Temporal variability of winter mixed layer in the mid-to high-latitude North Pacific

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• 作者：Eitarou Oka ; Lynne D. Talley and Toshio Suga
• 关键词：Winter mixed layer ; North Pacific ; temporal variability ; Argo
• 刊名：Journal of Oceanography
• 出版年：2007
• 出版时间：April, 2007
• 年：2007
• 卷：63
• 期：2
• 页码：293-307
• 全文大小：1,280 KB
• 刊物类别：Earth and Environmental Science
• 刊物主题：Earth sciences
  Oceanography
  Hydrobiology
  
• 出版者：Springer Netherlands
• ISSN：1573-868X

文摘

Temperature and salinity data from 2001 through 2005 from Argo profiling floats have been analyzed to examine the time evolution of the mixed layer depth (MLD) and density in the late fall to early spring in mid to high latitudes of the North Pacific. To examine MLD variations on various time scales from several days to seasonal, relatively small criteria (0.03 kg m?3 in density and 0.2°C in temperature) are used to determine MLD. Our analysis emphasizes that maximum MLD in some regions occurs much earlier than expected. We also observe systematic differences in timing between maximum mixed layer depth and density. Specifically, in the formation regions of the Subtropical and Central Mode Waters and in the Bering Sea, where the winter mixed layer is deep, MLD reaches its maximum in late winter (February and March), as expected. In the eastern subarctic North Pacific, however, the shallow, strong, permanent halocline prevents the mixed layer from deepening after early January, resulting in a range of timings of maximum MLD between January and April. In the southern subtropics from 20° to 30°N, where the winter mixed layer is relatively shallow, MLD reaches a maximum even earlier in December–January. In each region, MLD fluctuates on short time scales as it increases from late fall through early winter. Corresponding to this short-term variation, maximum MLD almost always occurs 0 to 100 days earlier than maximum mixed layer density in all regions.