5:15 PM - 7:15 PM
[MIS14-P25] The climate conditions of Okinawa during the Last Glacial Maximum (LGM) as calculated by the latest climate models
Keywords:LGM, East Asia, Climate model
During the Last Glacial Maximum (LGM) approximately 21,000 years ago, atmospheric CO2 concentration was 190 ppm, and extensive ice sheets in the Northern Hemisphere led to lowered sea levels. A previous study (Asami et al., 2021), using fossil shells and stalagmites from caves in southern Okinawa Island, reconstructed temperatures around Okinawa during the LGM. It suggested temperatures were about 6.3 C colder (2.5 C uncertainty) than modern times, with potential snowfall. Conversely, sea surface temperatures around Okinawa decreased by only 3.5 C (air temperatures 8.7-13.7 C, sea surface temperature 18.7 C), indicating a 7.5 C (2.5 C uncertainty) difference between surface and sea temperatures. In contrast, the temperature difference between land and sea is small today at 4.7 C, highlighting significant differences in land and ocean temperatures during the LGM. This study aims to assess whether current climate models used for future warming predictions can reproduce the winter climate conditions around Okinawa as suggested by Asami et al. (2021).
The analysis involves LGM experiments conducted with 13 climate models participating in the Paleoclimate Modeling Intercomparison Project phases 4 and 3 (PMIP4, 3), along with modern climate simulations (piControl) data. Specifically, it examines surface temperatures, sea surface temperatures, monsoon patterns, precipitation, and snowfall around Okinawa. Snowfall is classified if it exceeds 0.03 kg/m**2/day. Additionally, the study evaluates the fidelity of climate models' modern climate simulations using reanalysis data from ERA5.
Firstly, many models generally reproduce modern temperatures. Examining LGM temperatures reveals an average decrease of approximately 5 C compared to modern times, with 8 out of 13 models reproducing results similar to Asami et al. (2021). Furthermore, all models indicated a larger temperature difference between land and sea during the LGM, consistent with Asami et al. (2021). This difference is attributed to lower sea levels during the LGM, bringing continents closer to Okinawa and intensifying the influence of colder continental climates. Analysis of snowfall during the LGM in models with good surface temperature reproduction often showed occurrences, influenced more by cold conditions at the surface and 850 hPa levels rather than winter monsoon intensity. Combining these models with Asami et al. (2021) suggests that during the LGM, Okinawa experienced a climate resembling that of present-day southern Kyushu, influenced by continental effects.
The analysis involves LGM experiments conducted with 13 climate models participating in the Paleoclimate Modeling Intercomparison Project phases 4 and 3 (PMIP4, 3), along with modern climate simulations (piControl) data. Specifically, it examines surface temperatures, sea surface temperatures, monsoon patterns, precipitation, and snowfall around Okinawa. Snowfall is classified if it exceeds 0.03 kg/m**2/day. Additionally, the study evaluates the fidelity of climate models' modern climate simulations using reanalysis data from ERA5.
Firstly, many models generally reproduce modern temperatures. Examining LGM temperatures reveals an average decrease of approximately 5 C compared to modern times, with 8 out of 13 models reproducing results similar to Asami et al. (2021). Furthermore, all models indicated a larger temperature difference between land and sea during the LGM, consistent with Asami et al. (2021). This difference is attributed to lower sea levels during the LGM, bringing continents closer to Okinawa and intensifying the influence of colder continental climates. Analysis of snowfall during the LGM in models with good surface temperature reproduction often showed occurrences, influenced more by cold conditions at the surface and 850 hPa levels rather than winter monsoon intensity. Combining these models with Asami et al. (2021) suggests that during the LGM, Okinawa experienced a climate resembling that of present-day southern Kyushu, influenced by continental effects.