Relationship between the Northern Pacific Gyre Oscillation and tree-ring cellulose oxygen isotopes in northeastern Japan

Abstract

The North Pacific Gyre Oscillation (NPGO) significantly imprints on hydrological fluctuations of the East Asian summer monsoon (EASM) region, but this has not yet been observed in proxy-based hydroclimate reconstructions. This study reports a tree-ring cellulose oxygen isotope (δ 18 O) record from northeastern Japan spanning A.D. 1927-2010, overlapping with instrumental data, which we analyzed to determine if tree-ring δ 18 O in northeastern Japan records a signal consistent with the NPGO. Our results indicate that the tree-ring δ 18 O has a significant negative correlation with May-June (MJ) precipitation, as well as with short-term MJ relative humidity variation. Time-lagged temporal-domain comparisons indicate that the tree-ring δ 18 O is significantly correlated with the following year March-April (MA) and MJ NPGO index before the North Pacific climate transition in the late 1980s, particularly on decadal timescales. These relationships between our tree-ring δ 18 O and the climate patterns in the North Pacific are consistent with the actual early-summer precipitation. Spatial spring and early-summer sea-surface temperature anomalies exhibit a NPGO-like pattern in the following year. Spatial early-summer sea-level pressure anomalies also indicate North Pacific Oscillation (NPO) like patterns in the western North Pacific. These results suggest a lagged response of the NPGO to the EASM climate changes, and tree-ring δ 18 O in northeast Japan has a potential linkage with NPGO index from winter to early summer of the following year.

Assessment of Northeastern Japan Tree‐Ring Oxygen Isotopes for Reconstructing Early Summer Hydroclimate and Spring Arctic Oscillation

“…Significant correlations were found between tree-ring cellulose δ 18 O and early summer relative humidity at the Akita meteorological station (Figure 3c), but there were no significant correlations between our record to either temperature and precipitation at a 99% significance level (Figures 3a and 3b). We also directly compared tree-ring cellulose δ 18 O to MJJ Akita relative humidity to confirm similar variability (Figure 4), confirming that our tree-ring cellulose δ 18 O primarily reflects early summer relative humidity, which is consistent with previous work in central Japan (Li et al, 2015;Sakashita et al, 2016;Yamaguchi et al, 2010) and northeastern Japan (Sakashita, Miyahara, Yokoyama, Aze, Obrochta et al, 2017). Similar results were also found in the comparisons between our record and meteorological data in Fukaura, Aomori prefecture ( Figure S1), with the highest correlation coefficient occurring in June-July relative humidity (r = À0.43, p < 0.01, N = 54).…”

“…Window width is based on that used to explore interdecadal changes in the spring AO-EASM relationship using observational data (Chen et al, 2015). Similar results are obtained for the Miyagi tree-ring δ 18 O (Sakashita, Miyahara, Yokoyama, Aze, Obrochta et al, 2017) and April AO index during A.D. 1950-2010 ( Figure 6). Similar results are obtained for the Miyagi tree-ring δ 18 O (Sakashita, Miyahara, Yokoyama, Aze, Obrochta et al, 2017) and April AO index during A.D. 1950-2010 ( Figure 6).…”

“…Cellulose oxygen isotope ratios are theoretically controlled by relative humidity and the source water δ 18 O (McCarroll & Loader, 2004;Roden et al, 2000;Sternberg, 2009), and significant correlations are found in comparisons with early summer relative humidity in the Japanese region (e.g., Sakashita, Miyahara, Yokoyama, Aze, Yamaguchi et al, 2010). Tree-ring δ 18 O can extend the relatively short observational record of hydroclimate in northeastern Japan (e.g., Sakashita, Miyahara, Yokoyama, Aze, Obrochta et al, 2017), which exists in the northern limit of the EASM in the current climate. Tree-ring δ 18 O can extend the relatively short observational record of hydroclimate in northeastern Japan (e.g., Sakashita, Miyahara, Yokoyama, Aze, Obrochta et al, 2017), which exists in the northern limit of the EASM in the current climate.…”

“…However, annual hydroclimate reconstructions using tree-ring width are sparse in the East Asia (e.g., Cook et al, 2010). Hydroclimate reconstructions have already been successfully performed using tree-ring cellulose oxygen isotopes (δ 18 O) in Japan (Li et al, 2015;Nakatsuka et al, 2004;Sakashita et al, 2016;Sakashita, Miyahara, Yokoyama, Aze, Obrochta, et al, 2017;Tsuji et al, 2006Tsuji et al, , 2008Yamaguchi et al, 2010). Hydroclimate reconstructions have already been successfully performed using tree-ring cellulose oxygen isotopes (δ 18 O) in Japan (Li et al, 2015;Nakatsuka et al, 2004;Sakashita et al, 2016;Sakashita, Miyahara, Yokoyama, Aze, Obrochta, et al, 2017;Tsuji et al, 2006Tsuji et al, , 2008Yamaguchi et al, 2010).…”

“…1950(Sakashita, Miyahara, Yokoyama, Aze, Obrochta et al, 2017; Table 1). 1950(Sakashita, Miyahara, Yokoyama, Aze, Obrochta et al, 2017; Table 1).…”