This work package focuses on advancing our understanding of the response of the fully coupled Norwegian Earth system model (NorESM) to changes in process parameterizations. Changes will be made in individual model components and eventually combined allowing us to investigate the collective effect of the changes. The new knowledge will allow us to elucidate sources of uncertainties in NorESM projections as well as provide insights that feed directly into future model developments. To achieve this, WP6 coordinates a set of sensitivity simulations based on the key processes identified in WPs 3-5, and systematically assesses the projected changes in the Arctic/high-latitude climate in response to individual or collective changes in NorESM components. A customized diagnostic tool based on the ESMValTool will be implemented to support efficient evaluation of key climate metric responses to different process changes. Below is a list of potential processes to be considered in WP6 sensitivity experiments.
|No.||Sensitivity experiment||Component modifications|
|1.||Interactive ozone + VSLS tracer||Atmospheric chemistry and Ocean biogeochemistry|
|2.||Atmospheric boundary layer||Atmospheric physics|
|3.||Oceanic boundary layer||Ocean physics and biogeochemistry|
|4.||Eddy parameterization||Ocean physics|
|5.||Land ice sheet coupling||Ice sheet and land|
|6.||Ice formation in clouds||Cloud microphysics|
|7.||Snow dynamic over sea ice||Sea ice|
|8.||All changes combined||Atmospheric chemistry, ocean biogeochemistry, atmospheric physics, ocean physics, ice sheet, land, cloud microphysics, sea ice|
As an example, in one of the sensitivity experiments, the impact of improved upper-ocean processes on climate projection and feedback will be assessed through improvement in the oceanic planetary boundary layer vertical resolution. The current NorESM configuration (center panel in figure below) applies an isopycnal vertical layer with a bulk mixed layer at the surface layer, which constrains the near-surface stratification representation in the model. In KeyCLIM, a hybrid (right panel in figure below) vertical coordinate will be tested and its impact on high-latitude hydrography and climate dynamics will be determined.