1,721,124 research outputs found
Planktic foraminiferal test size and weight response to the late Pliocene environment
No full textAtmospheric carbon dioxide (pCO
2
atm) is impacting the ocean and marine organisms directly via changes in carbonate chemistry and indirectly via a range of changes in physical parameters most dominantly temperature. To assess potential impacts of climate change on carbonate production in the open ocean, we measured size and weight of planktic foraminifers during the late Pliocene at pCO
2
atm concentrations comparable to today and global temperatures 2 to 3 °C warmer. Size of all foraminifers was measured at Atlantic Ocean Deep Sea Drilling Project (DSDP) Site 610, Ocean Drilling Program (ODP) Site 999, and Integrated Ocean Drilling Program (IODP) Site U1313. Test size was smaller during the Pliocene than in modern assemblages under the same environmental conditions. During the cold marine isotope stage (MIS) M2, size increased at Site 999, potentially linked to intensified stratification of the surface ocean in response to the closure of the Central American Seaway. At Site U1313, test size tracks the warming throughout the late Pliocene. Size-normalized weight (SNW) of Globigerina bulloides at Site U1313 decreased during warmer temperature intervals. SNW of Globigerinoides ruber (white) at Site 999 displays high-frequency variability not correlated to temperature. Yet during the glacial period within MIS M2, test weight was higher during higher temperatures. Our results support studies in the modern ocean, which challenge the view that carbonate chemistry is the primary driver for calcification. To better understand processes driving changes in SNW, computer tomography was used to quantify calcite to volume ratios. During interglacial periods, lower calcite volume but higher test volume suggests less suitable conditions for calcification. As this signal is not evident in SNW, subtle changes in calcification might not be observed by the weight-based method.
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Record of 7 acritarch taxa, Mg/Ca sea-surface temperatures and palynological preparation data from the Miocene, Pliocene and Pleistocene of DSDP Hole 94-610A
No full textDEPTH, sediment [m] is given in mbsf. AGE [ka BP] gives the calibrated ages. <1 = present outside the regular counts, # = suspected reworking
Planktic foraminiferal test size and size normalised weight from DSDP Hole 94-610A during the Pliocene
No full textLast Interglacial biomarker, dinoflagellate cyst, and stable oxygen isotope data from sediment core GS16-204-22CC-B
No full textThe dataset contains measurements of organic biomarkers and sterols, dinoflagellate cyst census counts, and benthic and planktonic stable oxygen isotope data from core GS16-204-22CC-B on the Eirik Drift (58°02.83′N, 47°02.36′W; 3160 m water depth) for Marine Isotope Stage 6, 5e and 5d. Total Organic Carbon (TOC), the Highly Branched Isoprenoids (HBIs) IP25, HBI II, HBI III (Z), and HBI III (E), and the sterols brassicasterol, dinosterol, campesterol and sitosterol were measured in the organic geochemistry lab at the Alfred Wegener Institute, Bremerhaven, Germany. Biomarker values are presented as biomarker/g dry sediment and biomarker/g TOC. Dinoflagellate cysts were counted along non overlapping traverses at x40 magnification using a transmitted light microscope and classified to species level as much as possible. The dataset consists of raw counts, relative abundances and dinocyst concentrations (cysts/g dry sediment). Stable oxygen isotopes (δ18O) were measured on the planktic foraminifera Neogloboquadrina pachyderma (sinistral) and benthic foraminifera Cibicidoides wuellestorfi. Values are reported relative to Vienna Pee Dee Belemnite. The measurements were carried out at FARLAB, University of Bergen, Norway. The age model for core GS16-204-22CC-B was obtained by correlation of benthic and planktic δ18O measured in this core with previously published isotope records in Irvali et al. (2012; 2016) and a 14C age from Griem et al. (2019)
Limited exchange between the deep Pacific and Atlantic oceans during the warm mid-Pliocene and MIS M2 glaciation
No full textThe mid-Pliocene (3.3–3.0 Ma) is the most recent period in Earth’s history of sustained, global warmth analogous to predicted near-future climates. Despite considerable efforts to characterize and understand the climate dynamics of the mid-Pliocene, the deep ocean and its response to this warming remains poorly understood. Here we present new mid-Pliocene Mg/Ca and Δ47 (“clumped isotope”) temperatures from the deep Pacific and North Atlantic oceans. These records cover the transition from Marine Isotope Stage (MIS) M2 — considered the most pronounced “glacial” stage of the mid-Pliocene — to the warm KM5 interglacial. We find that a large (>4 °C) temperature gradient existed between these two basins throughout that interval, with the deep North Atlantic considerably warmer and likely saltier than at present. We interpret our results to indicate that the deep Pacific and North Atlantic oceans were bathed by water masses with very different physical properties during the mid-Pliocene, and that only limited deep oceanic exchange occurred between the two basins. Our results point to a fundamentally different mode of ocean circulation or mixing compared to the present, where heat and salt is distributed from the North Atlantic into the Pacific. The amplitude of cooling observed at both sites during MIS M2 suggests that changes in benthic δ18O associated with this cold stage were mostly driven by temperature change in the deep ocean rather than ice volume
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