scholarly journals Dynamics of sediment flux to a bathyal continental margin section through the Paleocene–Eocene Thermal Maximum

2018 ◽  
Vol 14 (7) ◽  
pp. 1035-1049 ◽  
Author(s):  
Tom Dunkley Jones ◽  
Hayley R. Manners ◽  
Murray Hoggett ◽  
Sandra Kirtland Turner ◽  
Thomas Westerhold ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Isotope ◽  
Continental Margin ◽  
The Body ◽  
Sediment Flux ◽  
Stratigraphic Correlation ◽  
Earth System ◽  
Accumulation Rates ◽  
Thermal Maximum ◽  
Organic Carbon Burial

Abstract. The response of the Earth system to greenhouse-gas-driven warming is of critical importance for the future trajectory of our planetary environment. Hyperthermal events – past climate transients with global-scale warming significantly above background climate variability – can provide insights into the nature and magnitude of these responses. The largest hyperthermal of the Cenozoic was the Paleocene–Eocene Thermal Maximum (PETM ∼ 56 Ma). Here we present new high-resolution bulk sediment stable isotope and major element data for the classic PETM section at Zumaia, Spain. With these data we provide a new detailed stratigraphic correlation to other key deep-ocean and terrestrial PETM reference sections. With this new correlation and age model we are able to demonstrate that detrital sediment accumulation rates within the Zumaia continental margin section increased more than 4-fold during the PETM, representing a radical change in regional hydrology that drove dramatic increases in terrestrial-to-marine sediment flux. Most remarkable is that detrital accumulation rates remain high throughout the body of the PETM, and even reach peak values during the recovery phase of the characteristic PETM carbon isotope excursion (CIE). Using a series of Earth system model inversions, driven by the new Zumaia carbon isotope record, we demonstrate that the silicate weathering feedback alone is insufficient to recover the PETM CIE, and that active organic carbon burial is required to match the observed dynamics of the CIE. Further, we demonstrate that the period of maximum organic carbon sequestration coincides with the peak in detrital accumulation rates observed at Zumaia. Based on these results, we hypothesise that orbital-scale variations in subtropical hydro-climates, and their subsequent impact on sediment dynamics, may contribute to the rapid climate and CIE recovery from peak-PETM conditions.

scholarly journals Orbital forcing of terrestrial hydrology, weathering and carbon sequestration during the Palaeocene-Eocene Thermal Maximum

2017 ◽  
Author(s):  
Tom Dunkley Jones ◽  
Hayley R. Manners ◽  
Murray Hoggett ◽  
Sandra Kirtland Turner ◽  
Thomas Westerhold ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
Organic Carbon ◽  
Radical Change ◽  
Transport Processes ◽  
The Body ◽  
Sediment Flux ◽  
Earth System ◽  
Accumulation Rates ◽  
Thermal Maximum ◽  
Organic Carbon Burial

Abstract. The response of the Earth System to greenhouse-gas driven warming is of critical importance for the future trajectory of our planetary environment. Hypethermal events – past climate transients with significant global-scale warming – can provide insights into the nature and magnitude of these responses. The largest hyperthermal of the Cenozoic was the Palaeocene-Eocene Thermal Maximum (PETM ~ 56 Ma). Here we present a new high-resolution cyclostratigraphy for the classic PETM section at Zumaia, Spain. With this new age model we are able to demonstrate that detrital sediment accumulation rates within this continental margin section increased more than four-fold during the PETM, representing a radical change in regional hydrology that drove dramatic increases in terrestrial to marine sediment flux. During the body of the PETM, orbital-scale variations in bulk sediment Si/Fe ratios are evidence for the continued orbital pacing of sediment erosion and transport processes, most likely linked to precession controls on sub-tropical hydroclimates. Most remarkable is that detrital accumulation rates remain high throughout the body of the PETM, and even reach peak values during the recovery phase of the characteristic PETM carbon isotope excursion (CIE). Using a series of Earth System Model inversions, we demonstrate that the silicate weathering feedback alone is insufficient to recover the PETM CIE, and that active organic carbon burial is required to match the observed dynamics of the CIE. Further, that the period of maximum organic carbon sequestration coincides with the peak in detrital accumulation rates observed at Zumaia. Based on these results, we hypothesize that precession controls on tropical and sub-tropical hydroclimates, and the sediment dynamics associated with this variation, play a significant role in the timing of the rapid climate and CIE recovery from peak-PETM conditions.

scholarly journals Reduced carbon cycle resilience across the Palaeocene–Eocene Thermal Maximum

2018 ◽  
Vol 14 (10) ◽  
pp. 1515-1527 ◽  
Author(s):  
David I. Armstrong McKay ◽  
Timothy M. Lenton
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Deep Ocean ◽  
Tipping Point ◽  
Tipping Points ◽  
Carbon Burial ◽  
Thermal Maximum ◽  
Organic Carbon Burial ◽  
Carbon Release ◽  
Hyperthermal Events

Abstract. Several past episodes of rapid carbon cycle and climate change are hypothesised to be the result of the Earth system reaching a tipping point beyond which an abrupt transition to a new state occurs. At the Palaeocene–Eocene Thermal Maximum (PETM) at ∼56 Ma and at subsequent hyperthermal events, hypothesised tipping points involve the abrupt transfer of carbon from surface reservoirs to the atmosphere. Theory suggests that tipping points in complex dynamical systems should be preceded by critical slowing down of their dynamics, including increasing temporal autocorrelation and variability. However, reliably detecting these indicators in palaeorecords is challenging, with issues of data quality, false positives, and parameter selection potentially affecting reliability. Here we show that in a sufficiently long, high-resolution palaeorecord there is consistent evidence of destabilisation of the carbon cycle in the ∼1.5 Myr prior to the PETM, elevated carbon cycle and climate instability following both the PETM and Eocene Thermal Maximum 2 (ETM2), and different drivers of carbon cycle dynamics preceding the PETM and ETM2 events. Our results indicate a loss of “resilience” (weakened stabilising negative feedbacks and greater sensitivity to small shocks) in the carbon cycle before the PETM and in the carbon–climate system following it. This pre-PETM carbon cycle destabilisation may reflect gradual forcing by the contemporaneous North Atlantic Volcanic Province eruptions, with volcanism-driven warming potentially weakening the organic carbon burial feedback. Our results are consistent with but cannot prove the existence of a tipping point for abrupt carbon release, e.g. from methane hydrate or terrestrial organic carbon reservoirs, whereas we find no support for a tipping point in deep ocean temperature.

Magnitude and profile of organic carbon isotope records from the Paleocene–Eocene Thermal Maximum: Evidence from northern Spain

2013 ◽  
Vol 376 ◽  
pp. 220-230 ◽  
Author(s):  
Hayley R. Manners ◽  
Stephen T. Grimes ◽  
Paul A. Sutton ◽  
Laura Domingo ◽  
Melanie J. Leng ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Isotope ◽  
Northern Spain ◽  
Organic Carbon Isotope ◽  
Thermal Maximum

scholarly journals Effects of eutrophication on sedimentary organic carbon cycling in five temperate lakes

2019 ◽  
Author(s):  
Annika Fiskal ◽  
Longhui Deng ◽  
Anja Michel ◽  
Philip Eickenbusch ◽  
Xingguo Han ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Water Column ◽  
Trophic State ◽  
Management Practices ◽  
Microbial Respiration ◽  
Accumulation Rates ◽  
Temperate Lakes ◽  
Artificial Lake ◽  
Eutrophic Lakes ◽  
Organic Carbon Burial

Abstract. Even though human induced eutrophication has severely impacted temperate lake ecosystems over the last centuries, the effects on total organic carbon (TOC) burial and mineralization are not well understood. We study these effects based on sedimentary records from the last 180 years in five Swiss lakes that differ in trophic state. We compare changes in content of TOC and modeled TOC accumulation rates through time to historical data on algae blooms, water column anoxia, wastewater treatment, artificial lake ventilation, and water column phosphorus (P) concentrations. We furthermore investigate the effects of eutrophication on rates of microbial TOC remineralization and vertical distributions of microbial respiration reactions in sediments. Our results indicate that the history of eutrophication is well reflected in the sedimentary record. Subsurface peaks in sedimentary TOC coincide with past periods of elevated P concentrations in lake water. Sediments of eutrophic lakes show overall higher rates of microbial respiration, and a higher relative contribution of methanogenesis to total respiration. Yet, a clear impact of lake trophic state on the zonation of microbial respiration reactions is absent. Moreover, even though water column P concentrations have been reduced by ~ 80 % (range: ~ 50–90 %) since the period of peak eutrophication in the 1970s, TOC burial and accumulation rates have only decreased significantly (~ 20 and 25 %) in two of the five lakes. Hereby we found no clear relationship between the magnitude of the decrease in P concentrations and the change in TOC burial and accumulation rate. Instead, artificial lake ventilation, which is used to prevent water column anoxia in eutrophic lakes, may help sustain high rates of TOC burial and accumulation in sediments despite strongly reduced water column P concentrations. Our results provide novel insights into how eutrophication and eutrophication management practices affect organic carbon burial and the distribution of microbial respiration reactions in temperate lakes. These insights are important to understanding how anthropogenic activities affect the size of the carbon pool that is stored globally in lacustrine sediments.

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