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Sea level anomaly on the Patagonian continental shelf: Trends annual patterns and geostrophic flows

机译:巴塔哥尼亚大陆架海平面异常:趋势年度格局和地转流

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摘要

We study the annual patterns and linear trend of satellite sea level anomaly (SLA) over the southwest South Atlantic continental shelf (SWACS) between 54ºS and 36ºS. Results show that south of 42°S the thermal steric effect explains nearly 100% of the annual amplitude of the SLA, while north of 42°S it explains less than 60%. This difference is due to the halosteric contribution. The annual wind variability plays a minor role over the whole continental shelf. The temporal linear trend in SLA ranges between 1 and 5 mm/yr (95% confidence level). The largest linear trends are found north of 39°S, at 42°S and at 50°S. We propose that in the northern region the large positive linear trends are associated with local changes in the density field caused by advective effects in response to a southward displacement of the South Atlantic High. The causes of the relative large SLA trends in two southern coastal regions are discussed as a function meridional wind stress and river discharge. Finally, we combined the annual cycle of SLA with the mean dynamic topography to estimate the absolute geostrophic velocities. This approach provides the first comprehensive description of the seasonal component of SWACS circulation based on satellite observations. The general circulation of the SWACS is northeastward with stronger/weaker geostrophic currents in austral summer/winter. At all latitudes, geostrophic velocities are larger (up to 20 cm/s) close to the shelf‐break and decrease toward the coast. This spatio‐temporal pattern is more intense north of 45°S.
机译:我们研究了西南南大西洋大陆架(SWACS)在54ºS和36ºS之间的卫星海平面异常(SLA)的年度模式和线性趋势。结果表明,在42°S以南,空间位阻效应解释了SLA年幅度的近100%,而在42°S以北,则解释不到60%。这种差异是由于滞后作用。在整个大陆架上,年风变率的作用很小。 SLA的时间线性趋势介于1-5 mm / yr(95%置信度)之间。在39°S以北,42°S和50°S处发现最大的线性趋势。我们建议在北部地区,大的正线性趋势与对流效应引起的密度场的局部变化有关,这是对南大西洋高地向南位移的响应。讨论了两个南部沿海地区SLA趋势相对较大的原因,作为子午风应力和河流流量的函数。最后,我们将SLA的年度周期与平均动态地形相结合,以估算绝对地转速度。该方法基于卫星观测结果,对SWACS循环的季节成分进行了首次全面描述。 SWACS的总体环流是东北的,夏季/冬季南半球的地转流偏强。在所有纬度上,接近陆架断裂的地转速度都较大(高达20 cm / s),而向海岸的方向则下降。在45°S以北,这种时空格局更加强烈。

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