Abstract
Falling between seasonal cycle variability and the impact of local drivers, the sea level in the Red Sea and Gulf of Aden has been given less consideration, especially with large-scale modes. With multiple decades of satellite altimetry observations combined with good spatial resolution, the time has come for diagnosis of the impact of large-scale modes on the sea level in those important semi-enclosed basins. While the annual cycle of sea level appeared as a dominant cycle using spectral analysis, the semi-annual one was also found, although much weaker. The first empirical orthogonal function mode explained, on average, about 65% of the total variance throughout the seasons, while their principal components clearly captured the strong La Niña event (1999–2001) in all seasons. The sea level showed a strong positive relation with positive phase El Niño Southern Oscillation in all seasons and a strong negative relation with East Atlantic/West Russia during winter and spring over the study period (1993–2017). We show that the unusually stronger easterly winds that are displaced north of the equator generate an upwelling area near the Sumatra coast and they drive both warm surface and deep-water masses toward the West Indian Ocean and Arabian Sea, rising sea level over the Red Sea and Gulf of Aden. This process could explain the increase of sea level in the basin during the positive phase of El Niño Southern Oscillation events.
Highlights
Oceanic and atmospheric teleconnection through large-scale modes is the most striking phenomenon that is associated with recent global warming
We evaluated the coErrOeFlaPtiCosn of the PCI1OtDime series oMf tEhIe sea level anomaly (SLA) wiEtAhWthRe climate modes indices (Table 2) to investigate wPCh1etwhienrtetrhe SLA0h.3a6s(0a.0r7e6m) ote 0r.e3s9p(o0n.0s5e6)or not.–P0.C401 is positively correlated with El Niño Southern Oscillation (ENSO) through the multivariate El Niño index (MEI) index during the spring, summer, and autumn seasons (0.66, 0.46, and 0.57, respectively) and nPeCg1atsipvreinlyg correlated with the win0te.6r6and sprin–g0.E47AWR index (–0.40 and – 0.46, respectively)
Using SLA data, we present a clear perspective on the impact of a large-scale mode on the Red Sea (RS) and GUAsi.nTghSeLtiAmdeastear,iewseofpPreCs1enotf aSLcAlearreflpeecrtssptehcetisvteroonngtLhae Nimiñpaa2c0t 0o0f–a20la0r1geev-secnatlethmrooudgehocnleathreSLRAS adnedcrGeaAsi.nTghdeutirminegsaelrliesesaosfoPnCs.1 of SLA reflects the strong La Niña 2000–2001 event through clear SLA decreTahseincgordruelraintigonalalnsaelayssoisnrse.veals that ENSO and East Atlantic/West Russia (EAWR) are the major contributors to SLA variability
Summary
Oceanic and atmospheric teleconnection through large-scale modes is the most striking phenomenon that is associated with recent global warming. Felis et al (2000) [32] used 245 years data of coral oxygen isotopes from the Ras Umm Sidd Northern RS and investigated the signal of El Niño Southern Oscillation (ENSO), North Atlantic oscillation (NAO), and North Pacific teleconnection They speculate that these modes consistently contribute to climate variability, where the cold NAO period increases the aridity conditions in the Northern RS, while the warm period decreases it.
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