A Discussion on the Benefits of the Inclusion of a RAFOS Float Project in the Proposed TRIANGLE Project
Olaf Boebel (Dept. of Oceanography, University of Cape Town, 7700 Rondebosch, South Africa)
e-mail: oboebel@physci.uct.ac.za
ABSTRACT
The Kuroshio Current of the North Pacific forrns a major component in the Pacific climate system, providing the connection of the tropical with the subtropical regions. East of the Izu-Ogasawara Trench, the Kuroshio Current Extension forms the boundary between the warm subtropical and the cold subarctic gyres. To investigate the interaction of Kuroshio Extension meanders with the gyre interiors, including cross frontal property transfers, a suite of projects have recently been proposed, forming the mid-latitude component of the ocean scale Triangle program.
Here the enhancement of these studies by a Lagrangian component is discussed. Weekly float deployments of neutrally buoyant RAFOS floats into the Kuroshio core near the Izu-Ogasawara Trench and into the surrounding waters at intermediate depths are proposed. Possible benefits of such an effort would be the direct observation of the trace of the Kuroshio Extension, including, meander propagation, ring formation and possible cross-frontal exchange processes. This component would be mutually beneficial with the other components of the Triangle Projects, in particular with regard to the proposed acoustic topography experiment, inverted echo sounder measurements and the planned moored CTD and current meter array in the Kuroshio Extension.
INTRODUCTION
The horizontal location of the Kuroshio Current has significant impact on the climate of Japan and its surrounding seas. These conditions, in turn, influence two processes crucial to the formation of North Pacific Intermediate Water (NPIW). Firstly, NP-DICE may influence the formation of low salinity water formation in the Okhotsk Sea. Subtle changes in the ventilation and verticai mixing processes necessary to form this NPIW predecessor [Talley, 1993; Yasuda, 1997], could lead to dramatically changed formation rates of this water type. Secondly, the location of the Kuroshio Extension, which obviously depends on the location of the Kuroshio when it departs from Honshu, significantly influences the process of cross-gyre exchanges that finally generates the salinity minimum layer characteristic for the NPIW [Yasuda et al., 1996]. In turn, the NPIW formation rate naight directly feed back into the global climate system, since the formation of this water mass deprives the atmosphere of CO2 [Yasuda et al., 1996], and hence exerts considerable influence on the further progression of global warming.
