[A-CC29] Ice cores and paleoenvironmental modeling

[ACC29-01] Changes in concentration and size of black carbon particles at Dome Fuji, Antarctica across the Last Glacial Termination

*Kumiko Goto-Azuma^1,2, Nobuhiro Moteki³, Kaori Fukuda¹, Jun Ogata¹, Tatsuhiro Mori³, Sho Ohata⁴, Yutaka Kondo¹, Makoto Koike³, Motohiro Hirabayashi¹, Kyotaro Kitamura¹, Ayaka Yonekura², Shuji Fujita^1,2, Fumio Nakazawa^1,2, Yoshimi Ogawa¹, Kenji Kawamura^1,2 (1.National Institute of Polar Research, 2.SOKENDAI (The Graduate University for Advanced Studies), 3.The University of Tokyo, 4.Nagoya University, Japan)

Keywords:Dome Fuji, Antarctica, Last Glacial Termination, Black carbon

Black carbon (BC) can affect Earth’s radiation budget by absorbing sunlight and reducing the albedo of snow and ice surfaces (e.g. Bond et al., 2013). It can also affect cloud microphysics by acting as cloud condensation nuclei or ice nucleating particles (e.g. Bond et al., 2013). Furthermore, BC emitted from large wildfires can affect air quality and ecosystems. BC can thus affect climate and the environment. Climate changes can in turn change frequencies and magnitudes of wildfires and hence BC emissions. Despite numerous studies through observations and aerosol/climate models, we have only limited knowledge on the impacts of BC on radiative forcing, albedo reduction, and cloud microphysics. Our knowledge on the impacts of climate change on BC emissions is also limited. Ongoing global warming could impact wildfires. But predictions are hampered by limited long-term records of natural wildfires. Ice core BC data can provide us with excellent records of past natural wildfires.

We analyzed the second Dome Fuji deep ice core drilled in East Antarctica for the depth interval between 200 and 640 m, which corresponds to the Last Glacial Maximum (LGM) to mid-Holocene period. To obtain continuous high-resolution data, we used a Continuous Flow Analysis (CFA) system developed at the National Institute of Polar Research. The CFA system enabled us to obtain high-resolution data of BC, stable isotopes of water, microparticles and 8 elements (Na, K, Mg, Ca, Fe, Al, Si and S). For BC analysis, we used a recently developed Wide-range (WR) SP2 (Single Particle Soot Photometer), which can detect BC particles in a size range between 70 and 4000 nm (Mori et al., 2016). A combination of WR-SP2 and a high-efficiency nebulizer allowed us accurate measurements of BC concentrations and size distributions. Here we present the first BC record for the LGM to the mid-Holocene period in East Antarctica.

BC mass concentration was high at LGM, decreased over the Last Glacial Termination, and increased again during the early Holocene. We also find that the temporal trends in BC number concentrations are different for different size ranges. The average mass of BC particles was larger in LGM and decreased during the Last Glacial Termination. The temporal trend in BC mass concentration found in Dome Fuji core is different from that found in WAIS Divide ice core, which shows low BC concentrations at LGM and an increasing trend during the Last Glacial Termination. The difference could be due to spatial variability in Antarctica and/or different size ranges of BC measurements.

References
Bond, T. C. et al., Bounding the role of black carbon in the climate system: A scientific assessment, J. Geophys. Res. Atmos., 118, 5380– 5552, doi:10.1002/jgrd.50171., 2013.

Mori, T. et al., Improved technique for measuring the size distribution of black carbon particles in liquid water, Aerosol Science & Technology, 50, 3, 242-254, DOI: 10.1080/02786826.2016.1147644, 2016.