Decadal and Long‐Term Variability of Sea Level in the Southwestern Pacific During 1948–2018. Issue 11 (7th June 2022)

• Record Type: Journal Article
• Authors: Sun, Jingxuan; Zhang, Linlin; Hu, Dunxin
• Is Part Of: Geophysical research letters. Volume 49:Issue 11(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-06-07
• Subjects: sea level -- Southwestern Pacific -- long‐term and decadal variability -- SAM -- IPO; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL098747
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Decadal and long‐term variability of sea level in the Southwestern Pacific (SWP) was investigated by using tide gauge measurements obtained near New Zealand during 1948–2018 and a 1.5‐layer reduced gravity model. After the removal of the global mean sea level, there still exists a prominent positive trend and strong decadal oscillations in SWP sea level, which are attributed to the Southern Annular Mode (SAM) and Interdecadal Pacific Oscillation (IPO), respectively. On the long‐term time scale, the intensification of local wind stress curl associated with strengthening SAM contributes to SWP sea level rise (SLR) through Ekman convergence. On the decadal scale, locally generated and westward propagating signals induced by IPO exert comparable influences on sea level variations in the SWP. Results from multivariable linear regression suggest that SAM can account for almost all the long‐term SLR, and IPO explains approximately 58% of the decadal variability. Plain Language Summary: Satellite altimeter observations show a prominent acceleration in sea level rise (SLR) in the western Pacific during 1993–2018, which has crucial implications for the economic development of and livelihoods in coastal countries. Regional sea level variations associated with basin‐scale climate modes differ significantly from the global average on both temporal and spatial scales. By removing the global average from the data, extensive studies have shown that the above apparent SLR in the western tropical Pacific during the altimetry era is essentially a decadal signal, which is generally considered to be generated by direct wind stress forcing in connection with Interdecadal Pacific Oscillation (IPO). Based on long‐term tide gauge records from near New Zealand, this work highlights the influence of different climate modes on the low‐frequency variability of sea level in the Southwestern Pacific (SWP) and their differences from the tropics in terms of characteristics and mechanisms. After the removal of the global mean sea level, there still exists a positive trend in sea level accompanied by pronounced decadal oscillations, which is associated with Southern Annular Mode and IPO, respectively. Physically, anomalous wind stress curl related to climate modes modulates sea level variability in the SWP via both local Ekman pumping and remote baroclinic Rossby waves. Key Points: Sea level data from 70‐year‐long tide gauge records near New Zealand show positive trend and pronounced decadal oscillations WSC anomalies associated with Southern Annular Mode and Interdecadal Pacific Oscillation modulate long‐term and decadal sea levels in the Southwestern Pacific Long‐term sea level trend is driven by local wind forcing, and decadal oscillations are dominated by both local and remote factors