전구대순환모형에서 모사한 북태평양 혼합층 깊이의 계절변동성

Abstract

Ocean mixed layer depth (MLD) is one of the most important factors in understanding the ocean's role in climate and climate change. Observations however are not enough both in spatial and temporal coverages to investigate thoroughly MLD physics. Ocean general circulation models (OGCMs) are then useful tools in compensating for lack of observation data, giving a more comprehensive picture. Here, using a global OGCM simulations, we present MLD variability over the North Pacific Ocean and impacts of vertical mixing schemes on it, based on several statistical measures such as annual mean difference (ME), root-mean-square difference (RMSD) and correlation coefficient(CC). The North Pacific Ocean was chosen mainly because it has relatively good data coverage so that model-data comparison would not affected much by data density. We have employed GFDL MOM1.1 of Bryan-Cox-Semtner ocean model with the horizontal resolution of 1° x 1°. The model has been started from the rest state with annual mean temperature and salinity distributions by Levitus (1982), forced by Hellerman and Rosenstein (1983) monthly-mean wind stress climatology, and integrated for about 30 years. Vertical mixing was calculated by three different schemes. The ME map between the model and a MLD climatology (NMLD) shows that the model able to simulate an annual mean MLD with an error of 20 m or less over most of the North Pacific Ocean, while the error is relatively large at high latitudes, in the Kuroshio region and central and eastern equatorial Pacific regions. The model reproduced well general patterns of MLD distributions in the climatology: deeper mixed layer around the Kuroshio region and the central equatorial Pacific region. But, all schemes show a systematic error pattern: overestimated MLD around the Kuroshio region and central and eastern equatorial Pacific regions and underestimated MLD between those regions. Correlation Coefficients is rather large around the Kuroshio region showing model su