Lake Gyres and Seiches
Ann Arbor, MI — Gyres and seiches are two prominent features of lakes. In addition to existing in large lakes, gyres and seiches are also found in estuaries and harbors. Gyres are circular, rotational circulation patterns. Seiches are standing waves of water level in lakes. Gyres transport sediments, nutrients, and algae largely in a horizontal direction. Seiches, on the other hand, can contribute to the vertical mixing in lakes. Vertical mixing is important for nutrient supply from the lake bottom to the lake surface, where sunlight is available for algal growth. The exchange of bottom waters with the surface water generally enhances biological productivity of the lake. Meteorological events can generate both gyres and seiches.
Researchers used theoretical analysis, statistical methods, and numerical models to investigate gyres and seiches in Lake Okeechobee, the largest subtropical/tropical lake in North America. The lake has a 1,730-km2 surface water area, a typical length of more than 50 km, and a mean depth of 3.2 m.
"The circulation in Lake Okeechobee is typically dominated by a two-gyre pattern, especially in the winter. The northwest wind or southeast wind leads to a cyclone (a counterclockwise rotation gyre) in the southwest and an anticyclone (a clockwise rotation gyre) in the northeast," says Zhen-Gang Ji, a scientist at the Minerals Management Service. "Lake Okeechobee has a seiche signal of 5 hours or so. The seiche range is typically around 10 cm."
The findings in this study should be useful to understand the lake processes, to guide field data collection programs, and to assist decisionmaking on lake management.
Original Publication Information
Results of this study "Gyres and Seiches in a Large and Shallow Lake," are reported by Zhen-Gang Ji and Kang-Ren Jin in the latest issue (Volume 32, No. 4, pp. 764-775) of the Journal of Great Lakes Research, published by the International Association for Great Lakes Research, 2006.
Contacts
For more information about the study, contact Zhen-Gang Ji, MMS, MS 4041, 381 Elden Street, VA 20170; jeff.ji@mms.gov; (703) 787-1145.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; editor@iaglr.org; (608) 692-1076.
Links
Since 1967, IAGLR has served as the focal point for compiling and disseminating multidisciplinary knowledge on North America's Laurentian Great Lakes and other large lakes of the world and their watersheds. In part, IAGLR communicates this knowledge through publication of the Journal of Great Lakes Research, available to members in print and electronic form. A searchable archive of the journal is available online and includes the abstracts of articles from the journal's inception in 1975 through the most recent issue. In addition, complete articles are available to members who have signed up for an electronic subscription.