Collaborative Research: Uncertainty in Antarctic Climate Change Projections and the Role of Sea Ice, Clouds and Ocean Structure

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Climate change in Antarctica and the Southern Ocean has major societal impacts in terms of global sea level rise, carbon storage into the ocean, and heat transport. The project goal of this study is to systematically assess the influence of long-standing atmospheric radiation and ocean structure components on the modelled climate of Antarctica and the Southern Ocean, using a state-of-the-art community climate model (CESM). The project will be co-led by female PIs at the University of Colorado (CU) and National Center for Atmospheric Research (NCAR), and will support the training and mentoring of a new graduate student at CU, and a science communication postdoc. Because public understanding of these issues can be very low, the project includes a substantial outreach and science communication component. An interactive museum display demonstrating the interpretation and implications of trends and variability in Antarctic sea ice will be developed, along with provision of training for K-12 educators nationwide that focuses on using the display, or a web variant.Large uncertainties in projected anthropogenic climate change impacts are related to Antarctica and the Southern Ocean. Projected changes in Antarctic surface mass balance, sea ice extent, and surface temperature differ widely amongst current-generation climate models. Such uncertainties likely have roots in the mean states (climatologies) of different models. Recent observational and modeling evidence has implicated ocean mean-state biases in particular for the general inability of climate models to simulate trends in annual Antarctic sea ice extent observed by remote sensing. Ocean biases may be driven in part by a long-standing bias in absorbed shortwave radiation over the Southern Ocean. The primary project goal is to systematically assess the influence of long-standing atmospheric radiation and ocean structure biases on the modelled climate of Antarctica and the Southern Ocean, using a state-of-the-art community climate model (CESM). It is anticipated that the mean state (climatology) bias reductions will alter the response of sea ice extent and volume, air temperature, precipitation, surface mass balance, and sea level rise to anthropogenic forcing. Proposed climate modeling experiments, together with existing numerical simulation experiments, will enable a more thorough and systematic assessment of the impact of mean-state biases on the simulation of climate variability and change across Antarctica and the Southern Ocean than has been previously possible.