Increased amplitude of the North Pacific Gyre Oscillation towards recent: Evidence from tree‐ring‐based reconstruction since 1596

Abstract

The North Pacific Gyre Oscillation (NPGO) is the second leading mode of the sea surface height (SSH) of the North Pacific Ocean, playing a key role in causing regional ecosystem changes and large-scale climate anomalies. However, its longterm evolution prior to the industrial era is largely unknown. This study provides a reconstruction of the NPGO from 1596 onwards from 19 NPGO-sensitive treering chronologies in the Himalayan Mountains, the Rocky Mountains, the Coastal Mountains and the Alaskan Mountain Range, which explained 57.1% of the observed NPGO variations. The selected tree-ring chronologies showed strong linkages with the NPGO but weak or no correlations with the Pacific Decadal Oscillation (PDO), another leading mode of the North Pacific Ocean. The reconstruction revealed that the NPGO variance and amplitude are not only the strongest towards recent in the instrumental period but also in the reconstruction period. The linkages between the NPGO and El Niño-Southern Oscillation (ENSO) became strengthened towards recent, which may be attributed to the increased occurrence of central Pacific ENSO during the anthropogenic warming period. In addition, close linkages were found between the NPGO and the multidecadal Pacific variability (MPV), the North Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation (AMO) at the interannual and multidecadal scales, indicative of strong teleconnections between the ocean-atmosphere modes of the Pacific and Atlantic.

The Northwestern Pacific corals unravel the NPGO/Victoria Mode-related temperature back to the 19th century

“…Additionally, several previous studies have suggested that the higher frequency of CPW climate variability due to anthropogenic warming may enhance NPGO variability and strengthen the linkage between them [50,51] . As shown in Fig.…”

“…There are some proxy-based NPGO reconstructions (tree-ring-based [51,55] and corals-based [26][27][28] ); however, the origins of the records are primarily centred in the central tropical Paci c and eastern Paci c. Our study is the rst longterm reconstruction of the NPGO/VM variability derived from the NWP reef-building coral skeleton archive, dating back to the 19th century. Sanchez et al [28] reported decadal NPGO variability from coral skeletal δ 18 O records from Clarion Island (in the eastern Paci c).…”

“…Clarion Island is located at the termination of the California Current System, which is characterised by cool (warm) and high (low) salinity water during positive (negative) NPGO [5,28] . Therefore, the complexity arising from multiple controlling factors possibly reduces the signal-to-noise ratio of the NPGO-related temperature and salinity signals in coral skeletal δ 18 O. Dong et al [51] reported the tree-ring-based NPGO reconstruction back to 1596. According to their report, the reconstruction represented negative NPGOs from the 1790s to 1810s, which cohered with the Dalton minimum (1790-1820).…”

“…Recent studies have shown a strong connection between CPW climate variability and NPGO, and this linkage has received great attention [49][50][51] . For the strong positive NPGO in the 2000s-2010s, it is reported that higher frequency in the CPW climate variability in recent decades may have strengthened the connections between NPGO and CPW [49] .…”

Decadal changes in rapid intensification of western North Pacific tropical cyclones modulated by the North Pacific Gyre Oscillation

“…This means that the NPGO can influence WNP RI activity on shorter timescales than the PDO. Third, the variance and amplitude of the NPGO have increased since 1950, and are generally comparable to the PDO (Litzow et al 2020, Dong et al 2022. The fraction of Pacific SST variability contributed by the NPGO has increased, with the NPGO surpassing the PDO as the dominant mode of North Pacific SST variability since the 1990 s (Bond et al 2003, Litzow et al 2020.…”