Timothy Ian Eglinton


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Eglinton

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Timothy Ian

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0000-0001-5060-2155

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Publications 1 - 10 of 62
  • Prominent bacterial heterotrophy and sources of 13C-depleted fatty acids to the interior Canada Basin
    Item type: Journal Article
    Shah, Sunita R.; Griffith, David R.; Galy, Valier V.; et al. (2013)
    Biogeosciences
    In recent decades, the Canada Basin of the Arctic Ocean has experienced rapidly decreasing summer sea ice coverage and freshening of surface waters. It is unclear how these changes translate to deeper waters, particularly as our baseline understanding of organic carbon cycling in the deep basin is quite limited. In this study, we describe full-depth profiles of the abundance, distribution and carbon isotopic composition of fatty acids from suspended particulate matter at a seasonally ice-free station and a semi-permanently ice-covered station. Fatty acids, along with suspended particulate organic carbon (POC), are more concentrated and 13C-enriched under ice cover than in ice-free waters. But this influence, apparent at 50 m depth, does not propagate downward below 150 m depth, likely due to the weak biological pump in the central Canada Basin. Branched fatty acids have δ13C values that are similar to suspended POC at all depths and are more 13C-enriched than even-numbered saturated fatty acids at depths above 3000 m. These are likely to be produced in situ by heterotrophic bacteria incorporating organic carbon that is isotopically similar to total suspended POC. Below surface waters, there is also the suggestion of a source of saturated even-numbered fatty acids which could represent contributions from laterally advected organic carbon and/or from chemoautotrophic bacteria. At 3000 m depth and below, a greater relative abundance of long-chain (C20–24), branched and unsaturated fatty acids is consistent with a stronger influence of re-suspended sedimentary organic carbon. At these deep depths, two individual fatty acids (C12 and iso-C17) are significantly depleted in 13C, allowing for the possibility that methane oxidizing bacteria contribute fatty acids, either directly to suspended particulate matter or to shallow sediments that are subsequently mobilized and incorporated into suspended particulate matter within the deep basin.
  • Thermal stability of ancient organic matter released from Arctic thaw slumps
    Item type: Other Conference Item
    Bolandini, Marco Andrea; Bröder, Lisa; Haghipour, Negar; et al. (2025)
    Abstract Volume 23rd Swiss Geoscience Meeting
  • Rising dissolved inorganic carbon in Alpine rivers evidence enhanced soil respiration driven by climatic warming over the past decades
    Item type: Other Conference Item
    Hagedorn, Frank; Rhyner, Timo; Storck, Florian; et al. (2025)
    EGUsphere
    Anthropogenically-induced climate change is rapidly altering Earth’s carbon cycles. However, information on long-term and large-scale responses of soil respiration—a key process releasing CO₂—remains limited. Soil CO₂ production, driven by rhizosphere and microbial respiratory activity, is inherently temperature sensitive. Yet, thermal adaptation, substrate depletion and other constraints such as drought may dampen responses to climate warming. Assessing soil respiration at broader temporal and spatial scales is hampered by its high variability and the labor-intensive nature of CO₂ flux measurements. Consequently, evidence for longer-term enhancement of soil respiration in response to ongoing climatic warming remains scarce. Here, we analyze 50-year long records of dissolved inorganic carbon (DIC) from Swiss rivers draining Alpine catchments to infer long-term and large-scale responses of soil CO₂ production. Riverine DIC flux originates from CO₂ dissolved in water, with approximately half derived from belowground respiratory activity and the remainder released through weathering processes. Our radiocarbon and stable isotope analyses confirm these sources in Swiss rivers. Long-term records from the Swiss national river surveillance program reveal that average DIC concentrations in rivers draining the Swiss Alps (Rhine, Inn, Ticino) have increased by 1.6% per decade since the 1980s. This decadal-scale rise in DIC concentrations correlated significantly with the increase in water temperatures by approximately 1.3°C in this period. The DIC increase is not linked to multi-annual variations in river discharge, which drive interannual variability. Analyzing the relationship between discharge and DIC concentrations shows that, for a given discharge, DIC concentrations in the Rhine, Inn, and Ticino have increased in recent decades compared to levels observed in the 1980s and 1990s. Export of DIC by Swiss rivers only accounts for approximately 2% of the CO2 released from Swiss ecosystems. Nevertheless, the decadal-scale increase in DIC indicates that CO2 production in the soil must have increased. The DIC increase occurred despite a decreasing CO₂ solubility with rising water temperatures. Linking the observed DIC increase to the warming of 0.35°C per decade yields a temperature dependency (Q₁₀) of 2.2. This aligns with values from annual monitoring efforts and short-term soil warming studies across Swiss ecosystems, ranging between 2.3 and 5.3. Our finding indicates a sustained, large-scale stimulation of soil respiration in Alpine environments driven by climate warming, with little thermal adaptation over decadal timescales.
  • Omission of organic layers in soil organic carbon models results in overestimation of carbon turnover rates: a 14C study of temperate and alpine forest soils
    Item type: Other Conference Item
    Brunmayr, Alexander Sohrab; Moreno Duborgel, Margaux; Minich, Luisa; et al. (2025)
    EGUsphere
    Soil organic carbon (SOC) is the largest terrestrial reservoir in the active carbon cycle, and it is predicted to be a crucial component of the terrestrial carbon sink in the present day and in future climate scenarios. However, commonly used SOC models have been shown to inadequately represent SOC turnover, as evidenced by their consistent overestimation of the radiocarbon (14C) content in forest soils. This implies that models have too fast turnover rates and do not accurately capture the persistence of carbon in the different soil pools. To reconcile observational data and modeling frameworks, we conduct a detailed 14C-based study of the SOC dynamics across climatic and environmental gradients in 54 forest sites in Switzerland. At each site, we gather 14C data for the organic layers and five chemical and density fractions in the mineral soil. Calibrating a novel SOC model with these layer- and fraction-specific 14C data reveals an improved representation of turnover times and environmental dependencies, contrasting with existing models. In particular, we find that, by ignoring organic carbon respiration in the organic layers, most existing soil models have to effectively increase the turnover rates of SOC to compensate for the strongly overestimated carbon inputs into the mineral soil. Our results have the potential to significantly improve the representation of SOC in models, particularly under climate and environmental change.
  • Radiocarbon signatures of dissolved black carbon in the early winter Beaufort Sea
    Item type: Conference Poster
    Speidel, Linn; Haghipour, Negar; Blattmann, Thomas; et al. (2024)
  • Thermal dissection and radiocarbon analysis of organic matter released from permafrost thaw slumps using online ramped oxidation-accelerator mass spectrometry (ORO-AMS).
    Item type: Conference Poster
    Bolandini, Marco Andrea; Haghipour, Negar; De Maria, Daniele; et al. (2024)
    The rapid warming of the Arctic is progressively thawing once-permanently frozen ground, known as permafrost. The destabilization of permafrost soils has far-reaching consequences, notably affecting drainage patterns, and subsequently inducing changes in downstream ecosystems. Furthermore, the soils of the permafrost region store nearly twice the amount of carbon currently present in the atmosphere. This extensive frozen reservoir of organic matter (OM) has been preserved for millennia. Upon thaw, microbial decomposition of OM held in permafrost soils can release greenhouse gases (GHGs) like carbon dioxide (CO2) and methane (CH4), thereby creating a positive feedback loop and exacerbating climate change. Retrogressive thaw slumps (RTS) are a striking example of landscape change and potential source of GHG emissions due to permafrost thaw. RTS result from thaw-driven erosion and are landslides expanding backwards as they thaw, creating large, teardrop-shaped scars on the landscape. Since the early 2000s, the Peel Plateau in the Northwest Territories, Canada, has experienced a significant increase in RTS activity. Large-scale mobilization of permafrost layers formed during the Pleistocene and the early Holocene, contributes to runoff with elevated amounts of old yet potentially labile OM. The reactivity of OM (and hence its susceptibility to conversion into GHGs) may be influenced by its chemical nature and physical environment (e.g. mineral protection), rendering it important to constrain these properties. Radiocarbon (14C) is a useful tool for tracing the sources and fate of organic matter, particularly in Arctic regions where the antiquity of permafrost carbon imparts a distinct signal. However, interpreting conventional bulk-level radiocarbon data is challenging due to the diverse components comprising OM. One approach to overcome this limitation involves serial oxidation of OM to CO2 at increasing temperatures, reflecting a gradient of thermal stability. Higher thermal stability is thought to also indicate greater resistance to microbial decomposition. This CO2, collected over specific temperature ranges (i.e., thermal fractions) is then analysed for its 14C content. This principle is here applied in an online ramped oxidation (ORO) setup, which is directly coupled via a double trap interface (DTI) to an accelerator mass spectrometry (AMS) system. This setup is utilized for analyzing samples collected from RTS features on the Peel Plateau, including the seasonally thawed active layer, Holocene and Pleistocene permafrost layers, recently thawed debris and exported particulate material. Earlier studies on the Peel Plateau's two largest RTS features revealed a mineral matrix primarily composed of silt, clay, and sand. Permafrost layer samples, runoff, and debris showed uniform grain size and carbon content, ranging from 1.2% to 1.5%, with F14C values ranging from 0.1530 to 0.0240, corresponding to the Holocene and Pleistocene Epochs (Bröder et al., 2021). In contrast, active layer samples exhibited higher carbon content, up to 16%, with F14C values ranging from 0.2912 to 0.7153, reflecting conventional 14C ages between approximately 10,000 and 2,600 years. Preliminary ORO analysis revealed comparable thermograms (CO2 concentration ppm vs temperature, °C) for permafrost samples, runoff, and debris and suggest a predominance of more resistant (recalcitrant) OM, in line with Bröder et al. (2021). In contrast, the active layer samples exhibited a thermal profile suggesting larger proportions of labile OM consistent with higher 14C (more modern organic carbon) content. Similarities in bulk F14C values and thermograms between debris and runoff suggest they primarily originate from the permafrost layers rather than the active layer, implying that some of the recalcitrant, permafrost OM could potentially persist during fluvial transport and export to the ocean. As part of this presentation, we will further examine the variability of F14C within the samples and the chemical fingerprinting of the distinct CO2 features observed in the thermograms.
  • Towards an online ramped oxidation approach for thermal dissection and serial radiocarbon measurement of complex organic matter
    Item type: Conference Poster
    Bolandini, Marco Andrea; De Maria, Daniele; Haghipour, Negar; et al. (2024)
    Radiocarbon (14C) measurements provide a powerful tool to deconvolute sources and dynamics of organic matter in the environment. However, interpretation of conventional bulk-level 14C data is challenging due to the myriad components comprising organic matter in soils and sediments. Thermally ramped oxidation provides one approach for overcoming this limitation, and involves subjecting a sample to gradually increasing temperatures, serially oxidizing the OC to CO2. Collected over prescribed temperature ranges (' thermal fractions'), this CO2 is then analyzed for 14C content using accelerator mass spectrometry (AMS). While effective, current ramped oxidation methods are mostly 'offline', involving manual collection and subsequent AMS analysis of evolved CO2, hindering sample throughput and reproducibility. Here, we introduce a compact, online ramped oxidation (ORO) setup in which CO2 from discrete thermal fractions is directly collected and measured for 14C by AMS equipped with a gas ion source. The setup comprises two modules: (i) an ORO unit with two sequential furnaces - the first, ramped from room temperature to 900 °C, holds the sample; the second, maintained at 900 °C, includes a catalyst ensuring complete oxidation to CO2; and (ii) a dual-trap interface (DTI) collection unit with two parallel molecular sieve traps alternately collecting and releasing CO2 from a given fraction for direct injection into the AMS. Preliminary results indicate reproducible data, evident in both thermograms and F14C results. Analysis of natural reference samples reveals that measured 14C values and their associated uncertainties align with those reported in the literature using conventional “off-line” ramped oxidation methods, affirming the utility of the new ORO-DTI-AMS setup. Our goal is to apply this new method for comprehensive investigation of a range of natural samples, with a particular focus on the improved understanding of the fate of OC held in permafrost soils in the context of on-going climate and carbon cycle change in high latitude ecosystems.
  • Organic matter dynamics in thaw slumps: insights from online ramped oxidation-14C analysis
    Item type: Other Conference Item
    Bolandini, Marco Andrea; De Maria, Daniele; Haghipour, Negar; et al. (2024)
    Understanding the origins and cycling of organic matter (OM) in the environment is crucial for tackling issues such as climate change and soil degradation. Permafrost soils in arctic regions are garnering particular attention due to their large carbon stocks and potential vulnerability to ongoing warming and hydrological changes. Radiocarbon (14C) is a powerful tool to understand carbon sources and dynamics, however, traditional bulk 14C analysis offers limited insights due to the complex composition of OM in soils and sediments. Thermally ramped oxidation, which segregates OM based on its decomposition under gradually increasing temperatures (thermal fractions) and 14C analysis of evolved CO2 by accelerator mass spectrometry (AMS), provides a means to overcome this limitation. Here, we present preliminary results from the application of a recently developed compact, online ramped oxidation (ORO) system to permafrost soils from the Canadian arctic. The ORO system allows for the direct collection and 14C measurement of CO2 from discrete thermal fractions using an AMS system equipped with a gas ion source. In this proof-of-concept study, we focused on Retrogressive Thaw Slumps (RTS) on the Peel Plateau, Canada. We examined different samples including those from the seasonally thawed active layer, Holocene and Pleistocene permafrost layers, recently thawed debris, and exported particulate material (runoff). In this presentation, we will elaborate on the technical specifications of the ORO unit coupled with a low-energy AMS (LEA), and present initial results obtained from the analysis of RTS in this rapidly changing permafrost region of the Canadian arctic.
  • Temporal variations of sinking particulate organic radiocarbon in the deep Sargasso Sea
    Item type: Other Conference Item
    Schnepper, Charlotte; Pedrosa-Pamies, Rut; Conte, Maureen; et al. (2024)
    EGUsphere
    The imprint of bomb radiocarbon on sinking particulate organic carbon (PO¹⁴C) intercepted by sediment traps, together with flux and elemental data, provides information about the origin and dynamics of oceanic particles (Hwang et al., 2010). Of particular interest is the question of the degree to which sinking POC in the deep ocean stems from overlying primary production, i.e., vertical supply via the biological pump, versus other processes such as advection and subsequent aggregation of resuspended sedimentary carbon originating from continental margins and other distal sources (Conte et al., 2019). In this context, natural abundance variations in 14C serves as a useful tracer given contrasting signatures recently fixed and pre-aged carbon sources. To quantify the seasonal to inter-annual variability in sinking PO¹⁴C, we have analyzed sediment trap samples from the Oceanic Flux Program (OFP) in the Sargasso Sea, a deep ocean time-series which has examined the particle flux and its composition at 500, 1500 and 3200 m water depths since 1978. Radiocarbon measurements of POC of all OFP samples spanning September 2012 to December 2015 reveal seasonal and subseasonal variations in sinking PO¹⁴C with an amplitude in Δ¹⁴C values of ca. 100 ‰. This variability in Δ¹⁴C values is inversely linearly correlated with the proportion of lithogenic material to POC (LM:POC; r2=4.2, p <0.01). This relationship suggests that POC with high Δ¹⁴C values and a low LM:POC ratio reflect the supply of particles that sink vertically via the biological pump. Conversely, lower Δ¹⁴C values and high LM:POC ratios indicate laterally transported materials originating from resuspended sediments containing pre-aged organic carbon. Significant deviations from the linear regression (p <0.01) correlate with δ13C values, indicating an increased state of POC remineralization that is independent of Δ¹⁴C variations attributable to particle provenance. Over the 3.3 year period of observation, POΔ¹⁴C decreased by ca. 26 %, exceeding the expected annual decline (~6 ‰) based on reconstructed surface DI14C. This decline potentially could be linked to different source(s) of laterally supplied aged organic carbon associated with lithogenic material and/or a shift in the POΔ¹⁴C of the overlying flux (e.g. from reduction in particle sinking speeds, enhanced decomposition, increased incorporation of aged suspended particles and/or dissolved organic carbon into the sinking flux). On-going work extending the OFP time-series will examine these multiyear trends and assess potential variability in the balance between vertically exported and laterally supplied POC to the deep ocean flux in the deep Sargasso Sea, enabling a better understanding of the underlying processes which control POC dynamics.
  • Mineral surface area of sinking particles in the deep ocean interior: Preliminary implications
    Item type: Other Journal Item
    Kim, Minkyoung; Blattmann, Thomas; Lin, Baozhi; et al. (2025)
    Limnology and Oceanography Letters
    Measurement of the mineral surface area (MSA) of sedimentary particles is a traditional approach for studying the transport and protection of organic carbon (OC) in marine systems. We investigated the application of MSA on the biological carbon pump in the deep ocean interior in the Ulleung Basin (UB), East/Japan Sea. This is the second study of sinking particle MSA, and the first in an ocean with no major riverine (terrestrial) input. We measured seasonal and vertical variations in the MSA of sinking particles and adjacent surface sediments in the UB. Mineral surface area values exhibit seasonal variations associated with particle composition, with a negative correlation with OC content and a strong positive correlation with the content of lithogenic material and the radiocarbon values of sinking OC. Our results indicate that the MSA of sinking particles may provide clues to the processes of particle resuspension and decomposition.
Publications 1 - 10 of 62