Climate Induced Speleothem Radiocarbon Variability on Socotra Island from the Last Glacial Maximum to the Younger Dryas

Abstract. In this study, the dead carbon fraction (DCF) variations in stalagmite M1-5 from Socotra Island in the western Arabian Sea were investigated through a new set of high-precision U-series and radiocarbon (14C) dates. The data reveal an extreme case of very high and also climate dependent DCF values. For M1-5 an average DCF of 56.2 ± 3.4 % is observed between 27 and 18 kyr BP. Such high DCF values indicate a high influence of aged soil organic matter (SOM) and nearly completely closed system carbonate dissolution conditions. Towards the end of the last glacial period decreasing Mg/Ca ratios suggest an increase in precipitation which caused a marked change in the soil carbon cycling as indicated by sharply decreasing DCF. This is in contrast to the relation of soil infiltration and reservoir age observed in stalagmites from temperate zones. For Socotra Island, which is influenced by the East African–Indian monsoon, we propose that more humid conditions and enhanced net-infiltration after the LGM led to denser vegetation and thus lowered the DCF by increased 14CO2 input into the soil zone. The onset of the Younger Dryas (YD) is represented in the record by the end of DCF decrease with a sudden change to much higher and extremely variable reservoir ages. Our study highlights the dramatic variability of soil carbon cycling processes and vegetation feedback on Socotra Island manifested in stalagmite reservoir ages on both long-term trends and sub-centennial timescales, thus providing evidence for climate influence on stalagmite radiocarbon. This is of particular importance for studies focussing on 14C calibration and atmospheric reconstruction through stalagmites which relies on largely climate independent soil carbon cycling above the cave.

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Climate-induced speleothem radiocarbon variability on Socotra Island from the Last Glacial Maximum to the Younger Dryas

Climate of the Past ◽

10.5194/cp-16-409-2020 ◽

2020 ◽

Vol 16 (1) ◽

pp. 409-421

Author(s):

Steffen Therre ◽

Jens Fohlmeister ◽

Dominik Fleitmann ◽

Albert Matter ◽

Stephen J. Burns ◽

...

Keyword(s):

Soil Carbon ◽

Carbon Cycling ◽

Last Glacial Maximum ◽

Younger Dryas ◽

Glacial Maximum ◽

Last Glacial ◽

Soil Carbon Cycling ◽

Socotra Island ◽

The Last Glacial Maximum ◽

The Last Glacial

Abstract. In this study, the dead carbon fraction (DCF) variations in stalagmite M1-5 from Socotra Island in the western Arabian Sea were investigated through a new set of high-precision U-series and radiocarbon (14C) dates. The data reveal an extreme case of very high and also climate-dependent DCF. For M1-5, an average DCF of 56.2±3.4 % is observed between 27 and 18 kyr BP. Such high DCF values indicate a high influence of aged soil organic matter (SOM) and nearly completely closed-system carbonate dissolution conditions. Towards the end of the last glacial period, decreasing Mg∕Ca ratios suggest an increase in precipitation which caused a marked change in the soil carbon cycling as indicated by sharply decreasing DCF. This is in contrast to the relation of soil infiltration and DCF as seen in stalagmites from temperate zones. For Socotra Island, which is influenced by the East African–Indian monsoon, we propose that more humid conditions and enhanced net infiltration after the Last Glacial Maximum (LGM) led to dense vegetation and thus lowered the DCF by increasing 14CO2 input into the soil zone. At the onset of the Younger Dryas (YD) a sudden change in DCF towards much higher, and extremely variable, values is observed. Our study highlights the dramatic variability of soil carbon cycling processes and vegetation feedback on Socotra Island manifested in stalagmite DCF on both long-term trends and sub-centennial timescales, thus providing evidence for climate influence on stalagmite radiocarbon. This is of particular relevance for speleothem studies that aim to reconstruct past atmospheric 14C (e.g., for the purposes of 14C calibration), as these would rely on largely climate-independent soil carbon cycling above the cave.

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Faculty Opinions recommendation of Quantitative assessment of the differential impacts of arbuscular and ectomycorrhiza on soil carbon cycling.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.725515063.793540708 ◽

2017 ◽

Author(s):

Paul Kardol

Keyword(s):

Soil Carbon ◽

Carbon Cycling ◽

Quantitative Assessment ◽

Soil Carbon Cycling

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Plant phosphorus-acquisition and -use strategies affect soil carbon cycling

Trends in Ecology & Evolution ◽

10.1016/j.tree.2021.06.005 ◽

2021 ◽

Author(s):

Wenli Ding ◽

Wen-Feng Cong ◽

Hans Lambers

Keyword(s):

Soil Carbon ◽

Carbon Cycling ◽

Phosphorus Acquisition ◽

Soil Carbon Cycling

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Rhizosphere bacterial carbon turnover is higher in nucleic acids than membrane lipids: implications for understanding soil carbon cycling

Frontiers in Microbiology ◽

10.3389/fmicb.2015.00268 ◽

2015 ◽

Vol 6 ◽

Cited By ~ 26

Author(s):

Ashish A. Malik ◽

Helena Dannert ◽

Robert I. Griffiths ◽

Bruce C. Thomson ◽

Gerd Gleixner

Keyword(s):

Nucleic Acids ◽

Soil Carbon ◽

Carbon Cycling ◽

Membrane Lipids ◽

Carbon Turnover ◽

Soil Carbon Cycling

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Geologic controls of soil carbon cycling and microbial dynamics in temperate conifer forests

Chemical Geology ◽

10.1016/j.chemgeo.2009.01.004 ◽

2009 ◽

Vol 267 (1-2) ◽

pp. 12-23 ◽

Cited By ~ 48

Author(s):

Katherine Heckman ◽

Amy Welty-Bernard ◽

Craig Rasmussen ◽

Egbert Schwartz

Keyword(s):

Soil Carbon ◽

Carbon Cycling ◽

Conifer Forests ◽

Microbial Dynamics ◽

Soil Carbon Cycling ◽

Geologic Controls

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Timing and structure of the Younger Dryas event and its underlying climate dynamics

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2007869117 ◽

2020 ◽

Vol 117 (38) ◽

pp. 23408-23417

Author(s):

Hai Cheng ◽

Haiwei Zhang ◽

Christoph Spötl ◽

Jonathan Baker ◽

Ashish Sinha ◽

...

Keyword(s):

Southern Hemisphere ◽

North Atlantic ◽

Time Scale ◽

Asian Monsoon ◽

Younger Dryas ◽

Tropical Pacific ◽

Last Glacial ◽

The North ◽

The North Atlantic ◽

The Last Glacial

The Younger Dryas (YD), arguably the most widely studied millennial-scale extreme climate event, was characterized by diverse hydroclimate shifts globally and severe cooling at high northern latitudes that abruptly punctuated the warming trend from the last glacial to the present interglacial. To date, a precise understanding of its trigger, propagation, and termination remains elusive. Here, we present speleothem oxygen-isotope data that, in concert with other proxy records, allow us to quantify the timing of the YD onset and termination at an unprecedented subcentennial temporal precision across the North Atlantic, Asian Monsoon-Westerlies, and South American Monsoon regions. Our analysis suggests that the onsets of YD in the North Atlantic (12,870 ± 30 B.P.) and the Asian Monsoon-Westerlies region are essentially synchronous within a few decades and lead the onset in Antarctica, implying a north-to-south climate signal propagation via both atmospheric (decadal-time scale) and oceanic (centennial-time scale) processes, similar to the Dansgaard–Oeschger events during the last glacial period. In contrast, the YD termination may have started first in Antarctica at ∼11,900 B.P., or perhaps even earlier in the western tropical Pacific, followed by the North Atlantic between ∼11,700 ± 40 and 11,610 ± 40 B.P. These observations suggest that the initial YD termination might have originated in the Southern Hemisphere and/or the tropical Pacific, indicating a Southern Hemisphere/tropics to North Atlantic–Asian Monsoon-Westerlies directionality of climatic recovery.

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Soil Microbiomes Under Climate Change and Implications for Carbon Cycling

Annual Review of Environment and Resources ◽

10.1146/annurev-environ-012320-082720 ◽

2020 ◽

Vol 45 (1) ◽

pp. 29-59

Author(s):

Dan Naylor ◽

Natalie Sadler ◽

Arunima Bhattacharjee ◽

Emily B. Graham ◽

Christopher R. Anderton ◽

...

Keyword(s):

Climate Change ◽

Soil Carbon ◽

Carbon Cycling ◽

Soil Microorganisms ◽

Climate Changes ◽

Soil Microbiome ◽

Complex Nature ◽

Soil Carbon Cycling ◽

Heterogeneous Soil ◽

The Impact

Communities of soil microorganisms (soil microbiomes) play a major role in biogeochemical cycles and support of plant growth. Here we focus primarily on the roles that the soil microbiome plays in cycling soil organic carbon and the impact of climate change on the soil carbon cycle. We first discuss current challenges in understanding the roles carried out by highly diverse and heterogeneous soil microbiomes and review existing knowledge gaps in understanding how climate change will impact soil carbon cycling by the soil microbiome. Because soil microbiome stability is a key metric to understand as the climate changes, we discuss different aspects of stability, including resistance, resilience, and functional redundancy.We then review recent research pertaining to the impact of major climate perturbations on the soil microbiome and the functions that they carry out. Finally, we review new experimental methodologies and modeling approaches under development that should facilitate our understanding of the complex nature of the soil microbiome to better predict its future responses to climate change.

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