> century warm period. The BIE position is likely to start advancing southward in next decade.展开更多
基金Supported by the China’s National Key Research and Development Projects(No.2016YFA0601803)the National Natural Science Foundation of China(Nos.41490641,41521091,U1606402)the Qingdao National Laboratory for Marine Science and Technology(No.2017ASKJ01)
文摘The co-variation of surface wind speed and sea surface temperature (SST) over the Gulf Stream frontal region is investigated using high-resolution satellite measurements and atmospheric reanalysis data. Results show that the pattern of positive SST-surface wind speed correlations is anchored by strong SST gradient and marine atmospheric boundary layer (MABL) height front, with active warm and cold-ocean eddies around. The MABL has an obvious transitional structure along the strong SST front, with greater (lesser) heights over the north (south) side. The significant positive SST-surface wind-speed perturbation correlations are mostly found over both strong warm and cold eddies. The surface wind speed increases (decreases) about 0.32 (0.41) m/s and the MABL elevates (drops) approximate 55 (54) m per 1℃ of SST perturbation induced by warm (cold) eddies. The response of the surface wind speed to SST perturbations over the mesoscale eddies is mainly attributed to the momentum vertical mixing in the MABL, which is confirmed by the linear relationships between the downwind (crosswind) SST gradient and wind divergence (curl).
文摘A preliminary attempt is made to address Stommel’s suggestion that the established offshore shear in the Gulf Stream’s surface velocity is large (up to 0.5 f, where f is the Coriolis parameter) and that this needs to be understood better. Using Bernoulli’s law in conjunction with the geostrophic relation leads to the prediction that the shear should equal f. If a certain sea level variation across the Stream is proposed within the warm Stream water, it is qualitatively possible to reduce the shear value below f, but more work in the future will confirm or refute this idea.
基金supported by the National Natural Science Foundation of China(Grant Nos.41106012,41176008,91028008)a grant from Sanya Institute of Deep-Sea Science and Engineering(Grant No.SIDSSE-201207)
文摘Based on high-resolution,Array for Real-time Geostrophic Oceanography(Argo)profiles and Sea Level Anomaly(SLA)data,this study statistically analyzes and compares turbulent diapycnal mixing profiles inside and outside mesoscale eddies in the Gulf Stream region.The result indicates that average diapycnal diffusivity at 300–540 m depths in anticyclonic eddies reaches4.0×10-5 m2 s-1.This is significantly higher than the 1.6×10-5 m2 s-1 outside eddies and 0.8×10-5 m2 s-1 in cyclonic eddies.Probabilities of diapycnal diffusivity greater than 10-4 m2 s-1 within anticyclonic and cyclonic eddies and outside eddies are29%,5%and 12%,respectively.However,magnitudes of average diapycnal diffusivity at 540–900 m depths in these three cases are of the same order,10-5 m2 s-1.Twenty-four of a total 38 anticyclonic eddies had enhanced mixing in the ocean interior,and 22 were observed during or shortly after strong winds.The coincidence between enhanced mixing and strong wind stress indicates that more wind-induced,near-inertial wave energy propagates downward in anticyclonic eddies.The deeper part of 12 profiles(below 540 m)in anticyclonic eddies had vertical overturns with Thorpe scale exceeding 5 m,among which three profiles had overturns reaching 20 m.Enhanced mixing may have occurred in deep layers of some profiles,although it was not evident in average conditions.
文摘利用公共大气模式(community atmosphere model version 5,CAM5)的数值试验结果,探究了湾流(gulf stream,GS)及其延伸体区海洋锋(简称为GS区海洋锋)对其上空的温带气旋内上升气流的影响机制。在模式控制试验中,对出现在GS区的气旋性扰动异常作了合成分析。结果表明,当气旋性扰动异常位于海洋锋上空时,扰动发展迅速,且海洋锋以南和扰动异常中心以北(50°N附近、海洋锋以北)出现了两支强上升流。通过能量收支分析发现,当气旋性扰动异常中心到达海洋锋上空时,其中心及北侧的涡动有效位能(eddy available potential energy,EAPE)和涡动动能(eddy kinetic energy,EKE)显著加强,这与海洋锋提供的热量和水汽密切相关。而海洋锋强度的对比试验结果表明,在气旋性扰动异常中心到达海洋锋上空前后,海洋锋对扰动异常区域内的EAPE和EKE方程各项的影响不同。在气旋性扰动异常前部到达海洋锋上空时,海洋锋主要通过影响向高纬的涡动热量和水汽输送增强了锋面以北的斜压产生项(EAPE方程中的源项),这为气旋性扰动异常中心北侧(锋面北侧)的EKE发展提供了能量来源。而在扰动异常中心到达海洋锋上空时,中心以北的上升运动和降水大幅加强,这主要增强了此处的非绝热加热项(EAPE方程中的另一个源项),并继续促进了气旋性扰动异常的发展。
文摘This is the first report of the Barents Sea Ice Edge (BIE) project. The BIE position has varied between latitude 76<span style="white-space:nowrap;">°</span>N and above 82<span style="white-space:nowrap;">°</span>N during the last 440 years. During the period 10,000 to 6000 years ago, Arctic climate was significantly warmer than today. We review various oceanic and atmospheric factors that may have an effect on the BIE position. The Gulf Stream beat with respect to alternations in flow intensity and N-S distribution plays a central role for the changes in climate and BIE position during the last millennium. This occurred in combination with external forcing from total solar irradiation, Earth’s shielding strength, Earth’s geomagnetic field intensity, Earth’s rotation, jet stream changes;all factors of which are ultimately driven by the planetary beat on the Sun, the Earth and the Earth-Moon system. During the last 20 years, we see signs of changes and shifts that may signal the end of the late 20<sup>th</sup> century warm period. The BIE position is likely to start advancing southward in next decade.
