Abstract: Ocean salinity has long been recognized as a tracer of the global hydrological cycle. In this talk, I will try to demonstrate the overlooked but critical role of ocean salinity in climate change. The enhancement of global hydrological cycle, a robust consequence of global warming, leads to an amplified pattern of ocean salinity. Through a series of climate model experiments, I demonstrate that surface salinification driven by the amplified dry conditions, primarily in the subtropical ocean, accelerates ocean heat uptake (OHU) and therefore moderates transient warming. The importance of subtropical salinity is also highlighted by its dominant role, relative to ocean temperature, in determining the inter-model spread in OHU efficiency in Coupled Model Intercomparison Project Phase 6 (CMIP6) models. Models with higher base-state upper-ocean subtropical salinity tend to have a weaker ocean stratification and therefore produce a deeper warming which, in turn, further reduces the ocean stratification, forming a positive feedback. In addition, extratropical Southern Ocean salinity statistically accounts for more than half of models’ spread in global shortwave cloud feedback through its regulation on local OHU. Southern Ocean heat uptake, primarily driven by bases-state extratropical salinity, leads to a stabilized lower troposphere in both local extra-tropics and remote subtropics and therefore increased low cloud cover. The physically sound impact of ocean salinity on OHU efficiency and cloud feedback is applied to statistically constrain the latter based on salinity observations and therefore have the potential to narrow the uncertainty in estimating future climate warming.
Short Bio: Dr. Maofeng Liu is currently a Postdoctoral Research Associate at the University of Miami. Dr. Liu received his B.S. from Tsinghua University, M.S. from Chinese Academy of Sciences, and Ph.D. from Princeton University. His current research focuses on the ocean salinity impact on ocean heat uptake and climate change. Dr. Liu has published 20+ peer-reviewed journal papers, including Nature Climate Change. He has also served as the reviewer for many top journals, including Nature Geoscience, Nature Communications, and Bulletin of the American Meteorological Society. He is also a guest editor for the special issue Extreme Tropical Cyclones in journal Atmosphere.