物理海洋学名词-E 123

Glossary of Physical Oceanography and Related Disciplines

Steven K. Baum Department of Oceanography Texas A&M University

May 26, 2004

 

EAC  Abbreviation for East Australian Current.
EAC  Abbreviation for East Arabian Current.
EAE  Abbreviation for Eastern Atlantic Experiment.
EASAP  Abbreviation for East Asian Seas Action Program.
East Africa Coast Current See Somali Current.
East Arabian Current A strong northeastward flowing current along the Saudi Arabian coast. It is part of the monsoonal circulation in the area and as such exists from about April through October, being fully established by mid-May with velocities ranging form 0.5-0.8 m/s. It is also part of a strong coastal upwelling system during those months when it flows strongest.East Arabian Sea Water See Bay of Bengal Water.East Auckland Current The continuation of the East Australian Current east of New Zealand. It forms and is part of an anticyclonic eddy near 37◦ S off of East Cape. This eddy is found in the same location throughout the years and as such is thought to be topographically controlled. The further extension of this current has a bimodal nature that changes seasonally. During the summer most of its transport continues along the New Zealand coast all the way to Chatham Rise as the East Cape Current. In the winter part of it separates from the shelf and continues as a zonal flow into the open ocean, forming a temperature front near 29◦ S that is distinguishable from another shallow front near 25◦ S called the Tropical Front, the northern limit of eastward flow in the subtropical gyre. See Tomczak and Godfrey [1994].
East Australian Current The western boundary current of the southern hemisphere in the Pacific Ocean. It is the weakest of the world’s boundary currents, carrying about 15 Sv in the annual mean near 30◦ N, yet is also associated with strong current instabilities. The relative weakness is due mostly to the flow through the Australasian Mediterranean Sea and the instabilities probably result from the current following the coast and then suddenly separating somewhere near 34◦ S to follow the east coast of New Zealand (where it is known as the East Auckland Current). It is stronger and reaches further inshore during the summer, with flow speeds reaching 1 m/s during the summer, and the maximum
transport has been estimated at around 30 Sv (although the intermittent nature of the current makes such estimates somewhat suspect). The path it follows from Australia to New Zealand is called the Tasman Front, which separates the warmer waters of the Coral Sea from the colder waters of the Tasman Sea. This front develops meanders which travel westward, impinge upon the Australian coast, and ultimately separate from the current and form eddies.

About 3 eddies are spawned per year (with 4-8 existing at any one time in recognizable form) with most being anticyclonic or warm core eddies since the meander closest to the coast always extends to the south. The meandering and eddy-shedding behavior of the current combined with its weak flow sometimes make it difficult to even distinguish it as a current, and the location of the Tasman Front can be meaningfully defined only in statistical terms.
The pronounced seasonal cycle is described by Ridgway and Godfrey [1997]:
    Maps of the annual-frequency component of the surface and depth-integrated steric heights ( h and P) show the development and progression of the EAC flow regime through
a complete seasonal cycle. The EAC has a strong seasonal cycle from 25S to 45S, with strongest southward flow in austral summer. The seasonal cycle in surface flow over the continental shelf is documented by two independent methods, geostrophically, using cross shelf sea level gradients derived from coastal tide gauge data and steric heights at the continentalshelf edge, and directly from merchant ship observations. The two estimates are in good agreement. The seasonal cycle in the EAC is more pronounced than in other mid-latitude western boundary currents for which data are available. At 28S, the strength of the total Tasman Sea transport (southward flow) varies between a minimum transport of 7 Sv in winter (July) to a maximum of 16 Sv in summer. The semiannual frequency components of h and P is important near 30S near the EAC outflow, but not elsewhere. The seasonal cycle of the EAC is not due to strong seasonal variations in Tasman Sea wind stress curl east of the region of interest. Seasonally reversing zonal flows occur offshore north of 25S, which are apparently locally forced by reversing wind stress curls; but if these flows were fed from the south by the EAC current system, the EAC would have to be weaker in summer, not stronger. The Leeuwin Current Extension along Australia’s west and south coasts may pass up the east coast of Australia, providing an important contribution to the enhanced southward flow of the EAC in summer. The vigorous anticyclonic eddies of the EAC also show a marked seasonal cycle and this is probably an important part of the mechanism for the strong seasonal cycle of the EAC south of 25S. The location of the strongest anticyclonic eddy in the EAC moves steadily southward throughout the summer season, and the phase of the coastal EAC appears also to move southward contrary to the expectations of linear theory, and to the hypothesis that the Leeuwin Current Extension is the major cause of the seasonal cycle.
See Ridgway and Godfrey [1997] and Tomczak and Godfrey [1994]
 

QY@108,20170718

共收到 0 | 阅读次数 16
发表评论
请先登录再发表评论