3:30 PM - 3:45 PM
[ACC26-07] Impacts of large scale atmospheric circulation on water isotopes of daily precipitation at Dome Fuji Station: A study with an isotope-enabled AGCM MIROC5-iso
Keywords:climate model, water isotopes, ice cores, paleo proxies, Antarctica
Thanks to water isotope records in polar ice cores, it has been possible to study past Earth’s climate variations at different time scales. However, the different contributions at regional and global scales determining the isotopic signal in these ice cores are still unclear. The observations at Dome Fuji Station, inland East Antarctica, and further analyses of weather situations have investigated the relationship between δ18O of daily precipitation (δ18Op) and the synoptic precipitation events, which are mostly accompanied by increased temperature [1,2], whereas the climatic understanding is not established.
One way to progress our understanding of the question is to make direct comparisons of isotopic data with simulation results from isotope-enabled General Circulation Models (GCMs). We here used such a model, the Japanese atmospheric GCM MIROC5-iso [3], and conducted a simulation with the horizontal winds nudged to the JRA-25 reanalysis [4] for 1981-2010. The simulation nicely reproduces the observed δ18Op at Dome Fuji, as well as the synoptic precipitation events.
We reveal that the large-scale atmospheric circulation variations, specifically related to the Southern Annular Mode, significantly affect the δ18Op at Dome Fuji during cold seasons (austral autumn, winter, and spring). This is because the advection of the warm air largely changes the local temperature and δ18Op, supporting previous studies [1]. However, in the austral summer, the contribution of the precipitation amounts relatively large for the variability of δ18Op, while temperature rise affects only a little the δ18Op signal.
Our result suggests the water isotopes in the ice cores do not capture the whole variations of local temperature, and precipitation events contribute to a warm bias in the cold seasons. Interpretation for past climate situations (e.g. Last Glacial Maximum) will be further investigated.
[1] Fujita and Abe, Geophys. Res. Lett., 33, L18503, 2006.
[2] Dittman et al., Atmos. Chem. Phys., 16, 6883-6900, 2016.
[3] Okazaki and Yoshimura, J. Geophys. Res. Atmos, 124, 8972–8993, 2019.
[4] Onogi et al., J. Meteor. Soc. Japan, 85(3), 369-432, 2007.
One way to progress our understanding of the question is to make direct comparisons of isotopic data with simulation results from isotope-enabled General Circulation Models (GCMs). We here used such a model, the Japanese atmospheric GCM MIROC5-iso [3], and conducted a simulation with the horizontal winds nudged to the JRA-25 reanalysis [4] for 1981-2010. The simulation nicely reproduces the observed δ18Op at Dome Fuji, as well as the synoptic precipitation events.
We reveal that the large-scale atmospheric circulation variations, specifically related to the Southern Annular Mode, significantly affect the δ18Op at Dome Fuji during cold seasons (austral autumn, winter, and spring). This is because the advection of the warm air largely changes the local temperature and δ18Op, supporting previous studies [1]. However, in the austral summer, the contribution of the precipitation amounts relatively large for the variability of δ18Op, while temperature rise affects only a little the δ18Op signal.
Our result suggests the water isotopes in the ice cores do not capture the whole variations of local temperature, and precipitation events contribute to a warm bias in the cold seasons. Interpretation for past climate situations (e.g. Last Glacial Maximum) will be further investigated.
[1] Fujita and Abe, Geophys. Res. Lett., 33, L18503, 2006.
[2] Dittman et al., Atmos. Chem. Phys., 16, 6883-6900, 2016.
[3] Okazaki and Yoshimura, J. Geophys. Res. Atmos, 124, 8972–8993, 2019.
[4] Onogi et al., J. Meteor. Soc. Japan, 85(3), 369-432, 2007.