[A-CG31] Climate Variability and Predictability on Subseasonal to Centennial Timescales

[ACG31-P05] Antarctic sea ice multidecadal variability revealed by reconstructed data and model simulations

*Yushi Morioka¹, Syukuro Manabe², Liping Zhang^3,4, Thomas L. Delworth³, William Cooke³, Masami Nonaka¹, Swadhin Behera¹ (1.Japan Agency for Marine-Earth Science and Technology, 2.Atmospheric and Oceanic Sciences Program, Princeton University, 3.Geophysical Fluid Dynamics Laboratory, NOAA, 4.University Corporation for Atmospheric Research, Boulder, Colorado)

Keywords:Antarctic Sea Ice, Multidecadal Variability, Reconstructed Data, Climate Model

Antarctic sea ice exerts great influences on Earth’s climate by exchanging heat, momentum, freshwater, and gases between the atmosphere and ocean. Antarctic sea ice extent has undergone a large variability with a multidecadal increase followed by a substantial decline since 2016. Here we utilize prolonged sea ice reconstruction and coupled model simulations and reveal natural variability of Antarctic sea ice extent at a multidecadal timescale. Stronger westerlies associated with a positive phase of Southern Annular Mode tend to enhance upwelling of warm and saline water from the subsurface ocean. The consequent salinity increase weakens the upper-ocean stratification, induces the Southern Ocean deep convection, and brings subsurface warm and saline water to the surface. This salinity-convection feedback provides favorable conditions for sea ice decrease on a multidecadal timescale. Processes acting in reverse are also found for sea ice increase, although they are relatively slower than the case for sea ice decrease. These findings help better understand and predict recently observed changes in the Antarctic sea ice extent.