Yoshinori Iizuka

Global warming has intensified boreal forest fires, which significantly influence the climate through the emission of greenhouse gases and organic aerosols (OA). While water-soluble tracers are commonly used to reconstruct past fire events in ice cores, they can be susceptible to redistribution or degradation within the ice matrix. In this study, we performed single particle analysis of non-volatile microparticles in the SE-Dome II ice core from southeastern Greenland (1799–2020) using micro-Raman spectroscopy and Fourier-transform infrared spectroscopy (FT-IR). Here, we report the first identification of oleamide, an insoluble fatty acid amide, within an ice core. Oleamide is likely formed through the dehydration condensation of plant-derived oleic acid and ammonia under high-temperature (300–500 °C) conditions during forest fires. The detection frequency of oleamide particles was notably higher in layers corresponding to major North American forest fires, such as those in 1908, 1961, and 1994. Due to its insolubility and chemical stability, oleamide serves as a robust tracer that ensures stable long-range transport and long-term preservation in ice sheets. Additionally, cooling experiments revealed that oleamide possesses low ice-nucleating ability, likely due to the formation of expanded-phase monolayers. These results establish oleamide as a powerful new insoluble organic marker for reconstructing Arctic wildfire history and understanding historical fire-climate interactions.

Global warming has intensified boreal forest fires, which significantly influence the climate through the emission of greenhouse gases and organic aerosols (OA). While water-soluble tracers are commonly used to reconstruct past fire events in ice cores, they can be susceptible to redistribution or degradation within the ice matrix. In this study, we performed single particle analysis of non-volatile microparticles in the SE-Dome II ice core from southeastern Greenland (1799–2020) using micro-Raman spectroscopy and Fourier-transform infrared spectroscopy (FT-IR). Here, we report the first identification of oleamide, an insoluble fatty acid amide, within an ice core. Oleamide is likely formed through the dehydration condensation of plant-derived oleic acid and ammonia under high-temperature (300–500 °C) conditions during forest fires. The detection frequency of oleamide particles was notably higher in layers corresponding to major North American forest fires, such as those in 1908, 1961, and 1994. Due to its insolubility and chemical stability, oleamide serves as a robust tracer that ensures stable long-range transport and long-term preservation in ice sheets. Additionally, cooling experiments revealed that oleamide possesses low ice-nucleating ability, likely due to the formation of expanded-phase monolayers. These results establish oleamide as a powerful new insoluble organic marker for reconstructing Arctic wildfire history and understanding historical fire-climate interactions.

Global warming has intensified boreal forest fires, which significantly influence the climate through the emission of greenhouse gases and organic aerosols (OA). While water-soluble tracers are commonly used to reconstruct past fire events in ice cores, they can be susceptible to redistribution or degradation within the ice matrix. In this study, we performed single particle analysis of non-volatile microparticles in the SE-Dome II ice core from southeastern Greenland (1799–2020) using micro-Raman spectroscopy and Fourier-transform infrared spectroscopy (FT-IR). Here, we report the first identification of oleamide, an insoluble fatty acid amide, within an ice core. Oleamide is likely formed through the dehydration condensation of plant-derived oleic acid and ammonia under high-temperature (300–500 °C) conditions during forest fires. The detection frequency of oleamide particles was notably higher in layers corresponding to major North American forest fires, such as those in 1908, 1961, and 1994. Due to its insolubility and chemical stability, oleamide serves as a robust tracer that ensures stable long-range transport and long-term preservation in ice sheets. Additionally, cooling experiments revealed that oleamide possesses low ice-nucleating ability, likely due to the formation of expanded-phase monolayers. These results establish oleamide as a powerful new insoluble organic marker for reconstructing Arctic wildfire history and understanding historical fire-climate interactions.

Precise age scales are essential for reconstructing past climate variability at high temporal resolution. Here, we present a new oxygen-isotope record for the SE-Dome II ice core from southeast Greenland and construct a multi-month-resolution age scale spanning 1871–2020 CE. The chronology, named SE2025iso, was developed by aligning oxygen-isotope variations in the ice core with isotope-enabled climate-model simulations. High snow accumulation at the SE-Dome site preserved multi-month variations of oxygen isotopes, allowing age determination beyond seasonal extremes. Although absolute validation at the monthly scale is challenging, the chronology has an estimated mean uncertainty of 2.0 months and is supported by multiple consistency evaluations, including melt and tritium horizons, seasonal accumulation comparisons, and also volcanic reference layers. The reconstructed snow accumulation rates correlate well with climate reanalysis data, except in summer. The reconstructed accumulation record shows that the weak seasonality at SE-Dome persisted throughout the past 150 years. This persistence suggests that the balance near the boundary between summer- and winter-dominated accumulation regimes across Greenland remained broadly stable despite recent Arctic warming. Applying the SE2025iso age scale to chemical records shows that hydrogen peroxide concentrations peak approximately 2–3 weeks after the summer solstice and that volcanic sulfate records exhibit reproducible post-eruption peaks at multi-month resolution. Overall, the SE2025iso chronology highlights the potential of high-accumulation ice-core sites for investigating multi-month-scale climate variability and aerosol deposition processes.

Precise age scales are essential for reconstructing past climate variability at high temporal resolution. Here, we present a new oxygen-isotope record for the SE-Dome II ice core from southeast Greenland and construct a multi-month-resolution age scale spanning 1871–2020 CE. The chronology, named SE2025iso, was developed by aligning oxygen-isotope variations in the ice core with isotope-enabled climate-model simulations. High snow accumulation at the SE-Dome site preserved multi-month variations of oxygen isotopes, allowing age determination beyond seasonal extremes. Although absolute validation at the monthly scale is challenging, the chronology has an estimated mean uncertainty of 2.0 months and is supported by multiple consistency evaluations, including melt and tritium horizons, seasonal accumulation comparisons, and also volcanic reference layers. The reconstructed snow accumulation rates correlate well with climate reanalysis data, except in summer. The reconstructed accumulation record shows that the weak seasonality at SE-Dome persisted throughout the past 150 years. This persistence suggests that the balance near the boundary between summer- and winter-dominated accumulation regimes across Greenland remained broadly stable despite recent Arctic warming. Applying the SE2025iso age scale to chemical records shows that hydrogen peroxide concentrations peak approximately 2–3 weeks after the summer solstice and that volcanic sulfate records exhibit reproducible post-eruption peaks at multi-month resolution. Overall, the SE2025iso chronology highlights the potential of high-accumulation ice-core sites for investigating multi-month-scale climate variability and aerosol deposition processes.

Global warming has intensified boreal forest fires, which significantly influence the climate through the emission of greenhouse gases and organic aerosols (OA). While water-soluble tracers are commonly used to reconstruct past fire events in ice cores, they can be susceptible to redistribution or degradation within the ice matrix. In this study, we performed single particle analysis of non-volatile microparticles in the SE-Dome II ice core from southeastern Greenland (1799–2020) using micro-Raman spectroscopy and Fourier-transform infrared spectroscopy (FT-IR). Here, we report the first identification of oleamide, an insoluble fatty acid amide, within an ice core. Oleamide is likely formed through the dehydration condensation of plant-derived oleic acid and ammonia under high-temperature (300–500 °C) conditions during forest fires. The detection frequency of oleamide particles was notably higher in layers corresponding to major North American forest fires, such as those in 1908, 1961, and 1994. Due to its insolubility and chemical stability, oleamide serves as a robust tracer that ensures stable long-range transport and long-term preservation in ice sheets. Additionally, cooling experiments revealed that oleamide possesses low ice-nucleating ability, likely due to the formation of expanded-phase monolayers. These results establish oleamide as a powerful new insoluble organic marker for reconstructing Arctic wildfire history and understanding historical fire-climate interactions.

Global warming has intensified boreal forest fires, which significantly influence the climate through the emission of greenhouse gases and organic aerosols (OA). While water-soluble tracers are commonly used to reconstruct past fire events in ice cores, they can be susceptible to redistribution or degradation within the ice matrix. In this study, we performed single particle analysis of non-volatile microparticles in the SE-Dome II ice core from southeastern Greenland (1799–2020) using micro-Raman spectroscopy and Fourier-transform infrared spectroscopy (FT-IR). Here, we report the first identification of oleamide, an insoluble fatty acid amide, within an ice core. Oleamide is likely formed through the dehydration condensation of plant-derived oleic acid and ammonia under high-temperature (300–500 °C) conditions during forest fires. The detection frequency of oleamide particles was notably higher in layers corresponding to major North American forest fires, such as those in 1908, 1961, and 1994. Due to its insolubility and chemical stability, oleamide serves as a robust tracer that ensures stable long-range transport and long-term preservation in ice sheets. Additionally, cooling experiments revealed that oleamide possesses low ice-nucleating ability, likely due to the formation of expanded-phase monolayers. These results establish oleamide as a powerful new insoluble organic marker for reconstructing Arctic wildfire history and understanding historical fire-climate interactions.

Global warming has intensified boreal forest fires, which significantly influence the climate through the emission of greenhouse gases and organic aerosols (OA). While water-soluble tracers are commonly used to reconstruct past fire events in ice cores, they can be susceptible to redistribution or degradation within the ice matrix. In this study, we performed single particle analysis of non-volatile microparticles in the SE-Dome II ice core from southeastern Greenland (1799–2020) using micro-Raman spectroscopy and Fourier-transform infrared spectroscopy (FT-IR). Here, we report the first identification of oleamide, an insoluble fatty acid amide, within an ice core. Oleamide is likely formed through the dehydration condensation of plant-derived oleic acid and ammonia under high-temperature (300–500 °C) conditions during forest fires. The detection frequency of oleamide particles was notably higher in layers corresponding to major North American forest fires, such as those in 1908, 1961, and 1994. Due to its insolubility and chemical stability, oleamide serves as a robust tracer that ensures stable long-range transport and long-term preservation in ice sheets. Additionally, cooling experiments revealed that oleamide possesses low ice-nucleating ability, likely due to the formation of expanded-phase monolayers. These results establish oleamide as a powerful new insoluble organic marker for reconstructing Arctic wildfire history and understanding historical fire-climate interactions.

Precise age scales are essential for reconstructing past climate variability at high temporal resolution. Here, we present a new oxygen-isotope record for the SE-Dome II ice core from southeast Greenland and construct a multi-month-resolution age scale spanning 1871–2020 CE. The chronology, named SE2025iso, was developed by aligning oxygen-isotope variations in the ice core with isotope-enabled climate-model simulations. High snow accumulation at the SE-Dome site preserved multi-month variations of oxygen isotopes, allowing age determination beyond seasonal extremes. Although absolute validation at the monthly scale is challenging, the chronology has an estimated mean uncertainty of 2.0 months and is supported by multiple consistency evaluations, including melt and tritium horizons, seasonal accumulation comparisons, and also volcanic reference layers. The reconstructed snow accumulation rates correlate well with climate reanalysis data, except in summer. The reconstructed accumulation record shows that the weak seasonality at SE-Dome persisted throughout the past 150 years. This persistence suggests that the balance near the boundary between summer- and winter-dominated accumulation regimes across Greenland remained broadly stable despite recent Arctic warming. Applying the SE2025iso age scale to chemical records shows that hydrogen peroxide concentrations peak approximately 2–3 weeks after the summer solstice and that volcanic sulfate records exhibit reproducible post-eruption peaks at multi-month resolution. Overall, the SE2025iso chronology highlights the potential of high-accumulation ice-core sites for investigating multi-month-scale climate variability and aerosol deposition processes.