| 1. |
- Chen, Peng, et al.
(författare)
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Holocene monsoon dynamics at Kunlun Pass on the northeastern Qinghai-Tibet Plateau
- 2021
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 771
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Tidskriftsartikel (refereegranskat)abstract
- Various proxy records have been used for the understanding of environmental and climate variations during the Holocene. Here, for the first time, we use meteoric Be-10 isotope measurements performed on sediments from a drill core collected at the Kunlun Pass (KP) on the northeastern Qinghai-Tibet Plateau (NETP) to investigate hydroclimate changes during the Holocene. The Be-10 flux suggests relative low levels in the Early Holocene, followed by a sharp increase to high values at around 4 ka BP (4 ka BP - 4000 years before present). Afterwards, the Be-10 flux remains on a high level during the Late Holocene, but decreases slightly towards today. These Be-10 deposition patterns are compared to moisture changes in regions dominated by the Indian Summer Monsoon (ISM), East Asian Summer Monsoon (EASM), and the Westerlies. Different from the gradual changes in monsoon patterns, the Be-10 data reveal low levels during the Early Holocene until similar to 4 ka BP when an obvious increase is indicated and a relative high level continues to this day, which is relatively more in agreement with patterns of the Westerlies. This finding provides a new evidence fora shift in the dominant pattern of atmospheric circulation the KP region from a more monsoonal one to one dominated by the Westerlies. Our results improve the understanding of non-stationary interactions and spatial relevance of the EASM, the ISM and the Westerlies on the Qinghai-Tibet Plateau.
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| 2. |
- Czymzik, Markus, et al.
(författare)
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Delayed Western Gotland Basin (Baltic Sea) ventilation in response to the onset of a Mid-Holocene climate oscillation
- 2021
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 273
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Tidskriftsartikel (refereegranskat)abstract
- The marine-terrestrial Baltic ecosystem is sensitive to a range of environmental forcing and thresholds. Multi-archive investigations of its evolution require a precise synchronization of the considered archives. Here, we apply globally common cosmogenic radionuclide production rate variations to synchronize 10Be records from brackish Western Gotland Basin (Baltic Sea) and terrestrial lake Tiefer See (NE Germany) sediments to the atmospheric 14C time-scale and investigate phase-relationships in proxy responses in the southern Baltic realm associated with the onset of a centennial Mid-Holocene climate oscillation ∼5800 a BP. Based on paired molybdenum and titanium records, we identify a 98 ± 81-year delay in Western Gotland Basin ventilation, compared to the terrestrial response at the onset of the recorded Mid-Holocene climate oscillation. Most plausible mechanism for this delay is strengthened stratification in response to enhanced freshwater input during the first decades of the oscillation.
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| 3. |
- Nantke, Carla K.M., et al.
(författare)
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Human influence on the continental Si budget during the last 4300 years : δ30Sidiatom in varved lake sediments (Tiefer See, NE Germany)
- 2021
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 258
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Tidskriftsartikel (refereegranskat)abstract
- The continental silicon (Si) cycle, including terrestrial and freshwater ecosystems (lakes, rivers, estuaries), acts as a filter and modulates the amount of Si transported to the oceans. In order to link the variation in the terrestrial Si cycle to aquatic ecosystems, knowledge on changes in vegetation cover, soil disturbance and the impact of human activity are required. This study on varved lake sediments from Tiefer See near Klocksin (TSK) in northeastern Germany investigates Si isotope variations in diatom frustules (δ30Sidiatom) over the last ∼4300 years. δ30Sidiatom values vary between 0.37 and 1.63‰. The isotopic signal measured in centric (mostly planktonic) and pennate (mostly benthic) diatoms shows the same trend through most of the record. A decrease in δ30Sidiatom coinciding with early deforestation between 3900 and 750 a BP in the catchment area, points to an enhanced export of isotopically light dissolved silica (DSi) from adjacent soils to the lake. The burial flux of biogenic silica (BSi) observed in the lake sediments increases with cultivation due to enhanced nutrient supply (N, P and Si) from the watershed and nutrient redistribution caused by wind-driven increased water circulation. When the cultivation intensifies, we observe a shift to higher δ30Sidiatom values that we interpret to reflect a diminished Si soil pool and the preferential removal of the lighter 28Si by crop harvesting. Human activity influences the DSi supply from the catchment and appears to be the primary driver controlling the Si budget in TSK. Our data shows how land use triggers variations in continental Si cycling on centennial timescales and provides important information on the underlying processes.
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