Suchergebnisse

Selver, Ayça Doğrul (Balikesir Author) ; Warming-induced erosion of permafrost from Eastern Siberia mobilises large amounts of organic carbon and delivers it to the East Siberian Arctic Shelf (ESAS). In this study Raman spectroscopy of carbonaceous material (CM) was used to characterise, identify and track the most recalcitrant fraction of the organic load: 1463 spectra were obtained from surface sediments collected across the ESAS and automatically analysed for their Raman peaks. Spectra were classified by their peak areas and widths into disordered, intermediate, mildly graphitised and highly graphitised groups and the distribution of these classes was investigated across the shelf. Disordered CM was most prevalent in a permafrost core from Kurungnakh Island and from areas known to have high rates of coastal erosion. Sediments from outflows of the Indigirka and Kolyma rivers were generally enriched in intermediate CM. These different sediment sources were identified and distinguished along an E-W transect using their Raman spectra, showing that sediment is not homogenised on the ESAS. Distal samples, from the ESAS slope, contained greater amounts of highly graphitised CM compared to the rest of the shelf, attributable to degradation or, more likely, winnowing processes offshore. The presence of all four spectral classes in distal sediments demonstrates that CM degrades much more slowly than lipid biomarkers and other traditional tracers of terrestrial organic matter and shows that alongside degradation of the more labile organic matter component there is also conservative transport of carbon across the shelf toward the deep ocean. Thus, carbon cycle calculations must consider the nature as well as the amount of carbon liberated from thawing permafrost and other erosional settings. ; NERC - NE/I024798/1 - NE/P006221/1 MMU studentship MMU-EERC research grant Swedish Research Council (VR) 621-2007-4631 621-2013-5297 621-2004-4039 Swedish Research Council (VR) (Distinguished Professors Grant) 2017-01601 European Research Council (ERC-AdG CC-TOP project) 695331 Government of the Russian Federation 14.Z50.31.0012 Knut and Alice Wallenberg Foundation Far Eastern Branch of the Russian Academy of Sciences US National Oceanic and Atmospheric Administration (OAR Climate Program Office) NA08OAR4600758 Russian Foundation of Basic Research 08-05-13572 08-05-00191-a 07-05-00050a Swedish Polar Research Secretariat Nordic Council of Ministers US National Science Foundation OPP ARC 0909546

Selver, Ayça Doğrul (Balikesir Author) ; The Siberian Arctic contains a globally significant pool of organic carbon (OC) vulnerable to enhanced warming and subsequent release by both fluvial and coastal erosion processes. However, the rate of release, its behaviour in the Arctic Ocean and vulnerability to remineralisation is poorly understood. Here we combine new measurements of microbial biohopanoids including adenosylhopane, a lipid associated with soil microbial communities, with published glycerol dialkyl glycerol tetraethers (GDGTs) and bulk delta C-13 measurements to improve knowledge of the fate of OC transported to the East Siberian Arctic Shelf (ESAS). The microbial hopanoid-based soil OC proxy R'(soil) ranges from 0.0 to 0.8 across the ESAS, with highest values nearshore and decreases offshore. Across the shelf R'(soil) displays a negative linear correlation with bulk delta C-13 measurements (r(2) = -0.73, p = < 0 : 001). When compared to the GDGT-based OC proxy, the branched and isoprenoid tetraether (BIT) index, a decoupled (non-linear) behaviour on the shelf was observed, particularly in the Buor-Khaya Bay, where the R'(soil) shows limited variation, whereas the BIT index shows a rapid decline moving away from the Lena River outflow channels. This reflects a balance between delivery and removal of OC from different sources. The good correlation between the hopanoid and bulk terrestrial signal suggests a broad range of hopanoid sources, both fluvial and via coastal erosion, whilst GDGTs appear to be primarily sourced via fluvial transport. Analysis of ice complex deposits (ICDs) revealed an average R'(soil) of 0.5 for the Lena Delta, equivalent to that of the Buor-Khaya Bay sediments, whilst ICDs from further east showed higher values (0.6-0.85). Although R'(soil) correlates more closely with bulk OC than the BIT, our understanding of the endmembers of this system is clearly still incomplete, with variations between the different East Siberian Arctic regions potentially reflecting differences in environmental conditions (e.g. temperature, pH), but other physiological controls on microbial bacteriohopanepolyol (BHP) production under psychrophilic conditions are as yet unknown. ; NERC Natural Environment Research Council NE/I024798/1 NE/I027967/1 Ministry of National Education - Turkey Swedish Royal Academy of Sciences through Knut and Alice Wallenberg Foundation Government of the Russian Federation 14 Z50.31.0012/03.19.2014 Russian Science Foundation (RSF) 15-17-20032 National Science Foundation (NSF) ANT-1203885/PLR-1500169 Knut & Alice Wallenberg Foundation Russian Academy of Sciences Swedish Research Council National Oceanic Atmospheric Admin (NOAA) - USA Russian Foundation for Basic Research (RFBR) Swedish Polar Research Secretariat Nordic Council of Ministers National Science Foundation (NSF) NERC Natural Environment Research Council NE/I024798/1 NE/I027967/1

Selver, Ayça Dogrul (Balikesir Author) ; Mobilisation of terrestrial organic carbon (terrOC) from permafrost environments in eastern Siberia has the potential to deliver significant amounts of carbon to the Arctic Ocean, via both fluvial and coastal erosion. Eroded terrOC can be degraded during offshore transport or deposited across the wide East Siberian Arctic Shelf (ESAS). Most studies of terrOC on the ESAS have concentrated on solvent-extractable organic matter, but this represents only a small proportion of the total terrOC load. In this study we have used pyrolysis-gas chromatography-mass spectrometry (py-GCMS) to study all major groups of macromolecular components of the terrOC; this is the first time that this technique has been applied to the ESAS. This has shown that there is a strong offshore trend from terrestrial phenols, aromatics and cyclopentenones to marine pyridines. There is good agreement between proportion phenols measured using py-GCMS and independent quantification of lignin phenol concentrations (r(2) = 0.67, p < 0.01, n = 24). Furfurals, thought to represent carbohydrates, show no offshore trend and are likely found in both marine and terrestrial organic matter. We have also collected new radiocarbon data for bulk OC (C-14(OC)) which, when coupled with previous measurements, allows us to produce the most comprehensive C-14(OC) map of the ESAS to date. Combining the C-14(OC) and py-GCMS data suggests that the aromatics group of compounds is likely sourced from old, aged terrOC, in contrast to the phenols group, which is likely sourced from modern woody material. We propose that an index of the relative proportions of phenols and pyridines can be used as a novel terrestrial vs. marine proxy measurement for macromolecular organic matter. Principal component analysis found that various terrestrial vs. marine proxies show different patterns across the ESAS, and it shows that multiple river-ocean transects of surface sediments transition from river-dominated to coastalerosion-dominated to marine-dominated signatures. ; NERC research grant - NE/I024798/1 NE/I027967/1 Ministry of National Education - Turkey Government of the Russian Federation - 14.Z50.31.0012 Knut & Alice Wallenberg Foundation Russian Academy of Sciences Swedish Research Council - 621-2004-4039 621-2007-4631 621-2013-5297 US National Oceanic and Atmospheric Administration (OAR Climate Program Office) - NA08OAR4600758 Russian Foundation for Basic Research (RFBR) - 08-05-13572 08-05-00191-a 07-05-00050a Swedish Polar Research Secretariat Nordic Council of Ministers National Science Foundation (NSF) - OPP ARC 0909546 NERC Natural Environment Research Council - NE/I024798/1 NE/I027967/1

'We have kicked the can down the road once again – but we are running out of road.' – Rachel Kyte, Dean of Fletcher School at Tufts University. We, in our capacities as scientists, economists, governance and policy specialists, are shifting from warnings to guidance for action before there is no more 'road.' The science is clear and irrefutable; humanity is in advanced ecological overshoot. Our over exploitation of resources exceeds ecosystems'capacity to provide them or to absorb our waste. Society has failed to meet clearly stated goals of the UN Framework Convention on Climate Change. Civilization faces an epochal crossroads, but with potentially much better, wiser outcomes if we act now. What are the concrete and transformative actions by which we can turn away from the abyss? In this paper we forcefully recommend priority actions and resource allocation to avert the worst of the climate and nature emergencies, two of the most pressing symptoms of overshoot, and lead society into a future of greater wellbeing and wisdom. Humanity has begun the social, economic, political and technological initiatives needed for this transformation. Now, massive upscaling and acceleration of these actions and collaborations are essential before irreversible tipping points are crossed in the coming decade. We still can overcome significant societal, political and economic barriers of our own making. Previously, we identified six core areas for urgent global action – energy, pollutants, nature, food systems, population stabilization and economic goals. Here we identify an indicative, systemic and time-limited framework for priority actions for policy, planning and management at multiple scales from household to global. We broadly follow the 'Reduce-Remove-Repair' approach to rapid action. To guide decision makers, planners, managers, and budgeters, we cite some of the many experiments, mechanisms and resources in order to facilitate rapid global adoption of effective solutions. Our biggest challenges are not technical, but social, economic, political and behavioral. To have hope of success, we must accelerate collaborative actions across scales, in different cultures and governance systems, while maintaining adequate social, economic and political stability. Effective and timely actions are still achievable on many, though not all fronts. Such change will mean the difference for billions of children and adults, hundreds of thousands of species, health of many ecosystems, and will determine our common future.