Interannual to Interdecadal Variability in the Japan Sea Based on a New Gridded Upper Water Temperature Dataset

Abstract

A new gridded water temperature dataset of upper 400-m depths (0, 50, 100, 200, 300, and 400 m) for the Japan Sea (or East Sea) is produced by using an optimal interpolation technique from 1930 to 1996, based on oceanographic observations collected in the World Ocean Database 1998. The temperature data are analyzed by a complex empirical orthogonal function (CEOF) with six levels combined using the data for a period from 1957 to 1996, during which most of gridded data are available. Before calculating the CEOFs, low-pass or highpass filters (cutoff period at 7 yr) are applied to separate interannual and decadal temperature changes, respectively. One interannual and two decadal CEOF modes are identified. The interannual first CEOF mode is characterized by the energetic variability around and south of the subpolar front in the western Japan Sea, accompanied by northward and northeastward phase propagations emanating from the Tsushima Strait. The decadal first CEOF mode exhibits a broad structure prevailing over the whole Japan Sea, but large amplitudes are trapped by the subpolar front, with 60Њ-90Њ phase lags between the northeastern and southwestern Japan Sea. The decadal second CEOF mode has a localized structure with strong correlations in the Yamato Basin. The relation between the atmosphere and ocean is analyzed by a correlation analysis of wintertime sea level pressures (SLPs) onto the temporal coefficients of the CEOF modes. The interannual first CEOF mode is accompanied by the SLP anomalies over the western North Pacific Ocean with steep SLP gradients over the Japan Sea, suggesting that this mode is forced by local wind anomalies associated with the SLP changes over the western North Pacific. The decadal first CEOF mode is likely to be caused by changes of the east Asian winter monsoon due to the SLP variability of the northern part of the Siberian high, which is closely associated with the decadal fluctuations of the Arctic Oscillation and the North Atlantic Oscillation. The second decadal CEOF mode is accompanied by high SLP correlations over the central North Pacific associated with strength changes of Aleutian lows, suggestive of remote forcing from the central North Pacific.

Interannual SST variability in the Japan/East Sea and relationship with environmental variables

“…Shortening of the temporal variability in the 1990s has also been discussed in earlier studies (Chu et al, 1998;Hirose and Ostrovskii, 2000;Morimoto and Yanagi, 2001;Minobe et al, 2004). This phenomenon seems to coincide with 1998/1999 changes over the North Pacific (Minobe, 2002).…”

“…This near-7-year periodicity seems to be consonant with earlier results, such as a period of 5~7 years in the dominant spectral energy density of JES SSTA during the period 1951~1996 (Park and Oh, 2000), and a period of 7 years in CEOF-1 of the northwestern Pacific SSTA (1945~1989) including JES (Trousenkov et al, 2001), regardless of their slightly-different temporal and spatial coverage. On the other hand, this near-7-year periodicity is not found in Minobe et al (2004) due to a cut-off period of 7 years. The 2~3-year event (1993~1995) includes record-breaking cold and hot summers in 1993 and 1994, respectively , the amplitude of which cannot be negligible.…”

“…Earlier studies have shown the connection of JES SSTA variability (sometimes northwestern Pacific SSTA including JES) to the northwestern Pacific sea level pressure (especially Aleutian Low), ENSO event, East Asian jet stream, East Asian monsoon, Siberian High, and Arctic Oscillation (Ponomarev et al, 1999;Lau et al, 2000;Park and Oh, 2000;Hong et al, 2001;Trousenkov et al, 2001;Minobe et al, 2004). These phenomena are interrelated (Wang et al, 2000;Gong et al, 2001;Wu and Wang, 2002;Lin et al, 2002;Gong and Ho, 2003).…”

“…The eastward propagating speed of this warm anomaly core near EKB is estimated as 0.02~0.03 m/s in time-distance plot (not shown). Minobe et al (2004) described a weak northward and northeastward propagation from the Korea/ Tsushima Strait to 135°E and 40°N on a timescale of interannual variability. According to a rough approximation on the basis of phase difference and the period of interannual variability, its propagation is compatible with the present result.…”

“…The connection with the El Niño/ Southern Oscillation (ENSO) event was further discussed by Park and Oh (2000) and Hong et al (2001). Minobe et al (2004) identified interannual to interdecadal thermal variability of the JES upper layer (surface to 400 m deep) by analyzing a three-dimensional 0.5° × 0.5° gridded tem-…”