EVALUATION OF THE COUPLED MODEL INTERCOMPARISON PROJECT PHASE 6 (CMIP6) HISTORICAL SIMULATIONS OF THE ARCTIC SEA ICE: PROGRESS, LIMITATIONS AND THEIR CAUSES

• Main Author: Watts, Matthew N.
• Other Authors: Maslowski, Wieslaw, Murphree, Tom, Stanton, Timothy P., Lee, Younjoo, Orescanin, Mara S., Oceanography (OC)
• Format: Thesis
• Language: unknown
• Published: Monterey, CA; Naval Postgraduate School 2021
• Subjects: Arctic Ocean; Arctic sea ice; Arctic amplification; Earth system models; global climate models; oceanic forcing; ocean heat convergence; Coupled Model Intercomparison Project; CMIP6; model biases; sea ice thickness; SIT; oceanic heat transport; OHT; sea ice area; SIA; sea ice extent; SIE; sea ice volume; SIV; Arctic; Climate change; Sea ice
• Online Access: https://hdl.handle.net/10945/68397

A decline of the Arctic sea ice in response to a warming climate is assessed in the historical sea ice simulations from state-of-the-art global climate models participating in Phase 6 of the Coupled Model Intercomparison Project (CMIP6). Accurate simulations of sea ice are important for projections of its regional and global effects on the air-sea exchanges, weather, and climate. The timing and rate of simulated sea ice decline is compared with available observations for sea ice area and volume. Analysis indicates multi-model means and long-term trends for these common sea ice metrics are well represented, but the individual CMIP6 model ability to represent the observed accelerated rate in sea ice decline remains a challenge. Local and regional sea ice biases are identified through spatial analysis metrics, like sea ice thickness distribution pattern and sea ice edge analysis. Large model spatial errors imply limitations in or lack of representation of some key physical processes. The oceanic heat transport (OHT) and its forcing of the pan-Arctic sea ice decline are examined as possible model limitations. CMIP6 models show a strong correlation between increasing OHT and decreasing sea ice trends but likely underestimate the northward OHT over the polar cap (70°–90°N). Isolating specific model limitations and identifying possible processes affecting them will guide future model improvements critical to our understanding and projection of Arctic climate change. Approved for public release. Distribution is unlimited. Commander, United States Navy