Analysis of the seasonality based on the angular calendar in paleo-climate simulations with AWI-ESM

• Main Author: Igbinosa, Endurance
• Format: Thesis
• Language: unknown
• Published: University of Bremen 2022
• Subjects: Antarctic; The Antarctic; Antarc*
• Online Access: https://epic.awi.de/id/eprint/55839/; https://epic.awi.de/id/eprint/55839/1/Master_Thesis_Endurance_Igbniosa.pdf; https://hdl.handle.net/10013/epic.3f9fd4ba-fa32-4ebe-9599-fff893a5732f

Orbital forcing is a major driver of climate variability on timescales of 10,000 to 100,000 years. The orbital parameters responsible for these changes are Eccentricity, Obliquity and Procession. For comparison between simulated paleo and present climate, biases in seasonality may emerge without the use of the angular calendar, as in the today’s classical calendar, the start/end of one season may correspond to different angles between the vernal equinox and the earth. On the other hand, model resolution is also an important factor for resolving some small-scale process in the simulated world. Hence, the Alfred Wegener Institute has established and developed the state-of-the-art high-resolution Earth system models AWI-ESM1 and AWI-ESM2, with the ice-ocean component being based on finite element/volume formation. In this study, we take advantage of the simulation results from AWI-ESM1 and AWI-ESM2. Climate variables such as surface temperature and precipitation are analyzed and compared between paleo and modern climate conditions. The simulations for mid-Holocene (MH, 6k B.P.) and Last Inter-glacial (LIG, 127k B.P.) were designed to examine the climate responses to changes in orbital forcings and greenhouse gases. The continental configuration remains unchanged with respect to the pre-industrial (PI) condition. Due to the insolation anomaly induced by orbital configuration, the seasonality for the MH is larger than today resulting from the positive anomaly of solar insolation in boreal summer and autumn, and negative anomalies during winter time. The Antarctic was colder in DJF and MAM and warmer in JJA and SON in the MH as compared to present. There was more precipitation in the MH over the tropical rain belt as a result of a northward shift of the inter-tropical convergence zone (ITCZ). Additionally, there is an enhanced seasonality in the LIG as compared to present-day for the simulated surface temperature with a cooling of up to 5 K in boreal winter and warming of more than 5 K for boreal summer. Furthermore, ...