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| Li, Chen; Jian, Zhimin; Jia, Guodong; Dang, Haowen; Wang, Jianxin. |
| Marine nitrogen fixation contributes to the budget of biologically available N, thus fuels phytoplankton productivity and carbon cycle through biological pump. Modern N‐fixation rates are proved to be constrained by oceanographic condition and nutrient supply to the surface waters. However, the paleoceanographic reconstruction of N‐fixation and its regulation mechanism remain highly uncertain in many regions. Here we present records of N‐fixation changes in the South China Sea (SCS) over the past 250,000 years reconstructed by compound‐specific nitrogen isotopes of individual amino acids. The δ15N of source amino acids (δ15NSrc), reflecting the δ15N of the substrate nitrate originating from the subsurface water, is distinctly lower during interglacial... |
| Tipo: Text |
Palavras-chave: Compound-specific delta N-15; Upper water structure; Bulk sedimentary delta N-15; Nitrogen fixation; Orbital time scale; South China Sea. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00509/62061/66237.pdf |
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| Jian, Zhimin; Wang, Yue; Dang, Haowen; Lea, David W.; Liu, Zhengyu; Jin, Haiyan; Yin, Yaqian. |
| The El Niño−Southern Oscillation (ENSO), which is tightly coupled to the equatorial thermocline in the Pacific, is the dominant source of interannual climate variability, but its long-term evolution in response to climate change remains highly uncertain. This study uses Mg/Ca in planktonic foraminiferal shells to reconstruct sea surface and thermocline water temperatures (SST and TWT) for the past 142 ky in a western equatorial Pacific (WEP) core MD01-2386. Unlike the dominant 100-ky glacial−interglacial cycle recorded by SST and δ18O, which echoes the pattern seen in other WEP sites, the upper ocean thermal gradient shows a clear half-precessional (9.4 ky or 12.7 ky) cycle as indicated by the reconstructed and simulated temperature (ΔT) and δ18O... |
| Tipo: Text |
Palavras-chave: Thermocline temperature; Half-precession; Western equatorial Pacific; Meridional gradient. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00614/72647/71649.pdf |
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| Wang, Tingting; Ravelo, Ana Christina; Ren, Haojia; Dang, Haowen; Jin, Haiyan; Liu, Jingjing; Jian, Zhimin. |
| We report the differences between δ15N of organic nitrogen bound in foraminifera tests (foraminifera‐bound δ15N, or FB‐δ15N), which is considered an effective recorder of thermocline nitrate δ15N in the oligotrophic areas, and bulk sedimentary δ15N (δ15Nbulk) of core MD12‐3433, located in the northern South China Sea (SCS), to explore possible causes of the offset between these two proxies in the SCS. The offset can be best explained by the influence of the terrigenous input on δ15Nbulk, as evidenced by its general correlation with sea level changes, C:N ratios, and inorganic nitrogen contribution to total nitrogen. Moreover, our new record is compared to six previously published δ15Nbulk records of the SCS based on their geographical proximity to the... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00441/55238/56719.pdf |
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| Dang, Haowen; Jian, Zhimin; Bassinot, Franck; Qiao, Peijun; Cheng, Xinrong. |
| The Holocene variability in sea surface and thermocline water temperatures (SST and TWT) in the Indo-Pacific Warm Pool (IPWP) has been reconstructed by planktonic foraminiferal Mg/Ca from sediments of the western tropical Philippine Sea. Afterward the Younger Dryas interval (YD), SST warmed gradually till similar to 10 ka and remained approximately constant afterwards, but TWT rose more rapidly to a peak between similar to 12 and similar to 10 ka and then declined by similar to 1.5 degrees C through the Holocene. The trend of TWT closely followed the boreal summer insolation and could be correlated to tropical climate changes represented by southward movement of the Inter-tropical Convergence Zone (ITCZ) and related changes in East Asian monsoons. |
| Tipo: Text |
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| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00266/37690/36815.pdf |
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| Fan, Weijia; Jian, Zhimin; Chu, Zhihui; Dang, Haowen; Wang, Yue; Bassinot, Franck; Han, Xiqiu; Bian, Yeping. |
| The hydrological characteristics, including temperatures and salinities, of the upper water over the last 30 ka from two sites connected by the Indonesian Throughflow (ITF) across the Makassar Strait are reconstructed and compared. The thermocline hydrological gradient in the strait was larger during 13.4~19 ka BP and 24.2~27 ka BP than that in the Holocene. The weakened ITF during those periods in the last glacial period, corresponding to the decreased trade wind stress under an El Niño-like climate mean state, likely accounts for the increased thermocline gradient. The thermocline water temperature variabilities of the two sites, in particular the highest peaks at ~7 ka BP, are different from the records of the open western Pacific. Reoccurrence of the... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00436/54756/56204.pdf |
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