Intergyre communication in a three-layer model

• Main Author: Chen, Lianggui
• Language: unknown
• Published: Florida State University Libraries
• Subjects: Physical Oceanography; Environmental Sciences; Mathematics; Dewar; North Atlantic
• Online Access: http://digitool.fcla.edu:80/R/?func=dbin-jump-full&object_id=119116&LOCAL_BASE=GEN01-FSU01

A three layer, wind driven, general circulation model involving both subtropical and subpolar gyres has been developed to study intergyre exchange. Following Schopp and Arhan (1986), the present work allows flow to cross the intergyre boundary baroclinically in a model with three active layer. Solutions with deep southward baroclinic exchange are emphasized. The two principal objectives of this work are to clarify the structure and maintenance of the permanent thermocline and to aid in understanding the distribution of deep water masses. A class of thermocline structures at the zero Ekman pumping line has been constructed which permit intergyre exchange, or communication. These so-called 'windows', which are where the communication occurs at the intergyre boundary, have several unique properties relative to those computed by Schopp and Arhan, and have richer structure due to the additional baroclinic degree of freedom. This study has successfully generalized Schopp's model to three active layers and fully describes the regime of dynamically consistent, continuous solutions in the entire basin. Analytical solutions with deep southward flow, as well as northward flow with outcrop in the subpolar region, have been found. The study shows that the addition of an active third layer has introduced qualitatively new structure to the solution, namely a second baroclinic 'window' is opened. This new window is physically and dynamically distinct from the first window, and most of the intergyre baroclinic transport can occur through it. It also supports the conjecture that the number of communication windows increases with the number of active layers. In addition to the model results, observed tracer distributions have been reexamined within the context of this model. Possible explanations for the potential vorticity contours in the North Atlantic Ocean, which connect the northern and southern gyres (McDowell et al. (1982)), and for some of the observed subtropical water anomalies found in the Local Dynamic Experiment (Ebbesmeyer et al. (1986)), which appeared to have sources in the subpolar gyre, are proposed. Source: Dissertation Abstracts International, Volume: 52-08, Section: B, page: 4099. Major Professor: William K. Dewar. Thesis (Ph.D.)--The Florida State University, 1991. A three layer, wind driven, general circulation model involving both subtropical and subpolar gyres has been developed to study intergyre exchange. Following Schopp and Arhan (1986), the present work allows flow to cross the intergyre boundary baroclinically in a model with three active layer. Solutions with deep southward baroclinic exchange are emphasized. The two principal objectives of this work are to clarify the structure and maintenance of the permanent thermocline and to aid in understanding the distribution of deep water masses. A class of thermocline structures at the zero Ekman pumping line has been constructed which permit intergyre exchange, or communication. These so-called 'windows', which are where the communication occurs at the intergyre boundary, have several unique properties relative to those computed by Schopp and Arhan, and have richer structure due to the additional baroclinic degree of freedom. This study has successfully generalized Schopp's model to three active layers and fully describes the regime of dynamically consistent, continuous solutions in the entire basin. Analytical solutions with deep southward flow, as well as northward flow with outcrop in the subpolar region, have been found. The study shows that the addition of an active third layer has introduced qualitatively new structure to the solution, namely a second baroclinic 'window' is opened. This new window is physically and dynamically distinct from the first window, and most of the intergyre baroclinic transport can occur through it. It also supports the conjecture that the number of communication windows increases with the number of active layers. In addition to the model results, observed tracer distributions have been reexamined within the context of this model. Possible explanations for the potential vorticity contours in the North Atlantic Ocean, which connect the northern and southern gyres (McDowell et al. (1982)), and for some of the observed subtropical water anomalies found in the Local Dynamic Experiment (Ebbesmeyer et al. (1986)), which appeared to have sources in the subpolar gyre, are proposed.