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- Galili, Nir, et al.
(författare)
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The geologic history of seawater oxygen isotopes from marine iron oxides
- 2019
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Ingår i: Science. - : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 365:6452, s. 469-473
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Tidskriftsartikel (refereegranskat)abstract
- The oxygen isotope composition (delta O-18) of marine sedimentary rocks has increased by 10 to 15 per mil since Archean time. Interpretation of this trend is hindered by the dual control of temperature and fluid delta O-18 on the rocks' isotopic composition. A new delta O-18 record in marine iron oxides covering the past similar to 2000 million years shows a similar secular rise. Iron oxide precipitation experiments reveal a weakly temperature-dependent iron oxide-water oxygen isotope fractionation, suggesting that increasing seawater d(18)O over time was the primary cause of the long-term rise in delta O-18 values of marine precipitates. The O-18 enrichment may have been driven by an increase in terrestrial sediment cover, a change in the proportion of high-and low-temperature crustal alteration, or a combination of these and other factors.
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2. |
- Meister, Philip, et al.
(författare)
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A global compilation of diatom silica oxygen isotope records from lake sediment - trends and implications for climate reconstruction
- 2024
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Ingår i: Climate of the Past. - 1814-9324. ; 20:2, s. 363-392
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen isotopes in biogenic silica (δ18OBSi) from lake sediments allow for quantitative reconstruction of past hydroclimate and proxy-model comparison in terrestrial environments. The signals of individual records have been attributed to different factors, such as air temperature (Tair), atmospheric circulation patterns, hydrological changes, and lake evaporation. While every lake has its own local set of drivers of δ18O variability, here we explore the extent to which regional or even global signals emerge from a series of paleoenvironmental records. This study provides a comprehensive compilation and combined statistical evaluation of the existing lake sediment δ18OBSi records, largely missing in other summary publications (i.e. PAGES network). For this purpose, we have identified and compiled 71 down-core records published to date and complemented these datasets with additional lake basin parameters (e.g. lake water residence time and catchment size) to best characterize the signal properties. Records feature widely different temporal coverage and resolution, ranging from decadal-scale records covering the past 150 years to records with multi-millennial-scale resolution spanning glacial-interglacial cycles. The best coverage in number of records (NCombining double low line37) and data points (NCombining double low line2112) is available for Northern Hemispheric (NH) extratropical regions throughout the Holocene (roughly corresponding to Marine Isotope Stage 1; MIS 1). To address the different variabilities and temporal offsets, records were brought to a common temporal resolution by binning and subsequently filtered for hydrologically open lakes with lake water residence times <100 years. For mid- to high-latitude (>45°N) lakes, we find common δ18OBSi patterns among the lake records during both the Holocene and Common Era (CE). These include maxima and minima corresponding to known climate episodes, such as the Holocene Thermal Maximum (HTM), Neoglacial Cooling, Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). These patterns are in line with long-term air temperature changes supported by previously published climate reconstructions from other archives, as well as Holocene summer insolation changes. In conclusion, oxygen isotope records from NH extratropical lake sediments feature a common climate signal at centennial (for CE) and millennial (for Holocene) timescales despite stemming from different lakes in different geographic locations and hence constitute a valuable proxy for past climate reconstructions.
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- Zahajská, Petra, et al.
(författare)
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Impact of Holocene climate change on silicon cycling in Lake 850, Northern Sweden
- 2021
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 31:10, s. 1582-1592
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Tidskriftsartikel (refereegranskat)abstract
- Diatom-rich sediment in a small subarctic lake (Lake 850) was investigated in a 9400 cal. yr BP sediment record in order to explore the impact of Holocene climate evolution on silicon cycling. Diatom stable silicon isotopes (δ30SiBSi ) and biogenic silica (BSi) indicate that high BSi concentrations in sediment throughout the Holocene are associated with a lighter Si isotope source of dissolved silica (DSi), such as groundwater or freshly weathered primary minerals. Furthermore, higher BSi concentrations were favoured during the mid-Holocene by low detrital inputs and possibly a longer ice-free period allowing for more diatom production to occur. The diatom δ30SiBSi signature shows a link to changes in regional climate and is influenced by length of diatom growth period and hydrological fluctuations. Lighter Si isotopic values occur during the mid Holocene, when climate is inferred to be more continental and drier, with pronounced seasonality. In contrast, a heavier Si isotopic signature is observed in the early and late Holocene, when oceanic influences are thought to be stronger and the climate wetter. The δ30SiBSi values have generally lighter signatures as compared with other studies, which supports a light DSi source.
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