| 摘要: |
| 采用中国科学院大气物理研究所的高分辨率逐日风场驱动的全球海洋模式(LICOM1.0)对北太平洋海域的潜沉(Subduction)过程和副热带模态水形成区潜沉率的年际变化进行了数值模拟 ，并将模拟结果与同化的海洋模式资料(SODA)进行了比较。研究结果表明 ，该高分辨率的海洋模式对北太平洋的绝大部分海域晚冬混合层底水质点的运动方向和路径的数值模拟结果较好 ，模式模拟的副热带环流比SODA资料中的副热带环流流速强;模式模拟的混合层深度比SODA资料中的混合层深度深 ，更接近观测;模式中副热带海域的潜沉率大于SODA资料中的副热带海域的潜沉率。模式结果表明 ，副热带环流和副极地环流交界处是潜沉过程发生的最主要区 ，该区气候平均的潜沉率超过100m/a ，最大为150m/a ，海面风变异引起的海洋平流的年际和年代际变化 ，是该区潜沉率发生年际和年代际变化的主要原因;在太平洋副热带东部模态水形成区 ，气候平均的潜沉率超过50m/a ，在该区潜沉率的年际变化中 ，局地风应力旋度决定的Ekman抽吸要比海洋平流效应更加重要。 |
| 关键词: 北太平洋,潜沉率,海面风,年际变化,年代际变化 |
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| 基金项目:国家自然科学基金重点资助项目,40333030号和40276009号 |
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| THE ROLE OF SEA SURFACE WIND IN “SUBDUCTION” RATE VARIATION IN NORTH PACIFIC |
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LIU Qin-Yu1, HU Hai-Bo1, LIU Hai-Long2, LIU Wei1
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1.Physical Oceanography Laboratory & Ocean-Atmosphere Interaction and Climate,Ocean University of China, Qingdao, 266003;2.State Key LASG, Institute of Physical Oceanography, Beijing, 100029
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| Abstract: |
| In order to prove and estimate the effect of sea surface wind on “subduction” process in subtropical North Pacific, the annual “subduction” rate in the Subtropical Mode Water (STMW) formation regions in the North Pacific was calculated in high-resolution general circulation model(LICOM1.0) and the Simple Ocean Data Assimilation (SODA) data in 2005. According to “subduction” rate equation put forward by Qiu and Huang in 1995, the “subduction” rate is defined as the sum of lateral induction rate and vertical pumping rate; both have close relationship with sea surface wind. The LASG/IAP Climate System Ocean Model (LICOM1.0) is quasi-global (75°S–65°N) in horizontal resolution of uniform 0.5° by 0.5° grid, and this model is from State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics in China. With running 900-year spin-up from initial motionless ocean, LICOM1.0 is driven by ERA40 daily wind stresses and climatological heat flux forcing for 44 years, and the output during last 42 years (1959–2000) is analyzed.
Comparing to the SODA data, the output data from LICOM1.0 model is better for describing the trajectories of the water particles released at the base of the March mixed layer in the North Pacific. In LICOM1.0 output result, the mixed layer depth is deeper than that from SODA data, and the subtropical gyre is stronger. The “subduction” rate simulated with this model is slightly larger than that from SODA data and “subduction” rate have been calculated in two specific “subduction” areas. The first area is in the boundary between the subtropical and subpolar gyre (34.5°–45.5°N, 155.0°–175.0°E ). The mean of the “subduction” rate exceeds 100m/a to the maximum at 150m/a, and the ocean circulation caused by local sea surface wind controls the interannual and decadal variability of the “subduction” rate in this area. The positive anomaly of “subduction” rate appeared during 1970–1984, and negative anomaly took place during 1985–2000. The variation of “subduction” rate agrees quite well with the variation of lateral induction rate in this area. In the second area of 29.5°–40.5°N, 145°–130°W, which is the eastern subtropical mode water formation area, the mean of “subduction” rate exceeds 50m/a. Here, Ekman upwelling caused by local sea surface wind curl is more important in determining variability of local “subduction” rate on interannual and decadal scales than oceanic advection effect. A close relationship between the “subduction” rate and sea surface wind curl has been recognized in the area, with the coefficient at 0.476. So in the first area the local sea surface wind velocity play domination role while in the second area the sea surface wind curl controls the interannual and decadal variability of “subduction” respectively. |
| Key words: North Pacific, “Subduction” rate, Sea surface wind, Interannual variability, Decadal variability |
