Quantitative reconstruction of paleoclimate in central Japan for the past 158,000 years based on a modern analogue technique of pollen composition

Abstract

In this study, quantitative climate information for central Japan for the past 158 ka is reconstructed on the basis of pollen composition data of NJ88 core from Lake Nojiri and those of TKN-2004 core from the lacustrine Takano Formation using a modern analogue technique. Reconstructed values at the sites around 36.6°N and 700 m altitude are as follows.In marine isotope stage (MIS) 6, the average annual mean temperature was about 2.1 °C, with a coldest month temperature of −11.8 °C, which suggest very cold climate conditions. The climates of MIS 4 and 2 were similarly cold, and the precipitation was low with ∼1050 mm for mean annual precipitations during these cold periods. In contrast, the annual mean temperatures of MIS 5e and MIS 1, among the warmest periods, averaged about 5.5 °C and 9.1 °C, respectively. The annual mean temperature of MIS 5e was significantly lower than that of the Holocene. We estimate that an intensely cold winter controlled the vegetation, which resulted in the lower temperature reconstruction for MIS 5e. The annual mean temperatures of intermediately warm periods such as MIS 5c and 5a were a slightly high, with averages of 4.4 °C and 5.1 °C, respectively. Annual precipitations increased up to ∼1400 mm on average in these warmer periods. Annual mean temperatures of MIS 5d and 5b were low with averages of about 3.0 °C.Annual mean temperatures reconstructed for MIS 3 fluctuated over short periodicities that correspond to Dansgaard–Oeschger cycles. For example, the annual mean temperature of the interstadial GI-8 (Greenland Interstadial 8), 38–39 cal ka BP (calendar ka before 1950 CE) was about 4.0 °C, and that of the stadial HE 4 (Heinrich event 4) in 42–43 cal ka BP was about 2.6 °C. From 14 to 12 cal ka BP, annual mean temperature increased significantly in a relatively short period, from 1.3 to 9.5 °C, and annual precipitation also increased from 1040 to 1380 mm. A cool event corresponding to the Younger Dryas was identified in this deglaciation process, but its intensity was much weaker than that in the North Atlantic region. The climate in the Holocene (MIS 1) was warm, with an average annual mean temperature of 9.0 °C with wide variation, by a maximum of about 2 °C, which suggests temporal change of the Arctic polar front situated in mid-latitude regions.