17:15 〜 18:30
[MIS16-P22] The mid-Pliocene Warm Period: climate sensitivity to atmospheric CO2 levels and inclusion of dynamic vegetation in the MIROC4m model
キーワード：Pliocene, climate modeling, dynamic vegetation, data-model comparison
The mid-Pliocene Warm Period (mPWP), 3.3-3 million years ago, was a period of sustained warmth before global cooling occurred and a shift to glacial cycles. It was also the most recent time in the history of Earth when atmospheric CO2 levels were similar to those of present day. The study of this period is thus of much importance, given the growing concerns over future climate change associated with anthropogenic emissions of greenhouse gases. A number of climate models have been used to investigate the mPWP climate, contributing to the Pliocene Model Intercomparison Project (PlioMIP), while a large collection of proxy data from both terrestrial and marine sources have become available. Reconciling model results and proxy data remains an important issue.
In our study, we use the mid-resolution MIROC4m coupled atmosphere-ocean general circulation model and apply ice sheet configuration, land-sea mask, orography and biome distribution based on PRISM data sets, as specified in the second phase of PlioMIP, one of the working groups of PMIP4. We conduct a series of experiments which include a range of atmospheric CO2 levels given the spread in values suggested by different sources of proxy data and show how various aspects of the climate respond. While sea surface temperatures (SST) for all CO2 levels show much less warming in the northern high latitudes as suggested by previous proxy data, there is improved agreement with more recent data in the tropical Pacific for 400ppm CO2. We will show these and other results. Additional experiments were carried out with MIROC4m coupled to a dynamic global vegetation model. Compared to the prescribed Pliocene vegetation, temperate forests expand at mid-latitudes across Asia and North America. Across North Africa, shrubs and bare ground expand, replacing regions of savanna. Global surface temperatures are slightly lower with the inclusion of dynamic vegetation.
In our study, we use the mid-resolution MIROC4m coupled atmosphere-ocean general circulation model and apply ice sheet configuration, land-sea mask, orography and biome distribution based on PRISM data sets, as specified in the second phase of PlioMIP, one of the working groups of PMIP4. We conduct a series of experiments which include a range of atmospheric CO2 levels given the spread in values suggested by different sources of proxy data and show how various aspects of the climate respond. While sea surface temperatures (SST) for all CO2 levels show much less warming in the northern high latitudes as suggested by previous proxy data, there is improved agreement with more recent data in the tropical Pacific for 400ppm CO2. We will show these and other results. Additional experiments were carried out with MIROC4m coupled to a dynamic global vegetation model. Compared to the prescribed Pliocene vegetation, temperate forests expand at mid-latitudes across Asia and North America. Across North Africa, shrubs and bare ground expand, replacing regions of savanna. Global surface temperatures are slightly lower with the inclusion of dynamic vegetation.