Corals Reveal an Unprecedented Decrease of Arabian Sea Upwelling During the Current Warming Era

Abstract

The thermal contrast between the Indian subcontinent and the Indian Ocean drives the Indian monsoon circulations (

A Simple Monte Carlo Approach to Estimate the Uncertainties of SST and δ18Osw Inferred From Coral Proxies

“…The stable oxygen isotopic composition of coral skeletons (δ 18 O c ) is also inversely correlated with water temperature, but in addition it is modulated by changes in the stable oxygen isotopic composition of ambient seawater (δ 18 O sw ; e.g., Juillet‐Leclerc & Schmidt, 2001; McCulloch et al., 1994; Morimoto et al., 2002; Shen et al., 2005; Weber & Woodhead, 1972). δ 18 O sw serves as a proxy for hydrological variations (e.g., ocean circulation, rainfall, and evaporation, Felis et al., 2018; Hennekam et al., 2018; Pfeiffer et al., 2019; Watanabe et al., 2019; Watanabe et al., 2021) and is calculated by removing the SST contribution from δ 18 O c . Paired measurements of a coral SST proxy (e.g., Sr/Ca) and δ 18 O c have been routinely used for δ 18 O sw determination (Hendy et al., 2002; McCulloch et al., 1994; Shen et al., 2005; Watanabe et al., 2001 ).…”

Giant clam (Tridacna) distribution in the Gulf of Oman in relation to past and future climate

“…This would not only further impair the population connectivity between coral reef habitats in the Gulf of Oman ecoregion and the Gulf of Aden and Red Sea ecoregions but could also amplify ocean acidification and its negative impacts on the mineralization and survival of calcifying marine organisms due to the low aragonite saturation state and pH of the upwelled high p CO 2 water 61 . In contrast, δ 18 O and Sr/Ca records of modern and fossil corals from the OUZ zone provide evidence that the Arabian Sea upwelling intensity was very stable over the last millennium and unprecedently declines during the current warming trend 43 . While a reduction of upwelling improves coral reef connectivity within the Somali-Arabian Seas biogeographic province, it lessens the positive cooling effect on the sea surface during summer heat.…”

“…( 2 ) for giant clams 41 to estimate palaeo-water temperature: where T is the seawater temperature in degree Celsius and Δδ 18 O is the difference between the stable isotopes ratio of the shell and of the seawater (δ 18 O shell 18 O seawater ) in VPDB. The combined measurement of Sr/Ca or Mg/Ca in biogenic calcite and aragonite and stable oxygen isotopes on the same material have been widely employed to calculate the δ 18 O palaeoseawater by subtracting the SST contribution inferred from Sr/Ca or Mg/Ca from δ 18 O 16 , 31 , 42 , 43 . However, there is no significant correlation between Sr/Ca and δ 18 O in both records (Supplementary Table S3 ), indicating that Sr/Ca ratio in the shell aragonite was not thermodynamically controlled.…”

Sub‐Annual to Interannual Arabian Sea Upwelling, Sea Surface Temperature, and Indian Monsoon Rainfall Reconstructed Using Congruent Micrometer‐Scale Climate Proxies

“…The anti-phase relationship and the inconsistent coherence can be attributed to the variable time lag of CCaT due to the signal propagation time through the system (<3-5 years; Schmidt et al [2020]). Indeed, the 3-year moving mean of CCaT anomalies, calculated from the 1948-1992 mean for consistency with the Webster-Yang monsoon index, captures the weakening of western Arabian Sea upwelling and southwest monsoon circulation over the latter half of the twentieth century (Figure 7d; Swapna et al, 2017;Watanabe et al, 2021). Further, shifting the 3-year moving mean of CCaT anomalies progressively earlier in time improves the similarity between the CCaT and the monsoon index, suggesting CCaT lags the southwest Indian summer monsoon winds by ∼1-4 years (Figure 7d), consistent with current advection time from the western to the eastern Arabian Sea (Schmidt et al, 2020).…”