Large Scale Modes of Ocean Surface Temperature Since the Late Nineteenth Century

Abstract

There is increasing evidence of coherent patterns of variability on near quasi-bidecadal time scales in a range of climatic data from many parts of the world. Folland et al. (1984) found peaks at periods of 16 and 21 years respectively in spectra of globally- averaged sea surface temperature (SST) and night marine air temperature (NMAT) for 1856–1981. Newell et al. (1989) found variations near a period of 21 years in global and Southern Hemisphere NMAT for 1856–1986, and to a lesser extent in Northern Hemisphere NMAT and global and hemispheric SST. Ghil and Vautard (1991) drew attention to variations on approximately 20-year time-scales in globally-averaged anomalies of combined land surface air temperature and SST for 1854–1988, though Allen and Smith (1996) question the statistical significance of their results. Mann and Park (1994) found a 15–18 year mode in fields of mainly land surface air temperature anomalies for 1891–1990. They suggested that this mode, which had a pattern similar to that of the thermal signature of the interannual El Niño-Southern Oscillation (ENSO), may be a manifestation of long timescale modulation of ENSO as well as being the reason for Ghil and Vautard’s (1991) global-average result. Latif and Barnett (1996) discussed near bidecadal variations in SST and atmospheric circulation over the North Pacific in both observations and a coupled model, and the consequential variations of temperature and precipitation over North America. In the Southern Hemisphere, Venegas et al. (1996) found a coupled mode in South Atlantic SST and mean sea level pressure (MSLP) data for 1953–1992, with significant variations on near 15-year timescales and provided evidence that the atmosphere was forcing the ocean.