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通过2014年和2019年观测资料分析了渤海夏季底层水体氧亏损空间分布的年际差异,同时首次揭示了黄河口东侧莱州湾口区域的氧亏损现象,并利用三维物理生态耦合模式ROMS-CoSiNE探究了氧亏损分布年际差异的影响因素。2014年秦皇岛外氧亏损区(以溶解氧(dissolved oxygen, DO)饱和度小于70%为统计范围)主要向东扩展,而2019年则向东南向扩展; 2014年黄河口外氧亏损区主要位于浅滩西南侧的深水洼地,而2019年则从浅滩西侧洼地延伸至黄河口外及莱州湾口区域。通过估算跃层存在期间底层水体的氧收支,得到垂向扩散和生物耗氧分别是底层DO浓度变化的主要源和汇。2014年和2019年秦皇岛外氧亏损空间分布的年际差异,与垂向扩散的差异有关,垂向扩散较弱的区域DO降低速率及降低量较大,氧亏损较强。2019年莱州湾口区域氧亏损与垂向扩散及跃层持续时间有关,较强的黄河径流与南风,有利于冲淡水的扩散,使得莱州湾口区域的跃层强度较大,垂向扩散较弱,DO降低速率较大,跃层持续时间较长,氧亏损强于2014年。此外, 2014年秦皇岛外区域和黄河口外洼地区域DO较低也主要是由2014年跃层持续... 相似文献
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利用2016年夏季长江河口现场水文特性与湍流微结构观测资料, 分析了长江河口水体温盐结构、层化发育、湍流与混合特征。结果表明: 1)夏季长江河口水体密度层化结构明显, 根据各层水体密度梯度差异, 可将水体分为底部混合层和上层密度跃层, 两部分的密度层化界限与浮力频率等值线lg N 2 = - 4.0接近。2)底部混合层湍动能耗散率大, 层化结构弱, 水体分层稳定性弱; 上层密度跃层湍动能耗散小, 层化结构强, 水体分层稳定性强, 这有利于河口内波的发育与传播。3)在密度层化的作用下, 水体的湍动能耗散率、湍动能剪切生成及浮力通量的能量关系在一定范围内符合湍动能局部能量平衡方程。不同层之间的湍流弗劳德数Frt和湍流雷诺数Ret在Frt-Ret平面上呈现明显的分区, 与经典的分层剪切流理论基本吻合。 相似文献
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The annual subduction rate of the North Pacific was calculated based on isopycnally averaged hydrographic climatology (HydroBase), high-resolution winter mixed-layer climatology (NWMLC), and various wind stress climatologies from ship reports, numerical weather prediction products, and satellite products. The calculation was performed using Lagrangian coordinates in the same manner as in previous works, except a less smoothed oceanic climatology (HydroBase and NWMLC) was used instead of a World Ocean Atlas. Differences in the wind stress climatologies have very little effect on subduction rate estimates. The subduction rate census for density classes showed peaks corresponding to subtropical mode water (STMW), central mode water (CMW), and eastern subtropical mode water (ESTMW). The deeper mixed layer and the associated sharper mixed-layer fronts in the present climatology resulted in a larger lateral induction, which boosted the subduction rate, especially for the potential density anomaly (σθ) range of the lighter STMW (25.0 < σθ < 25.2 kg m−3) and lighter CMW (26.0 < σθ < 26.2 kg m−3), compared to previous estimates. The renewal time of permanent pycnocline water was estimated as the volume of water divided by the subduction rate for each σθ class: 2–4 years for ESTMW (24.5 < σθ < 25.2 kg m−3), 2 years for the lighter STMW (25.0 < σθ < 25.3 kg m−3), 5–9 years for the denser STMW (25.3 < σθ < 25.6 kg m−3), 10–20 years for the lighter CMW (26.0 < σθ < 26.2 kg m−3), 20–30 years for the middle CMW (26.2 < σθ < 26.3 kg m−3), and 60 years or longer for the denser CMW (26.3 < σθ < 26.6 kg m−3). A comparison of the water volume and subduction rate in potential temperature–salinity (θ–S) space indicated that the upper permanent pycnocline water (25.0 < σθ < 26.2 kg m−3) was directly maintained by nondiffusive subduction of winter surface water, including STMW and lighter CMW. The lower permanent pycnocline water (26.2 < σθ < 26.6 kg m−3) may be maintained through the subduction of fresher and colder water from the subarctic–subtropical transition region and subsequent mixing with saltier and warmer water. Diagnosis of the potential vorticity (PV) of the subducted water demonstrated that the low PV of STMW was mainly due to the large subduction rate, whereas that of both ESTMW and CMW was due mainly to the small density advection rate (cross-isopycnal flow). Additionally, a relatively large subduction rate probably contributes to the low PV of part of the lighter CMW (ESTMW) formed in the region around 38°N and 170°W (28°N and 145°W), which is characterized by a relatively thick winter mixed layer and an associated mixed-layer front, causing a large lateral induction rate. 相似文献
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Steven Emerson Yutaka W. Watanabe Tsuneo Ono Sabine Mecking 《Journal of Oceanography》2004,60(1):139-147
We present a compilation of apparent oxygen utilization (AOU) changes observed in the upper pycnocline of the North Pacific
Ocean over the last several decades. The goal here is to place previously-published data in a common format, and assess the
causes of the observed changes. The general trend along repeat cross sections of the eastern and western subtropical ocean
and the subarctic ocean is an increase in AOU from the mid 1980s to the mid 1990s. AOU has also been increasing in a time-series
study in the northwest subarctic Ocean off of Japan since the late 1960s. Observed AOU changes south of 35°N in the subtropical
ocean are 10–20 μmol kg−1, with much greater changes, reaching 60–80 μmol kg−1 in isolated areas, in the subtropical/subarctic boundary and the subarctic ocean. Analysis of changes in both AOU and salinity
on isopycnals suggests that there are significant salinity-normalized increases that must be due to alteration in the rate
of ventilation or organic matter degradation. A common feature in the data is that the maximum increase in AOU is centered
near the density horizon σθ= 26.6. Time series results from the Oyashio Current region near the winter outcrop area of this density horizon indicate
that surface waters there have become fresher with time, which may mean this density surface has ceased to outcrop in the
latter decades of the 20th century. Whether this is due to natural decadal-scale changes or anthropogenic influences can be
decided by determining future trends in AOU on these density surfaces.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Oceanic pycnocline depth retrieval from SAR imagery in the existence of solitary internal waves 总被引:2,自引:1,他引:1
Oceanic pycnocline depth is usually inferred from in situ measurements. It is attempted to estimate the depth remotely. As solitary internal waves occur on oceanic pycnocline and propagate along it, it is possible to retrieve the depth indirectly in virtue of the solitary internal waves. A numerical model is presented for retrieving the pycnocline depth from synthetic aperture radar (SAR) images where the solitary internal waves are visible and when ocean waters are fully stratified. This numerical model is constructed by combining the solitary internal wave model and a two-layer ocean model. It is also assumed that the observed groups of solitary internal wave packets on the SAR imagery are generated by local semidiurnal tides. A case study in the East China Sea shows a good agreement with in situ CTD (conductivity-temperature-depth) data. 相似文献
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利用ADCP对东海大陆架定点(26°30.052′N,122°35.998′E)连续观测6个多月的海流数据进行分析研究,结果表明:层化对该海域潮流的垂向结构有显著影响,层化导致潮流流速、潮流椭圆长轴、椭圆率和倾角在通过密度跃层时发生较大改变。9月份,东海大陆架存在较强的密度跃层,层化加强,海流流速、M2分潮潮流倾角和M2分潮潮流椭圆率在跃层深度以浅随深度显著增大,跃层处达最大,跃层以深随深度迅速减小;2月份,上层海洋混合较强,密度跃层强度最弱,潮流流速、潮流椭圆长轴、椭圆率和倾角在垂向上变化不大。 相似文献