Advancing understanding of Arctic sea ice variability and diagnostic predictability in ESMs with regional-to-global-scale process- oriented evaluation

In this proposal for MAPP Competition 2, Addressing Key Issues in CMIP6-era Earth System Models, we propose to characterize and understand biases in CMIP6 Arctic sea ice variability. We will focus on determining relationships between modeled quantities that are observable and quantities that characterize processes, so that we can simultaneously evaluate an observable and sea ice processes. We seek to understand when biases are due to missing physics or poor tuning and what makes some models outliers. We will use this understanding to recommend essential
model physics and future directions in sea ice modeling.

The objectives of this proposal focused on creating metrics are threefold. (1) Categorize the spatial and temporal nature of sea ice variability across the multi-model ensemble, in both the unforced intrinsic variation and forced response. This will give us a basis from which to evaluate the role of ocean-ice and atmosphere-ice processes on the sea ice. (2) Characterize the spatio-temporal variability of atmosphere-ice and ocean-ice interface fluxes associated with sea ice variability (3) Quantify ocean stratification strength, the amplitude and vertical structure of atmospheric meridional energy fluxes into the Arctic and radiative variability associated with clouds and sea ice and how each impacts sea ice variability.

We will develop process-oriented metrics in order to understand inter-model spread in the drivers of sea ice variability and to place the models in the context of observations. The metrics are designed to identify parameterizations and model physics that need improvements. We will test proposed improvements in the developmental Community Earth System Model (CESM) and work with the CESM working groups to communicate necessary changes to other climate model developers.

Relevance to the NOAA MAPP Competition and NOAA’s Long-Term Goal: Our project is about understanding the source of the coupled atmosphere-sea ice-ocean biases that
affect sea ice variability. We propose to develop systematic process-oriented analysis methods and scripts for community use in collaboration with MDTF and SIMIP that can be used with CMIP6 output. By evaluating processes relevant to sea ice variability, and ultimately identifying ways to improve model accuracy, our project is aligned with MAPP’s mission to “enhance the Nation’s capability to understand and predict natural variability and changes in Earth’s climate system”, and NOAA’s long-term goal of “providing the essential and highest quality environmental information vital to our Nation’s safety, prosperity and resilience.”