| Popis: |
The Last Glacial Maximum (~21 ka) is the most recent glacial period when the ice sheetcoverage was at its greatest extent (8% of Earth's surface), and the atmospheric CO2concentration was ~190 ppm. During this period, the continental shelves were exposed andthe global-mean sea level was lower by ~130 m compared to today. This project hypothesizesthat decrease in sea level caused tidal-energy dissipation to shift from the shelves to the open-ocean resulting in enhanced vertical mixing in the deep ocean. The aim of this project is tostudy the global ocean circulation and the marine biogeochemical processes of the LGMclimate state using an energetically consistent ocean mixing scheme: Internal WaveDissipation, Energy, and Mixing (IDEMIX) in the fully coupled isotope-enabled EarthSystem Model (iCESM1.2). For this study, only the tidal-induced mixing is investigated.Hence the tidal forcing is considered as the only source for generating internal waves inIDEMIX parameterisation. The model uses the "KPP+IDEMIX" approach as the combinedvertical mixing parameterization. While the KPP is activated only in the mixed layer (up to ~1 km), IDEMIX is applied only to the interior ocean, where the dissipation is generated by thetidal forcing at the ocean floor. In our simulations, we use 2° resolution for the atmosphereand 1° for the ocean, and we simulate LGM and pre-industrial climate states with and withoutIDEMIX. The modal bandwidth tuning parameter (j★) in IDEMIX determines the number ofexcited vertical modes, which affects how fast the energy propagates from the bottom to theupper ocean. We perform the sensitivity experiments by using different j★ values in our LGMsimulations and investigate its impact on the vertical mixing and the ocean state. |
