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  • 1
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    PANGAEA
    In:  Supplement to: Cléroux, Caroline; deMenocal, Peter B; Arbuszewski, Jennifer; Linsley, Braddock K (2013): Reconstructing the upper water column thermal structure in the Atlantic Ocean. Paleoceanography, 28(3), 503-516, https://doi.org/10.1002/palo.20050
    Publication Date: 2020-01-17
    Description: The thermal structure of the upper ocean (0-1000 m) is set by surface heat fluxes, shallow wind-driven circulation, and the deeper thermohaline circulation. Its long-term variability can be reconstructed using deep-dwelling planktonic foraminifera that record subsurface conditions. Here we used six species (Neogloboquadrina dutertrei, Globorotalia tumida, Globorotalia inflata, Globorotalia truncatulinoides, Globorotalia hirsuta, and Globorotalia crassaformis) from 66 core tops along a meridional transect spanning the mid-Atlantic (42°N to 25°S) to develop a method for reconstructing past thermocline conditions. We estimated the calcification depths from d18O measurements and the Mg/Ca-temperature relationships for each species. This systematic strategy over this large latitudinal section reveals distinct populations with different Mg/Ca-temperature relationships for G. inflata, G. truncatulinoides, and G. hirsuta in different areas. The calcification depths do not differ among the different populations, except for G. hirsuta, where the northern population calcifies much shallower than the southern population. N. dutertrei and G. tumida show a remarkably constant calcification depth independent of oceanographic conditions. The deepest dweller, G. crassaformis, apparently calcifies in the oxygen-depleted zone, where it may find refuge from predators and abundant aggregated matter to feed on. We found a good match between its calcification depth and the 3.2 ml/l oxygen level. The results of this multispecies, multiproxy study can now be applied down-core to facilitate the reconstruction of open-ocean thermocline changes in the past.
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 2
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    PANGAEA
    In:  Supplement to: Gibbons, Fern T; Oppo, Delia W; Mohtadi, Mahyar; Rosenthal, Yair; Cheng, Jun; Liu, Zhengyu; Linsley, Braddock K (2014): Deglacial d18O and hydrologic variability in the tropical Pacific and Indian Oceans. Earth and Planetary Science Letters, 387, 240-251, https://doi.org/10.1016/j.epsl.2013.11.032
    Publication Date: 2020-01-17
    Description: Evidence from geologic archives suggests that there were large changes in the tropical hydrologic cycle associated with the two prominent northern hemisphere deglacial cooling events, Heinrich Stadial 1 (HS1; ~19 to 15 kyr BP; kyr BP = 1000 yr before present) and the Younger Dryas (~12.9 to 11.7 kyr BP). These hydrologic shifts have been alternatively attributed to high and low latitude origin. Here, we present a new record of hydrologic variability based on planktic foraminifera-derived d18O of seawater (d18Osw) estimates from a sediment core from the tropical Eastern Indian Ocean, and using 12 additional d18Osw records, construct a single record of the dominant mode of tropical Eastern Equatorial Pacific and Indo-Pacific Warm Pool (IPWP) hydrologic variability. We show that deglacial hydrologic shifts parallel variations in the reconstructed interhemispheric temperature gradient, suggesting a strong response to variations in the Atlantic Meridional Overturning Circulation and the attendant heat redistribution. A transient model simulation of the last deglaciation suggests that hydrologic changes, including a southward shift in the Intertropical Convergence Zone (ITCZ) which likely occurred during these northern hemisphere cold events, coupled with oceanic advection and mixing, resulted in increased salinity in the Indonesian region of the IPWP and the eastern tropical Pacific, which is recorded by the d18Osw proxy. Based on our observations and modeling results we suggest the interhemispheric temperature gradient directly controls the tropical hydrologic cycle on these time scales, which in turn mediates poleward atmospheric heat transport.
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 3
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    PANGAEA
    In:  Supplement to: Iwatani, Hokuto; Yasuhara, Moriaki; Rosenthal, Yair; Linsley, Braddock K (2018): Intermediate-water dynamics and ocean ventilation effects on the Indonesian Throughflow during the past 15,000 years: Ostracod evidence. Geology, https://doi.org/10.1130/G40177.1
    Publication Date: 2020-01-17
    Description: The Indonesian Throughflow (ITF) is thought to influence thermohaline circulation dynamics and is important for understanding global climate and the marine ecosystem. The physical and chemical properties of North Pacific Intermediate Water (NPIW) and the underlying deep water incorporated into the ITF appear to be the result of climate-related preconditioning in the North and South Pacific. Thus, these high-latitude source waters play an important role in the Indo-Pacific oceanography. Here, we present the results of down-core faunal analyses of fossil ostracods (Crustacea) that we argue reflect NPIW variability in the central part of the Makassar Strait in the ITF over the past 15 k.y. The results show that the warm-water and low-oxygen–water fauna, and species diversity, rapidly increased at ca. 12 ka, reaching maxima during the Younger Dryas (YD). We interpret the faunal change and the diversity maximum at ca. 12 ka as a response to the stagnation of intermediate water due to the decline in ITF intensity during the YD. After ca. 7 ka, the ostracod faunal composition clearly changed from a relatively shallower, warmer, and low-oxygen fauna to a relatively deeper, colder, and high-oxygen fauna. Our interpretation is that the ostracod fauna was responding to the deglacial–early Holocene sea-level rise and the ventilation variations due to the mixing of the NPIW and the underlying deep water. The intermediate-water environment and the ecosystem in the ITF could have been driven by the intensification of the influence of the underlying deep water, caused by changes in the southern high-latitude source due to the latitudinal displacements of the southwesterly winds.
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 4
    Publication Date: 2020-01-17
    Type: Dataset
    Format: text/tab-separated-values, 157 data points
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  • 5
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    PANGAEA
    In:  Supplement to: Rosenthal, Yair; Lear, Caroline H; Oppo, Delia W; Linsley, Braddock K (2006): Temperature and carbonate ion effects on Mg/Ca and Sr/Ca ratios in benthic foraminifera: Aragonitic species Hoeglundina elegans. Paleoceanography, 21(1), PA1007, https://doi.org/10.1029/2005PA001158
    Publication Date: 2020-01-17
    Description: Core top samples from Atlantic (Little Bahama Banks (LBB)) and Pacific (Hawaii and Indonesia) depth transects have been analyzed in order to assess the influence of bottom water temperature (BWT) and aragonite saturation levels on Mg/Ca and Sr/Ca ratios in the aragonitic benthic foraminifer Hoeglundina elegans. Both the Mg/Ca and Sr/Ca ratios in H. elegans tests show a general decrease with increasing water depth. Although at each site the decreasing trends are consistent with the in situ temperature profile, Mg/Ca and Sr/Ca ratios in LBB are substantially higher than in Indonesia and Hawaii at comparable water depths with a greater difference observed with increasing water depth. Because we find no significant difference between results obtained on "live" and "dead" specimens, we propose that these differences are due to primary effects on the metal uptake during test formation. Evaluation of the water column properties at each site suggests that in situ CO3 ion concentrations play an important role in determining the H. elegans Mg/Ca and Sr/Ca ratios. The CO3 ion effect is limited, however, only to aragonite saturation levels ([DeltaCO3]aragonite) below 15 µmol/kg. Above this level, temperature exerts a dominant effect. Accordingly, we propose that Mg/Ca and Sr/Ca in H. elegans tests can be used to reconstruct thermocline temperatures only in waters oversaturated with respect to the mineral aragonite using the following relationships: Mg/Ca = (0.034 ± 0.002)BWT + (0.96 ± 0.03) and Sr/Ca = (0.060 ± 0.002)BWT + (1.53 ± 0.03) (for [DeltaCO3]aragonite 〉 15 µmol/kg). The standard error associated with these equations is about ±1.1°C. Reconstruction of deeper water temperatures is complicated because in undersaturated waters, changes in Mg/Ca and Sr/Ca ratios reflect a combination of changes in [CO3] and BWT. Overall, we find that Sr/Ca, rather than Mg/Ca, in H. elegans may be a more accurate proxy for reconstructing paleotemperatures.
    Type: Dataset
    Format: application/zip, 3 datasets
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  • 6
    Publication Date: 2020-01-17
    Type: Dataset
    Format: text/tab-separated-values, 115 data points
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  • 7
    Publication Date: 2020-01-17
    Type: Dataset
    Format: text/tab-separated-values, 13 data points
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  • 8
    Publication Date: 2020-01-17
    Type: Dataset
    Format: text/tab-separated-values, 37 data points
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  • 9
    Publication Date: 2020-01-17
    Type: Dataset
    Format: text/tab-separated-values, 276 data points
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  • 10
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    PANGAEA
    In:  Supplement to: Tierney, Jessica E; Oppo, Delia W; Rosenthal, Yair; Russell III, James M; Linsley, Braddock K (2010): Coordinated hydrological regimes in the Indo-Pacific region during the past two millennia. Paleoceanography, 25(1), PA1102, https://doi.org/10.1029/2009PA001871
    Publication Date: 2020-01-17
    Description: Instrumental data suggest that major shifts in tropical Pacific atmospheric dynamics and hydrology have occurred within the past century, potentially in response to anthropogenic warming. To better understand these trends, we use the hydrogen isotopic ratios of terrestrial higher plant leaf waxes (DDwax) in marine sediments from southwest Sulawesi, Indonesia, to compile a detailed reconstruction of central Indo-Pacific Warm Pool (IPWP) hydrologic variability spanning most of the last two millennia. Our paleodata are highly correlated with a monsoon reconstruction from Southeast Asia, indicating that intervals of strong East Asian summer monsoon (EASM) activity are associated with a weaker Indonesian monsoon (IM). Furthermore, the centennial-scale oscillations in our data follow known changes in Northern Hemisphere climate (e.g., the Little Ice Age and Medieval Warm Period) implying a dynamic link between Northern Hemisphere temperatures and IPWP hydrology. The inverse relationship between the EASM and IM suggests that migrations of the Intertropical Convergence Zone and associated changes in monsoon strength caused synoptic hydrologic shifts in the IPWP throughout most of the past two millennia.
    Type: Dataset
    Format: application/zip, 3 datasets
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