Abstract
Abstract. Strong regional sea-level trends, mainly related to basin-wide wind stress anomalies, have been observed in the western tropical Pacific over the last 3 decades. Analyses of regional sea level in the densely populated regions of the neighbouring Australasian Mediterranean Sea (AMS; also called tropical Asian seas) are hindered by its complex topography and respective studies are sparse. We used a series of global eddy-permitting ocean models, including a high-resolution configuration that resolves the AMS with 120∘ horizontal resolution, forced by a comprehensive atmospheric forcing product over 1958–2016 to characterize the patterns and magnitude of decadal sea-level variability in the AMS. The nature of this variability is elucidated further by sensitivity experiments with interannual variability restricted to either the momentum or buoyancy fluxes, building on an experiment employing a repeated-year forcing without interannual variability in all forcing components. Our results suggest that decadal fluctuations of the El Niño–Southern Oscillation (ENSO) account for over 80 % of the variability in all deep basins of the region, except for the central South China Sea (SCS). Changes related to the Pacific Decadal Oscillation (PDO) are most pronounced in the shallow Arafura and Timor seas and in the central SCS. On average, buoyancy fluxes account for less than 10 % of decadal SSH variability, but this ratio is highly variable over time and can reach values of up to 50 %. In particular, our results suggest that buoyancy flux forcing amplifies the dominant wind-stress-driven anomalies related to ENSO cycles. Intrinsic variability is mostly negligible except in the SCS, where it accounts for 25 % of the total decadal SSH variability.
Highlights
Between the early 1990s and mid-2010s sea-level trends of up to 10 mm yr−1, which exceeds 3 times the global mean rate, were observed in the western tropical Pacific and found to be related to an intensification of the Pacific trade wind regime (Timmermann et al, 2010; Merrifield, 2011; Merrifield and Maltrud, 2011; McGregor et al, 2012; Merrifield et al, 2012; Moon and Song, 2013; Moon et al, 2013; Qiu and Chen, 2012)
Both hindcast simulations slightly underestimate the amplitude of standard deviation (SD), in particular in the western tropical Pacific, by 1 to 2 cm (REF025 and REF005, respectively) but reproduce the spatial pattern well (Fig. 2b, c)
We determine the characteristics of decadal sea-level variability in the Australasian Mediterranean Sea and their relation to large-scale climate modes of El Niño–Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) by using a series of global ocean model experiments
Summary
Between the early 1990s and mid-2010s sea-level trends of up to 10 mm yr−1, which exceeds 3 times the global mean rate, were observed in the western tropical Pacific and found to be related to an intensification of the Pacific trade wind regime (Timmermann et al, 2010; Merrifield, 2011; Merrifield and Maltrud, 2011; McGregor et al, 2012; Merrifield et al, 2012; Moon and Song, 2013; Moon et al, 2013; Qiu and Chen, 2012) This strong sea-level rise had severe consequences for the population of the low-lying islands in the region (Becker et al, 2012), whose inhabitants are regularly referred to as the first climate refugees.
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