A113-0017
Linkages between hydrological cycle, ocean heat uptake and climate sensitivity

Friday, 11 December 2020
Poster
Maofeng Liu1, Brian J. Soden2, Gabriel Andres Vecchi3, Wenchang Yang4 and Bosong Zhang2, (1)University of Miami, Rosenstiel School of Marine and Atmospheric Science, Miami, FL, United States, (2)University of Miami, Rosenstiel School for Marine and Atmospheric Science, Miami, FL, United States, (3)Princeton University, Department of Geosciences and Princeton Environmental Institute, Princeton, NJ, United States, (4)Princeton University, Department of Geosciences, Princeton, NJ, United States
Abstract:
The large-scale changes in the atmospheric hydrological cycle in response to a warming climate can amplify the existing patterns of P-E, which in turn, amplifies the spatial contrast in salinity. We propose that surface salinification due to intensified hydrological cycle provides a buoyancy sink to help compensate enhanced thermal stratification due to near-surface ocean warming, and thus plays an important role in the rate of ocean heat uptake as well as the pattern of surface warming - and leading to changes in transient and equilibrium climate sensitivity. We quantify the impact of sea surface salinity (SSS) in response to climate warming by a set of CO2 doubling experiments (i.e., annual CO2 increase by 1% until doubling) using two versions of a coupled climate model: a standard version and a modified version in which SSS is nudged with seasonally-varying control climatology. In response to CO2-induced warming, the existing dry conditions (P-E < 0) in the subtropical oceans are amplified due to enhanced hydrological cycle, resulting in increased SSS in salty regions and an increased rate of ocean heat uptake in the standard CO2 doubling run relative to the SSS nudging runs. The largest increase in ocean heat content (OHC) for the standard run occurs in the southern subtropical Pacific and the tropical and subtropical Atlantic Ocean where SSS shows the largest increase. Consistent with changes in the ocean heat uptake, the SSS nudging run produces a transient climate response approximately 0.4 K greater than the standard run. The SSS nudging run also shows a slightly lower strength of radiative feedback (-1.45 W/m2/K) than the standard run (-1.55 W/m2/K) over the CO2 stabilization period, indicating a greater equilibrium climate sensitivity. The lower radiative feedback mainly comes from the lapse rate feedback, consistent with that the enhanced surface warming in the SSS nudging run over the standard run is more distributed in midlatitudes than tropics.
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