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DECADAL/INTERDECADAL CLIMATE EVENTS

 

Indication of Decadal Variability in the Oceanic Frontal Zones: Preliminary Results

 

Alexander S. Kazmin (Frontier Research System for Global Change/Institute for Global Change Research, SEAVANS N 7F, 1-2-1 Shibaura, Minato-ku, Tokyo 105-6791,Japan)

e-mail: kazmin@frontier.esto.or.jp

 

ABSTRACT

 

Satellite sea surface temperature data for the period of 1982-97 have been used to obtain some evidences of decadal variability in the North Pacific subpolar and subtropical oceanic frontal zones. Changes in position, magnitude and structure of the frontal zones associated with the climatic shift in mid-latitude North Pacific from‘cool’(until late 1980s) to‘warm’(1990s) conditions, are documented.

 

INTRODUCTION

 

The large-scale oceanic frontal zones (OFZ) are prominent features that originate from and are maintained by the global distribution of surface momentum and heat flux forcing. The importance of variability in the OFZ for understanding the thermodynamic balance of the ocean and, accordingly, the climate-related problems has been the subject of several investigations since the mid-1970s. Reliable satellite measurements of sea surface temperature (SST) in the early 1980s provided a new basis for frontal investigations and a number of regional studies have been performed. However, while very informative, previous studies were local and did not utilize one of the main advantages of the satellite-derived data i.e., global coverage at fair spatio-temporal resolution. Still, those advantages make satellite data most suitable for frontal investigations. Global, weekly averaged SST products are now available for a period of more than 16 years and make it possible to investigate OFZ variability on timescales from seasonal to decadal. Seasonal and interannual variability in the main OFZ have been addressed recently using global satellite SST data (e.g., Kazmin and Rienecker 1996). However, while ocean-atmosphere system is known to fluctuate also with decadal timescale, the OFZ's own response to decadal variability (in terms of SST gradient magnitude and spatial structure) is still poorly investigated.

 

 

 

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