Western Pacific thermocline structure and the Pacific marine Intertropical Convergence Zone during the Last Glacial Maximum

Leech, Peter J.; Lynch‐Stieglitz, Jean; Zhang, Rong

doi:10.1016/j.epsl.2012.12.026

Cited by 29 publications

(21 citation statements)

References 44 publications

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“…Generally, our surface and subsurface δ 18 O SW ‐salinity regressions are within the range of published WPWP regressions (Fairbanks et al, ; Leech, Lynch‐Stieglitz, & Zhang, ; LeGrande & Schmidt, ; Morimoto et al, ). However, slope and/or intercept differ from previous regression lines.…”

Section: Discussionsupporting

confidence: 86%

“…However, slope and/or intercept differ from previous regression lines. Especially, the regressions of Fairbanks et al () and LeGrande and Schmidt () and the surface regression of Leech et al () show shallower slopes (around 0.3) and, accordingly, larger intercepts (between −10.47 and −9.14) than our regressions. The regression of Morimoto et al () is almost identical to our PNG surface equation (δ 18 O SW = 0.42 × S ‐14.3).…”

Section: Discussionsupporting

confidence: 75%

“…Black lines indicate regression lines for the entire study area and colored lines for the subareas. Gray stippled lines show regional δ 18 Osw‐salinity equations published by (1) Fairbanks et al (), (2) Morimoto et al (), (3/5) Leech et al (), and (4) LeGrande and Schmidt (). Bars indicate laboratory standard deviations for oxygen isotope measurements.…”

Section: Resultsmentioning

confidence: 98%

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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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Section: Discussionsupporting

confidence: 86%

Section: Discussionsupporting

confidence: 75%

Section: Resultsmentioning

confidence: 98%

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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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“…2a) (Liu et al, 2004). Leech et al (2013) also illustrate this relationship between wind stress curl and DOT in their paleo-record from the western Pacific. As stated above, the DOT record from core MD05-2896/7 reveals a shoaling DOT in cold and glacial intervals and a depressed DOT in warm and interglacial intervals (Figs.…”

Section: Thermocline Changes and East Asian Monsoonmentioning

confidence: 93%

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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“…[], using the transfer function developed by Andreasen and Ravelo [], showed that the thermocline depth in the central part of the WPWP was shallowest during the LGM. Lastly, a multispecies comparison of Mg/Ca suggested a shoaling of the thermocline during the LGM in the extreme west of the Pacific [ Sagawa et al ., ], in agreement with a cross‐equatorial transect of Δδ 18 O isotopes which showed a shoaling of the thermocline in the southwest Pacific around 7°S to 10°S [ Leech et al ., ]. Those contrasting results that are based on similar approaches need to be reconciled by means of new reconstructions of past stratification, especially in the southwest subequatorial Pacific, where a single study [ Leech et al ., ] has investigated the past state of the thermocline, in a setting with relatively low sedimentation rate environments.…”

Section: Introductionmentioning

confidence: 99%

Progressive shoaling of the equatorial Pacific thermocline over the last eight glacial periods

et al. 2015

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International audienceThe depth of equatorial Pacific thermocline is diagnostic of the main modes of tropical climates. Past estimates of Pacific thermocline dynamics have been reconstructed either for the Last Glacial Maximum or on longer timescales at low resolution. Here we document a new high-resolution set of reconstructed past sea surface and subsurface waters temperatures from the southwestern subequatorial Pacific, core MD05-2930, in the Gulf of Papua, over the last 800ka. We used two morphotypes of Globigerinoides ruber known to live at different water depths to reconstruct past stratification. We estimated calcification temperature of each morphotypes by Mg/Ca paleothermometry. Our subequatorial Pacific thermocline paleotemperature record indicates a response of the thermocline to both direct orbital forcing and glacial-interglacial changes. Our stratification record shows a systematic shallower glacial thermocline, whereas sea surface temperatures are characterized by precessional forcing. The record is indicative of a progressive long-term shoaling of the thermocline during the glacial stages during the late Pleistocene. The shoaling of the subequatorial Pacific thermocline is consistent with regional estimates. An enhanced South Pacific shallow overturning wind-driven circulation could have driven this progressive shoaling. We speculate that this late Pleistocene glacial shoaling of the thermocline could be related to an increase in the amplitude of the obliquity

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Western Pacific thermocline structure and the Pacific marine Intertropical Convergence Zone during the Last Glacial Maximum

Cited by 29 publications

References 44 publications

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

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

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

Progressive shoaling of the equatorial Pacific thermocline over the last eight glacial periods

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