Regime Shifts in the North Pacific Simulated by a COADS-driven Isopycnal Model

• Published in: Advances in atmospheric sciences Vol. 20; no. 5; pp. 743 - 754
• Main Author: 王佳 吴立新 刘征宇 王东晓
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Nature B.V 01.09.2003; Guangzhou Institute of Tropical Ocean and Meteorology, CMA, Guangzhou 510080%International Arctic Research Center, University of Alaska Fairbanks, Alaska 99775-7340, USA%Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, Wisconsin 53706-1695, USA; LED, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301
• Subjects: Atmospheric data; Atmospheric models; Boundary conditions; Climate models; Computer applications; Enthalpy; Fluxes; Fresh water; Freshwater; Heat content; Inland water environment; Interdecadal variability; Mathematical analysis; Meteorology; Momentum flux; Momentum transfer; Numerical experiments; Ocean models; Ocean-atmosphere interaction; Oceans; Physics; Planetary waves; Potential vorticity; Salinity; Sea surface; Simulation; Subduction; Surface salinity; Thermocline; Variability; Ventilation; Vorticity; Wave propagation; 北太平洋; 海洋气象学; 状态变化; 等密度模型; 通风变温层; Pacific Ocean; IN, North Pacific; isopycnal model; regime shift; ventilated thermocline; North Pacific
• ISSN: 0256-1530; 1861-9533
• DOI: 10.1007/bf02915399

The Miami Isopycnal Coordinate Ocean Model (MICOM) is adopted to simulate the interdecadal variability in the Pacific Ocean with most emphasis on regime shifts in the North Pacific. The compu-tational domain covers 60°N to 40°S with an enclosed boundary condition for momentum flux, whereas there are thermohaline fluxes across the southern end as a restoring term. In addition, sea surface salinity of the model relaxes to the climatological season cycle, which results in climatological fresh water fluxes.Surface forcing functions from January 1945 through December 1993 are derived from the Comprehensive Ocean and Atmospheric Data Set (COADS). Such a numerical experiment reproduces the observed evo-lution of the interdecadal variability in the heat content over the upper 400-m layer by a two-year lag.Subduction that occurs at the ventilated thermocline in the central North Pacific is also been simulated and the subducted signals propagate from 35°N to 25°N, taking about 8 to 10 years, in agreement with the eXpendable Bathy Thermograph observation over recent decades. Interdecadal signals take a southwest-ward and downward path rather than westward propagation, meaning they are less associated with the baroclinic planetary waves. During travel, the signals appear to conserve potential vorticity. Therefore,the ventilated thermocline and related subduction are probably the fundamental physics for interdecadal variability in the mid-latitude subtropics of the North Pacific.