북태평양 혼합층깊이 변동과 그 변동이 클로로필 농도에 미치는 영향

Abstract

This study investigates variability of mixed layer depth (MLD) and its relation with chlorophyll (CHL) in the North Pacific Ocean (NP) on seasonal to year-to-year timescales. The Pacific MLD field was calculated from SODA (Simple Ocean Data Assimilation; version 2.1.6) covering 51 years from January 1958 to December 2008. The CHL data, which cover the period of 1998-2008, were taken from SeaWiFS (Sea-viewing Wide Field-of-view Sensor). The North Pacific MLD changes appear to be associated with ENSO and global warming. The NP MLD at mid-latitudes increases during La Niña years, while it decreases during El Niño years, with about a two month lag. The annual cycle in CHL in the NP shows a 3-4 year fluctuation, possibly through ENSO modulation of the NP MLD, but it cannot be confirmed because of the short data period. On the other hand, MLD in the Kuroshio Extension regions shoals continuously for the time period (1958-2008) in this study, suggesting global warming effects. In some regions, CHL was relatively low in 1998-2004, and high in 2005-2008 periods (reverse in other areas), indicating possible contribution of the Pacific Decadal Oscillation to NP CHL changes.