11:15 〜 11:30
[U03-08] Land carbon cycle and vegetation distributions in the preindustrial, mid-Holocene, and last interglacial conditions
★Invited Papers
キーワード：間氷期、植生
Investigation of past interglacials is expected to provide fundamental knowledge of feedback mechanisms that operate between the atmosphere, sea ice, and land surface under warmer climatic conditions (e.g. Otto-Bliesner et al., 2021). The climates of the mid-Holocene (6 ka; MH) and the Last Interglacial (LIG) are characterized by warmer and humid land climate conditions, which would be attributed to the different configurations of the astronomical forcing (Bracconot et al, 2007; 2012; Otto-Bliesner et al., 2017; 2021; Noda et al., 2016; Ohgaito and Abe-Ouchi, 2007; O’ishi and Abe-Ouchi, 2011; Chikira et al, 2022). Paleoclimate proxy indicates that the global mean temperature was ~0.7 and ~1.3 K higher than the preindustrial condition for the MH and LIG, respectively (Turney and Jones, 2010; Marcott et al., 2013; Fischer et al., 2018). The warming is especially enhanced over land areas, which implies the amplification by feedback mechanisms between atmosphere and sea ice over the Arctic Ocean and/or climate and vegetation feedback over land areas of the northern-hemisphere high latitudes (e.g. Otto-Bliesner et al., 2006; O’ishi et al., 2021). This would have also contributed to the warming over Greenland and Antarctica, and hence the sea-level rise of 6–9 m during the LIG (e.g. NEEM community members, 2013; Jouzel et al., 2007; Dutton et al., 2015). Although climate models reproduce the trend of the warming during the MH and LIG, the magnitudes of the amplified warmings over high latitudes have not been fully explained (e.g., Masson-Delmotte et al., 2013). Therefore, high latitude processes over land and ocean would be critical for a further understanding of the climate warming during the past interglacials. In this presentation, we first review the recent advancement in the understanding of the MH and the LIG climates. We further show the response of the land carbon cycle and vegetation distribution for the preindustrial, MH, and LIG conditions using the dynamical vegetation model MRI-LPJ (Watanabe et al., in prep.), which is developed based on the vegetation model included in LPJ-LMfire model (Pfeiffer et al., 2013). We drive our model using the meteorological forcings for the preindustrial, MH, and LIG conditions, which is calculated using the MRI-ESM 2.0 (Yukimoto et al., 2019) following the PMIP4 protocol (Otto-Bliesner et al., 2017). We further compare the results with the MH and LIG simulations conducted using the MIROC4m-LPJ, which couples an atmosphere general circulation model and a dynamical global vegetation model (O’ishi and Abe-Ouchi, 2009; O’ishi et al., 2021).
We show that the boundary for the boreal forest and tundra regions shifts northward during the MH and LIG conditions simulated by MRI-LPJ model owing to the different astronomical forcing and the associated climate changes, which is consistent with the previous studies (O’ishi and Abe-Ouchi, 2009; Tabor et al., 2014). We also show the forest at mid-latitudes of North America and Eurasia tends to shift to grassland during the LIG when compared with the preindustrial condition, which decreases the gross and net primary productions and the leaf area index over these regions, affecting the global carbon cycle. These results indicate that the vegetation cover over the northern hemisphere would affect the climate over land during the interglacial periods. We further discuss that the transition of the vegetation cover on northern hemisphere high latitudes would have been important not only in affecting the interglacial climates but also in driving the glacial cycles during the Pleistocene (e.g., Watanabe et al., 2023b).
We show that the boundary for the boreal forest and tundra regions shifts northward during the MH and LIG conditions simulated by MRI-LPJ model owing to the different astronomical forcing and the associated climate changes, which is consistent with the previous studies (O’ishi and Abe-Ouchi, 2009; Tabor et al., 2014). We also show the forest at mid-latitudes of North America and Eurasia tends to shift to grassland during the LIG when compared with the preindustrial condition, which decreases the gross and net primary productions and the leaf area index over these regions, affecting the global carbon cycle. These results indicate that the vegetation cover over the northern hemisphere would affect the climate over land during the interglacial periods. We further discuss that the transition of the vegetation cover on northern hemisphere high latitudes would have been important not only in affecting the interglacial climates but also in driving the glacial cycles during the Pleistocene (e.g., Watanabe et al., 2023b).