Shoaling of the western equatorial Pacific thermocline during the last glacial maximum inferred from multispecies temperature reconstruction of planktonic foraminifera

Sagawa, Takuya; Yokoyama, Yūsuke; Ikehara, Minoru; Kuwae, Michinobu

doi:10.1016/j.palaeo.2012.06.002

Cited by 39 publications

(33 citation statements)

References 79 publications

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“…3c) in core MD06-3067 (6°31′N, 126°30′E, water depth: 1575 m) from the Philippine Sea (Bolliet et al, 2011). Based on temperature reconstruction using Mg/Ca in multi-species of planktonic foraminifera, Sagawa et al (2012) studied the thermocline depth evolution in the WPWP and found that the thermocline in the Late Holocene was deeper than in the LGM, supporting the present scenario with deeper thermocline in the warmer West and shallower thermocline in the cooler East Pacific. Likewise, therefore, the DOT in the southern SCS as a whole was likely deeper in interglacials but shallower in glacials, as found in our records from MD05-2896/7.…”

Section: Discussionsupporting

confidence: 73%

Hydroclimate Implications of Thermocline Variability in the Southern South China Sea Over the Past 180,000 yr

Dong

et al. 2015

Quat. res.

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a b s t r a c t a r t i c l e i n f oArticle history: Received 10 February 2014 Available online xxxx Keywords: U 37 K′ TEX 86 H Depth of thermocline (DOT) East Asian Monsoon (EAM) South China Sea (SCS) El Niño-Southern Oscillation (ENSO) Based on core-top calibration, the TEX 86 H -derived temperature has been considered as representing subsurface sea temperature (SSST), and the difference between the U K 0 37 -derived sea-surface temperature (SST) and the TEX 86 H -derived SSST can be used to reflect the depth of thermocline (DOT) in the South China Sea region (Jia et al., 2012). We evaluated the DOT dynamics in late Quaternary records using this approach on paired analysis of samples from core MD05-2896/7 in the southern South China Sea. The reconstructed DOT over the last 180,000 yr (180 ka) displays a shoaling trend in glacial periods, which may be attributed to the strengthened cyclonic gyre by the enhanced East Asian winter monsoon and Walker circulation with prominent La Niña-like state, and vice versa in interglacial periods corresponding to reduced winter monsoon with enhanced El Niño-like state. These upper-water thermal variations testify that enhanced winter monsoon was the direct cause of an uplifted local thermocline during glacial or La Niña-like states with strengthened cyclonic gyre due to positive wind stress curl in the southern South China Sea. Our results provide insights into the relationship between monsoon and ENSO on both glacial and millennial time scales.

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Section: Discussionsupporting

confidence: 73%

Hydroclimate Implications of Thermocline Variability in the Southern South China Sea Over the Past 180,000 yr

Dong

et al. 2015

Quat. res.

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“…For the temperature range relevant for this study, the regression lines of G. tumida fall next to the multispecies regression lines of Anand et al () and Sagawa et al (). However, especially slope and intercept of the Sagawa et al () regression differ from those of our species‐specific regression (Table ) and it is important to note that the slope affects the amplitude of temperature variations in paleorecords. The regression lines of G. sacculifer , P. obliquiloculata , and N. dutertrei deviate from previously published correlations (Figure 5).…”

Section: Discussionmentioning

confidence: 99%

“…There is an ongoing debate how the thermocline depth varied throughout the past. For example, some records indicate a thermocline deepening during the Last Glacial Maximum (e.g., Bolliet et al, ), others indicate a thermocline shoaling during the same period (Andreasen & Ravelo, ; Beaufort et al, ; de Garidel‐Thoron et al, ; Regoli et al, ; Sagawa et al, ), and yet others indicate no change compared to the modern ocean (Patrick & Thunell, ). Many of these reconstructions are based on the calculation of differences between shell Mg/Ca‐derived temperature and/or δ 18 O of planktic foraminifera calcifying at different depth levels to estimate vertical temperature gradients within the upper water column (e.g., Bolliet et al, ; de Garidel‐Thoron et al, ; Regoli et al, ).…”

Section: Introductionmentioning

confidence: 99%

Stable Oxygen Isotopes and Mg/Ca in Planktic Foraminifera From Modern Surface Sediments of the Western Pacific Warm Pool: Implications for Thermocline Reconstructions

et al. 2017

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Mg/Ca and stable oxygen isotope compositions (δ18O) of planktic foraminifera tests are commonly used as proxies to reconstruct past ocean conditions including variations in the vertical water column structure. Accurate proxy calibrations require thorough regional studies, since parameters such as calcification depth and temperature of planktic foraminifera depend on local environmental conditions. Here we present radiocarbon‐dated, modern surface sediment samples and water column data (temperature, salinity, and seawater δ18O) from the Western Pacific Warm Pool. Seawater δ18O (δ18OSW) and salinity are used to calculate individual regressions for western Pacific surface and thermocline waters (δ18OSW = 0.37 × S‐12.4 and δ18OSW = 0.33 × S‐11.0). We combine shell δ18O and Mg/Ca with water column data to estimate calcification depths of several planktic foraminifera and establish regional Mg/Ca‐temperature calibrations. Globigerinoides ruber, Globigerinoides elongatus, and Globigerinoides sacculifer reflect mixed layer conditions. Pulleniatina obliquiloculata and Neogloboquadrina dutertrei and Globorotalia tumida preserve upper and lower thermocline conditions, respectively. Our multispecies Mg/Ca‐temperature calibration (Mg/Ca = 0.26exp0.097*T) matches published regressions. Assuming the same temperature sensitivity in all species, we propose species‐specific calibrations that can be used to reconstruct upper water column temperatures. The Mg/Ca temperature dependencies of G. ruber, G. elongatus, and G. tumida are similar to published equations. However, our data imply that calcification temperatures of G. sacculifer, P. obliquiloculata, and N. dutertrei are exceptionally warm in the western tropical Pacific and thus underestimated by previously published calibrations. Regional Mg/Ca‐temperature relations are best described by Mg/Ca = 0.24exp0.097*T for G. sacculifer and by Mg/Ca = 0.21exp0.097*T for P. obliquiloculata and N. dutertrei.

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“…Oxygen isotope and Mg/Ca studies for G. ruber in a core from the northern WPWP region indicate that the calcification depth of G. ruber is ∼ 60 m in the surface mixed layer (Sagawa et al, 2012). The temperature in the surface mixed layer shows little variation on seasonal and interannual timescales in the WPWP (Data from Locarnini et al, 2010).…”

Section: Response Of Scs Ssts To Orbital Forcingmentioning

confidence: 99%

The East Asian winter monsoon variability in response to precession during the past 150 000 yr

et al. 2013

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Abstract. The response of the East Asian winter monsoon variability to orbital forcing is still unclear, and hypotheses are controversial. We present a 150 000 yr record of sea surface temperature difference ( SST) between the South China Sea and other Western Pacific Warm Pool regions as a proxy for the intensity of the Asian winter monsoon, because the winter cooling of the South China Sea is caused by the cooling of surface water at the northern margin and the southward advection of cooled water due to winter monsoon winds. The SST showed dominant precession cycles during the past 150 000 yr. The SST varies at precessional band and supports the hypothesis that monsoon is regulated by insolation changes at low-latitudes (Kutzbach, 1981), but contradicts previous suggestions based on marine and loess records that eccentricity controls variability on glacial-interglacial timescales. Maximum winter monsoon intensity corresponds to the May perihelion at precessional band, which is not fully consistent with the Kutzbach model of maximum winter monsoon at the June perihelion. Variation in the East Asian winter monsoon was anti-phased with the Indian summer monsoon, suggesting a linkage of dynamics between these two monsoon systems on an orbital timescale.

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Shoaling of the western equatorial Pacific thermocline during the last glacial maximum inferred from multispecies temperature reconstruction of planktonic foraminifera

Cited by 39 publications

References 79 publications

Hydroclimate Implications of Thermocline Variability in the Southern South China Sea Over the Past 180,000 yr

Hydroclimate Implications of Thermocline Variability in the Southern South China Sea Over the Past 180,000 yr

Stable Oxygen Isotopes and Mg/Ca in Planktic Foraminifera From Modern Surface Sediments of the Western Pacific Warm Pool: Implications for Thermocline Reconstructions

The East Asian winter monsoon variability in response to precession during the past 150 000 yr

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