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首页> 外文期刊>Journal of Geophysical Research, C. Oceans: JGR >Evaluation of Labrador Sea Water formation in a global Finite-Element Sea-Ice Ocean Model setup, based on a comparison with observational data
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Evaluation of Labrador Sea Water formation in a global Finite-Element Sea-Ice Ocean Model setup, based on a comparison with observational data

机译：基于与观测数据的比较，在全球有限元海冰海洋模型中评估拉布拉多海水的形成

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摘要

The deep water formation in the Labrador Sea is simulated with the Finite-Element Sea-Ice Ocean Model (FESOM) in a regionally focused, but globally covered model setup. The model has a regional resolution of up to 7 km, and the simulations cover the time period 1958-2009. We evaluate the capability of the model setup to reproduce a realistic deep water formation in the Labrador Sea. Two classes of modeled Labrador Sea Water (LSW), the lighter upper LSW (uLSW) and the denser deep LSW (dLSW), are analyzed. Their layer thicknesses are compared to uLSW and dLSW layer thicknesses derived from observations in the formation region for the time interval 1988-2009. The results indicate a suitable agreement between the modeled and observational derived uLSW and dLSW layer thicknesses except for the period 2003-2007 where deviations in the modeled and observational derived layer thicknesses could be linked to discrepancies in the atmospheric forcing of the model. It is shown that the model is able to reproduce four phases in the temporal evolution of the potential density, temperature, and salinity, since the late 1980s, which are known in observational data. These four phases are characterized by a significantly different LSW formation. The first phase from 1988 to 1990 is characterized in the model by a fast increase in the convection depth of up to 2000 m, accompanied by an increased spring production of deep Labrador Sea Water (dLSW). In the second phase (1991-1994), the dLSW layer thickness remains on a high level for several years, while the third phase (1995-1998) features a gradual decrease in the deep ventilation and the renewal of the deep ocean layers. The fourth phase from 1999 to 2009 is characterized by a slowly continuing decrease of the dLSW layer thickness on a deeper depth level. By applying a composite map analysis between an index of dLSW and sea level pressure over the entire simulation period from 1958 to 2009, it is shown that a pattern which resembles the structure of the North Atlantic Oscillation (NAO) is one of the main triggers for the variability of LSW formation. Our model results indicate that the process of dLSW formation can act as a low-pass filter to the atmospheric forcing, so that only persistent NAO events have an effect, whether uLSW or dLSW is formed. Based on composite maps of the thermal and haline contributions to the surface density flux we can demonstrate that the central Labrador Sea in the model is dominated by the thermal contributions of the surface density flux, while the haline contributions are stronger over the branch of the Labrador Sea boundary current system (LSBCS), where they are dominated by the haline contributions of sea ice melting and formation. Our model results feature a shielding of the central Labrador Sea from the haline contributions by the LSBCS, which only allows a minor haline interaction with the central Labrador Sea by lateral mixing. Based on the comparison of the simulated and measured LSW layer thicknesses as well as vertical profiles of potential density, temperature, and salinity it is shown that the FESOM model is a suitable tool to study the regional dynamics of LSW formation and its impact on a global, not regional restricted, scale.
机译：使用有限元海冰海洋模型（FESOM）对拉布拉多海中的深水形成进行了模拟，该模型以区域为中心，但被全球覆盖。该模型具有高达7 km的区域分辨率，并且模拟涵盖了1958-2009年的时间段。我们评估了模型设置在拉布拉多海中再现真实深水形成的能力。分析了两类建模的拉布拉多海水（LSW），较轻的上部LSW（uLSW）和较浓的深LSW（dLSW）。将其层厚与uLSW和dLSW层厚进行比较，这些层厚取自1988-2009年时间间隔内在地层区域中的观测结果。结果表明，除了2003-2007年期间，建模和观测的uLSW和dLSW层厚度之间存在适当的一致性，在2003-2007年期间，建模和观测的层厚度的偏差可能与大气强迫的差异有关。结果表明，自1980年代后期以来，该模型能够再现势能密度，温度和盐度随时间变化的四个阶段，这在观测数据中是已知的。这四个阶段的特征是LSW形成明显不同。该模型的特征是1988年至1990年的第一阶段，对流深度迅速增加到2000 m，同时春季拉布拉多海水（dLSW）的春季产量增加。在第二阶段（1991-1994年）中，dLSW层厚度一直保持较高水平，而第三阶段（1995-1998年）的特征是深层通风逐渐减少，深海层更新。从1999年到2009年是第四阶段，其特征是dLSW层厚度在较深的深度水平上缓慢持续减小。通过在1958年至2009年整个模拟期间的dLSW指数与海平面压力之间进行复合图分析，结果表明，类似于北大西洋涛动（NAO）结构的模式是造成该现象的主要诱因之一。 LSW形成的可变性。我们的模型结果表明，dLSW的形成过程可以作为大气强迫的低通滤波器，因此，无论是uLSW还是dLSW，只有持续的NAO事件才有影响。基于热和盐度对表面密度通量的合成图，我们可以证明模型中的拉布拉多海由表面密度通量的热贡献支配，而盐度的贡献在拉布拉多分支上更强海边界洋流系统（LSBCS），其中海冰融化和形成的盐分作用占主导地位。我们的模型结果以LSBCS对拉布拉多海中部的盐分保护为掩护，仅允许通过横向混合与拉布拉多海中部进行少量的盐碱相互作用。通过对模拟和测量的LSW层厚度以及势密度，温度和盐度垂直剖面的比较，表明FESOM模型是研究LSW形成的区域动力学及其对全球影响的合适工具。 ，不受区域限制，规模。

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