Paleoprecipitation record from coral Sr/Ca and δ18O during the mid Holocene in the northern South China Sea

Abstract

Coupled high-resolution Sr/Ca and δ18O records of a modern and a mid-Holocene coral from Sanya in the southern Hainan Island, northern South China Sea (SCS), were reported and the residual δ18O (Δδ18O) were calculated to indicate precipitation change in this region. Unlike other paleoclimate studies, this study focused on changes of precipitation time rather than precipitation amount. As negative Δδ18O peaks in coral generally correspond to peak precipitations or rainy seasons in the surrounding region, the time offsets between negative Δδ18O peaks and other seasonal indicators, such as sea surface temperature (SST), can well indicate the time of rainy seasons, and the precise time offsets can be estimated by the method of cross spectral analysis. The results of the modern coral indicate that the variation of the coral Δδ18O lags that of the instrumental measured precipitation by about 2 months, and about 3 months to the SST derived from coral Sr/Ca ratios. This agrees well with the modern observation that the salinity change in the southern coastal regions generally lags that of the precipitation in Hianan Island by about 2 months, and the precipitation change lags about 1 month behind the SST in this region. Thus, coral Δδ 18O records can be a reliable proxy for the change of rainy seasons in this region. The results of the mid-Holocene coral show about 2.5 months’ leading of the Δδ18O variation ahead of the SST. By compensating the approximate 3 months’ lag of the Δδ18O variation behind the SST in modern time, the occurrence of rainy seasons during the mid Holocene may have advanced about 5—6 months. In detail, it may start around December and end around April to May with maximum occurring around February. Therefore, rainy seasons mainly occur in winter through early spring during the mid Holocene, compared with that from May through October in modern times. Such precipitation patterns appear to agree with the mid-Holocene pollen records in this region. Variations of large-scale circulation may possibly result in such a different precipitation pattern. Further studies, in particular climate model studies collaborated with meteorologists, are required for a better understanding of the mechanism.

Variations in the Pacific Decadal Oscillation since 1853 in a coral record from the northern South China Sea

“…Coral skeletal δ 13 C and δ 18 O analyses were performed using a GV Isoprime II stable isotope ratio mass spectrometer (IRMS) coupled with a MultiPrep carbonate device that used 102% H 3 PO 4 at 90°C to extract CO 2 from the coral samples, following the procedures described by Deng et al . []; the IRMS was located at the State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China. Isotope data were normalized to the Vienna Pee Dee Belemnite (V‐PDB) using the NBS‐19 standard (δ 13 C = 1.95‰, δ 18 O = –2.20‰).…”

Evaluation of annual resolution coral geochemical records as climate proxies in the Great Barrier Reef of Australia

“…Coral Dd 18 O reflects changes in the d 18 O of the surrounding seawater, and so, can also provide information regarding rainfall amounts (McCulloch et al 1994;Shen et al 2005;Deng et al 2009). Therefore, the Dd 18 O series from 10AR2 records, the most characteristic variations in rainfall since 1943 as the correlation between Dd 18 O from 10AR2 and rainfall, is better than that between Dd 18 O from 10AR1 and rainfall (Fig.…”

“…0.2 mg) and following the procedures described by Deng et al (2009). Isotope data were normalized to the Vienna Pee Dee Belemnite (V-PDB) using the NBS-19 standard (d 13 C = 1.95 %, d 18 O = -2.20 %).…”

“…To acquire seasonal to monthly climatic information, most studies sample coral skeletons at very high-resolution intervals (ca. 1 mm or less; e.g., McCulloch et al 1994;Alibert and McCulloch 1997;Gagan et al 1998;McCulloch et al 1999;Sun et al 2004;Wei et al 2007;Deng et al 2009;Duprey et al 2012;DeLong et al 2013). However, high-resolution sampling requires a considerable number of subsamples for analysis, which makes coral-based climate reconstructions time consuming, labor intensive, and expensive.…”

Akurasi Rekonstruksi Suhu Permukaan Laut Dan 18o Air Laut (Salinitas) Untuk Interpretasi Iklim Masa Lampau Dari Karang Mati (Fosil)

“…Gambar 6 menunjukkan hasil kalibrasi antara Sr/Ca idea (Sr/Ca idea + noise) dengan SPL untuk karang dari Tahiti. Rekonstruksi  18 O air laut (selanjutnya disebut  18 Osw) dilakukan berdasarkan pasangan unsur geokimia dalam karang yaitu  18 O dan Sr/Ca telah banyak dilakukan pada penelitain terdahulu yaitu (Cahyarini et al,2008;Ren et al, 2002;Deng et al, 2009;Mitsuguchi et al, 2003;Gagan et al, 1998). Cahyarini et al (2008) (Schmidt, 1999;Schmidt et al, 2011;Aharon, 1991) (Cahyarini et al, 2008;Cahyarini et al, 2009 …”