Pathways and variability of the Antarctic Intermediate Water in the western equatorial Pacific Ocean
Pathways and variability of the Antarctic Intermediate Water in the western equatorial Pacific Ocean
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DOI：
10.1016/j.pocean.2005.05.003
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发表时间：
2005-10
影响因子：
4.1
通讯作者：
W. Zenk;G. Siedler;A. Ishida;J. Holfort;Y. Kashino;Y. Kuroda;T. Miyama;T. Müller
中科院分区：
文献类型：
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作者：
W. Zenk;G. Siedler;A. Ishida;J. Holfort;Y. Kashino;Y. Kuroda;T. Miyama;T. Müller
在赤道西太平洋，在800 m左右的深度处发现了南极中层水（AAIW）的低盐度核心，其位密度水平为σθ=27.2 ~ 27.3。研究了AAIW从俾斯麦海到加罗林盆地再到纬向赤道流系统的路径及其核心的退化。使用历史和新的观测资料，以及数值环流模式运行的结果。观测包括德国和日本研究船的水文站，以及欧拉和拉格朗日海流测量。该模式是以模块海洋模式（海洋模式2）为基础的JAMSTEC高分辨率数值模式。观测结果和模型结果之间的一般一致性使我们能够诊断属性并提供有关AAIW的新信息。分析证实了最重要的影响，地形的AAIW舌头的新几内亚北部的扩展。在东俾斯麦海发现了两个AAIW岩心。一个核心来自维蒂亚兹海峡，另一个来自圣乔治海峡，可能是通过气旋路径到达的。它们在西俾斯麦海合并，总含盐量没有太大变化，而当在加罗林盆地混合时，统一的核心含盐量大大增加。水文和系泊流观测以及模型结果表明，在新几内亚的AAIW核心的盐度和速度有一个独特的年度信号。这似乎与该区域近地表沃茨通常存在的季风变化有关。拉格朗日数据被用来调查的结构，新几内亚海岸深层暗流，相关的越赤道流和涡结构，并嵌入纬向赤道流系统。从17中性浮力RAFOS浮子，压载漂移在AAIW核心层的结果进行了比较与数值跟踪实验。在模型中，从J站（2.5°N，142°E）每隔五天释放73个粒子，模拟新几内亚北部一个停泊时间序列站的海流。观察到的和模型的轨道模式是相当一致的空间和季节。漂浮物最好在Cenderawasih湾以北穿越赤道，在新几内亚以北的这一地区漩涡运动的范围最大。在135°E处的北向路径也反映在低盐度舌体上，可达3°N。在那个经度上，浮标似乎忽略了纬向排列的赤道暗流。然而，在更远的东部（139-145°E），浮标观测结果与低纬度的中间海流带一致。
In the western equatorial Pacific the low-salinity core of Antarctic Intermediate Water (AAIW) is found at about 800m depth between potential density levels σθ=27.2 and 27.3. The pathways of AAIW and the degradation of its core are studied, from the Bismarck Sea to the Caroline Basins and into the zonal equatorial current system. Both historical and new observational data, and results from numerical circulation model runs are used. The observations include hydrographic stations from German and Japanese research vessels, and Eulerian and Lagrangian current measurements. The model is the JAMSTEC high-resolution numerical model based on the Modular Ocean Model (MOM 2). The general agreement between results from the observations and from the model enables us to diagnose properties and to provide new information on the AAIW. The analysis confirms the paramount influence of topography on the spreading of the AAIW tongue north of New Guinea. Two cores of AAIW are found in the eastern Bismarck Sea. One core originates from Vitiaz Strait and one from St. George’s Channel, probably arriving on a cyclonic pathway. They merge in the western Bismarck Sea without much change in their total salt content, and the uniform core then increases considerably in salt content when subjected to mixing in the Caroline Basins. Hydrographic and moored current observations as well as model results show a distinct annual signal in salinity and velocity in the AAIW core off New Guinea. It appears to be related to the monsoonal change that is typically found in the near-surface waters in the region. Lagrangian data are used to investigate the structure of the deep New Guinea Coastal Undercurrent, the related cross-equatorial flow and eddy-structure, and the embedment in the zonal equatorial current system. Results from 17 neutrally buoyant RAFOS floats, ballasted to drift in the AAIW core layer, are compared with a numerical tracking experiment. In the model 73 particles are released at five-day intervals from Station J (2.5°N, 142°E), simulating currents at a moored time series station north of New Guinea. Observed and model track patterns are fairly consistent in space and season. Floats cross the equator preferably north of Cenderawasih Bay, with a maximum range in eddy-motion in this region north of New Guinea. The northward route at 135°E is also reflected in a low-salinity tongue reaching up to 3°N. At that longitude the floats seem to ignore the zonally aligned equatorial undercurrents. Farther to the east (139–145°E), however, the float observations are consistent with low-latitude bands of intermediate currents.