3:30 PM - 5:00 PM
[U03-P05] Frequent cold summer years at Sannai-Maruyama site during the 4.2 ka event: results from TraCE-21ka simulations
Keywords:4.2 ka event, extreme weather, climate model, cold summer, Jōmon period, climate variability
The 4.2 ka event, a climate change event about 4200 years ago, is recognized to affect civilizations by cooling and droughts globally. In Japan, the Sannai-Maruyama site in Aomori Prefecture, a representative archaeological site of the Jomon period, is thought of as an example of such sudden communities collapse at ~4.2 ka. Sea surface temperature (SST) reconstructions at Mutsu Bay near the site indicated a decrease in SST of approximately 2°C; the communities collapse may be caused by a decrease in chestnut yield due to the cold climate (Kawahata et al., 2009). However, when considering the communities collapse, it is necessary to take into account the climate on the time scale of people's lives.
In this study, the climate in the northern Tohoku region at that time was investigated by using monthly data for 6000-200 yr BP of the transient climate model experiments (TraCE-21ka; He, 2011). We counted the year of cold summer based on the Japan Meteorological Agency definition (the mean surface air temperature (SAT) in the lower third of June-August). As a result, the frequency of cold summer significantly increased at around 4100 yr BP.
A previous study, which also applied TraCE-21ka to the 4.2 ka event, showed that the North Atlantic Oscillation (NAO; North Atlantic Oscillation) was the primary factor for cooling across the Northern Hemisphere (Yan and Liu, 2019). This study further examined the relationship between the NAO and SAT in the northern Tohoku region by regression analyses for monthly time-series of the NAO index and SAT. The results showed that the negative NAO was associated with the frequency and intensity of cold summers, which occurred in the northern Tohoku region around 4100 yr BP.
Our results suggest that the frequent cold summers associated with the NAO around 4.2 ka could contribute to communities collapse at the Sannai-Maruyama site with the chestnuts crop failures. For further work, we will analyze other climatic factors to deepen our understanding of the climate at that time. Investigate whether the NAO was recorded in proxies is also necessary.
1. He, F. SIMULATING TRANSIENT CLIMATE EVOLUTION OF THE LAST DEGLACIATION WITH CCSM3. Ph.D Dissertation at the UNIVERSITY OF WISCONSIN-MADISON (2011).
2. Kawahata, H. et al. Changes of environments and human activity at the Sannai-Maruyama ruins in Japan during the mid-Holocene Hypsithermal climatic interval. Quat. Sci. Rev. 28, 964–974 (2009).
3. Yan, M. & Liu, J. Physical processes of cooling and mega-drought during the 4.2 ka BP event: results from TraCE-21ka simulations. Clim. Past 15, 265–277 (2019).
In this study, the climate in the northern Tohoku region at that time was investigated by using monthly data for 6000-200 yr BP of the transient climate model experiments (TraCE-21ka; He, 2011). We counted the year of cold summer based on the Japan Meteorological Agency definition (the mean surface air temperature (SAT) in the lower third of June-August). As a result, the frequency of cold summer significantly increased at around 4100 yr BP.
A previous study, which also applied TraCE-21ka to the 4.2 ka event, showed that the North Atlantic Oscillation (NAO; North Atlantic Oscillation) was the primary factor for cooling across the Northern Hemisphere (Yan and Liu, 2019). This study further examined the relationship between the NAO and SAT in the northern Tohoku region by regression analyses for monthly time-series of the NAO index and SAT. The results showed that the negative NAO was associated with the frequency and intensity of cold summers, which occurred in the northern Tohoku region around 4100 yr BP.
Our results suggest that the frequent cold summers associated with the NAO around 4.2 ka could contribute to communities collapse at the Sannai-Maruyama site with the chestnuts crop failures. For further work, we will analyze other climatic factors to deepen our understanding of the climate at that time. Investigate whether the NAO was recorded in proxies is also necessary.
1. He, F. SIMULATING TRANSIENT CLIMATE EVOLUTION OF THE LAST DEGLACIATION WITH CCSM3. Ph.D Dissertation at the UNIVERSITY OF WISCONSIN-MADISON (2011).
2. Kawahata, H. et al. Changes of environments and human activity at the Sannai-Maruyama ruins in Japan during the mid-Holocene Hypsithermal climatic interval. Quat. Sci. Rev. 28, 964–974 (2009).
3. Yan, M. & Liu, J. Physical processes of cooling and mega-drought during the 4.2 ka BP event: results from TraCE-21ka simulations. Clim. Past 15, 265–277 (2019).