Critical Southern Ocean climate model biases traced to atmospheric model cloud errors

Area of Science:

• Climate Science
• Oceanography
• Atmospheric Science

Background:

• The Southern Ocean is crucial for global climate regulation.
• Existing climate models exhibit significant biases in Southern Ocean upper-ocean temperatures, clouds, and winds.
• Accurate representation of this region is vital for reliable climate projections.

Purpose of the Study:

• To identify the primary causes of sea surface temperature biases in Southern Ocean climate models.
• To investigate the feedback mechanisms influencing these biases.
• To propose targeted improvements for climate models.

Main Methods:

• Analysis of Atmospheric and Coupled Model Inter-comparison Project (AMIP5/CMIP5) simulations.
• Integration of observational data.
• Application of equilibrium heat budget theory.

Main Results:

• Sea surface temperature biases in the Southern Ocean are mainly driven by atmospheric model net surface flux errors, linked to cloud short-wave radiation biases.
• Local sea surface temperature feedbacks and wind feedbacks exacerbate upper-ocean thermal structure biases.
• Models with small net heat flux biases often achieve this through compensating errors.

Conclusions:

• Targeted improvements in cloud parameterizations are essential for enhancing Southern Ocean representation in climate models.
• Addressing cloud-related errors can mitigate biases and improve climate projections.
• Better model representation of the Southern Ocean is critical for understanding global climate dynamics.