Use of Foraminifera in Climate Science

2019 ◽  
Author(s):  
Gerhard Schmiedl
Keyword(s):  
Stable Isotope ◽  
Trace Element ◽  
Ocean Circulation ◽  
Transfer Functions ◽  
Isotope Composition ◽  
Sediment Cores ◽  
Environmental Data ◽  
Geochemical Data ◽  
Climate History ◽  
Sediment Types

The understanding of past changes in climate and ocean circulation is to a large extent based on information from marine sediments. Marine deposits contain a variety of microfossils, which archive (paleo)-environmental information, both in their floral and faunal assemblages and in their stable isotope and trace element compositions. Sampling campaigns in the late 19th and early 20th centuries were dedicated to the inventory of sediment types and microfossil taxa. With the initiation of various national and international drilling programs in the second half of the 20th century, sediment cores were systematically recovered from all ocean basins and since then have shaped our knowledge of the oceans and climate history. The stable oxygen isotope composition of foraminiferal tests from the sediment cores delivered a continuous record of late Cretaceous–Cenozoic glaciation history. This record impressively proved the effects of periodic changes in the orbital configuration of the Earth on climate on timescales of tens to hundreds of thousands of years, described as Milankovitch cycles. Based on the origination and extinction patterns of marine microfossil groups, biostratigraphic schemes have been established, which are readily used for the dating of sediment successions. The species composition of assemblages of planktic microfossils, such as planktic foraminifera, radiolarians, dinoflagellates, coccolithophorids, and diatoms, is mainly related to sea-surface temperature and salinity but also to the distribution of nutrients and sea ice. Benthic microfossil groups, in particular benthic foraminifera but also ostracods, respond to changes in water depth, oxygen, and food availability at the sea floor, and provide information on sea-level changes and benthic-pelagic coupling in the ocean. The establishment and application of transfer functions delivers quantitative environmental data, which can be used in the validation of results from ocean and climate modeling experiments. Progress in analytical facilities and procedures allows for the development of new proxies based on the stable isotope and trace element composition of calcareous, siliceous, and organic microfossils. The combination of faunal and geochemical data delivers information on both environmental and biotic changes from the same sample set. Knowledge of the response of marine microorganisms to past climate changes at various amplitudes and pacing serves as a basis for the assessment of future resilience of marine ecosystems to the anticipated impacts of global warming.

Antarctic Climate History and Global Climate Changes

2017 ◽  
Author(s):  
Pontus Lurcock ◽  
Fabio Florindo
Keyword(s):  
Ocean Circulation ◽  
Climate Changes ◽  
Numerical Models ◽  
Global Climate ◽  
Sediment Cores ◽  
Ice Sheets ◽  
Global Ocean ◽  
Climate History ◽  
Global Climate Changes ◽  
Planetary Albedo

Antarctic climate changes have been reconstructed from ice and sediment cores and numerical models (which also predict future changes). Major ice sheets first appeared 34 million years ago (Ma) and fluctuated throughout the Oligocene, with an overall cooling trend. Ice volume more than doubled at the Oligocene-Miocene boundary. Fluctuating Miocene temperatures peaked at 17–14 Ma, followed by dramatic cooling. Cooling continued through the Pliocene and Pleistocene, with another major glacial expansion at 3–2 Ma. Several interacting drivers control Antarctic climate. On timescales of 10,000–100,000 years, insolation varies with orbital cycles, causing periodic climate variations. Opening of Southern Ocean gateways produced a circumpolar current that thermally isolated Antarctica. Declining atmospheric CO2 triggered Cenozoic glaciation. Antarctic glaciations affect global climate by lowering sea level, intensifying atmospheric circulation, and increasing planetary albedo. Ice sheets interact with ocean water, forming water masses that play a key role in global ocean circulation.

scholarly journals Barium stable isotopes as a fingerprint of biological cycling in the Amazon River basin

2020 ◽  
Vol 17 (23) ◽  
pp. 5989-6015
Author(s):  
Quentin Charbonnier ◽  
Julien Bouchez ◽  
Jérôme Gaillardet ◽  
Éric Gayer
Keyword(s):  
Organic Matter ◽  
Stable Isotope ◽  
Trace Element ◽  
Isotope Composition ◽  
Silicate Weathering ◽  
Biological Cycling ◽  
Biological Uptake ◽  
Dissolved Load ◽  
Silicate Rocks

Abstract. The biological cycle of rock-derived nutrients on the continents is a major component of element transfer between the Earth's surface compartments, but its magnitude currently remains elusive. The use of the stable isotope composition of rock-derived nutrients, which can be fractionated during biological uptake, provides a promising path forward with respect to quantifying biological cycling and its overall contribution to global element cycling. In this paper, we rely on the nutrient-like behaviour of the trace element barium (Ba) and use its elemental and stable isotope compositions in dissolved and sediment load river samples to investigate biological cycling in the Amazon Basin. From these measurements, we show that dissolved Ba mainly derives from silicate rocks, and a correlation between dissolved Ba and K abundances suggests that biological cycling plays a role in the Ba river budget. Furthermore, the isotope composition of Ba (δ138Ba) in the dissolved load was found to be significantly different from that of the parent silicate rocks, implying that dissolved Ba isotopic signatures are affected by (i) the precipitation of soil-forming secondary phases as well as (ii) biological uptake and release from dead organic matter. Results from an isotope mass balance method applied to the river dissolved load data indicate that, after its release to solution by rock weathering, Ba is partitioned between the river dissolved load, secondary weathering products (such as those found in soils and river sediments), and the biota. In most sub-catchments of the Amazon, river Ba abundances and isotope compositions are significantly affected by biological cycling. Relationships between estimates of Ba cycled through biota and independent metrics of ecosystem dynamics (such as gross primary production and terrestrial ecosystem respiration) allow us to discuss the role of environmental parameters such as climate or erosion rates on the biological cycling of Ba and, by extension, the role of major rock-derived nutrients. In addition, catchment-scale mass and isotope budgets of Ba show that the measured riverine export of Ba is lower than the estimated delivery of Ba to the Earth surface through rock alteration. This indicates the existence of a missing Ba component, which we attribute to the formation of Ba-bearing particulate organics (possibly accumulating as soil organic matter or currently growing biomass within the catchments) and to organic-bound Ba exported as “unsampled” river particulate organic matter. Given our findings on the trace element Ba, we explore whether the river fluxes of most major rock-derived nutrients (K, Mg, Ca) might also be significantly affected by biological uptake or release. A first-order correction of river-derived silicate weathering fluxes from biological cycling shows that the carbon dioxide (CO2) consumption by silicate weathering at the mouth of the Amazon could be several times higher than the previously reported value of 13 × 109 mol CO2 yr−1 (Gaillardet et al., 1997). Overall, our study clearly shows that the chemical and isotope compositions of rivers in the Amazon – and most likely in other large river basins – bear a biological imprint, thereby challenging common assumptions made in weathering studies.

Antarctic Climate History and Global Climate Changes

2017 ◽  
Author(s):  
Pontus Lurcock ◽  
Fabio Florindo
Keyword(s):  
Ocean Circulation ◽  
Climate Changes ◽  
Numerical Models ◽  
Global Climate ◽  
Sediment Cores ◽  
Ice Sheets ◽  
Global Ocean ◽  
Climate History ◽  
Global Climate Changes ◽  
Planetary Albedo

Antarctic climate changes have been reconstructed from ice and sediment cores and numerical models (which also predict future changes). Major ice sheets first appeared 34 million years ago (Ma) and fluctuated throughout the Oligocene, with an overall cooling trend. Ice volume more than doubled at the Oligocene-Miocene boundary. Fluctuating Miocene temperatures peaked at 17–14 Ma, followed by dramatic cooling. Cooling continued through the Pliocene and Pleistocene, with another major glacial expansion at 3–2 Ma. Several interacting drivers control Antarctic climate. On timescales of 10,000–100,000 years, insolation varies with orbital cycles, causing periodic climate variations. Opening of Southern Ocean gateways produced a circumpolar current that thermally isolated Antarctica. Declining atmospheric CO2 triggered Cenozoic glaciation. Antarctic glaciations affect global climate by lowering sea level, intensifying atmospheric circulation, and increasing planetary albedo. Ice sheets interact with ocean water, forming water masses that play a key role in global ocean circulation.

Monitoring activities in several caves along a transect stretching from the Adriatic Sea to the Aggtelek Karst (NE-Hungary): trace element and stable isotopic compositions of drip waters and cave carbonates

2020 ◽  
Author(s):  
György Czuppon ◽  
Attila Demény ◽  
Neven Bocic ◽  
Nenad Buzjak ◽  
Krisztina Kármán ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Trace Element ◽  
Adriatic Sea ◽  
Isotope Composition ◽  
Winter Precipitation ◽  
Trace Element Composition ◽  
Drip Water ◽  
Cave System ◽  
The Mediterranean ◽  
Monitoring Activities

<p>Several caves have been monitored along a transect stretching from the Adriatic Sea to the Aggtelek Karst (NE-Hungary) including two caves in Croatia and three caves in Hungary:  1) Cerovacke cave (~25 km far from the sea, Velebit Mt.), 2) Baraceve cave (~70 km far from the sea), 3) Csodabogyós Cave (~320 km far from the sea, Keszthely Mt.), 4) Béke and Baradla Caves (~700 km far from the sea, Aggtelek Karst). The monitoring activities in each caves included microclimate measurements, analyses of the elemental and stable isotope compositions of drip water and precipitation, as well as stable isotope measurements of modern calcite precipitates formed on light bulbs or glass plates.</p><p>The stable isotope compositions of the drip waters in all cases (except one) show systematically lower values than those found in amount-weighted annual precipitation suggesting that the source of the infiltrating water dominantly derives from winter precipitation. Moreover, the relative contribution of winter precipitation can vary even within same cave system reflecting also the local morphology of the karst above the cave. The d-excess values of the drip waters show an increasing trend from the Aggtelek Karst towards to Adriatic Sea, showing higher values than 10‰ (Béke-C.: 10.3‰; Csodabogyós-C.: 11‰, Baraceve-C.: 12‰, Cerovacke: 15‰). These observations indicate significant contribution from moisture originated from the Mediterranean Basin to the infiltrating water. The monitoring of the precipitation support these findings as among the marine moisture source the Mediterranean is the most dominant even relative far from the sea.</p><p>The trace element systematics in drip waters indicate that PCP likely took place during relatively dry periods. In some caves the change of the hydrological condition affected both the trace element composition of the drip water and the stable isotope composition of the modern calcite precipitates. Although the calcite-water isotope fractionations show significant scatter even within individual caves, the majority of the data fall close to the Coplen (2007) and the Tremaine et al. (2011) fractionation values in both Croatian and Hungarian caves.</p><p>The research was supported by the Ministry for Innovation and Technology, the National Research, Development and Innovation Office (project No. PD 121387).</p>

The Holocene paleolimnology of Lake Issyk-Kul, Kyrgyzstan: trace element and stable isotope composition of ostracodes

2001 ◽  
Vol 176 (1-4) ◽  
pp. 207-227 ◽  
Author(s):  
Richard D Ricketts ◽  
Thomas C Johnson ◽  
Erik T Brown ◽  
Kenneth A Rasmussen ◽  
Vladimir V Romanovsky
Keyword(s):  
Stable Isotope ◽  
Trace Element ◽  
Isotope Composition ◽  
Stable Isotope Composition ◽  
The Holocene

scholarly journals Formation mechanisms of macroscopic globules in andesitic glasses from the Izu–Bonin–Mariana forearc (IODP Expedition 352)

2020 ◽  
Vol 176 (1) ◽  
Author(s):  
Raúl O. C. Fonseca ◽  
Lina T. Michely ◽  
Maria Kirchenbaur ◽  
Julie Prytulak ◽  
Jeffrey Ryan ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Trace Element ◽  
Isotope Fractionation ◽  
Experimental Studies ◽  
Trace Element Analysis ◽  
Geochemical Data ◽  
Formation Mechanisms ◽  
Chemical Compositions ◽  
Stable Isotope Fractionation ◽  
Textural Evidence

AbstractThe Izu–Bonin–Mariana volcanic arc is situated at a convergent plate margin where subduction initiation triggered the formation of MORB-like forearc basalts as a result of decompression melting and near-trench spreading. International Ocean Discovery Program (IODP) Expedition 352 recovered samples within the forearc basalt stratigraphy that contained unusual macroscopic globular textures hosted in andesitic glass (Unit 6, Hole 1440B). It is unclear how these andesites, which are unique in a stratigraphic sequence dominated by forearc basalts, and the globular textures therein may have formed. Here, we present detailed textural evidence, major and trace element analysis, as well as B and Sr isotope compositions, to investigate the genesis of these globular andesites. Samples consist of $$\hbox {K}_2\hbox {O}$$ K 2 O -rich basaltic globules set in a glassy groundmass of andesitic composition. Between these two textural domains a likely hydrated interface of devitrified glass occurs, which, based on textural evidence, seems to be genetically linked to the formation of the globules. The andesitic groundmass is Cl rich (ca. $$3000\, \mu \hbox {g/g}$$ 3000 μ g/g ), whereas globules and the interface are Cl poor (ca. $$300\, \mu \hbox {g/g}$$ 300 μ g/g ). Concentrations of fluid-mobile trace elements also appear to be fractionated in that globules and show enrichments in B, K, Rb, Cs, and Tl, but not in Ba and W relative to the andesitic groundmass, whereas the interface shows depletions in the latter, but is enriched in the former. Interestingly, globules and andesitic groundmass have identical Sr isotopic composition within analytical uncertainty ($$^{87}\hbox {Sr}/^{86}\hbox {Sr}$$ 87 Sr / 86 Sr of $$0.70580 \pm 10$$ 0.70580 ± 10 ), indicating that they likely formed from the same source. However, globules show high $$\delta ^{11}$$ δ 11 B (ca. + 7$$\permille$$ ‱ ), whereas their host andesites are isotopically lighter (ca. – 1 $$\permille$$ ‱ ), potentially indicating that whatever process led to their formation either introduced heavier B isotopes to the globules, or induced stable isotope fractionation of B between globules and their groundmass. Based on the bulk of the textural information and geochemical data obtained from these samples, we conclude that these andesites likely formed as a result of the assimilation of shallowly altered oceanic crust (AOC) during forearc basaltic magmatism. Assimilation likely introduced radiogenic Sr, as well as heavier B isotopes to comparatively unradiogenic and low $$\delta ^{11}\hbox {B}$$ δ 11 B forearc basalt parental magmas (average $$^{87}\hbox {Sr}/^{86}\hbox {Sr}$$ 87 Sr / 86 Sr of 0.703284). Moreover, the globular textures are consistent with their formation being the result of fluid-melt immiscibility that was potentially induced by the rapid release of water from assimilated AOC whose escape likely formed the interface. If the globular textures present in these samples are indeed the result of fluid-melt immiscibility, then this process led to significant trace element and stable isotope fractionation. The textures and chemical compositions of the globules highlight the need for future experimental studies aimed at investigating the exsolution process with respect to potential trace element and isotopic fractionation in arc magmas that have perhaps not been previously considered.

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